8/4- Neuro

What sensory area does the illioinguinal nerve provide

The ilioinguinal nerve primarily provides sensory innervation to the upper medial thigh and genital region. It accompanies the spermatic cord through the superficial inguinal ring; injury during pelvic or hernia surgery can lead to chronic suprapubic or groin pain.

What sensory area is provded by the obturator nerve. What motor?

The obturator nerve is typically injured in anterior hip dislocation or pelvic surgery. Sensory symptoms occur in the medial thigh and are often associated with weakness in the adductor muscles.

What is housed in the substantia nigra

he substantia nigra contains dopaminergic neurons. In Parkinson disease, these neurons are depletex

The patient says that her sight in the right eye is "narrower" than in the left. She also suffers from intermittent lower limb claudication and has had 2 prior episodes of transient vision loss in her right eye. Visual field testing reveals a right nasal hemianopia. MRI/magnetic resonance angiography of the head and neck reveal a right internal carotid artery aneurysm. Which of the following portions of the visual pathway is most likely disrupted in this patient?

*Right perichiasmal region* Light from the nasal visual field strikes the temporal side of each retina, and optic nerve fibers from the temporal part of the retina travel laterally through the optic chiasm to pass into the ipsilateral optic tract. Lesions involving the lateral aspects of the optic chiasm can cause ipsilateral nasal hemianopia by damaging these uncrossed, temporal retinal fibers. This may occur with aneurysm of the internal carotid artery (eg, cavernous or ophthalmic segments), as seen in this patient. D- in the photo

Abdominal CT shows an advanced bladder tumor compressing a nerve that passes through the obturator canal. Which of the following actions would most likely be impaired in this patient?

*Adduction of the thigh* The obturator nerve arises from the lumbar plexus and carries fibers from the L2-L4 spinal segments. It descends posteromedial to the iliopsoas muscle and courses along the lateral aspect of the lesser pelvis before descending through the obturator canal. The obturator nerve is the only major nerve that exits the pelvis through this canal. Once the nerve has entered the thigh, it supplies the obturator externus muscle and divides into anterior and posterior branches that supply the rest of the thigh adductor muscles (eg, adductor longus, brevis, magnus). The anterior division of the nerve gives off a terminal cutaneous branch that provides sensation over the distal medial thigh. Obturator nerve injury is most commonly caused by compression due to pelvic trauma, surgery, or tumors (eg, bladder cancer). Patients typically present with weakness on thigh adduction and sensory loss in the distal medial thigh.

A 62-year-old, right-handed man is evaluated for an episode of left leg weakness that spontaneously resolved within 30 minutes of onset. The patient also has had transient vision loss in the right eye. Medical history is significant for hypertension and diabetes mellitus. Evaluation reveals an atherosclerotic plaque in the extracranial portion of the supplying artery. During percutaneous stenting of the lesion, the vascular catheter is inserted into the right common femoral artery and gradually advanced to the level of the aortic arch. Which of the following is the most likely path of the catheter before stenting of the culprit lesion can be performed?

*Aorta --> brachiocephalic --> CCA --> ICA This patient is having transient episodes of focal neurologic impairment, concerning for transient ischemic attacks (TIA), which often occur due to emboli originating from atherosclerotic plaques. The internal carotid artery supplies blood to the cerebral hemispheres, including the motor cortex, which controls the contralateral limbs. However, the ophthalmic artery, which gives rise to the retinal artery, originates from the ipsilateral internal carotid artery. Therefore, the combination of left leg weakness and vision loss in the right eye (amaurosis fugax) suggests a lesion in the right internal carotid artery. Because TIAs are a risk factor for future stroke, intervention is warranted. After cannulation of the femoral artery, the catheter is advanced through the aorta. From there, the catheter can access much of the cerebrovascular circulation. The left common carotid and subclavian arteries branch directly from the aortic arch. However, on the right, the brachiocephalic (innominate) artery branches from the aortic arch then divides into the right subclavian and right common carotid. The common carotid then divides into the external carotid, which supplies blood to the face and neck, and the internal carotid, which supplies blood to the brain.

A 34-year-old woman is evaluated for several months of moderate hearing loss. She has also noticed a ringing in her left ear. On physical examination, the auditory canals are patent and tympanic membranes appear gray with a well-visualized light reflex. Hearing is diminished on the left side. Neurologic examination shows left-sided facial numbness, an asymmetric smile, and diminished corneal reflex response in the left eye. This patient's condition suggests an intracranial mass in which of the following locations?

*B/w the cerebellum and lateral pons* This patient's unilateral hearing loss with associated facial numbness and weakness, is highly suggestive of a vestibular schwannoma, the most common cause of cerebellopontine angle (ie, between the cerebellum and lateral pons) tumors in adults. Vestibular schwannomas most often arise from the vestibular portion of the vestibulocochlear nerve (CN VIII). Spontaneous vestibular schwannomas are usually unilateral, whereas bilateral vestibular schwannomas are associated with neurofibromatosis type 2. The facial nerve (CN VII) and trigeminal nerve (CN V) are in proximity to CN VIII at the cerebellopontine angle and may be compressed by vestibular schwannomas. Symptoms can vary based on the pattern of nerve involvement: Impairment of the cochlear portion of CN VIII leads to ipsilateral sensorineural hearing loss and tinnitus (ringing in the ear), and damage to the vestibular portion causes unsteadiness and disequilibrium. Compression of CN V may cause loss of ipsilateral facial sensation with interruption of the afferent limb of the corneal reflex. CN VII compression can result in ipsilateral facial muscle paralysis (eg, asymmetric smile).

A 28-year-old woman comes to the office due to right hand tremors for the past several weeks. The patient has difficulty performing daily activities and feels embarrassed in social gatherings. She has a history of the remitting-relapsing form of multiple sclerosis. There is no family history of tremors. On physical examination, no abnormal hand movement is observed at rest. When the patient is instructed to touch an object on the table, a coarse tremor is observed that gradually increases as the hand moves closer to its target. Dysfunction of which of the following structures is the most likely cause of this patient's tremor?

