Neuro Ch. 14- brainstem III: Internal Structures and Vascular Supply

Case 4: A 56-year-old male auto mechanic had 1 month of episodic diplopia and unsteadiness and then suddenly developed persistent right face numbness, hearing loss, and right-sided clumsiness. Past history was notable for severely elevated cholesterol and cigarette smoking. About 1 month prior to admission, the patient developed transient episodes consisting of light-headedness, nausea, unsteadiness ("staggering like I was drunk"), diagonal diplopia with the right image higher than the left, perioral numbness, and a generalized headache. The episodes were precipitated by his standing up and walking around, lasted 5 or 6 minutes, and occurred up to four or five times per day. The episodes gradually improved over time and nearly stopped. Given this patient's history, what diagnosis should be seriously considered, and what should be done? -------------------- The patient did not seek medical attention for his symptoms. On a Friday night 3 days prior to admission, the patient abruptly developed right facial numbness, decreased hearing in the right ear, slurred speech, right hand clumsiness (occasionally dropping things), and unsteady gait. When he returned to work at the garage on Monday, he had trouble working on the cars, so he finally came to the emergency room. Mental status: Alert and oriented × 3. Naming and repetition intact. Mildly decreased attention; for example, skipped November when naming months backward. Recalled 1/3 words after 5 minutes, but got 3/3 with prompting. Cranial nerves: Pupils 4 mm, constricting to 2.5 mm bilaterally. Fundi normal. Extraocular movements full, with fine horizontal nystagmus (direction of fast phase was not specified). Light touch and pinprick sensation slightly decreased in right V2 and V3 distribution. Right corneal reflex decreased. Face symmetrical. Hearing decreased on the right. On the Weber test sounds were louder on the left. Speech slightly slurred. Normal palate elevation. Shoulder shrug and sternomastoids normal. Tongue midline. Motor: No drift. Normal tone. 5/5 power throughout. Reflexes: +1 Achilles. No Babinski's sign. Coordination: Mild dysmetria on finger-to-nose testing on the right. Right finger tapping and foot tapping were slightly slow and dysrhythmic. Gait: Slightly wide based. Able to do only two or three steps of tandem gait because of unsteadiness. When the patient stood or walked during the exam, he did not have symptoms of the transient episodes described above. Sensory: Intact light touch, pinprick, vibration, and joint position sense On the basis of the symptoms and signs shown in bold above, what is the most likely location for the lesion? Which blood vessel(s) may be involved? What is the most likely diagnosis?

Given the pt's vascular risk factors and the fact that the episodes occur in situations that may lower the patient's systemic BP (standing up), the most likely diagnosis = TIAs in the vertebrobasilar system, possibly caused by basilar stenosis. This is life-threatening, pt should be brought immediately to the hospital for evaluation including MRA. -------------- The patient's findings are compatible w/ R lateral caudal pontine syndrome, most likely by a right AICA infarct. Decreased hearing may be due to labyrinthine artery involvement. Impaired R facial sensation may be due to infarction of the R trigeminal nucleus and tract; R sided appendicular ataxia, slurred speech, and nystagmus may be involved of R middle cerebellar peduncle and vestibular nuclei. The patient has mildly decreased attention, which is a nonspecific finding that could have many causes, including brainstem ischemia. Most likely clinical diagnosis = R caudal lateral pons, AICA territory The patient's vascular risk factors and antecedent episodes of transient symptoms make infarction in the R AICA territory the most likely diagnosis.

Case 6: A 53-year-old man was brought to the emergency room with acute onset of decreased responsiveness and left-sided weakness. Past history was notable for cigarette smoking, hypertension, and hypertriglyceridemia. He worked as the chef on a Japanese navy ship. Four days prior to admission, he developed bilateral frontal and retro-orbital headaches. At 10:00 a.m. on the day of admission, his headache worsened and he developed generalized weakness and nausea. At 10:30 a.m. he had a transient episode of right-sided weakness and went to see the ship's doctor. Lunchtime was approaching, however, and he had to return to work. At 2:00 p.m. he had sudden onset of blurred vision, dysarthria, and gait difficulty, which rapidly evolved into decreased responsiveness with left-sided weakness. Fortunately, the ship was docked at a major city, and the patient was urgently transferred to the emergency room, arriving within a half hour of symptom onset. Neurologic exam: Mental status: Lethargic, arousable to voice, but needed repeated stimulation to get a response. Correctly followed simple commands and imitated gestures. Cranial nerves: Pupils 3 mm, constricting to 2 mm. Intact blink to visual threat bilaterally. Extraocular movements full except for left gaze preference and inability to move either eye fully to the right, even with oculocephalic maneuvers. Upgaze was also somewhat limited. Corneal reflexes intact. Left facial weakness, sparing the forehead. Unable to protrude tongue on command. Motor: Strong, purposeful movements of the right arm and leg. Left arm had weak purposeful movements, and left leg had triple flexion only in response to pain. Plantar responses: Upgoing bilaterally. Toward the end of the exam, the patient became less responsive and began having shivering movements and bilateral right greater than left extensor posturing. He was urgently intubated and taken for a head CT and emergency angiogram at 3:00 p.m. (1 hour after symptom onset). On the basis of the symptoms and signs shown in bold above, what is the most likely localization? What is the most likely diagnosis?

