BRAINSTEM EVOKED POTENTIALS IN PATIENTS WITH CENTRAL POST-STROKE PAIN. Ian Mackenzie*, Francis McGlone, and G;jran Leijon, Pain Research Institute, Walton Hospital, Liverpool L9 lAE, U.K.

AIM OF INVESTIGATION: To determine the state of the

Poster 91 BROWN Mon-Tuer ACC Hall E Abs No 398

brainstem in cases of stroke producing somatosensory deficit and pain. METHODS: Pure tone audiograms were performed on 17 CPSP patients with

lesions localised by magnetic resonance scanning. Pure tone audiograms showed that none of these subjects had a hearing deficit in excess of 45 dB. 2048 clicks at 70 dBSL were applied successively to each ear, and recordings made from electrodes placed on both mastoid processes and the vertex, and recorded and averaged on a Medelec Sensor.

RESULTS : In all cases, the latency between waves I (acoustic nerve) and V (midbrain) was prolonged, compared with published normal material (Stockard & Rossiter, Neurology, 27, 1977). In 8 cases the latency on the side contralateral to the lesion was extended; in 7 of these, the ipsilateral latency was also slightly increased, while in the other it was decreased. In 7 cases the ipsilateral latency was prolonged, with the contralateral latency also being extended, but less so, in 6, and the contralateral latency being reduced in one. In the other two cases, both contra- and ipsi- lateral latencies were equally extended.

CONCLUSIONS: These results reveal evidence of infratentorial conduction abnormalities in all cases. These will be discussed in relation to magnetic resonance image, findings, which in some cases revealed multiple lesions.

J.Lankers, A.Frieling, B.Bromm, Inst. of Physiology, _I

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University of Hamburg, 2000 Hamburg 20, FRG Abs No 399

FUNCTIONAL MONITORING OF PAIN AND TEMPERATURE SENSITIVITY Poster 92 IN PATIENTS WITH SYRINGOMYELIA BY C02-LASER EVOKED CEREBRAL BROWN Mon-Tues POTENTIALS.

The most frequent symptoms in patients with syringomyelia are an impair- ment of both pain and temperature sensitivity. The aim of this study was to objectify these symptoms with neurophysiological methods.

Late cerebral potentials (latencies of more than 100 ms) evoked by a CO -laser (LEP) were investigated in 10 patients (8 men, 2 women) with MR$- or CT-confirmed syringomyelia. Stimuli (20 ms duration, 5 mm beam diameter, 15 and 20 W intensity, randomized order) were applied to the most affected and to the contralateral skin area, for comparison. In ad- dition, conventional somatosensory evoked potentials (SEP, early and late components) were measured.

Whereas in all clinical cases the late components of the SEP were nor- ma1 , the LEP was absent in 8 cases, delayed and diminished in 1 case. In 1 patient with loss in temperature but undiminished pain sensitivity, the LEP was normal. In 3 patients early components of the SEP were ab- sent (1 case) or delayed (2 cases). These 3 patients also had disturban- ces of mechanosensibility.

To sum up: In all cases with a strict dissociated sensory loss, LEP was significantly decreased whereas the SEP remained unaffected. As such, LEP are a useful supplement to SEP in the investigation of spinal pathways.

Supported by DFG (Br 310/16); we thank the Dept. of Neurology for the referral of the patients.