*Cerebellum* This patient has developed a large-amplitude (ie, coarse) tremor that worsens as the hand approaches the target, suggesting a cerebellar tremor. Cerebellar tremor can result from multiple pathologies that affect the cerebellum, most commonly multiple sclerosis, as in this patient. Other common causes include stroke, fragile X syndrome, and cerebellar degeneration. Tremors due to cerebellar lesions are classically low frequency (ie, "slow," <5 Hz) and high amplitude (ie, coarse) because they involve the proximal, as well as the distal, muscles. The tremor classically increases in amplitude as an action approaches a target (ie, intention tremor). It is often accompanied by other cerebellar signs, including ataxia, dysmetria, and/or impaired rapidly alternating movements.

MRI of the shoulder shows a partial rotator cuff tear, and the patient is scheduled for surgical repair. Immediately before the surgery, he receives anesthesia with an injection between the right anterior and middle scalene muscles in order to block the C3 through C7 nerve roots of the cervical and brachial plexuses. Which of the following muscles is most likely to be paralyzed due to the anesthesia?

*Diaphragm The brachial plexus originates from the C5-T1 spinal nerve roots, which combine into 3 trunks and pass between the anterior and middle scalene muscles (scalene triangle) in the posterior neck. The trunks then differentiate into divisions, cords, and terminal nerve branches. The brachial plexus supplies all sensory and motor innervation to the upper extremity, except for an area of skin near the axilla which is innervated by the intercostobrachial nerve and the trapezius muscle which is innervated by the accessory nerve (CN XI). An interscalene nerve block is a regional anesthesia technique used for procedures involving the shoulder and upper arm. In this technique, anesthetic is administered to the brachial plexus roots and trunks between the anterior and middle scalene muscles. Anesthetic also traverses along the interscalene sheath and affects the roots of the phrenic nerve (C3-C5), which causes transient ipsilateral diaphragmatic paralysis. Therefore, an interscalene nerve block should be avoided in patients with conditions that could be worsened by unilateral diaphragmatic paralysis (eg, chronic lung disease, contralateral phrenic nerve dysfunction).

The boy tried to break the fall by grabbing the tree branch with his right hand. He landed safely on his feet with no head injury or loss of consciousness. On physical examination, he has difficulty performing fine finger movements with the right hand. Which of the following structures is most likely injured in this patient

*Lower trunk of brachial plexus* Sudden upward jerking of the arm at the shoulder can cause injury to the lower trunk of the brachial plexus. The lower trunk carries nerve fibers from the C8 and T1 spinal levels that ultimately contribute to the median and ulnar nerves. Together, these nerves innervate all of the intrinsic muscles of the hand (eg, lumbricals, interossei, thenar, hypothenar). Injury to the lower trunk of the brachial plexus may cause paralysis of all the intrinsic hand muscles (Klumpke's palsy). Weakness of lumbricals causes impaired flexion of the metacarpophalangeal joints and impaired extension of the interphalangeal joints. Relative sparing of the extrinsic flexors and extensors of the hand contributes to the total claw hand deformity seen in this condition. Sensory loss can also occur over the medial aspect of the hand/forearm. Involvement of the T1 nerve root proximal to the sympathetic trunk may cause concomitant Horner's syndrome (eg, ipsilateral ptosis, miosis, anhidrosis).

A 34-year-old man comes to the clinic with a 3-week history of difficulty hearing. He finds it increasingly difficult to tolerate everyday sounds. He also complains of ear pain and often avoids public places as a result. The patient has no past medical history and takes no medications. Injury to which of the following cranial nerves is most likely responsible for his condition?

*Facial N.* The middle ear cavity contains 3 auditory ossicles (malleus, incus, and stapes) and 2 skeletal muscles (tensor tympani and stapedius) that participate in the transmission of sound from the tympanic membrane to the cochlea. The stapedius muscle arises from the wall of the tympanic cavity and inserts on the neck of the stapes. It is innervated by the stapedius nerve, a branch of the facial nerve (CN VII). The stapedius muscle functions to stabilize the stapes; paralysis of the muscle (secondary to an injury or lesion to the facial nerve) causes the stapes to oscillate more widely, producing hyperacusis. Patients will typically complain of increased sensitivity to everyday sounds (eg, shutting doors, ringing phones, traffic) and will often withdraw socially as a result. Treatment consists of retraining (or sound) therapy using broadband noise (eg, "white noise"). The tensor tympani muscle arises from the cartilaginous portion of the auditory tube and the adjoining part of the sphenoid bone and inserts into the malleus. It functions to contract the tympanic membrane medially, thereby increasing its tension and dampening sound transmission. It is innervated by the mandibular branch of the trigeminal nerve (CN V3). Ipsilateral hyperacusis is a common finding associated with Bell's palsy (unilateral/peripheral facial paralysis).

A 36-year-old woman comes to the office due to firm, nontender swelling of her right cheek for the past 4 months. The patient has had no fever, runny nose, sore throat, or cough. She drinks a glass of wine with dinner on most nights but does not use tobacco. Physical examination shows fullness of the preauricular space on the right side. An MRI of the region identifies a 2.2-cm mass in the right parotid gland, and a follow-up core needle biopsy shows the lesion to be neoplastic. If left untreated, this patient is most likely to develop which of the following?

*Facial droop* The extracranial portion of the facial nerve (CN VII) carries motor innervation to the muscles of facial expression. This nerve exits the skull through the stylomastoid foramen and courses within the substance of the parotid gland. Within this gland, the facial nerve divides into its 5 terminal branches (temporal, zygomatic, buccal, mandibular, and cervical). Parotid gland tumors can compress and disrupt the ipsilateral facial nerve and its branches, causing facial droop. In fact, most parotid gland tumors causing facial nerve paralysis are malignant neoplasms.

Physical examination shows swelling of the left knee with focal tenderness just above the patella. She is unable to raise the left leg against gravity while in the supine position. Imaging confirms a complete tear of the quadriceps tendon, but no fractures are identified. Surgical repair is planned. Lidocaine injection near which of the following sites is most likely to provide adequate anesthesia for the procedure?

*Inguinal ligament* The femoral nerve (L2-L4) innervates the quadriceps muscles (enabling extension at the knee and flexion at the hip) and provides sensation for the arch of the foot, shin, and anteromedial thigh. The nerve emerges between the psoas and iliacus muscles and passes under the inguinal ligament (lateral to the femoral artery) into the thigh before branching in the femoral triangle into an anterior and posterior division. The optimal site for a femoral nerve block is right below the inguinal ligament (ie, in the inguinal crease) at the lateral border of the femoral artery. Injecting at this site anesthetizes the skin and muscles of the anterior thigh, femur, and knee and can be used during repair of the quadriceps tendon. The block also anesthetizes structures supplied by the saphenous nerve (ie, the terminal extension of the femoral nerve) to decrease sensation in the medial leg below the knee.

