What is the treatment for peroneal mononeuropathy?

Treatment of Peroneal Mononeuropathy

The primary treatment for peroneal mononeuropathy involves specific padding to prevent pressure on the fibular head, avoidance of direct pressure on the nerve, and in refractory cases, surgical decompression may be necessary. 1

Etiology and Clinical Presentation

Peroneal neuropathy is the most common compressive neuropathy of the lower extremity 2. It typically presents with:

• Foot drop (weakness of ankle dorsiflexion)
• Numbness/paresthesia over the dorsum of the foot and lateral lower leg
• Pain along the lateral aspect of the knee and leg
• Gait abnormalities

Common causes include:

• Compression at the fibular head (most common site)
• Stretch injuries
• Entrapment as the nerve exits the lateral compartment
• Trauma or surgery
• Prolonged positioning (crossing legs, squatting)
• Weight loss
• Prolonged bed rest

Diagnostic Approach

1. Clinical examination:

   • Assess muscle strength (ankle dorsiflexion, toe extension, foot eversion)
   • Evaluate sensation over the dorsum of the foot and lateral leg
   • Check for Tinel's sign at the fibular head

2. Electrodiagnostic studies:

   • Motor and sensory nerve conduction studies
   • Electromyography to distinguish from L5 radiculopathy
   • Conduction block on nerve studies indicates better prognosis 3

Treatment Algorithm

First-Line Management:

1. Protective Padding:

   • Apply specific padding between the outside of the leg below the knee to prevent contact of the peroneal nerve at the fibular head with hard surfaces 1
   • Avoid excessively tight or restrictive padding 1

2. Positioning Modifications:

   • Avoid pressure near the fibular head from contact with hard surfaces or rigid supports 1
   • Avoid prolonged positioning that stretches or compresses the nerve (crossing legs, squatting)
   • Avoid tight casts, braces, or bandages around the knee

3. Supportive Measures:

   • Ankle-foot orthosis (AFO) for foot drop to improve gait and prevent falls
   • Physical therapy to maintain range of motion and prevent contractures

Second-Line Management:

1. Pharmacological Treatment (for neuropathic pain if present):

   • Gabapentin or pregabalin for neuropathic pain
   • Capsaicin cream may be considered for pain management 1
   • Note: Neuropathic pain is relatively uncommon in peroneal neuropathy at the fibular head 4

2. Electrical Stimulation:

   • Percutaneous electrical nerve stimulation should be considered for treatment of neuropathic pain 1

Refractory Cases:

1. Surgical Intervention:
   • Microsurgical decompression of the nerve at the fibular head 5
   • Indicated when conservative management fails after 3-6 months
   • Surgical release involves circumferential nerve dissection, fascial opening, and isolation of the major branches 5

Prognosis

• Approximately 90% of patients with non-traumatic acute-onset compressive peroneal mononeuropathy recover to a muscle strength of grade 4 or 5 3
• Positive prognostic factors include:
  • Conduction block on nerve conduction studies
  • Younger age
  • Less severe initial weakness 3
• Poor prognostic factors:
  • Denervation on needle electromyography
  • Older age
  • Severe initial weakness 3
  • Delayed treatment (>2 weeks) 6

Monitoring and Follow-up

• Regular follow-up to assess recovery of motor function
• Repeat electrodiagnostic studies may be helpful to monitor recovery
• Patients with poor prognostic factors should be monitored closely to facilitate timely surgical intervention if weakness persists 3

Clinical Pitfalls and Caveats

1. Don't confuse peroneal neuropathy with L5 radiculopathy or sciatic neuropathy - electrodiagnostic studies are essential for differentiation.

2. Inappropriate use of padding (too tight) may actually increase the risk of neuropathy rather than prevent it 1.

3. Failure to address the underlying cause (e.g., habitual leg crossing, ill-fitting furniture) may lead to recurrence.

4. Delayed treatment can lead to permanent nerve damage and persistent foot drop.

5. In cases with significant axonal damage, recovery may be prolonged or incomplete despite appropriate treatment.