Anatomy: Neuro Lab 2

2 nerves arise directly from the trunks of the brachial plexus. Which 2 nerves and from which levels? Also, name the innervated muscles.

Upper/superior trunk gives off both nerves. 1. suprascapular n, C5-C6, innervates supraspinatous and infraspinatous mm. 2. nerve to subclavius, C5-C6, innervates subclavian m. The middle and inferior trunks do not have branches directly.

What is vasovagal syncope? What is the mechanism behind it?

Vasovagal syncope = fainting as a result of overreaction to certain stimuli, such as the sight of blood or when one is in extreme emotional distress. MoA: Trigger causes autonomic dysfunction temporarily, with decreased HR and decreased BP. This leads to reduced brain perfusion, causing fainting.

Name the spinal levels encompassed by the following plexuses: lumbar plexus sacral plexus coccygeal plexus

Ventral spinal rami = T12-Co1 (spans all the lower plexuses; this is literally just ventral rami) lumbar plexus = T12-L4 sacral plexus = L4-S4 coccygeal plexus = S5-Co1

Where are the watershed areas, and what is the significance of these areas relating to stroke?

Watershed areas are parts of the brain supplied by terminal branches of 2 major cerebral arteries. The most commonly affected area is between the ACA and MCA. The watershed areas are very susceptible to stroke.

What nerve injury is most likely to cause foot drop?

common fibular n. is most often injured in the lower limb and likely to result in foot drop, which is a loss of dorsiflexion and eversion, so the toes cannot lift to clear the floor when walking, the patient must lift the foot extra high.

what is lumbar radiculopathy?

compression of the lumbar nerve roots, causing nerve pain that radiates down the backs of the legs. Usually caused by lumbar herniation. This is AKA sciatica

The anterior cerebral a. is divided in 3 segments. Name each one, and name the branches off the appropriate segments.

A1 = horizontal segment. A1 branches: medial lenticulostriate aa (basal ganglia), recurrent a of Heubner (head of caudate), anterior communcating a. A2 = vertical segment (orbitofrontal a.) A3 = collsal segment (aka pericallosal a.)

Which segments of the ICA have branches, and which do not? While you're at it, name all 7 segments.

Branches = mostly evens + C7 C2 petrous segment C4 cavernous segment C6 opthalmic segment C7 communicating segment NO branches = odds EXCEPT C7 C1 cervical segment C3 lacerum segment C5 clinoid segment

Name the branches off segments C2, C4, C6, and C7.

C2 = caroticotympanic a., anastamoses w/external carotid a. C4 = inferior hypophyseal a. C6 = opthalmic a., superior hypophyseal a. C7 = posterior communicating a, anterior choroidal a, anterior cerebral a, middle cerebral a

Name all CNs and spinal levels emitting parasympathetic fibers.

CN III CN VII CN IX CN X S2-S4

Name the functions of the parasympathetic CNs and S2-S4

CN III = constriction of pupil in response to light CN VII = submandibular and sublingual salivary glands, lacrimal glands CN IX = parotid gland CN X = acts on organs for rest/digest functions S2-S4 = empty bladder, opening internal urethral sphincter, gut motility, sexual functionality

Describe the pathway of CN parasympathetics and sacral parasympathetics from the spinal cord.

CNs = preganglionic neurons come directly from the brainstem and synapse on the corresponding target organ S2-S4 = preganglionic neurons exit the SC at the ventral root and travel through pelvic splanchnic nerves, synapsing on target organs.

The branches are the most terminal nerves coming off the brachial plexus. Name each branch coming off the lateral cord, including spinal levels.

Lateral cord, C5-C7 - musculocutaneous n, C5-C7 (visible) biceps brachii flexion --> lateral cutaneous nerve of forearm is a branch - lateral branch of median n. (median comes off both lateral and medial cords)

Trace the major routes for sympathetic signals from the spinal cord.

Lateral horn > anterior horn > spinal nerve > white ramus communicans > paravertebral ganglia > gray ramus communicans > target (may synapse at, above/below, or through splanchnics to a target organ.)