The patient has squamous cell carcinoma of the right upper lobe that has invaded the pleura and the 4th and 5th ribs. She has had severe right sided chest pain that is exacerbated by movement or cough. A nerve block procedure is planned to control the pain by injecting a local anesthetic agent in the vicinity of the involved neural structure. Which of the following is the most appropriate treatment target?

*Intercostal nerve block* This patient has severe chest wall pain due to cancer invading the parietal pleura and ribs. She is unable to take opioid medication due to intolerable adverse effects, so she should be offered other interventional pain management strategies. Options include nerve blocks (eg, injection of anesthetic near the nerve), neurolysis (eg, physical or chemical nerve destruction), and neuromodulation (eg, spinal cord stimulation). This patient is undergoing an intercostal nerve block to improve her pain control. Sensation from the parietal pleura, ribs, and overlying skin is mediated by thoracic intercostal nerves that derive from the ventral rami of the thoracic spinal nerves. An intercostal nerve block provides anesthesia over the dermatomal distribution of the nerve that is anesthetized. The intercostal vein, artery, and nerve lie in the subcostal groove along the lower border of the rib and therefore provide a straightforward target for a nerve block.

A 55-year-old man comes to the office due to progressive headaches over the past 2 months. The headaches are throbbing, often associated with nausea, and worsen whenever the patient coughs or bears down during a bowel movement. Medical history is significant for episodic migraine without aura. MRI of the brain with gadolinium reveals a cystic mass in the left cerebellum. What finding is likely seen on physical exam?

*Left dysdiadochokinesia* This patient has an expanding cystic neoplasm (likely a hemangioblastoma) in the left cerebellar hemisphere causing progressive headaches that worsen with Valsalva (maneuver increases intracranial pressure). The cerebellum is the largest structure in the posterior fossa and consists of the vermis at the midline and 2 cerebellar hemispheres. The cerebellar hemispheres are primarily responsible for motor planning and coordination of the ipsilateral extremities via their connections with the lateral descending motor systems (eg, lateral corticospinal tract, rubrospinal tract). Consequently, lesions affecting the left cerebellar hemisphere typically result in left dysdiadochokinesia (impaired rapid alternating movements), limb dysmetria (overshoot/undershoot during targeted movement), and intention tremor (tremor during targeted movement). The cerebellar vermis modulates axial/truncal posture and coordination via connections with the medial descending motor systems (eg, anterior corticospinal, reticulospinal, vestibulospinal, and tectospinal tracts). Lesions to this region result in truncal ataxia (eg, wide-based, unsteady gait). Vertigo and nystagmus may also occur due to disruption of the inferior vermis and the flocculonodular lobe.

After 72 hours following rewarming, he remains comatose with fixed and dilated pupils. There is no direct or consensual pupillary response to light. MRI of the brain reveals diffuse loss of grey-white matter differentiation with sulcal effacement. Damage to which of the following areas of the brain is the most likely cause of this patient's pupillary findings?

*Midbrain* This patient's presentation and MRI findings (eg, loss of grey-white matter differentiation with sulcal effacement) are consistent with anoxic brain injury due to cardiac arrest. The presence of nonreactive pupils to light stimulation following cardiac arrest carries a poor prognosis and indicates anoxic damage to the brainstem at the level of the upper midbrain. During the normal pupillary reflex, the retina as well as the optic nerve and tract transmit the light stimulus to the midbrain at the level of the superior colliculus where it is received by the pretectal nucleus and subsequently relayed to the bilateral Edinger-Westphal nuclei. These nuclei subsequently project preganglionic parasympathetic fibers through the oculomotor nerve (CN III) to the ciliary ganglion, which then projects postganglionic fibers that innervate the sphincter pupillae muscle (constricts the pupil). When light is shone in one eye, both the ipsilateral pupil (direct response) and contralateral pupil (consensual response) constrict.

An anxiety disorder is diagnosed and fluoxetine is prescribed. The patient's anxiety begins to improve over the next 4-6 weeks. The physician explains that the medication inhibits the reuptake of a neurotransmitter released by a specific set of neurons. These neurons are most likely part of which of the following structures?

*Raphe nucleus = serotonin* In the central nervous system (CNS), serotonergic (serotonin-releasing) neurons are primarily found in the raphe nuclei of the brainstem. The raphe nuclei are located in the midbrain, pons, and medulla, and axons from these cell bodies project widely throughout the CNS to synapse on structures such as the cerebral cortex, thalamus, hypothalamus, cerebellum, hippocampus, and spinal cord. These neurons play a role in the sleep-wake cycle, anxiety, mood, psychosis, sexuality, eating behavior, and impulsivity. Medications that target serotonin neurons are widely used in psychiatric disorders. Serotonergic antidepressants are the primary pharmacotherapy for most depressive and anxiety disorders. Antidepressants such as selective serotonin reuptake inhibitors (SSRIs [eg, fluoxetine]), serotonin-norepinephrine reuptake inhibitors, and tricyclic antidepressants work by prolonging the amount of time that serotonin spends in the synaptic clefts of these neurons before being taken up by presynaptic neurons.

On physical examination, he has mild periorbital ecchymosis, enophthalmos, and limited vertical movement of the right eye. Visual acuity and left eye examination are normal. CT scan of the head reveals an orbital floor fracture. Which of the following additional findings is most likely to be seen in this patient?

*Reduced sensation over the right upper lip* Fractures to the orbital floor, which is composed of the zygomatic bone and maxilla, most commonly result from direct frontal trauma to the orbit due to assault, motor vehicle crashes, or sports injuries. The infraorbital nerve (continuation of the maxillary nerve) runs along the orbital surface of the maxilla in the infraorbital groove before traversing the infraorbital canal and exiting the skull via the infraorbital foramen (just below the orbit). Damage can result in numbness and paresthesia of the upper cheek, upper lip, and upper gingiva. In addition, displacement of the orbital contents through the floor may cause enophthalmos, and entrapment of the inferior rectus muscle (as seen in above CT) can impair vertical gaze.