Patient had symptoms and signs suggestive of waxing, waning and then suddenly worsening dysfunction of several bilateral regions supplied by the vertebrobasilar system. The alternating right, then left, and then right hemiparesis w/ bilateral Babinski's signs is strongly suggestive of basilar artery stenosis affecting the bilateral basis pontis. Presence of wrong-way eyes (L weakness w/ L gaze preference) suggests extension to the R pontine tegmentum. Limited gaze and impaired consciousness suggest impaired function of midbrain tegmentum. Shivering = characteristic of pontine dysfunctions. Given pt's vascular risk factors, the overall picture is compatible w/ evolving basilar thrombosis, possibly in the setting of preexisting basilar stenosis.

Path of the vertebral arteries toward the brain:

The blood supply to the posterior fossa structures arises from the vertebrobasilar system The paired vertebral arteries arise from the subclavian arteries at the base of the neck and then ascend through the foramina transversaria of cervical vertebrae C6 through C2. enter cranial cavity via foramen magnum run along the ventral aspect of the medulla and join at the pontomedullary junction to form a single basilar artery split at the pontomesencephalic junction into the two posterior cerebral arteries, which connect via the posterior communicating arteries (Pcomms) to the internal carotid arteries of the anterior circulation. The vertebrobasilar system gives rise to multiple branches to provide the blood supply to the brainstem and cerebellum. In addition, most parts of the thalamus, as well as the inferior-medial occipital and temporal lobes, are supplied by the posterior cerebral arteries arising from the top of the basilar artery largest branches = the posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), superior cerebellar artery (SCA), and posterior cerebellar artery (PCA)

Case 7: A 72-year-old man with a history of hypertension and hypercholesterolemia was watching TV one night and suddenly saw two faces on the screen diagonally displaced. This diplopia went away when he covered one eye. In order not to alarm his wife, he quietly made his way to bed, but the next morning the diplopia was unchanged, and he also noticed gait unsteadiness with staggering to the right. He tried using a friend's walker, but then also noticed that his right hand was clumsy. For example, he had difficulty picking up a credit card from the table with his right hand. On exam, his left eye would elevate by only 1 mm, adduct by only 2 mm, and depress by only 3 mm. Left eye abduction was normal. He had diagonal diplopia, which was tested with a red glass over the right eye. There was a left ptosis, with the palpebral fissure measuring 4 mm on the left and 9 mm on the right. The left pupil had a slightly irregular shape but reacted normally to light. The patient also had mild right ataxia on finger-to-nose and heel-to-shin testing, and an unsteady gait, tending to list to the right. The remainder of the exam was normal, except for the right plantar response, which was equivocal. What is the cause of the eye movement abnormalities? A lesion in what region of the brain could cause these abnormalities along with right ataxia? What is the most likely diagnosis?

The eye movement abnormalities represent a left third-nerve palsy. The pupil is not dilated but has irregular shape- this may represent midbrain corectopia, which can occasionally be seen w/ midbrain lesions. The fact that elevation of the contralateral eye was normal suggests that the lesion involves the third nerve fascicles in the midbrain rather than the entire oculomotor nucleus (fibers from the superior rectus subnuclei project contalaterally). The R sided ataxia may be caused by involvement of the fibers of the superior cerebellar peduncle in the L midbrain The subtle right plantar abnormality could result from mild-involvement of the L cerebral peduncle in the midbrain. The most likely clinical localization is L midbrain tegmentum, including the oculomotor nerve fascicles and superior cerebellar peduncle fibers (Claude's syndrome). Given the sudden onset and hx, most likely diagnosis is L midbrain infarct caused by occlusion of penetrating vessels at the top of the basilar artery and proximal L PCA. A far less likely possibility is a small hemorrhage in this region.

Blood supply of the medulla:

The medial medulla is supplied by paramedian branches of the anterior spinal artery in more caudal regions and by paramedian branches of the vertebral arteries in more rostral regions the lateral medulla is supplied by penetrating branches from the vertebral artery and the PICA

blood supply of the pons:

The medial pons is supplied by paramedian branches of the basilar artery A small variable portion of the superior dorsolateral pons (and dorsal midbrain) receives from the superior cerebellar artery (SCA) The rostral lateral pons is supplied by circumferential branches of the basilar artery. (pontine arteries) In the more caudal regions, the lateral pons is supplied by the AICA

Case 3: A 48-year-old man with a history of diabetes, hypertension, and elevated cholesterol awoke on the day prior to admission with a funny "numb" feeling of his right arm and leg. In explaining what he meant by "numb" he said that he had difficulty reaching for and holding onto objects with his right hand. He also had trouble walking, dragging his right foot. His wife noted that his speech sounded slurred and his face looked twisted. These symptoms gradually became worse, so the next day the patient came to the emergency room. On exam he had right facial weakness and mildly dysarthric speech (confirmed by his wife's comparison to baseline). In addition, his right arm and leg had 2/5 to 4/5 weakness. He was unable to walk due to weakness. The remainder of his examination was unremarkable. On the basis of the symptoms and signs shown in bold above, what is the most likely location for the lesion? What is the most likely diagnosis?

