What is Peroneal Neuropathy

WHAT IS INVOLVED

Peroneal Nerve

LOCATION

– Most frequently at the Head of the Fibula
– Could be just above or below it involving the Common Peroneal Nerve or the Deep or Superficial branches selectively

COMMON SYMPTOMS

– Foot drop
– Patient unable to pull foot or toes up
– Usually unilateral, could be bilateral
– No associated pain
– Main complaint is tripping, falling
– Occasional leg/top of foot numbness
– Symptoms always present, no night/day preference

ONSET

– May be Sudden
– Or Gradual over a few days

RISK FACTORS

– No gender preference
– Diabetes or family history of Diabetes, Alcoholism or other occupational or nutritional causes of Neuropathies, HIV infection
– Can be seen following rapid weight loss from a drastic diet
– Usually from leg crossing
– Can be from knees leaning against a sharp edge (desk, waste basket under desk)

EXAM

– When first seen, weakness but no muscle atrophy
– Patient unable to pull foot or toes up
– Check for non-Peroneal muscles involvement such as Posterior Tibialis or Flexor Digitroum Longus to make sure this is not a root lesion
– May have positive Tinel (tingling upon tapping nerve) sign at the Fibular Head

LOCALIZATION

– Check the Peroneus Longus by foot eversion, Tibialis Anterior by foot dorsiflexion and sensation over dorsum of foot:
– If Peroneus Longus + Tibialis Anterior involved + decreased dorsum foot sensation -> Common Peroneal lesion at or above Fibualr Head
– If Peroneus Longus involved + decreased dorsum foot sensation but Tibialis Anterior spared -> Superficial Peroneal lesion usually below Fibualr Head
– If Peroneus Longus spared and dorsum foot sensation preserved but Tibialis Anterior involved -> Deep Peroneal lesion usually below Fibualr Head

EMG

– Very Good for localization across the Fibular Head
– Very Good for Prognostic value:
– In pure myelin lesions (conduction block), recovery may occur after three weeks to a month
– In moderate/severe axonal lesions, recovery may take from 6 months to a year
– In mixed lesions, somewhere in between

– Shows slowing and/or drop in Extensor Digitorum Brevis amplitude across compression area in myelin lesions (slowing seen in segmental demyelination, amplitude drop seen in conduction block)
– Diffuse drop in Extensor Digitorum Brevis amplitude with or without slowing in axonal lesions
– Mixture of above in mixed lesions
– Superficial Peroneal sensory spared in lesions of the Deep Peroneal, affected in lesions of the Comon Peroneal Nerve
– Always check to make sure non-Peroneal muscles (such as Posterior Tibialis and or Flexor Digitorum Longus) were sampled to rule out a root lesion

RECOMMENDATIONS

– Symptomatic treatment
– Stop/decrease cause, change/stop diet
– Leg brace (plastic) to maintain heel in dorsal flexion and prevent falls, also to help prevent tightening of Achilles tendon which will make recovery difficult
– Brace specially useful in moderate to severe axonal lesions which take longer to recover
– Passive foot, toes Range of Motion by PT

WHAT ELSE COULD IT BE?

– Can be a severe long standing Neuropathy
– If accompanied by bowel/bladder symptoms, could be Cauda Equina lesion
– Can be seen in late stages of Multiple Sclerosis
– Suspect (Amyotrophic Lateral Sclerosis) ALS if other muscles are involved and/or Fasciculations are present
– Very rarely, Myotonic Dystrophy may cause weak, wasted legs and bilateral foot drop