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The patient was a modest 69 year old man, the retired director of a large firm. He consulted me in May 1984 because of trouble with his legs. This had started in December of the previous year, with altered sensation in his feet; at first they felt “itchy”, then gradually “leathery”. In February the back of his thighs had started to feel numb, later his left buttock as well. In the past month his sexual potency had decreased and he had twice been incontinent of faeces. On examination muscle power was completely normal. I confirmed decreased skin sensation in the feet, the back of the left thigh, and in the perineal region. Both ankle jerks were absent and the left knee jerk was decreased; the plantar responses were normal.
Given the combination of sensory deficits in sacral dermatomes and disturbances of voiding and erection, I suspected a problem in the conus medullaris or (despite the absence of pain) in the cauda equina—perhaps a tumour. For the benefit of the younger readers I should clarify that at this time MRI was not yet anywhere in sight on the medical scene. The patient was admitted for a myelogram of the lumbar region, which showed only a dural cyst at the level of the S2 root on one side. The CSF showed one white cell/mm3 and a slightly increased protein level. After some hesitation—on my part as well as that of the neurosurgeons—this abnormality was surgically explored but nothing other than a cerebrospinal fluid filled cyst was found. A subsequent EMG showed positive waves and fibrillations in the quadriceps, gastrocnemius, and erector spinae, at several levels.
These EMG findings should have alerted me …