The pt had dysarthria hemiparesis. Most common localization = posterior limb of the internal capsule on the L side or L basis pontis involving the corticospinal and corticobulbar tracts. Given risk factors, the most likely diagnosis is infarct in the L internal capsule or L basis pontis. Gradual progression of sx over the course of a day could be consistent w/ waxing and waning small-vessel and lacunar infarction; however, given young age, other diagnoses should also be considered, including demyelination, hemorrhage, brain abscess, or tumor

Signs of pontine dysfunction:

bilateral Babinski signs generalized weakness perioral numbness "salt and pepper" pins and needles facial tingling bilat upper or lower vision loss or blurring caused by impaired blood flow from the basilar artery to both PCAs) irregular respirations ocular bobbing (eyes dip downward quickly and then gradually to mid position before dipping again) shivering palatal myoclonus (affecting central tegmental tract) abducens palsy or horizontal gaze palsy bilateral small but reactive pupils (disruption of descending sympathetic fibers) extensor (decerebrate) posturing impaired consciousness

Cheyne-Strokes respiration:

breathing becomes progressively deeper with each breath, then progressively shallower with each breath to the point of apnea. The cycle then repeats, and breathing gradually becomes deeper again, in a continual crescendo-decrescendo pattern. not typically harmful in and of itself. usually seen in bilateral lesions at or above the level of the upper pons (including lesions of the cerebral cortex), but it can also be seen in mountain climbers sleeping at high altitudes and in medical conditions such as cardiac failure.

Case 1: A 22-year-old woman suddenly developed left posterior neck pain, vertigo, ataxia, left facial numbness, and hoarseness after chiropractic neck manipulation. The patient had been well until 4 months previously, when she injured her neck in a car accident. She saw a chiropractor daily for neck pain. On the day of admission, after her neck was "snapped," she suddenly felt increased pain in the left posterior neck region. As she left the chiropractor's office, she felt dizzy and nauseated and staggered out to her car, falling toward the left. She noticed her vision bouncing or swaying (oscillopsia) but had no diplopia. She vomited twice, and when she reached home her husband noticed that her voice sounded hoarse. She also felt a numbness and tingling on the left side of her face. The symptoms did not improve after a brief nap, so she came to the emergency room. Neurologic exam: Mental status: Alert and oriented × 3. Normal language. Named months forward and backward with no errors. Recalled 3/3 words after 4 minutes. Cranial nerves: Left pupil 2.5 mm, constricting to 2 mm. Right pupil 3.5 mm, constricting to 2 mm. Visual fields full. Right-beating horizontal and counterclockwise rotatory nystagmus, which increased with rightward gaze. Patient reported an associated perception of the visual field moving back and forth (oscillopsia). Extraocular movements full. Left ptosis. Decreased pinprick and temperature sensation in left ophthalmic, maxillary, and mandibular divisions of CN V. Decreased left corneal reflex. Face symmetrical. Taste not tested. Hearing intact. Voice hoarse. Decreased palate elevation on the left, and decreased left gag reflex. Normal sternomastoid and trapezius strength. Tongue midline. Reflexes: +1 achilles. No Babinski's sign. Coordination: Mild ataxia on finger-to-nose testing on the left. Toe tapping on the left was irregular in rhythm (dysrhythmic). Gait: Unable to stand because of severe dizziness. Sensory: Decreased pinprick and temperature sensation in the right limbs and trunk below the neck. Intact light touch, vibration, and joint position sense. On the basis of the symptoms and signs shown in bold above, where is the lesion? Given the sudden onset of deficits and neck pain following neck manipulation, what is the most likely diagnosis? What are some other possibilities?

Virtually all the clinical features of Wallenberg's syndrome. Lateral medullary syndrome is usually caused by thrombosis, most often involving the vertebral artery. Given the pt's recent neck manipulation, neck pain, young age, lack of other stroke risk factors, verebral dissection should be strongly considered.

Lateral Medullary Syndrome: Also called: what vascular supply affected? 6 major structures affected? clinical features?

Wallenberg's syndrome vertebral artery thrombosis = most common cause; more common than PICA affected structures: -inferior cerebellar peduncle -vestibular nuclei -spinothalamic tract (only contralateral finding- contralateral body decreased pain and temp sense) -descending sympathetic fibers (Horner's syndrome) -nucleus ambiguus (laryngoscopy shows ipsilateral vocal cord paralysis) -nucleus solitarius (decreased taste to ipsilateral tongue)

Locked-in syndrome:

can sometimes be mistaken for coma unlike coma, these pts are conscious and may be able to communicate through vertical eye movements or eye blinks

Transient loss of consciousness is usually caused by:

cardiac or other medical conditions (much less commonly caused by neurologic disorderds such as seizures or brainstem ischemia)

Medial medullary syndrome: what vascular supply affected? 3 major structures affected? clinical features?

caused by occlusion of the paramedian branches of the anterior spinal or vertebral arteries infarction of the pyramidal tract results in contralateral arm and leg UMN weakness sparing the face (can resemble a cervical cord lesion) ipsilateral tongue weakness from infarction of exiting CNXII fascicles or, depending on how far the infarct extends from the ventral surface of the medulla, from infarction of the hypoglossal nucleus.(tongue is involved in only 50% of the time or less) depending on how far dorsally the infarct extends, there may be contralateral decreased vibration and joint position sense caused by infarction of the medial lemniscus.

Of all the focal brainstem vascular syndromes, only 2 are common:

lateral medullary syndrme (usually caused by vertebral thrombosis) & medial basis pontis infarcts (usually caused by lacunar disease)

Lesions leading to respiratory dysfunction: medulla pons midbrain

lesions of the medulla can cause respiratory arrest and death ->lesions of the medulla that do not cause respiratory arrest can lead to ataxic respiration, an ominous pattern of very irregular breathing that may ultimately progress to respiratory arrest. Lesions of the rostral pons (in the medial parabrachial Kölliker-Fuse area located dorsal to the motor nucleus of CN V) can rarely cause apneustic respiration, in which the patient has brief 2- to 3-second respiratory pauses at full inspiration. Midbrain lesions may lead to central neurogenic hyperventilation.

