Wahba Part 1 - Foot Drop + CIDP Flashcards
Differential for unilateral foot drop
Common peroneal neuropathy, L5 radiculopathy, lumbosacral plexopathy, sciatic n. lateral trunk
Differential for chronic bilateral foot drop
Myotonia atrophica, Charcot Marie Tooth, polyneuropathy, ALS, distal myopathy (rare)
What’s spared with peroneal mononeuropathy?
Ankle inversion, plantar flexion, and ankle jerk
Presentation of CMT1
Distal weakness/wasting, pes cavus, arreflexia, mild sensory loss, thick peripheral nerves
Presentation of CMT2
Later onset; nerve conduction velocity relatively normal - axonal>demyelinating pathology; Dx w/ slow nerve conduction, segmental demyelination, hypertrophy
Anatomical course of common peroneal nerve
L5-S3 of sciatic nerve, travels w/ tibial division - motor branch to short head of biceps femoris, sensation to lateral knee. Separates in popliteal fossa, travels around fibular head, pass thru fibular tunnel, divides into superficial+deep peroneal nerves
Presentation for compression at fibular head
Lose dorsiflexion, eversion; lose sensation to anterolateral leg+dorsum of foot. Pt would have tendency to invert foot and high stepping gait
Presentation for entrapment of deep peroneal nerve in anterior tarsal tunnel
Weak toe dorsiflexion, sensory loss in 1st dorsal web space, spares eversion, foot drop, high stepping gait
Presentation for entrapment of superficial peroneal nerve at fascial exit on anterolateral leg
Weak eversion, sensory loss to anterolateral leg/dorsum of foot, dorsiflexion spared
Sensory loss for L5 Root
BIG TOE, MORE MEDIAL
Etiology of L5 radiculopathy
L4-5 disc herniation, spinal canal stenosis, prolapsed disc
Features of L5 radiculopathy
Lower back pain, pain radiating down leg (sciatica), weakness in extensor hallucis longus+ankle dorsiflexors+ peroneal muscles, ankle inversion+toe flexion weak, lose big toe sensation
S1 radiculopathy
Weak gastrocnemius+soleus+no ankle jerk
Innervation of gluteus muscles and tensor fascia lata
Gluts medius+maximus by L5-S1; TFL by L5
Other causes of foot drop
Pushing something heavy (disc herniation?), pelvic surgery (retroperiotoneal hematoma of lumbosacral plexus), cancer of pelvis, tight cast,
Muscles innervated by tibial nerve L5
Paraspinals, gluteus medius, TFL, flexor digitorum longus, tibialis posterior
3 reasons to EMG a foot drop (instead of MRI)
1) asymptomatic discs (I’m assuming she meant the disc may not always cause the foot drop so MRI is less helpful) 2) MRI can miss lateral disc herniation 3) Pts in which MRI is xindicated
Interpretation of Sensory Nerve Action Potential (SNAP)
Slow or absent across fibular head = common peroneal head entrapment; sural-saphenous SNAP absent = sciatic (higher); Normal SNAP = lesion in root only; SNAP gone = lesion in plexus or peripheral nerve
Causes of peroneal nerve compression @ fibular head
Anesthesia/surgery, prolonged hospitalization, THA?, braces/cases, leg crossing, DM, polyneuropathy, Baker’s cysts
What to do if you see a foot drop in first 12-24 hrs
Do stuff! Admit to hospital, consult neuro, imaging STAT, steroids
Chronic Inflammatory Demyelinating Polyneuropathy -“GAINS” mnemonic
GRADUAL progressive weaknessARREFLEXIAINCREASED CSF w/o increase cell countNERVE demyelinationSTOCKING-glove pattern
Stepwise progression in CIDP
Stepwise w/ periods of plateau - symmetric prox+distal weakness (esp hip flexors), mostly motor Sx, may start focal, spares breathing muscles
Spinal tap findings for CIDP
Same as MS - increased protein >45, increased IgG, oligoclonal bands
EMG findings
F WAVE
Etiologies of CIDP
CTD, CMV, Hodgkin’s lymphoma, hepatitis, HIV, IBS, Lyme, MS, radiculoplexopathy
Other issues w/ CIDP
Heme issues (M protein spike)
