Peroneal Nerve Palsy: A Comprehensive Overview
Peroneal nerve palsy is a common neurological condition that affects the lower extremity. It is most often caused by compression of the peroneal nerve, leading to a condition commonly known as foot drop. The peroneal nerve is responsible for the motor control of the muscles involved in dorsiflexion and eversion of the foot. When this nerve is impaired, it can lead to a significant loss of function, causing difficulty with walking, standing, and overall mobility.
Anatomy of the Peroneal Nerve
The common peroneal nerve (CPN) is derived from the nerve roots L4, L5, S1, and S2 as part of the sciatic nerve. It travels down the lateral and posterior aspect of the thigh, giving off several branches. The nerve splits at the upper popliteal fossa to form the superficial and deep peroneal nerves, which are responsible for motor and sensory functions in the leg and foot.
At its most vulnerable point, the peroneal nerve runs around the fibular head, making it susceptible to compression at this site. This anatomical feature is one of the primary reasons why the fibular head is the most common location for peroneal nerve entrapment. The deep peroneal nerve (DPN), which controls dorsiflexion of the foot, is particularly prone to injury due to its proximity to the fibula .
Causes of Peroneal Nerve Palsy
Peroneal nerve palsy can arise from a variety of causes, with compression being the most frequent. External pressure, such as prolonged sitting, leg crossing, or the use of restrictive devices like casts, can cause temporary compression. Trauma, such as knee dislocations or fractures, is another common cause, especially when the fibular head is impacted . Other factors include diabetes, which can lead to peripheral neuropathies, as well as iatrogenic causes such as surgical positioning or surgical procedures on the knee, hip, or ankle.
A significant risk factor for peroneal nerve palsy is rapid weight loss, which can lead to reduced subcutaneous fat around the fibular head, making the nerve more exposed to external forces . Additionally, habitual leg crossing and squatting have been identified as contributing factors to nerve compression .
Symptoms and Diagnosis
The hallmark symptom of peroneal nerve palsy is foot drop, which results in difficulty lifting the foot while walking. Patients often experience a steppage gait, where they raise their knee higher than normal to avoid dragging the foot . Sensory deficits, such as numbness or tingling along the lateral leg, dorsum of the foot, or the first web space, are also common. In some cases, patients may experience pain, particularly if the nerve injury is traumatic .
Physical examination plays a crucial role in diagnosing peroneal nerve palsy. A thorough assessment of the patient’s gait, muscle strength, and sensory function can provide vital clues. The “steppage gait” is often a key indicator, along with weakness in foot dorsiflexion and eversion . Electrodiagnostic studies, including nerve conduction velocity (NCV) and electromyography (EMG), are valuable for pinpointing the location of the nerve injury and evaluating the severity .
Management of Peroneal Nerve Palsy
The treatment of peroneal nerve palsy varies depending on the severity and cause of the condition. Most cases of mild or moderate palsy improve with nonsurgical treatment, which may include activity modification, the use of orthotics, and physical therapy. Bracing, such as a custom ankle-foot orthosis, can help patients with foot drop maintain proper foot clearance during walking .
In cases where conservative measures fail or if the nerve injury is severe, surgical intervention may be necessary. Nerve decompression is commonly performed to relieve pressure on the peroneal nerve at the fibular head. For traumatic injuries or lesions involving compressive masses, surgery may be required to repair or excise the affected tissue .
If a compressive mass such as an intraneural ganglion is identified, surgical removal may be indicated to prevent further nerve damage . Additionally, tendon transfer procedures, such as transferring the posterior tibial tendon to restore ankle dorsiflexion, can be used in cases where the nerve cannot recover fully .
Surgical Techniques for Nerve and Tendon Transfer
In cases where nerve decompression or repair does not yield satisfactory results, tendon transfers can be used to restore some function. The posterior tibial tendon (PTT) is commonly transferred to the lateral cuneiform to assist in restoring dorsiflexion . This procedure has shown promising results, particularly in patients with severe peroneal nerve injury. By transferring the PTT, it helps alleviate the deforming force that prevents normal foot movement.
Surgical tendon transfer may be performed either through a subcutaneous or interosseous membrane approach, with the latter offering biomechanical advantages by providing better dorsiflexion with minimal pronation .
Conclusion
Peroneal nerve palsy is a debilitating condition that significantly affects a patient’s mobility and quality of life. Early diagnosis and treatment are crucial for the best outcomes. While many patients recover with nonsurgical methods, surgical intervention may be required for more severe cases or those involving compressive masses. Advanced techniques such as tendon transfers and nerve decompression offer hope for restoring function in refractory cases .
