Spinal nerve roots, plexus Flashcards
Positioning of fibers in the cauda equina?
head is medial, sides add on as going down to legs most lateral
Disc herniations cause involvement of what nerve root? Which direction do they usually herniate?
The lower one, usually herniate laterally
Where do most nerve roots exit compared to the vertebrae?
What is the exception?
Thoracic, lumbar, sacral roots exit below the numbered vertebrae.
Cervical nerve roots exit above, except C8, which exits between C7-T1
Spot common for spread of mets / infx in the spinal cord?
Batson’s plexus: mesh of epidural veins
ligament causing hypertrophy and compression in spinal cord
Ligamentum flavum
Two nerve systems (3 nerves) responsible for sensation of face/head (dermatomes)
Trigeminal and C2 (greater and lesser occipital nerves)
Dermatome shoulder
C5
Dermatome lateral arm and first two digits
C6
Dermatome middle digit
C7
Dermatome fourth/fifth digits
C8
Dermatome anteromedial shin?
L4
Dermatome anterolateral shin and dorsum of foot / big toe?
L5
Dermatome small toe, lateral foot, sole, calf
S1
Most common cervical disc herniation problem and its symptoms?
C7 roots from C6-7 herniation, causes weakness of tricep, loss of tricep reflex, loss of sensation in third finger.
Symptoms of C4-5 disc problem?
C5 nerve root damage causing weakness of delt, infraspinatus, bicep, decr bicep/pectoralis reflex, and loss of sensation of shoulder, upper lateral arm
Symptoms of C6 nerve root problem?
Weakness of bicep, wrist extension, loss of bicep/BR dtr, loss of sensation of lateral forearm and sensation of 1st/2nd fingers
Sx of C8 radiculopathy?
Weakness of intrinsic hand muscles, loss of sensation of 4/5th digits and medial forearm
Sx of T1 radiculopathy
just medial arm numbness without motor. Can also cause horner’s.
Sx of L4 radiculopathy?
Weak iliopsoas and quad, loss of knee dtr, loss of sens of knee, medial lower leg
How to distinguish femoral neuropathy from L4 radiculopathy?
Weak thigh adduction in radiculopathy
Sx of weak foot dorsiflexion, big toe extension, foot inversion/eversion, and loss of sensation of foot dorsum, big toe
L5 radiculopathy (L4-L5 herniation)
Peroneal neuropathy vs L5 radiculopathy
weak foot inversion with radiculopathy
What is neurapraxia?
Temporary impairment after mild mechanical disruption, lasting hours-wks
Rate of axonal regeneration if structural elements are intact after Wallerian degeneration of distal nerves
1mm/day
Abs in Myasthenia? (two)
Anti-AchR-Ab: against POST-synaptic nicotinic ACh receptors (85% in generalized, 50% in ocular)
Anti-MuSK Ab: muscle specific tyrosine kinase Abs if neg AChR Ab
In MG, what do you see with RNS at 3/sec?
Decrement in CMAP amplitude >10%
Percent of MG with thymoma?
12%
Acronym for Brachial Plexus?
RTDCB: Roots, trunks, divisions, cords, branches: RT Drinks Cold Beer
Thumb movements act out:
in plane abduction?
in plane adduction?
Opposition?
Radial, ulnar, median:
R spread, U unite, M oppose (meet)
Supply for thumb abduction perpendicular to plane of palm? Why important?
Median nerve branch abductor pollicus brevis after passage through carpal tunnel, so should be WEAK in CT!
Name the nerve branches of the posterior cord
STAR: Subscapularis, Thoracodorsal, Axillary, Radial
Muscles innervated by the musculocutaneous nerve?
BBC: biceps, brachialis, coracobrachialis
What is Erb Duchenne palsy? What is involved, what is the position?
Upper brachial plexus TRUNK injury of C5 and C6, causing Bellman’s / Waiter’s tip position with arm held at side, internally rotated, and wrist flexed with spared hand and fingers.
Weak shoulder, elbow, wrist extensor.
What is a lower trunk injury called, what does it involve, and what is the positioning.
Klumpke’s palsy - C8-T1, causes hand and finger weakness, ulnar side sensory loss of hand/forearm, atrophy of hypothenar muscles
Causes of lower brachial plexus trunk injury: 3
- upward traction (grabbing tree branch during fall)
- thoracic outlet
- pancoast
nerve damaged in upper humeral fracture and what does it cause?
Axillary: deltoid weakness, shoulder numbness
What is Parsonage-Turner syndrome?
brachial plexitis (inflammatory) causing burning shoulder and lateral neck pain with weakness lasting 6-12 wks
What is spared of the median nerve supply in Carpal tunnel?
wrist flexion, 2/3 digit flexion, and sensation over thenar eminance b/c branches are before the carpal tunnel. BUT thumb abduction out of plane should be weak
Nerve branch for hip flexion, knee extension with sensory loss medial LE and knee cap? How does this occur?
femoral nerve, can occur from neuropathy in pelvic area issues or from meralgia paresthetica in obesity, pregnancy with entrapment in inguinal ligament
Nerve branch for thigh adduction, and small inner thigh patch sensation?
obturator
Nerve for knee flexion, sensation of lateral foot / leg, bottom of foot
Sciatic
Nerve for plantarflexion, foot inversion, toe flexion, sensory sole of foot
tibial
nerve for foot eversion, sensory lateral leg and top of foot
superficial peroneal
nerve for foot dorsiflexion and toe extension, and inner big toe sensation?
deep peroneal (palsy causes foot drop)
What is recruitment on EMG? What is the pattern with myopathic vs neuropathic conditions?
Recruitment is continuous firing pattern when muscle is voluntarily contracted.
In myopathy it is continuous / increased b/c more motor units are activated to get force, but amplitude is decreased.
In neuropathy it is reduced/interrupted b/c some motor units aren’t activated by the voluntary contraction.
Motor unit potentials are small in duration and amplitude in neuropathic or myopathic conditions?
myopathic
third digit sensory disturbance
What radiculopathy?
C7 radiculopathy
C5 vs C6 radiculopathy?
Both have shoulder abduction and external rotation and elbow flexion weakness. C5 sensory is shoulder and upper lateral arm.
C6 has more motor issues with forearm pronation and wrist extension and radial flexion weakness, and sensory for C6 is lateral forearm and 1st two digits
radiculopathy in finger abduction, thumb opposition and abduction weakness and sensory digit 4/5 and medial forearm/arm
C8/T1
scapular winging
long thoracic nerve causing serratus anterior winging
Saturday night palsy?
radial nerve palsy with arm stuck flexed at elbow and wrist, pronated, and fingers flexed, and radial sensory loss in posterior arm/hand.
arcade of Frohse?
like radial nerve saturday night palsy but with elbow spared due to posterior interosseus nerve entrapment
Benediction sign
ulner nerve palsy with claw hand, hyperextension of 4/5th digit which are flexed and can’t extend
