WHAT IS INVOLVED

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Peroneal Nerve


LOCATION

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- 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

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- 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

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- May be Sudden

- Or Gradual over a few days


RISK FACTORS

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- 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

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- 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

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- 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

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- 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

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- 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?

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- 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