A 64-year-old man comes to the emergency department due to left lower extremity weakness. Medical history is significant for hypertension, diabetes mellitus, and myocardial infarction. Left lower extremity examination shows motor power is 0/5, deep tendon reflexes are 3+, and Babinski sign is present. An abnormality in which of the following structures is the most likely cause of this patient's symptoms?

*Right ACA* This patient with atrial fibrillation (irregularly irregular pulse, tachycardia) has isolated left lower extremity motor deficits, most likely caused by a cardioembolic stroke in the right anterior cerebral artery (ACA) territory. The ACA supplies the medial aspects of the frontal and parietal lobes, a region which contains the upper motor neurons responsible for contralateral lower extremity motor control. Occlusion of the ACA characteristically causes contralateral lower limb weakness with upper motor neuron signs (eg, hyperreflexia, Babinski sign). The most common etiology of ACA stroke is cardiac embolization due to atrial fibrillation, which can cause blood flow stasis resulting in thrombus formation in the left atrial appendage. Atrial thromboemboli frequently travel to and obstruct branches of ACA or middle cerebral artery (MCA), causing cerebral ischemia with associated neurologic defects.

A 66-year-old, right-handed man w/ left-sided numbness and weakness. The patient woke with left-hand clumsiness that rapidly progressed to profound left-sided weakness, affecting the left arm more than the left leg. He has a history of hypertension and has smoked a pack of cigarettes daily for the past 40 years. Neurologic examination reveals impaired touch discrimination in the left arm with left facial weakness sparing the forehead, 2/5 muscle strength in the left upper limb, and 4/5 muscle strength in the left lower limb. Right-sided strength and visual field examinations are normal. What artery was likely occluded?

*Right MCA* This patient has most likely had an acute ischemic stroke involving the territory supplied by the right middle cerebral artery (MCA). Patients with MCA occlusion usually present with contralateral hemiparesis and hemisensory loss involving the face and upper limb due to infarction of the corresponding motor and sensory cortices. The contralateral lower limb is typically less affected. Other features may include spatial neglect of the contralateral side (damage to the nondominant parietal lobe) and contralateral homonymous quadrantanopia (damage to the optic radiations in the subcortical temporoparietal lobe). If the stroke affects the dominant (usually left) hemisphere, the speech areas of the brain can be damaged. Consequently, patients with left MCA stroke (right-sided motor and sensory deficits) also often have expressive or receptive aphasia due to infarction of the Broca and Wernicke areas, respectively

The patient frequently uses a screwdriver at work. Neurologic examination shows preserved sensation in the upper limbs. There is weakness on extension of the fingers and thumb in the right hand. Strength is otherwise intact. Triceps reflexes are 2+ and bilaterally symmetric. The nerve affected in this patient was most likely injured at which of the following locations?

*Supinator muscle* The radial nerve enters the forearm anterior to the lateral epicondyle and divides into superficial and deep branches. The superficial branch provides purely somatic sensory innervation to the radial half of the dorsal hand, and the deep branch innervates the extensor compartment muscles in the forearm. After passing between the superficial and deep parts of the supinator muscle, the deep branch continues as the posterior interosseous nerve, which innervates muscles involved in finger and thumb extension. Injury to the deep branch of the radial nerve at the supinator muscle may occur due to repetitive pronation/supination of the forearm (eg, frequent screwdriver use), direct trauma, or dislocation of the head of the radius. Patients typically have weakness on finger and thumb extension (ie, finger drop). The triceps brachii (responsible for elbow extension and triceps reflex) and extensor carpi radialis longus (responsible for wrist extension) are typically unaffected because the branches supplying these muscles diverge proximal to the supinator muscle. Cutaneous sensory branches are similarly preserved.

A 64-year-old smoker is evaluated for nagging right shoulder pain that radiates to the ipsilateral arm. The patient also has weakness in the right upper extremity. He has partial right-sided ptosis with fully intact extraocular movements. His pupils are asymmetric in dim light with 2 mm on the right and 4 mm on the left, but both are reactive to light. The pupils become more symmetric in bright light. The right upper extremity has 3/5 strength and absent deep tendon reflexes. This patient's autonomic dysfunction is most likely a result of a lesion involving which of the following?

*Sympathetic ganglion* This patient's smoking history, upper limb pain/weakness, and ipsilateral ptosis and miosis are highly suggestive of a Pancoast tumor. Pancoast tumors are usually non-small cell lung cancers (eg, squamous cell carcinoma, adenocarcinoma) that arise near the superior sulcus (the groove produced by the subclavian artery). Clinical manifestations are determined by the extent of local spread. Compression and invasion of the brachial plexus can cause ipsilateral shoulder pain, upper limb paresthesias, and areflexic arm weakness. Involvement of the cervical sympathetic ganglia may lead to Horner's syndrome, which is characterized by ipsilateral: Partial ptosis (drooping of upper eyelid), due to denervation of the sympathetically controlled superior tarsal muscle of the upper eyelid. Miosis (constricted pupil), due to interruption of the sympathetic fibers to the dilator pupillae muscle, which leads to unopposed parasympathetic influence. Pupil asymmetry is more prominent when examined in dim light due to increased sympathetic activity exacerbating the defect. Anhidrosis (impaired sweating), due to loss of sympathetic innervation of the facial sweat glands. Horner's syndrome can result from disruption at any point along the sympathetic pathway to the eye. First order sympathetic neurons are located in the hypothalamus. Their axons descend through the brainstem to the C8-T2 segments of the spinal cord (ciliospinal center of Budge), where they synapse on second order neurons found in the intermediolateral cell column. Second order axons exit the spinal cord through the anterior nerve roots and white communicating rami to reach third order neurons located in the superior cervical ganglion. From here, postganglionic fibers travel along the carotid arteries to reach target tissues in the face and head.

The patient cannot feel the right side of her body. Physical examination shows loss of touch, temperature, and vibratory sensation affecting the right upper and lower extremities. Sensation is also diminished over the right side of the face. Muscle strength is 5/5 throughout. This patient has most likely suffered a stroke affecting which of the following brain structures?