Area postrema:

located along the caudal lateral wall of the fourth ventricle in the medulla contains the chemotactic trigger zone In this region, the blood-brain barrier is incomplete, allowing endogenous substances or exogenous toxins in the bloodstream to trigger nausea and vomiting. Nausea and vomiting can also be triggered by a circuit beginning with the release of serotonin (5-HT) from cells in the stomach and small intestine walls in response to emetic agents. 5-HT stimulates the endings of afferent fibers traveling with the vagus to reach the nucleus solitarius in the brainstem. Vagal afferents also project to the nearby area postrema, which is stimulated by circulating 5-HT as well. Activation of the area postrema or nucleus solitarius may also play a role in the nausea and vomiting seen in disorders of the vestibular system or cerebellum, and in elevated intracranial pressure

Paramedian pontine infarcts: most common distribution? symptoms?

most common distribution involves the paramedian basis pontis unilaterally Infarction of the corticospinal and corticobulbar tracts causes a lacunar syndrome (just like that affecting the internal capsule) of contralateral face, arm, and leg weakness, together with dysarthria, also known as dysarthria hemiparesis or pure motor hemiparesis Involvement of the pontine nuclei and pontocerebellar fibers can cause ataxia, which is usually contralateral (on the same side as the hemiparesis), resulting in the syndrome called ataxic hemiparesis A variant of this condition seen mainly with paramedian basis pontis infarcts is dysarthria-clumsy hand syndrome, in which there is dysarthria along with motor disturbances affecting the contralateral arm more than the leg.

Pontine hemorrhage: most commonly seen in the setting of- pontine hemorrhages are often -

most commonly seen in the setting of chronic hypertension, causing fragility of small, penetrating blood vessels usually involves the paramedian branches of the basilar artery, at the junction between the tegmentum and basis pontis. pontine hemorrhages are often large and bilateral, resulting in catastrophic bilateral cranial nerve deficits, long-tract signs, coma, and a poor prognosis.

Basilar thrombosis;

often catastrophic bilateral infarctions of multiple regions of the pons and other regions supplied by the basilar artery, including the cerebellum, midbrain, thalamus, and occipital lobes usually results from thrombosis of a previously narrowed basilar artery in the setting of atherosclerotic disease. Patients often develop multiple cranial nerve abnormalities, long-tract signs, and coma, typically with a poor prognosis.

Midbrain and thalamus blood supply:

penetrating branches arising from the top of the basilar artery and from the proximal PCAs supply both the midbrain and thalamus Paramedian branches arising from the top of the basilar enter the interpeduncular fossa to supply the medial midbrain and thalamus Sometimes these arteries bifurcate after their origin, giving rise to the so-called arteries of Percheron, which supply the bilateral medial midbrain and thalamus. Occlusion of an artery of Percheron before it bifurcates can lead to bilateral medial midbrain or thalamic infarcts

brainstem control of breathing: what nucleus receives input regarding cardiorespiratory function? what nuclei of the medulla is considered the pacemaker of respiration? what cervical spinal segments control the phrenic nerve efferents?

respiratory rhythms occur automatically under the control of circuits in the medulla. -> other regions of the nervous system have strong modulatory influences on the respiratory pattern. Respiratory rhythms can also be superseded temporarily by voluntary control mediated by the forebrain There are numerous inputs to respiratory circuits, including peripheral chemoreceptors for blood oxygen level and pH, and stretch receptors in the lungs, many of which project to the cardiorespiratory portion of the nucleus solitarius. In addition, there are inputs from central nervous system neurons including chemoreceptors for pH in the medulla, some of which contain serotonin and stimulate respiration the pre-Bötzinger complex located in the medulla has been described as a pacemaker for respiration Cervical spinal segments C3 to C5 control phrenic nerve efferents that contract the diaphragm during inspiration, while thoracic levels control thoracic inspiratory and expiratory muscles.

Signs of midbrain dysfunction:

third-nerve palsy unilateral or bilateral pupil dilation ataxia flexor (decorticate) posturing impaired consciousness

Coma: what time length distinguishes it from transient disorders of consciousness? what 2 possible locations can coma be localized to dysfunction? What quality distinguishes coma from brain death?

unarousable unresponsiveness in which the pt lies w/ eyes closed minimum duration = 1 hr to distinguish coma from transient disorders of consciousness such as concussion or syncope Coma can be localized to dysfunction in two possible locations: (1) bilateral widespread regions of the cerebral hemispheres, or (2) the upper brainstem-diencephalic activating systems (or both 1 and 2). In coma, there is profoundly impaired function of the cerebral cortex and diencephalic-upper brainstem arousal systems. Unlike brain death, many simple or even complex brainstem reflex activities may occur in coma. However, psychologically meaningful or purposeful responses mediated by the cortex are absent Example: you may see reflex eye movements (vestibuloocular reflex, respiratory movements, or posturing, but no purposeful movements like limb abduction in response to pain, localizing painful stimulus, or responses demonstrating volition) cerebral metabolism is typically reduced by at least 50%, in agreement with the lack of significant cortical functions. Although coma can be induced either by cortical or subcortical pathology, once coma is present, both cortical and subcortical arousal systems are depressed The most consistent abnormality of the EEG in coma is that it is typically monotonous, with little variability over time, unlike the normally varying EEG seen in different sleep stages Patients in coma are unarousable even w/ vigorous stimulation and patients in coma do not undergo cyclical variations of state as seen during sleep. Coma is not generally a permanent condition. Within 2-4 weeks of onset nearly all patients either deteriorate or emerge into other states of less profoundly impaired arousal. Following an initial catastrophic brain insult causing coma (most commonly, trauma or anoxia), some patients may enter a perplexing state in which they regain sleep-wake cycles and other primitive orienting responses and reflexes mediated by the brainstem and diencephalon but remain unconscious. This condition is referred to as a vegetative state

