Daniel G. Hackam and Thomas J. Zwimpfer

Abstract: Objective: Presentation of an unusual case of congenital entrapment of the lateral cutaneous nerve of the calf (LCNC) mimicking a peroneal sensory neuropathy. Methods: We report the case of a 16-year-old girl with a 3 year history of progressive tingling, numbness and pain in her right calf precipitated by athletic activities involving repeated flexion and extension of the knee. A Tinel's sign was present over the common peroneal nerve in the distal popliteal fossa but absent at the fibular 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 resulted in complete and permanent relief of symptoms. Significance and Conclusion: The proximal location of the Tinel's sign, absence of motor or sensory deficits and normal electrophysiology suggested, preoperatively, that this was not an entrapment of the common peroneal nerve at the fibular neck but rather a more proximal abnormality likely involving only a part of the peroneal nerve or one of its sensory branches. As a result, more proximal exposure of the peroneal nerve within the popliteal fossa revealed entrapment of the LCNC due to its anomalous course through the biceps femoris tendon. This case has two noteworthy features. It is a unique example of an entrapment neuropathy of the common peroneal nerve or one of its branches, due to a normal nerve piercing an otherwise normal tendon. Secondly, there are no previously reported cases of surgically documented compression of the LCNC in an otherwise normal patient (i.e., non-diabetic).

Can. J. Neurol. Sci. 1998; 25: 168-170