*Ventral posterior thalamus* This patient with right-sided pure hemisensory loss has likely suffered from a thalamic stroke. The thalamic ventral posterior lateral nucleus (receives input from the spinothalamic tract and dorsal columns) and ventral posterior medial nucleus (receives input from the trigeminal pathway) send somatosensory projections to the cortex via thalamocortical fibers. Damage to these nuclei (eg, due to ischemia, hemorrhage) may result in complete contralateral sensory loss (eg, touch, pain/temperature, vibration/proprioception). Severe proprioceptive defects may cause unsteady gait

A month ago, he started to intermittently experience a "pins and needles" sensation in his right hand that is worse at night. On physical examination, there is loss of sensation over the right fifth digit. There is no swelling, redness, or warmth of the hand. The patient is most likely to have weakness of which of the following movements?

*Wrist adduction* The ulnar nerve originates from the medial cord of the brachial plexus, courses with the brachial artery in the upper arm, and enters the forearm after passing posterior to the medial epicondyle of the humerus (cubital tunnel). It innervates flexor carpi ulnaris (wrist flexion and adduction) and the medial portion of flexor digitorum profundus before entering the wrist through Guyon canal (between the hook of the hamate and pisiform). In the hand, the superficial branch of the ulnar nerve provides cutaneous innervation to the fifth digit, medial half of the fourth digit, and the hypothenar eminence. The deep motor branch supplies most of the intrinsic muscles of the hand. The ulnar nerve is most commonly injured at the elbow due to trauma (eg, medial epicondyle fracture) or compression (eg, resting on a hard surface while using a computer). Ulnar neuropathy at the elbow usually presents with discomfort and loss of sensation/paresthesia in the ulnar distribution. Severe cases can also result in impaired wrist flexion and adduction (ie, ulnar deviation) along with finger weakness/clumsiness. The nerve can also be injured more distally at the wrist as it runs through Guyon canal, resulting in more pronounced clawing of the 4th and 5th digits (ulnar claw) due to sparing of the flexor digitorum profundus.

Transection of the radial nerve results in what deficit

*weakened wrist extension* The radial nerve is the largest branch of the brachial plexus and receives fibers from C5-T1. It innervates all of the extensor muscles of the upper limb below the shoulder and provides sensory innervation to the skin of the posterior arm, forearm, and dorsal lateral hand. This nerve tracks within the radial groove on the humerus; therefore, it is vulnerable to traumatic injury (eg, penetrating stab wound) at the humeral midshaft. The nerve can also be injured during its superficial course within the axilla. Patients with proximal radial neuropathy typically have weakness during wrist and finger extension (wrist drop) and variable sensory loss over the posterior arm and forearm.

Atrophy of the lentiform nucleus is seen in what condition

Atrophy of the lentiform nucleus (eg, globus pallidus and putamen) occurs in Wilson disease (hepatolenticular degeneration), which is characterized by liver (eg, hepatitis, cirrhosis), psychiatric (eg, depression, personality changes), and neurologic (eg, dysarthria, movement disorder) abnormalities

Lateral pontine syndrome symptoms

FACIAL DROOP means AICA's pooped Occlusion of the anterior inferior cerebellar artery causes lateral pontine syndrome. Patients with this condition typically have ipsilateral loss of pain or temperature in the face (trigeminal nucleus), ipsilateral facial weakness (facial nucleus), ipsilateral hearing impairment (cochlear nucleus), contralateral loss of pain and temperature in the trunk and extremities (lateral spinothalamic tract), and cerebellar dysfunction (eg, ataxia, dysmetria).

Basilar artery occlusion damages what structure?

Basilar artery occlusion usually damages the base of the pons, which contains the corticospinal and corticobulbar tracts, and the paramedian tegmentum. Consequently, patients typically have quadriplegia, bulbar dysfunction (eg, facial weakness, dysarthria), and oculomotor deficits (eg, horizontal gaze palsy).

A 46-year-old man comes to the office with left upper limb weakness and numbness. He has had chronic neck pain since being involved in a motor vehicle collision 4 years ago. He has no other medical problems. Neurological evaluation reveals that the tendon reflex shown in the image below is absent. Reflexes in the right upper extremity and both lower extremities are normal. Imaging studies reveal degenerative changes in the spine causing mild spinal cord compression. There is absent biceps reflex in th patient. Which of the following spinal segments is most likely affected in this patient?

C5-C6 This patient has an absent biceps reflex. The test is performed by quickly tapping a reflex hammer against the biceps brachii tendon as it passes through the cubital fossa. This action activates the muscle's stretch receptors that communicate via the musculocutaneous nerve with lower motor neurons in the anterior horn of the C5-C6 spinal level. Axons from these motor neurons return along the musculocutaneous nerve and cause involuntary biceps muscle contraction and jerking of the forearm. The C5-C6 nerves also control the brachioradialis reflex. A stronger than normal reflex suggests an upper motor neuron lesion whereas an absent or decreased reflex indicates a lower motor neuron lesion at the corresponding spinal cord level.

A 4-day-old premature infant in the neonatal intensive care unit becomes hypotonic and less responsive. She was delivered vaginally at 30 weeks gestation, and her birth weight was 1,200 g (2 lb 10 oz). Physical examination shows a lethargic infant with weak and high-pitched crying, prominent scalp veins, and tense fontanelles. Cranial ultrasound reveals blood in the lateral ventricles. Which of the following structures is the most likely source of the bleeding?

Germinal matrix hemorrhage Intraventricular hemorrhage (IVH) is a common complication of prematurity that can lead to long-term impairment in neurodevelopment. IVH almost always manifests within the first 5 postnatal days in infants born before 32 weeks gestation and/or with birth weight <1,500 g (3 lb 5 oz). IVH in a newborn can be clinically silent or present with altered level of consciousness, hypotonia, and decreased spontaneous movements. If the bleeding is severe, catastrophic deterioration can occur with a bulging anterior fontanelle, hypotension, tonic-clonic seizures, irregular respirations, and coma. IVH in preterm infants usually originates from the germinal matrix, a highly cellular and vascularized layer in the subventricular zone (source of neurons and glial cells during brain development). The matrix contains numerous fragile, thin-walled vessels lacking the glial fibers that support other blood vessels throughout the brain, making them more susceptible to hemorrhage. Between 24-32 weeks gestation, the germinal matrix starts to become less prominent, and its cellularity and vascularity decrease, leading to a reduced risk of IVH in infants born after 32 weeks.

The patient was diagnosed with a pure sensory stroke and received the appropriate treatment. Her symptoms improved and she returned home to live with her daughter after a few weeks of physical rehabilitation. Five years later, the patient dies of a large myocardial infarction. On autopsy, there are two 5- to 6-mm cavities in the deep structures of her brain filled with clear fluid. Which of the following processes was most likely responsible for the patient's brain findings?