Name all the nerves and their spinal levels, coming off the lumbar plexus.

Lumbar plexus is formed from T12-L4. subcostal n. = T12 iliohypogastric n., ilioinguinal n., genital branch of genitofemoral n. = L1 femoral branch of genitofemoral n., lateral femoral cutaneous n. = L2 femoral n. = L2-L4 saphenous n. (branch off femoral) = L3-L4 obturator n. = L2-L4

The middle cerebral artery has 4 segments. Name each and their branches when present.

M1 = sphenoidal segment branches = lateral and medial lenticulostriate aa. M2 = insular/Sylvian segment (in sylvian fissure) M3 = opercular segment M4 = cortical segment

What is an opthalmic artery occlusion? Be sure to mention which artery the opthalmic comes off, and which segment of that artery.

Obstruction or rupture of the opthalmic branch of the ICA, which comes off segment C6. Common in diseases like diabetes.

The posterior cerebral artery has 4 segments. Name each, and their branches when present.

P1 = pre-communicating segment P2 = ambient segment branch = posterior choroidal a. (anterior choroidal branches off C7 of ICA) P3 = quadrigeminal segment P4 = cortical segment branch = calcarine a.

3 main vessels supply the cerebellum. Name all 3. From which artery does each cerebellar artery originate?

PICA - branches off paired vertebral aa AICA and SCA - branches off the basilar a

what is bicycle seat nueropathy? what might it cause?

Perineal numbness/pain caused by compression of the pudendal n. May cause sexual dysfunction.

ID the pontine aa and labyrinthine aa. From which vessels does each branch? What does each vessel supply?

Pontine = branch off basilar a, supplies pons Labyrinthine = branch off AICA 80% of time, supplies vestibular system and cochlea

Describe the setup of the brachial plexus, including the order (cords, roots, etc.). You don't have to discuss the terminal branches yet...

Real Texans Drink Cold Beer roots = C5-T1, originates at SC trunks = superior (C5-C6), middle (C7), inferior (C8-T1) divisions = 3 anterior and 3 posterior divisions cords = lateral (C5,6,7), posterior (all), medial (C8,T1) use axillary artery as reference point branches = musculocutaneous, axillary, radial, median, ulnar

What is an intracerebral hemorrhagic stroke? What is the MCC and clinical presentation?

Rupture of blood vessels withing the brain. MCC is hypertension or head trauma. Symptoms vary, but may include headaches, nausea, confusion, sudden weakness.

Name the NTs and receptors associated with pre- and post-ganglionic sympathetic and parasympathetic NS. What is the exception to the usual rule with the sympathetic NS?

Sweat glands use ACh in pre and post-ganglionic neurons.

What is true of the synapse of sympathetic nerves running through the splanchnics?

Sympathetic signals that go through splanchnic nn. exit without synapsing at the paravertebral ganglion. Instead, they synapse at the prevertebral ganglion at the target organ.

What is PCA syndrome, and how would it present?

Syndrome occurring when blood supply to the PCA is restricted. Occipital lobe symptoms most common.

From what spinal levels do sympathetics originate?

T1-L2

What is the function of splanchnic nerves?

They carry sympathetic signals that directly supply abdominal and pelvic viscera, synapsing at the prevertebral ganglia directly at the organ (instead of paravertebral chain ganglia).

What type of gait may result from superior gluteal n. entrapment?

Trendelenburg gait

what is a supraclavicular nerve block? what is the key landmark for this procedure?

another anesthetic procedure to numb the brachial plexus. subclavian artery is the key landmark.