Top of the basilar syndrome: (what is basilar scrape syndrome?)

usually caused by embolus that lodges in the distal basilar artery, causing infarcts of multiple vascular territories Clinical features include visual disturbances resulting from infarcts of the visual cortex; memory disturbances from infarcts of the bilateral medial thalami or temporal lobes; eye movement abnormalities from infarction of the oculomotor nuclei and third-nerve fascicles in the midbrain; somnolence, delirium, or vivid visual hallucinations ("peduncular hallucinosis") caused by infarction of the midbrain reticular formation; and ataxia resulting from cerebellar infarcts. Corticospinal involvement is often relatively mild in top-of-the-basilar syndrome Sometimes, as an embolus migrates up the basilar artery toward the top, it occludes various penetrator arteries in the pons, producing a series of transient deficits referred to as the basilar scrape syndrome.

SCA infarcts:

usually involve mainly the superior cerebellum, causing ipsilateral ataxia A variable region of the rostrolateral pons may also be involved, occasionally causing some features of lateral tegmental syndrome.

Signs of medullary dysfunction:

vertigo ataxia nystagmus N/V respiratory arrest autonomic instability hiccuping

Minimally conscious state what is one of the earliest signs of emergence into the minimally conscious state?

Appearance of visual tracking may be one of the earliest signs of emergence into the minimally conscious state can occur as a further stage of recovery from vegetative state or as a primary disorder patients have some minimal or variable degree of responsiveness, including the ability to follow simple commands, say single words, or reach for and hold objects. By definition, minimally conscious patients do not have reliable interactive verbal or nonverbal communication and do not have reliable functional use of objects

Clinical approach to a pt in coma; bilateral cerebral dysfunction vs brainstem dysfunction what are the 3 things to immediately give as precautionary to a patient w/ coma given that these 3 things are readily treatable causes of coma?

Coma is a neurologic emergency because many causes of coma are reversible if treated promptly but can cause permanent damage that becomes progressively more severe as time goes on. The most common causes of bilateral cerebral dysfunction are global anoxia, other toxic/metabolic disorders, and head trauma. Bilateral ischemic infarcts can also cause coma, usually by involving first one and then the second hemisphere. Brainstem dysfunction causing coma can be due to either extrinsic compression from cerebral or cerebellar mass lesions or intrinsic brainstem lesions, most commonly infarct or hemorrhage. As in any other emergency situation, when evaluating coma the initial priorities are airway, breathing, circulation. When it is clinically appropriate, the patient should be intubated and cardiopulmonary resuscitation should be initiated. Establishing prompt intravenous access is also essential. Intravenous thiamine, dextrose, and naloxone should be given immediately, even before laboratory results are obtained, * because thiamine deficiency, hypoglycemia, and opiate overdose are readily treatable causes of coma. neurologic exam, blood tests, had CT Once the danger of herniation has been excluded by head CT, patients with coma of unknown cause should undergo a lumbar puncture for CSF analysis if the cause of coma remains unknown after this evaluation, an EEG should be obtained immediately so that subtle or non-convulsive status epilepticus can be detected and treated if present.

Case 8: A 60-year-old retired businesswoman was sent to the emergency room by her physician because of 2 months of worsening episodes of memory loss, sparkling lights, and blurry or double vision. Her past medical history was notable for anticardiolipin (antiphospholipin) antibody syndrome (a condition causing hypercoagulability; see Table 10.5), including elevated anticardiolipin antibodies (IgG 2407, IgM 38, IgA < 10), a first-trimester miscarriage, left subclavian stenosis, and Raynaud's phenomenon. She had been treated in the past with warfarin oral anticoagulation, but she elected to take aspirin instead. She also had a long history of brief (1- to 2-minute) episodes of migraine-like visual scintillations that she described as "like firecrackers going off in front of my eyes," associated with multiple other vague complaints, including epigastric, pleuritic, and back pain, which were attributed to fibromyalgia or stress. There was a strong family history of migraine. The patient's sister had died 2 months prior to admission, and shortly afterward the patient began having recurrent episodes of memory loss lasting several minutes each, along with worsening of all her other complaints. She was somewhat evasive and vague in describing the episodes, and her physicians initially believed them to be psychiatrically based. Memory lapses included forgetting whether her sister had been buried or cremated and forgetting a real estate deal she had recently completed. On the day of admission, she saw her physician because of a new complaint she had developed a few days earlier of blurred and then double vision to the point where it was difficult for her to stand up and walk. On initial examination she was alert and fluent but had mildly reduced attention, able to repeat only 5/7 digits forward, and recalling 2/3 objects after 3 minutes. Her right pupil was slightly enlarged at 4 mm, constricting sluggishly to 2.5 mm, and her left pupil was 3 mm, constricting briskly to 2 mm. She had limited upward gaze with both eyes. In addition, medial gaze was reduced with the right eye, and she had a right ptosis. Exam was otherwise unremarkable. Her physician sent her to the emergency room, where she was examined by a neurologist, but by the time she arrived she had normal eye movements, with the only abnormality on exam being a mild residual anisocoria. She was admitted for further evaluation, and the next morning she was found again to have limited upgaze bilaterally, right ptosis, and right limited medial gaze, with a somewhat dilated right pupil. Anticoagulation with intravenous heparin was initiated; however, during the subsequent days she had waxing and waning somnolence and delirium to the point of being unarousable at times. At other times, despite being transferred to the intensive care unit, she would wake up, pull out all her intravenous lines, and walk down the hallway to use the bathroom. Her eye movement abnormalities persisted, and in addition she developed bilateral ataxia on finger-to-nose testing (when she was awake enough to cooperate) and decreased blink to visual threat on the left side. Dysfunction in what location can cause these eye movement abnormalities along with an impaired level of consciousness and ataxia? Given the history of hypercoagulability and the addition of a left visual field deficit, as well as episodes of memory loss, what vascular syndrome (specify the blood vessels involved) can cause this combination of deficits?