Lacunes are small (<15 mm) cavitary infarcts located within the basal ganglia, posterior limb of the internal capsule, pons, and cerebellum. The infarcts result from occlusion of the small penetrating arteries that supply these deep brain structures (eg, lenticulostriate arteries), most commonly in the setting of chronic uncontrolled hypertension or diabetes mellitus. Lipohyalinosis and microatheromas are believed to be the primary causes of lacunar infarcts. Lipohyalinosis occurs secondary to leakage of plasma proteins through damaged endothelium and is characterized by hyaline thickening of the vascular wall, collagenous sclerosis, and accumulation of mural foamy macrophages. Microatheromas result from atherosclerotic accumulation of lipid-laden macrophages within the intimal layer of a penetrating artery near its origin off the parent vessel. These changes predispose to small-vessel occlusion and infarction of central nervous system (CNS) tissue with liquefactive necrosis and the formation of a fluid-filled cavity.

ACA damage presents with what

Occlusion of the anterior cerebral artery causes contralateral motor and sensory deficits, with the lower limb being affected more than the upper limb. Bilateral anterior cerebral artery occlusion can cause significant behavioral symptoms (eg, abulia), primitive reflexes (eg, Moro, grasp), and urinary incontinence due to damage of the prefrontal cortex.

why is the macula spared in a stroke of the posterior cerebral artery?

Posterior cerebral artery territory infarction typically results in contralateral hemianopia due to infarction of the visual cortex. The macula is often spared due to collateral circulation from the MCA.

A 43-year-old woman comes to the office due to acute back pain after dragging a heavy box. The pain is located in her lower back and radiates down the right posterior thigh to the foot. The patient describes the pain as "shooting" and grades it 8/10 in intensity. She has no bowel or bladder symptoms. The patient has tried over-the-counter analgesics with limited symptomatic relief. Vital signs are within normal limits. On physical examination, straight leg raise testing is positive on the right. Right hip extension is weaker when compared to the left. Knee jerk reflexes are 2+ and bilaterally symmetric, but the right ankle jerk reflex is absent. Which of the following nerve roots is most likely affected in this patient?

S1 This patient's presentation is consistent with sciatica, a nonspecific term for low back pain that radiates down the leg. This condition occurs due to compression of the lumbosacral nerve roots and is most commonly caused by vertebral disc herniation or spinal foraminal stenosis (eg, due to degenerative arthritis of the spine). Irritation of the nerve roots results in characteristic dermatomal and myotomal deficits (radiculopathy) depending on the level of involvement. Patients may have worsening of their radicular pain when the symptomatic leg is extended at the knee and the hip is passively flexed by the examiner (straight leg raise test). The sciatic nerve is derived from the L4-S3 nerve roots and compression most often occurs at the level of L5 or S1. S1 radiculopathy is characterized by pain and sensory loss down the posterior thigh and calf to the lateral aspect of the foot. Patients may also have weakness on thigh extension (eg, due to denervation of the gluteus maximus), knee flexion (hamstrings), and foot plantarflexion (gastrocnemius) with an absent ankle jerk reflex. Conversely, compression of the L5 root results in pain/paresthesia radiating down the lateral thigh and calf to the dorsal foot. Patients often have weakness on foot dorsiflexion and inversion (eg, due to denervation of the tibialis anterior), foot eversion (peroneus), and toe extension (extensor digitorum brevis) (Choice D).

Saccular anyeurism of the posterior and anterior communicating arteries present how

Saccular aneurysms often affect the anterior and posterior communicating arteries in the circle of Willis. Anterior communicating artery aneurysms can compress the central optic chiasm, causing bitemporal hemianopia. Posterior communicating artery aneurysm frequently compresses the oculomotor nerve, producing ipsilateral mydriasis, ptosis, and "down and out" eye deviation.

What is the red nucleus?

Structure in the rostral midbrain involved in motor coordination. It is pale pink in color; the color is believed to be due to iron, which is present in the red nucleus in at least two different forms: hemoglobin and ferritin.[1] It is located in the tegmentum of the midbrain next to the substantia nigra. The red nucleus and substantia nigra are subcortical centers of the extrapyramidal motor system.

Damage to the superior orbital fissure would affect what nerves?

The corneal reflex involves cranial nerves V1 (sensory) and VII (motor) and processing in the pons. It can be impaired by trauma to the superior orbital fissure because cranial nerves III, IV, V, and VI pass through this structure.

What is Locus Ceruleus for?

The locus ceruleus houses norepinephrine-secreting neurons that participate in activation of the "fight or flight" response to physical and emotional stressors. It is located in the dorsal pons.

What nerves are contained within the medulla

The medulla contains the glossopharyngeal (CN IX) and vagus (CN X) nerves, which provide the afferent and efferent limbs of the gag reflex, respectively.

What is the nucleus basalis of maynert

The nucleus basalis of Meynert houses the cell bodies of cholinergic neurons. In Alzheimer disease, these neurons secrete decreased amounts of acetylcholine.

What center/ and what nerves are contained within the pons

The pons contains the horizontal gaze center, which helps mediate the oculocephalic (doll's eye) reflex. It also contains the trigeminal (CN V) and facial (CN VII) nerves, which mediate the afferent and efferent limb of the corneal reflex, respectively. Bilateral pontine injury is associated with pinpoint pupils due to damage of the descending sympathetic fibers.

Describe the tests of sciatica

The sciatic nerve arises from the L4-S3 nerve roots. Compression of the nerve (or contributing nerve roots) can occur at the spine (eg, herniated disc), piriformis muscle, greater sciatic foramen, or posterior thigh. Sciatica is a classic (though nonspecific) syndrome characterized by back and buttock pain that radiates down the posterior thigh to the foot; associated features include lower extremity weakness and a positive straight leg raise test.

A 72-year-old man is brought to the emergency department due to involuntary movements of his right arm that started several hours ago. He was watching television when his arm "threw the remote control across the room." His past medical history is significant for long-standing hypertension and diabetes mellitus. The patient does not use alcohol, tobacco, or illicit drugs. Physical examination shows wild, large-amplitude, flinging movements affecting the proximal muscles of his right arm. Which of the following areas of the brain is most likely injured in this patient?

