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Nerve Entrapment Guide: Thigh / Leg / Foot Problems

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