The ventral rami span C1-C4. Draw out/know the following, including spinal level of origin and muscle innervated: ansa cervicalis (superior and inferior roots) punctum nervosum, including: lesser occipital n great auricular n transverse cervical n supraclavicular nn phrenic n.

ansa cervicalis (superior and inferior roots) - C1-C3, motor portion of cervical plexus! - superior root = suprahyoid mm - inferior root = infrahyoid mm punctum nervosum (AKA Erb's Point, C2-C4), including: lesser occipital n (C2) = sensation of lateral/posterior scalp great auricular n (C2-C3) = sensatin of skin over auricle of ear and mastoid process transverse cervical n (C2-C3) = sensation of anterolateral neck supraclavicular nn (C3-C4) = sensation of lower neck, upper thorax, and superior shoulder phrenic n (C3-C5) = motor innervation to diaphragm

The proximal cervical plexus has dorsal rami and ventral rami. For dorsal rami C1-C3, what nerve comes off each level? Which muscles does each of those nerves innervate?

dorsal rami = C1-C3 C1 = suboccipital n., intrinsic posterior neck muscles C2 = greater occipital n., intrinsic posterior neck muscles C3 = 3rd occipital n., intrinsic nuchal posterior neck muscles

describe dysautonomia, and name some examples

general term that describes abnormal function of the autonomic nervous system. may be overactivity or failure to work properly. examples: orthostatic hypotension, POTS, syncope, erectile dysfunction

Review functions of the list of nerves: genitofemoral obturator superior gluteal inferior gluteal sciatic tibial superficial peroneal deep peroneal pudendal

genitofemoral = cremasteric muscle obturator = adduction of thigh superior gluteal = abduct thigh, medial rotation of thigh inferior gluteal = extends, abducts, and laterally rotates thigh. sciatic = adduct thigh, flex knee tibial = plantar flexion of foot superficial peroneal = plantar flexion of foot, eversion of foot deep peroneal = dorsiflexion of foot, inversion of foot, extends toes pudendal = sexual function

what is the purpose of an interscalene nerve block, and why is it named such? What is the key muscular landmark for the procedure?

interscalene nerve block is used to anesthetize the brachial plexus, usually for shoulder surgery. the ROOTS of the plexus are at the interscalene groove, which is between the anterior and middle scalene muscles. you use the posterior border of sternocleidomastoid as a landmark.

what is thoracic outlet syndrome? what is the major cause?

involves compression of the lower/inferior trunk of the brachial plexus. often caused by a rib or pancoast tumor. messes up muscles of the hand, causing intrinsic hand muscle atrophy.

The distal brachial plexus consists of cords and branches. What are the 3 divisions of the cords? Which root levels does each cord cover?

lateral = C5-C7 medial = C8-T1 posterior = C5-T1

Name the nerves that come directly off each cord, and their levels also.

lateral cord = C5-C7 - ansa pectoralis, formed by medial and laterl pectoral nerves looping - lateral pecoral n. C5-C7 medial cord = C8-T1 - ansa pectoralis - medial pectoral n., C8-T1 - medial antebrachal cutaneous n. C8-T1 (visible on body) - medial brachial cutaneous n. T1 posterior cord = C5-T1 - subscapular nn. (3 of them) --> upper subscapular n, C8-T1 --> middle subscapular n/thoracodorsal, C8-T1 (visible) --> lower subscapular n, C5-C6

The branches are the most terminal nerves coming off the brachial plexus. Name the nerve coming off BOTH the medial and lateral cords, including spinal levels and that nerve's 3 branches.

medial AND lateral branches - median n. comes off both the lateral and medial cords - median n, C5-T1, and its 3 branches - anterior interosseous n. - recurrent branch of median n. - common and proper digital branches

The branches are the most terminal nerves coming off the brachial plexus. Name each branch coming off the medial cord, including spinal levels.

medial cord, C8-T1 - ulnar n. C8-T1, has common and proper digital branches - innervates flexor carpi ulnaris, abductor digiti minimi, 3rd/4th lumbricals - medial branch of median n. - median n. innervates MEATLOAF (lumbricals 1/2, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)

What is meralgia parasthetica, and what nerve compression causes it?

neurological condition including numbness, tingling, and sometimes pain in the outer thigh. Occurs from compression of lateral femoral cutaneous n. (L2-L3) usually by the inguinal ligament.

describe carpal tunnel syndrome. which nerve is most likely affected? how does this present clinically? which muscles are impacted?

