B7-013 Peripheral Neuropathies Flashcards
the spinal cord ends at what vertebral level
L1
the lowest portion of the spinal cord is the
conus medullaris
where does C8 nerve root exit the spinal cord?
below C7 vertebrae
above T1 vertebrae
roots C1-C7 exit […] their respective vertebrae
above
lumbosacral and thoracic roots exit […] the correspondingly numbered vertebral bones
below
lumbrosacral roots travel several levels […] before exiting the spinal canal
caudally
typically, a disk herniation will effect the […] roots
lower
central disc herniations at the level of […] can impinge roots lower than the level of herniation
cauda equina
central disc herniations above […] can compress the cord causing conus medullaris syndrome
L1
extreme lateral disc herniations can effect the […] root
upper
apical lung lesions and thoracic outlet syndrome would effect the […] brachial plexus
lower
the upper brachial plexus is most commonly affected by […] in adults
trauma
the […] plexus runs through the retroperitoneal space
lumbosacral
**can be damaged by retroperitoneal hematoma or psoas abscess
cause of meralgia parethetica
lateral femoral cutaneous being trapped below the ilioinguinal ligament
cause of piriformis sciatica
sciatic nerve entrapped beneath the piriformis muscle
cause of peroneal nerve entrapment
entrapment of the common fibular nerve at the fibular head
cause of carpal tunnel syndrome
median nerve entrapment at carpal tunnel
cause of cubital tunnel syndrome
ulnar nerve entrapment at cubital tunnel
cause of Guyon’s canal
ulnar nerve entrapment at the wrist
why do disc herniations in the lumbar spine affect the lower root?
posterolateral dislocation impinges the root on its way to the next level
NCS typically measure the function of […]
large myelinated nerves
this is why patients with small fiber neuropathy can have normal NCS
if you have a disease causing nerves to die, the […] will be decreased on NCS
amplitude
if you have a disease affecting the myelin, the […] will be decreased on NCS
velocity
relatively preserved amplitude of response
myelinopathy
very slow velocities, long latencies, conduction block
myelinopathy
low amplitude response
axonopathy
relatively preserved velocities
axonopathy
spontaneous muscle activity on EMG shows
fibrillation (acute nerve denervation)
fasciculation
a single muscle fiber spontaneously firing
fibrillation
(acute denervation)
an entire motor unit spontaneously firing
fasciculation
(like eyelid twitch)
what would this pattern indicate?
chronic denervation/reinnervation
how are compound muscle action potentials measured?
using two stimulation points
how are sensory nerve action potentials measured?
directly off the nerve
typical nerves conduction velocities are around
50 m/sec
relatively preserved amplitude, slow conduction
demyelinating neuropathy
decreased amplitude, normal conduction velocity
axonal neuropathy
M waves
compound motor action potential
F waves
retrograde conduction to spinal cord along the motor axon
H reflex
deep tendon reflex stimulated electrically
describe EMG changes from acute denervation
fibrillations
describe EMG changes from chronic denervation
subsequent reinnervation causes large, wide complicated motor units
SNAPs are […] in radiculopathies
normal
(abnormal in plexopathy)
why are SNAPs normal in radiculopathies?
the sensory nerve cell body is distal to the damage so the axon doesn’t die
situations where NCV/EMG has poor sensitivity [4]
early disease
mild disease
focal neuropathy
small fiber neuropathy
SNAPs are […] in plexopathies
abnormal
fibrillation potentials in the cervical paraspinals would indicate damage to
cervical nerve root
paraspinals are innervated by the dorsal root
cervical nerve roots exiting the vertebral formina exit […] the correspondingly numbered vertebrae
above
located anatomically near the brachial plexus
mediates pupillary dilation
ascending sympathetics
in a patient with weakness/numbness of the arm, involvement of the ascending sympathetics indicates involvement of the
brachial plexus
burning pain between the thumb and index finger is caused by
handcuff neuropathy due to compression of the superficial radial nerve
generally, are EMG/NCS helpful for focal neuropathies?
no
when pathology is distal to the root, the paraspinal muscles will be […] on EMG
spared
when pathology involves the root, paraspinal muscles will be […] on EMG
affected
causes of meralgia parethetica
weight gain
tight belts
tool belts
leprosy has what pattern?
cool dependent pattern of involvement
(used to be the most common cause of cool dependent neuropathy)
