LE PNS Disease Flashcards
sciatic neuropathy
Hx posterior trauma, posterior hip dislocation, posterior approach hip replacement, tight piriformis
may affect tibial or common fibular n.; usually common fibular fibers (dorsiflexion, eversion)
Px: weakness w knee flexion +/- ankle and toe mover weakness
sciatic neuropathy EDX
NCS: abnormal sural (courses posterior leg and around lateral malleolus) and superficial fibular (coruses anterior ankle from common fibular and tibial n.) SNAPs abnormal EDB (deep fibular n.) and AbH (tibial n) CMAP
EMG: decreased recruitment (machine gun) MUAPs, fibs/sharps in all sciatic n. muscles, polyphasicity
all: esp hamstrings; if normal, lesion may be more distal in common fibular/tibial pathway
common fibular neuropathy
injury to common fibular n. (squatting, crossing legs) typically as it wraps around the fibular head → foot drop, toe extension weakness, eversion weakness + abnormal sensation to entire dorsum of foot (except 1st web space) and lateral leg
sciatic n. posterior thigh → tibial and fibular branches → fibular splits to superficial and deep fibular n. →
superficial: fibularis longus, fibularis brevis (plantar flexors and evertors) + sensation to dorsum of foot (except 1st web space) and lateral leg
deep: (anterior compartment muscles) TA, EDL, EHL, EDB
common fibular neuropathy EDX
PE: positive Tinel at fibular head
NCS: abnormal superficial fibular and sural SNAPs
normal medial and lateral plantar SNAPs
abnormal EDB and TA CMAP (?conduction block across fibular head)
EMG: decreased recruitment, fibs/sharps in TA, EHL, EDB, fib longus, fib brevis; polyphasicity
DDx superficial v deep fibular neuropathy - PE
superficial fibular n. → lateral compartment → fibularis longus, fibularis brevis → foot eversion weakness; abnormal sensation over lateral leg and dorsum of foot EXCEPT 1st web space
deep fibular n. → anterior compartment → TA, EDB, EDL, EHL → foot drop and weakness with toe extension; abnormal sensation in 1st web space
DDx superficial v deep fibular neuropathy EDX
superficial
NCS: abnormal superficial fibular SNAP
EMG: abnormal activity in fibularis longus and brevis
deep
NCS: normal superficial fibular SNAP
EMG: abnormal activity in TA/EHL/EDL/EDB
tarsal tunnel syndrome Px
intrinsic foot weakness, abnormal plantar sensation (medial/plantar terminal branches of tibial n.)
PE: +tinel at ankle
tarsal tunnel syndrome EDX
NCS: abnormal medial and plantar SNAPs
abnormal CMAP to AH (medial plantar n.)
EMG: abnormal activity in AH, lumbricals, interossei, ADQP
femoral neuropathy Px
weakness of knee extensors (knee buckling), abnormal sensation to anterior thigh and medial leg (saphenous n.)
usually d/t diabetic lumbosacral plexopathy; also consider anterior hip dislocation, retroperitoneal hematoma, compression under inguinal ligament
femoral neuropathy EDX
NCS: abnormal saphenous n. SNAP and femoral nerve CMAP (rectus femoris)
EMG: abnormal activity in quads
be sure to test obturator (L2, 3, 4) n. muscles: adductor, gracilis → if abnormal, suggests L3 radiculopathy rather than femoral neuropathy
L3 radiculopathy v femoral neuropathy - DDx on EDX
test obturator (L2, 3, 4) n. → adductor muscles and gracilis
if abnormal, suggests L3 radiculopathy rather than isolated femoral neuropathy
saphenous neuropathy
Hx knee arthroscopy, trauma
courses between vastus medialis and sartorius
Px abnormal sensation to medial leg +/- medial knee
saphenous neuropathy EDX
NCS: abnormal saphenous SNAP
EMG: normal
saphenous n. is pure sensory branch for femoral n. (L2, 3, 4)
obturator neuropathy
obturator n. (L2, 3, 4) → thigh adductor longus/magnus/brevis inn.
Hx pelvic fx, trauma
adductor weakness + abnormal sensation medial thigh
obturator neuropathy EDX
NCS: normal routine SNAPs (sural, superficial fibular)
normal routine CMAPs (EDB, AH)
EMG: abnormal activity in thigh adductors
lateral femoral cutaneous neuropathy
AKA meralgia paresthetica
usually d/t tight inguinal ligament
Hx rapid weight loss, tight belt, obesity
Px: abnormal sensation and burning pain over ovoid patch atnerolateral thigh d/t entrapment/irritation of LFCN
LFCN EDX
NCS: abnormal SNAP to LFCN
EMG: normal
lumboscaral plexopathy v radiculopathy
EMG paraspinals (solely inn’d by dorsal rami of lumbosacral plexus) → if abnormal, suggests radiculopathy
ventral rami of L1-S4 → lumboscaral plexus
lumbosacral plexopathy EDX
variable findings
paraspinals normal (inn’d by dorsal rami)
ventral rami → plexus
radiculopathy EDX Dx pearls
NCS: normal SNAPs - injury is proximal to DRG and we are testing peripheral nerves distal to DRG
abnormal CMAPs to muscles belonging to affected n. roots
abnormal H1 reflex in S1 radiculopathy
EMG: abnormal activity in all muscles inn’d by injured n. root
- must test 6 muscles in a “root screen”
- paraspinals at affected level will be abnormal; v normal in plexus injury (injury distal to n. roots)
- must demonstrate abnormalities in 2 muscles that share same n. root but have diff peripheral n. inn (e.g., C6 radiculopathy showing abnormalities in PT (C6,7 → median n.) and BR (C5, 6 → radial n.)
n. root avulsion
tearing off n. roots d/t trauma, very poor prognosis bc n. must grow all the way down extremity, won’t realistically happen
p/w numbness in affected dermatome and weakness in affected myotome
NCS: normal SNAPs, absent CMAPs
SNAPs normal bc peripheral axon is still intact
EMG: abnormal spontaneous activity in muscles of affected myotome + abnormal spontaneous activity in affected paraspinals