occurs when there is compression of (usually) the median nerve, usually by the transverse carpal ligament presents with pain and tingling, atrophy of thenar eminence, but sparking of sensation because the palmar cutaneous branch is external to the carpal tunnel. median n. innervates MEATLOAF (lateral 2 lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis)

what is cervical spondylosis? which nerve roots are most often affected?

osteroarthritis of the cervical spine from wearing down of vertebral discs. may cause compression most often in C6 and C7. symptoms include: pain in neck, headaches, neck stiffness, neuropathy of arms, etc.

what is Klumpke's palsy? injury at what spinal levels causes this palsy? clinical presentation?

paralysis of the forearm and hand muscles damage to INFERIOR trunk, C8-T1 claw hand, Horner's syndrome (due to T1 involvement of sympathetics) often caused by pulling baby out of vagina by arm

what is Erb's palsy? what does it look like clinically? what is a common cause in newborns?

paralysis of the muscles of the shoulder and arm due to injury of the SUPERIOR trunk of the brachial plexus (C5-C6) clinically, patient has a waiter's tip position, with adducted shoulder, medially rotated arm, and extended elbow. MCC is shoulder dystocia at birth (shoulder gets caught under pubic bone)

The branches are the most terminal nerves coming off the brachial plexus. Name the nerves from the posterior cord, including spinal levels.

posterior cord = C5-T1 - axillary n, C5-C6 (innervates teres minor) - radial n, C5-T1 (innervates triceps brachii, brachioradialis, extensor muscles of the hand) - superficial radial n - posterior interroseous/deep radial n.

radial neuropathy can cause saturday night palsy/wrist drop. describe these clinically.

radial neuropathy occurs from compression of the radial n. causes a partial or complete loss of movement or sensation. saturday night palsy/honeymoon palsy = both occur from compression or trauma to radial n. wrist drop = cannot extend the wrist or fingers, so the relaxed wrist assumes a partially flexed position since the radial n. cannot oppose flexion.

Which 2 nerves, and from which spinal levels, arise directly from the roots of the brachial plexus? Which muscles do those 2 nerves innervate?

roots = C5-T1 dorsal scapular n. = C5, innervates levator scapulae and rhomboids long thoracic n. = C5-C7, innervates serratus anterior to pull scapula forward

Name all the nerves and spinal levels of those nerves coming off the sacral plexus.

sacral plexus = L4-S4 lumbosacral trunk = L4-L5 superior gluteal n = L4-S1 inferior gluteal n = L5-S2 n. to piriformis = S1-S2 n. to obturator internus = L5-S1 n. to quadratus femoris = L5-S1 posterior femoral cutaneous n. = S1-S3 pudendal n = S2-S4 sciatic n. = L4-S3 sciatic has 2 branches = 1) tibial n. L4-S3, tibial branches into sural n. S1-S2 and medial/lateral plantar nn. S1-S3 2) common fibular L4-S2, branches into superficial fibular L5-S1, and deep fibular L4-L5

What is the difference between sciatica and piriformis syndrome?

sciatica = lumbar radiculopathy piriformis syndrome = piriformis muscle in specific irritates sciatic nerve. similar presentation, different cause.

what is an infraclavicular nerve block?

targets the 3 cords, causing blockage to axillary, radial, median, ulnar, and musculocutaneous nn. used in hand, elbow, wrist surgeries.

what causes ulnar claw? how does it present?

ulnar claw is caused by an ulnar n injury, leading to motor and sensory loss in the hand. since the ulnar n innervates the medial lumbricals and flexors of the fingers, loss of the nerve causes ring and pinky fingers to "claw", and hyperflexion of DIP and PIP.

what deficits result from femoral neuropathy?

weakened thigh flexion and weakened knee extension, loss of patellar reflex

what is a winged scapula? injury to what nerve causes it? at what level does that nerve originate?

winged scapula is caused by paralysis of the serratus anterior m., and the scapula appears to pop out of the back. patient cannot abudct the arm above horizontal without serratus anterior. injury to the long thoracic n. (C5-C7 root origin)