Dysfunction in the midbrain tegmentum could cause vertical gaze abnormalities through (1) involvement of the rostral interstitial nucleus of the MLF in the rostral midbrain, (2) right third-nerve dysfunction through involvement of the R third nerve fascicles or nucleus; (3) somnolence and delirium through involvement of the reticular formation; (4) bilateral ataxia through involvement of the superior cerebellar peduncle fibers ============= The above deficits can be localized to the midbrain tegmentum, which is supplied by small penetrating vessels arising from the top of the basilar artery and proximal PCAs. The L visual deficit could be explained by an infarct of the R occipital lobe, which is supplied by the R PCA. In addition, the episodes of memory loss could have been caused by TIAs involving the bilateral medial thalami or medial temporal lobes (supplied by PCAs). Therefore, the above deficits could all be caused by vascular insufficiency at the top of the basilar artery and proximal PCAs (top-of the-basilar syndrome) - usually caused by thrombosis

Case 9: A 50-year-old woman developed a bilateral retro-orbital headache associated with nasal discharge 2 weeks prior to presentation. She was treated with oral antibiotics for presumed sinusitis, and her symptoms resolved. On review of her past history, she described an episode 14 years previously of vertigo, nystagmus, and dysarthria but an MRI had never been done. Because of these previous symptoms, an MRI scan was scheduled; however, she then suddenly developed intractable hiccups lasting 5 days, causing her to come back to her physician's office. General exam and neurologic exam were entirely normal. Lesions in what general region of the CNS are associated with hiccups? Assuming that this patient's previous neurologic symptoms are related to her present complaints, what are some possibilities for the diagnosis?

Headache is associated w/ intracranial pathology. Hiccups can be caused by lesions of the posterior fossa, particularly in the medulla. Givne the occurrence of sx possibily related to brainstem disorder many years earlier, a chronic or recurrent lesion of the brainstem, especially the medulla, is the most likely diagnosis. Some possibilities include demyelination, low-grade tumor, small recurrent hemorrhage in AV malformation or cavernous angioma, vertebrobasilar migraine, vasculitis, immune-mediated disorders of the CNS

Brainstem control of cardiovascular function:

Inputs to the caudal nucleus solitarius is crucial, as are circuits in the nearby medullary reticular formation The nucleus solitarius receives inputs from baroreceptors in the carotid body and aortic arch via cranial nerves IX and X, respectively Many circuits project directly from the nucleus solitaris to parasympathetic and sympathetic preganglionic neurons in the brainstem and spinal cord Presympathetic neurons in the rostral ventrolateral medulla project to preganglionic sympathetic neurons in the spinal cord intermediolateral cell column and are crucial for maintaining normal blood pressure. interruption causes reduced blood pressure seen in spinal shock the cardiorespiratory portion of the nucleus solitarius also projects rostrally to the forebrain, largely via relays in the parabrachial nucleus of the rostral pons Inputs from the nucleus solitarius to the limbic system may be important in mediating emotional responses to altered cardiorespiratory function, and they have been postulated to play a role in triggering panic attacks.; an emotional state manifested as limbic system activity has a strong effect on autonomic function through projections to the brainstem reticular formation.

Symptoms of midbrain syndromes: Weber's syndrome vs Claude's syndrome vs Benedikt's syndrome:

Midbrain syndromes have been described involving different regions of the basis, tegmentum, or both. basis = oculomotor nerve fascicles & cerebral peduncles tegmentum = oculomotor fascicles and Red nucleus Infarction of the cerebral peduncles in the midbrain basis causes contralateral hemiparesis; infarction of the third-nerve nucleus or fascicles causes an ipsilateral third-nerve palsy; and infarction of the red nucleus and fibers of the superior cerebellar peduncle (above the decussation) causes a contralateral tremor and ataxia. Larger infarcts of the midbrain that affect the midbrain reticular formation cause impaired consciousness

Case 2: A 53-year-old man with a history of cigarette smoking and hypercholesterolemia was driving home from the airport and had a 1-hour episode of pins and needles in his right perioral area, arm, and leg. He reached home, and later while he was walking the dog these symptoms recurred, together with difficulty walking and clumsiness and weakness of the right arm and leg. Unfortunately, because of the time when he arrived at the emergency room, he was unable to receive acute reperfusion therapy. On exam, he had decreased tone and 3/5 to 4/5 strength in the right arm and leg, an upgoing toe on the right, and decreased vibration and joint position sense in the right arm and leg. There was only a trace decrease in the right nasolabial fold at rest, and his smile was symmetrical. Tongue was midline. On the basis of the symptoms and signs shown in bold above, what is the most likely location for the lesion? What is the most likely diagnosis?

