Common peroneal nerve (CPN), the most common nerve involved in lower limb neuropathies across all age groups. Ordinarily, non-traumatic  common peroneal mononeuropathies are not explored beyond electrophysiological studies (EPS) and aetiology often remains unknown.

Consecutive patients presenting with symptoms and signs of non-traumatic common peroneal mononeuropathy were recruited over a period of 3 years.  Patients were also screened for specific causes of mono-neuropathy as decided by the treating physician; Hansen’s disease was ruled out by relevant clinical examination and investigations. All patients had nerve conduction studies (NCS) and electromyography (EMG) for lesion localisation. In patients with localisation along CPN by EPS were advised MRN.

Thirty-two patients (26 males) with clinical diagnosis of common peroneal mononeuropathy underwent EPS.  Median age at presentation and time from onset to EPS were 37.28 years (range 9-70 years) and 14.4 months (range: 1-18 months) respectively. Electrophysiology could localise lesion along the CPN in 30 patients (93.75%); two patients had isolated involvement of deep peroneal nerve.  MRN was available in 19 (59.38 %) patients. MRN could confirm the involvement of CPN in 17 out of 19 patients. Peroneal neuritis (n=7) was the commonest cause of common peroneal neuropathy, followed by nerve sheath tumour (n=4). Compression of CPN by ganglion cyst, osteochondroma and neurofibroma were seen in 3,2,1 patients respectively. MRN and EPS were in agreement in 18 (94.74%) patients.

Our study identified various aetiologies of common peroneal mononeuropathy;  peroneal neuritis was the commonest cause identified followed by nerve sheath tumour. A high degree of correlation between MRN and EPS was also observed in our cohort. This study reinforces the role of MRN in the evaluation and management of patients with mononeuropathies.