What is Peroneal Neuropathy

The peroneal nerve is a branch of the sciatic nerve, which supplies movement and sensation to the lower leg, foot and toes. Common peroneal nerve dysfunction is a type of peripheral 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 Digitorum 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:

• Common Peroneal lesion at or above Fibular Head: If Peroneus Longus + Tibialis Anterior involved + decreased dorsum foot sensation
• Superficial Peroneal lesion usually below Fibular Head: If Peroneus Longus involved + decreased dorsum foot sensation but Tibialis Anterior spared
• Deep Peroneal lesion usually below Fibular Head: If Peroneus Longus spared and dorsum foot sensation preserved but Tibialis Anterior involved

EMG

EMG is very good for localization across the Fibular Head and for prognostic value.

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

Findings

• 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 Common 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