CONGENITAL ENTRAPMENT OF THE LATERAL CUTANEOUS NERVE OF THE CALF PRESENTING AS A PERONEAL SENSORY NEUROPATHY

Objective: Presentation of an unusual case of congenital entrapment of the lateral cutaneous nerve of the calf (LCNC) mimicking a peroneal s ensory neuropathy. Methods: We report the case of a 16-year-old girl w ith a 3 year history of progressive tingling, numbness and pain in her right calf precipitated by athletic activities involving repeated fle xion and extension of the knee. A Tinel's sign was present over the co mmon peroneal nerve in the distal popliteal fossa but absent at the fi bular neck. Motor and sensory examination of the common peroneal nerve was normal as were electrophysiological studies and MRI. Results: At surgery, the LCNC, a sensory branch of the common peroneal nerve, was entrapped at a point where it pierced the tendon of the biceps femoris muscle. Transection of the part of the tendon overlying the LCNC resu lted in complete and permanent relief of symptoms. Significance and Co nclusion: The proximal location of the Tinel's sign, absence of motor or sensory deficits and normal electrophysiology suggested, preoperati vely, that this was not an entrapment of the common peroneal nerve at the fibular neck but rather a more proximal abnormality likely involvi ng only a part of the peroneal nerve or one of its sensory branches. A s a result, more proximal exposure of the peroneal nerve within the po pliteal fossa revealed entrapment of the LCNC due to its anomalous cou rse through the biceps femoris tendon. This case has two noteworthy fe atures. It is a unique example of an entrapment neuropathy of the comm on peroneal nerve or one of its branches, due to a normal nerve pierci ng an otherwise normal tendon. Secondly, then are no previously report ed cases of surgically documented compression of the LCNC in an otherw ise normal patient (i.e., non-diabetic).