The subthalamic nucleus is a lens-shaped structure located ventral (inferior) to the thalamus, dorsal (superior) to the substantia nigra, and medial to the internal capsule. It is a component of the basal ganglia and plays an important role in the modulation of basal ganglia output. Damage to the subthalamic nucleus can decrease excitation of the globus pallidus internus, thereby reducing inhibition of the thalamus. This may result in contralateral hemiballism, a movement disorder characterized by wild, involuntary, large-amplitude, flinging movements involving the proximal limbs (eg, arm and/or leg) on one side of the body. This most commonly occurs in the setting of lacunar stroke, which is often a consequence of long-standing hypertension and diabetes mellitus.

A 65-year-old man comes to the emergency department due to acute-onset slurred speech and right-sided weakness. Neurologic examination shows right-sided lower facial droop with sparing of the forehead muscles. Motor strength is 3/5 on the right and 5/5 on the left with a Babinski response on the right. There is also dysmetria and dysdiadochokinesia involving his right upper and lower extremities. MRI of the brain reveals an acute lacunar infarct in the brainstem affecting the left medial pons at the level of the middle cerebellar peduncle. Which of the following cranial nerves exits the brainstem closest to the level affected by this patient's stroke?

The trigeminal nerve (CN V) exits the brainstem at the lateral aspect of the mid-pons at the level of the middle cerebellar peduncles (a key neuroanatomic landmark for locating the nerve). The trigeminal sensory nuclei (eg, principal sensory, spinal, mesencephalic) run from the midbrain to the upper cervical spine and receive afferent signals for facial sensation via all 3 nerve branches (ophthalmic, maxillary, and mandibular). The motor nucleus is located in the lateral mid-pons and sends efferent signals to the muscles of mastication (eg, temporalis, masseter, pterygoids) via the mandibular branch. Infarcts involving the anterior pons can affect the corticospinal tract (contralateral hemiparesis, Babinski sign) and corticobulbar tract (contralateral lower facial palsy, dysarthria). Disruption of the corticopontine fibers that convey motor information from the cortex to the ipsilateral pontine gray matter may also result in contralateral dysmetria and dysdiadochokinesia (ataxic hemiparesis). The cerebellar deficits are contralateral to the lesion as the pontocerebellar fibers arising from the pontine gray matter decussate and enter the cerebellum through the contralateral middle cerebellar peduncle.

A 45-year-old woman is evaluated for numbness and painful tingling of the right hand. The symptoms began 2 months ago and are especially prominent after she plays tennis. On examination, there is diminished sensation in the lateral palm, thenar eminence, and palmar aspect of the first 3½ digits of the right hand. This patient most likely has an injury involving a nerve that courses between which of the following structures?

This patient has diminished sensation that involves the entire sensory distribution of the median nerve and is exacerbated by repetitive, forceful pronation (eg, tennis). This presentation is most consistent with compression of the median nerve as it passes between the two heads of the pronator teres (ie, pronator teres syndrome). The median nerve arises from the medial and lateral cords of the brachial plexus and travels with the brachial artery in the medial bicipital groove (ie, longitudinal hollow between the biceps brachii and triceps brachii muscles) of the upper arm. In the forearm, the median nerve courses between the humeral and ulnar heads of the pronator teres muscle and between the flexor digitorum superficialis and flexor digitorum profundus muscles before entering the hand through the carpal tunnel. Median nerve compression at the carpal tunnel, which is distal to the takeoff of the palmar branch, typically impairs sensation to the palmar aspects of the first 3½ digits. In contrast, compression by the pronator teres occurs proximal to the takeoff of the palmar branch; therefore, sensation is impaired not only to the palmar aspect of the first 3½ digits but also to the entire lateral palm and thenar eminence (ie, sensory distribution of the palmar branch).

Spine imaging reveals degenerative joint changes and a large osteophyte compressing the spinal nerve root exiting through the right neural foramen between the L5 and S1 vertebrae. Which of the following examination findings is most likely present in this patient due to the nerve lesion?

This patient has lumbosacral radiculopathy due to an osteophyte at the L5-S1 neural foramen resulting in compression of the L5 nerve root. Spinal nerves in the lumbosacral spine exit below their corresponding vertebral body level (eg, L5 nerve root exits between L5 and S1 vertebral bodies). However, because of the presence of multiple spinal nerve roots in the lumbosacral area (ie, cauda equina), nerve root compression can occur at different vertebral levels through 2 distinct mechanisms: 1. Spinal spondylosis: Degenerative changes and osteophyte formation can narrow the neural foramina. This leads to nerve root compression as it passes through the neural foramina (in this patient, an osteophyte is compressing the exiting L5 nerve root). 2. Vertebral disc herniation: A tear in the intervertebral disc annulus can lead to herniation of the nucleus pulposus. If this occurs laterally, it can compress the exiting nerve root as it passes through the neural foramina. However, if it occurs more centrally, it can protrude into the spinal canal and compress other nerves in the cauda equina that exit one or more levels below the area of herniation. L5 radiculopathy causes sensory loss and back pain that radiates down the leg in an L5 dermatomal distribution (eg, buttocks, lateral thigh and calf, dorsal foot). Weakness occurs in muscles innervated by fibers from the L5 spinal root, which include the tibialis anterior (foot dorsiflexion and inversion), peroneus (foot eversion), and extensor hallucis longus (great toe extension).

A 56-year-old man comes to the office for evaluation of right leg pain and numbness. The pain started 2 days ago during an 8-hour car ride during which the patient was a backseat passenger in a small car. Midway through the car ride, he began to have numbness and burning pain over the lateral aspect of the right thigh. The patient has tried stretching to relieve the pain, but it has only worsened and he is now unable to wear a belt due to the discomfort. He has type 2 diabetes mellitus and has gained 11.3 kg (25 lb) over the past year. BMI is 42 kg/m2. On examination, lower extremity strength is 5/5 bilaterally. The right leg has a large area of numbness over the upper lateral thigh. Straight leg raise is negative. Reflexes are symmetrical and intact. Compression of which of the following nerves is the most likely cause of this patient's presentation?

