Ischaemic sensory loss in patients with spinal and cerebral lesions.

In an investigation which has already been reported (Gilliatt and Wilson, 1954), sensation in the fingers was studied during periods of ischaemia of the arm, the ischaemia being produced artificially by inflating pneumatic cuffs to above arterial pressure round the limb. In a group of normal subjects examined after the inflation of a pneumatic tourniquet above the elbow, the mean duration of ischaemia required to produce subjective numbness of the finger-tips was 14 minutes, but when patients with peripheral nerve lesions were tested in this way, it was found that sensation failed with abnormal rapidity in areas of skin supplied by a damaged nerve, so that an area in which sensation was initially only mildly disturbed might, within five or 10 minutes, become sharply demarcated from the rest of the hand. The abnormally rapid failure of sensation during ischaemia in an area of initial sensory impairment did not appear to be due solely to the local effect of asphyxia on damaged fibres, as it occurred in patients with dorsal root lesions and with nerve lesions proximal to the site of the pneumatic cuff. As an explanation it was suggested that while some of the sensory fibres in an ischaemic nerve would be blocked by the ischaemia, a proportion would continue to conduct impulses under the pneumatic cuff; of these, however, a further proportion would be blocked by any lesion at a higher level, so that the total effect on sensation would be an additive one. This suggested that a sensory deficit at any level in the nervous system might be exaggerated by the addition of a partial peripheral nerve block, the peripheral block by itself being insufficient to produce sensory loss. The present investigation of patients with spinal and cerebral lesions was undertaken to explore this possibility.