R arm and leg UMN weakness sparing the face could be caused by a lesion in the L medulla or in the R cervical spinal cord. Paresthesias and decreased vibration and joint position sense in the R body could be a lesion in the L brainstem involving the medial leminscus or in the R cervical spinal cord involving the posterior columns. The subtle R facial weakness makes spinal cord location less likely. Since the face was nearly spared, the lesion is unlikely to lie above the facial nerve exit point (pontomedullary junction) because if it did, more prominent facial involvement would be expected This leaves the medial medulla as a likely location, involving the L corticospinal fibers in the medullary pyramid and the L medial leminscus. The lack of tongue motor inolvement is interesting, but according to literature, tongue involvement is involved in only 50% of cases The most likely clinical localization = L medial medulla involving the pyramid and medial leminscus but sparing the hypoglossal nucleus and CN XII fascicles Given age and hx, most likely diagnosis is L medial medullary infarction. Usually caused by occlusion of paramedian branches of the vertebral or anterior spinal arteries. The R perioral pins and needles experienced by the pt suggests some possible ischemia affecting the spinal trigeminal nucleus - this can occasionally occur in medial medullary syndrome.

Psychiatric disorders to distinguish from coma:

Several psychiatric disorders can cause patients to appear as if in a coma. In addition to catatonia and severe depression, patients may be unresponsive when in a dissociative state, often resulting from severe emotional trauma. Somatoform disorders such as conversion disorder, somatization disorder, or factitious disorder can also sometimes produce states resembling coma, sometimes called "pseudocoma." Often these can be distinguished from coma by a carefully performed neurologic exam, although in some cases the diagnosis may not be obvious.

Case 5: A 52-year-old woman with a history of Crohn's disease was walking in a shopping mall and suddenly had to sit down because she felt sweaty and the left side of her face felt "funny." Her husband noticed a "lazy eye" on the left. She was taken to the hospital, where on initial exam she had slurred speech with good comprehension. She also had weakness and decreased sensation of the left face, arm, and leg, and she was ataxic (side not specified). At the time of this patient's presentation acute reperfusion therapies were unfortunately not yet available. On the basis of the symptoms and signs shown in bold above, what is the most likely general location for the lesion? Given this patient's history, what diagnosis should be seriously considered? ------------------------ She was admitted to the hospital for further evaluation. That evening at 9:00 p.m., the patient suddenly had a respiratory arrest requiring intubation, and she was found to have decerebrate posturing (see Figure 3.5B). The next morning on exam, she was intubated and unable to move her extremities, but she was awake and able to answer yes/no questions appropriately by using eye blinks or vertical eye movements. She had no horizontal eye movements, even with oculocephalic maneuvers, but she did have voluntary vertical eye movements. She also had ocular bobbing (fast phase down, slow phase up) and a skew deviation, with the left eye higher than the right. There was no movement of the limbs in response to commands. In response to pain, the left arm did not move, the right arm had extensor (decerebrate) posturing, and both legs had triple flexion. Reflexes were absent, and both toes were upgoing.

The sx and exam findings are strongly suggestive of brainstem dysfunction, possibly from vertebrobasilar disease. Of note, inflammatory bowel disease can sometimes cause a hypercoagulability, so brainstem stroke w/ incipient worsening thrombosis in the vertebrobasilar system should be strongly considered. ------------ Onset w/ respiratory arrest suggests possible medullary involvement. The other findings - including lack of horizontal eye movements, ocular bobbing, skew deviation, and bilat UMN type paralysis w/ extensor posturing - all suggestive of extensive bilateral involvement of the pons. The fact that consciousness and vertical eye movement were preserved suggests midbrain was spared. The clinical picture is consistent w/ locked-in syndrome caused by extensive bilateral pontine and possibly medullary infarcts, sparing the midbrain. clinical course: MRA showed absent flow in vertebrobasilar system suggestive of basilar artery thrombosis

it is essential to document the patient's level of alertness with

a specific statement of what the patient did in response to particular stimuli. For example, if pressure applied to a nail bed or to the supraorbital ridge causes a patient to briefly open their eyes, moan, and push away the examiner with one hand before lapsing back into unresponsiveness, the patient is not in a coma. Documenting impaired consciousness and the specific response elicited is the most practical way to follow changes in patients of this kind.

Vegetative state: in what conditions may you see this? what time frame marks it as persistent? how does the presentation differ from that of coma?

also known as unresponsive wakefulness syndrome a perplexing state in which pts regain sleep-wake cycles and other primitive orienting responses and reflexes mediated by the brainstem and diencephalon but remain unconscious can also occur in certain end-stage dementias, as well as neurodegenerative or congenital disorders. If duration is longer than 1 month it is called a persistent vegetative state. When vegetative state lasts longer than 3 months following non-traumatic causes or longer than 12 months following trauma, prognosis for recovery is very poor. As in coma, patients in vegetative state have no meaningful responses to stimuli, and they have diffuse cortical dysfunction evidenced by over 50% reduction in cerebral metabolism. However, patients in vegetative state do open their eyes and arouse in response to stimulation, and they may turn their eyes and heads toward auditory or tactile stimuli, presumably through brainstem- and diencephalon-mediated pathways. Patients in vegetative state may produce unintelligible sounds and move their limbs, but they do not have meaningful speech or gestures, do not make purposeful movements, do not track visual stimuli, and are incontinent.