This patient has pain and decreased sensation in the distribution of the lateral femoral cutaneous nerve (LFCN), consistent with meralgia paresthetica (MP). The LFCN is a branch of the lumbar plexus, originating from L2-L3. It runs lateral to the psoas muscle and exits the abdomen beneath the inguinal ligament. MP is a compression mononeuropathy of the LFCN at the inguinal ligament, typically caused by tight clothing (eg, belts) or by injury during surgery (eg, hip arthroplasty). Those with obesity, increased lumbar lordosis (eg, pregnancy), or diabetes mellitus are at increased risk. MP presents with pain, paresthesia, and numbness in the lateral thigh above the knee. However, strength is normal because the LFCN does not contain motor fibers. The diagnosis is usually based on clinical findings. Most patients are managed with weight loss and avoidance of tight clothing.

A 53-year-old man comes to the office due to double vision. The patient lives in a two-story house and has had difficulty walking down stairs but does not have significant problems walking upstairs. The patient is also frustrated because he has trouble reading certain things, such as the morning newspaper and work-related documents. A lesion affecting which of the following structures is most likely responsible for this patient's visual symptoms?

This patient likely has trochlear nerve (CN IV) palsy. The trochlear nerve innervates the superior oblique muscle, which causes the eye to intort (internally rotate) and depress while adducted. The nerve is particularly susceptible to injury due to its long course and small caliber. Most cases of neuropathy are traumatic or idiopathic in origin, although a proportion of idiopathic cases may actually be due to microvascular nerve ischemia in the setting of diabetes mellitus. Patients with trochlear nerve palsy typically present with vertical diplopia, which is most noticeable when the affected eye looks down and toward the nose (eg, up-close reading, walking down stairs). Examination may show impairment of downgaze with the eye in the adducted position. In severe cases, the affected eye can appear vertically deviated (hypertropia). Symptoms often improve when the chin is tucked and the head is tilted away from the affected eye as this compensates for hypertropia and extorsion.

A 54-year-old man is brought to the emergency department by his wife after he develops difficulty speaking. When asked about the onset of his symptoms, the patient slowly responds with "I... weak... morning..." and becomes very frustrated. His wife says that he was able to grasp a pen without any problem while completing medical release forms, but had trouble signing his name. On examination, he is able to state his first name but with difficulty, and correctly points to different body parts on command. He also has mild weakness involving his right arm and face. This patient's speech difficulties are most likely caused by a lesion affecting which of the following brain areas?

This patient most likely has Broca (motor, nonfluent) aphasia. This condition classically results from damage to Broca area of the brain, the region responsible for all communicative motor planning. Individuals are able to communicate meaningfully, but their speech is slow and consists primarily of nouns and verbs. Speech may be punctuated by pauses after each word as the patient attempts to verbalize the next. Patients also often have difficulty writing and signing, and become frustrated as they have insight into their expressive language difficulties. They can understand spoken language and follow commands (intact speech comprehension) as Wernicke area is unaffected. Broca area is in the caudal part of the inferior frontal gyrus of the dominant (usually left) hemisphere (Brodmann areas 44 and 45). Patients may have associated right hemiparesis involving the upper limb and face due to this region's proximity to the primary motor cortex.

A 65-year-old man is brought to the emergency department due to acute-onset, right-sided weakness and slurred speech. He also has a severe headache and nausea. Medical history is significant for poorly controlled hypertension and chronic tobacco use. Blood pressure is 240/120 mm Hg and pulse is 104/min. On physical examination, the patient is lethargic with right hemiparesis and lower facial weakness, right hemisensory loss, and dysarthria. CT shows hemorrhage in the putamen area. What cerebral vessel is affected?

This patient's CT findings (eg, hyperdense mass) are consistent with an acute putaminal hemorrhage (ie, affecting the basal ganglia). Because of their location, putaminal hemorrhages almost always affect the adjacent internal capsule, leading to dysarthria, contralateral hemiparesis, and contralateral hemisensory loss due to disruption of the corticobulbar, corticospinal, and somatosensory fibers. As the hemorrhage expands, it leads to increase intracranial pressure (headache, nausea/vomiting, and altered mental status), midline shift from mass effect, and possible cerebral herniation. Hypertensive vasculopathy involving the small, penetrating branches of the major cerebral arteries is the most common cause of spontaneous deep intracerebral hemorrhage. Chronic hypertension leads to the formation of Charcot-Bouchard aneurysms, which may ultimately rupture and bleed within the deep brain structures. The most frequently affected locations include the basal ganglia (putamen), cerebellar nuclei, and pons. The basal ganglia are supplied by the lenticulostriate arteries, which are deep, small vessel branches off the middle cerebral arteries.

Describe Huntington's disease

This patient's cognitive decline, chorea (jerky, nonpurposeful movements), and family history of similar symptoms are highly suggestive of Huntington disease (HD). This autosomal dominant disease results from an excessive number of CAG trinucleotide repeats in the huntingtin gene, causing a gain-of-function mutation that results in the accumulation of toxic mutant huntingtin protein. The abnormal protein buildup causes loss of inhibitory (GABA) neurons in the caudate nucleus, leading to the characteristic movement abnormalities observed in HD. Although the diagnosis of HD is confirmed by genetic analysis, imaging studies can support the clinical findings and typically show atrophy of the caudate nuclei, causing enlargement of the lateral ventricles. The caudate nucleus is a curved or C-shaped structure in its complete form. The head of the caudate can be identified in the inferolateral walls of the frontal horns of the lateral ventricles. The caudate nucleus and putamen together make up the striatum, which is critical for movement control and coordination along with behavioral regulation.

Further evaluation shows that he has left-right disorientation and is unable to carry out simple calculations, read, or write. Noncontrast CT scan of the head reveals no acute intracranial hemorrhage. Which of the following brain areas is most likely affected in this patient?

This patient's presentation is consistent with an acute ischemic stroke affecting the angular gyrus of the dominant parietal lobe, a brain region supplied by the middle cerebral artery. The angular gyrus is part of the parietal association cortex, an area that integrates multisensory (eg, visual, tactile, verbal) information to comprehend events and solve problems. Specifically, it is important for semantic processing, word reading and comprehension, and number processing. Damage to this area classically results in Gerstmann syndrome, a neurologic disorder characterized by a constellation of the following signs: Agraphia (inability to write) Acalculia (inability to carry out mathematical calculations) Finger agnosia (inability to identify individual fingers on the hand) Left-right disorientation Although Gerstmann syndrome may occur as an isolated syndrome, lesions to the angular gyrus may also be associated with alexia (inability to read) and aphasia (impaired speech).