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The answer to the case “Leg Numbness and Tingling” (JW Neurol May 4 2010) is bilateral compression/entrapment of the saphenous nerves at or near the adductor canal, in the area of the medial epicondyle of the femur.
Approximately 60% of respondents had the correct diagnosis. Of the incorrect diagnoses, peroneal neuropathies, lumbar compression, and Lyme disease were mentioned several times. Myositis ossificans was mentioned twice.
In this patient, the need to exert excessive pressure to adduct the thighs to be able to stay on her unruly mount resulted in compression of both saphenous nerves. Her being overweight increased the pressure needed to avoid being bucked off. Numbness of the medial lower extremity from knee to ankle is seen in saphenous nerve lesions and may also be seen with L4 radiculopathies, but one would expect the knee jerk to be decreased, which it was not in this patient.
This case provides two important lessons: First, when the physician is confronted with what seems to be a peripheral nerve lesion, it is useful to compare the sensory findings to sensory maps found in standard texts such as Peripheral Nerve Injuries: Principles of Diagnosis by Haymaker and Woodhall. This would have eliminated peroneal neuropathy as a possibility. Second, attention to detail in the patient's history may give important clues to the anatomic localization and to the pathophysiology. As Charcot, the father of neurology, famously stated, “Listen and the patient will give you the diagnosis.”