Brain death:

an extreme and irreversible form of coma all cortical, subcortical, and brainstem function is irreversibly lost brain death is defined on the basis of clinical examination demonstrating no evidence of forebrain or brainstem function, including no brainstem reflexes Only spinal cord reflexes may persist in brain death. When an EEG is done as a confirmatory test in brain death, it shows "electrocerebral inactivity," or a flat pattern, less than 2 microvolts in amplitude. Cerebral perfusion and metabolism are likewise reduced to zero in brain death.

What features are strongly suggestive of hemispheric involvement rather than brainstem involvement?

aphasia, hemineglect, hemianopia (loss of vision in half the field), seizures

AICA:

arises from proximal basilar artery at the level of the caudal pons, usually just after the vertebral arteries fuse supplies lateral caudal pons and small regions of the cerebellum

SCA:

arises from the top of the basilar artery at the level of the rostral pons and supplies the superior cerebellum as well as small regions of the rostral laterodorsal pons

PCA:

arises from the top of the basilar artery just beyond the SCA the oculomotor nerve pass between the SCA and the PCA wraps around the midbrain, supplying it, as well as most of the thalamus, medial occipital lobes, and inferior-medial temporal lobes.

PICA:

arises from the vertebral artery at the level of the medulla and wraps around the lateral medulla and inferior cerebellum

Status epilepticus:

continuous seizure activity Often, seizure activity is clinically obvious. However, sometimes only subtle twitching or no motor activity at all is present. whenever the cause of coma cannot be found, or when there is a history of seizures, an EEG should be performed promptly so that anticonvulsant therapy can be initiated when needed.

What features are strongly suggestive of brainstem involvement rather than hemispheric involvement?

crossed signs - decreased sensation on one side of the face and contralateral body, or weakness on one side of the face and contralateral body cranial nerve abnormalities, especially those causing eye movement abnormalities, such as dysconjugate gaze, wrong-way eyes, pupillary abnormalities, or nystagmus

Medial pontine basis and tegmentum infarcts: 3 major symptoms Foville's syndrome vs Millard-Gubler syndrome

extend farther into the tegmentum toward the fourth ventricle When the basis pontis is involved together with the facial colliculus, there is ipsilateral facial weakness, an ipsilateral horizontal gaze palsy (due to involvement of the abducens nucleus or paramedian pontine reticular formation), and contralateral hemiparesis (Foville's syndrome) ipsilateral horizontal gaze palsy = "wrong-way eyes" caused by a pontine lesion Slightly more laterally placed infarcts that involve the pontine basis and facial nerve fascicles without the abducens nucleus can cause ipsilateral facial weakness and contralateral hemiparesis (Millard-Gubler syndrome). Other regions of the pontine tegmentum that can variably be involved in paramedian infarcts are the medial lemniscus (causing contralateral position and vibration sense loss) and the medial longitudinal fasciculus (causing an internuclear ophthalmoplegia

Unlike carotid stenosis, vertebral and basilar stenosis:

have not shown proven benefit from endarterectomy, angioplasty, or stenting.

What symptom helps localize syndrome to the medulla rather than the pons?

hoarseness and loss of taste sensation

Inner ear blood supply:

internal auditory (labyrinthine) artery - usually arises as a branch of the AICA

AICA infarcts:

involve mainly the caudal lateral pons resulting lateral brainstem tegmentum syndrome may resemble the lateral medullary syndrome in some ways (presence of hoarseness or loss of taste localizes to the medulla rather than the pons; The labyrinthine artery usually it arises as a branch of the AICA). in addition to a lateral tegmental syndrome including ipsilateral ataxia, vertigo, nystagmus, pain and temperature sensory loss in the ipsilateral face and contralateral body, and an ipsilateral Horner's syndrome, AICA infarcts can also cause unilateral hearing loss.

What symptom could narrow AICA involvement rather than lateral medullary syndrome?

presence of ipsilateral hearing loss

akinetic mutism, abulia, and catatonia:

states of profound apathy in the extreme that can resemble coma or vegetative state dysfunction of circuits involving the frontal lobes, diencephalon, and ascending dopaminergic projections important to the initiation of motor and cognitive activity. akinetic mutism: pt appears fully awake and unlike pts in vegetative state, pts visually track the examiner. However, they do not respond to any commands -> primary deficit is in motor initiation rather than consciousness -> extreme form of abulia Abulia: often results from frontal lesions ; pts usally sit passively but may occasionally respond to questions or commands after a long delay -> in some pts, these disorders can be reversed w/ dopaminergic agonists Catatonia: akinetic state that can occasionally be seen in advanced cases of schizophrenia Other, related akinetic-apathetic states include advanced parkinsonism, severe depression, and neuroleptic malignant syndrome.

Paramedian branches:

tend to respect the midline individual branches supply the R or L paramedian regions extend a variable distance from the ventral surface of the brainstem, with the longest branches reaching all the way to the ventricle