Short-latency somatosensory-evoked potentials in healthy Thais.

Median, ulnar and tibial short-latency somatosensory-evoked potentials were recorded from 112 neurologically normal subjects. Absolute latencies and interpeak latencies were analysed. Absolute latencies were correlated with height (r=0.37-0.59, P<0.01) but not with age (r=0.16-0.55, P>0.05). Interpeak latencies were not correlated either with height or age, except median/ulnar N9-N19 which were correlated with age and height (r=0.34, .044, P<0.01). Males had longer absolute and interpeak latencies than females (P<0.05) which were probably due to height difference (P<0.001). Hence, height is the most important variables for predicting absolute latencies, except in age group over 60 year old that the absolute and interpeak latencies were significantly delayed (P<0.05). The equations foe such predictions were verified. Hence, any absolute latencies should be corrected for height prior to considering them to be abnormal.

Diagnostic values of short latency somatosensory evoked potentials in stroke.

Short latency somatosensory evoked potentials (SSEPs) were elicited by stimulation of the median and tibial nerves in 55 patients with cerebrovascular diseases. There were 28 males and 27 females. The mean age was 52.7+14.9 years (range 20-83). Every patient presented as an acute hemiplegic with and without sensory loss. The CT findings were classified into 6 groups, thalamic, internal capsule, subcortical white matter, basal ganglia, occlusion of proximal branch of middle cerebral artery and transient ischemic attack. The abnormality rate of median SSEPs was 63.6 percent (35/55) and tibial SSEPs was 67.3 percent (37/55). In thalamic stroke both median and tibial SSEPs abnormality rates were 80 percent (8/10), in ganglionic stroke the rates were 75 percent (9/12). The internal capsule abnormality rates were 75 percent (9/15). Subcortical white matter there was 57.1 percent (4/7) and 80 percent (8/10) in occlusion of the main branch of middle cerebral artery. The SSEPs specificity, positive and negative predictive values between cerebral hemorrhage and infarction were 42.8, 47.4 and 87.2 percent respectively. Hence, SSEPs might be of value in localizing anatomical lesions but not to differentiate between hemorrhagic and ischemic stroke.

Sex influence on somatosensory evoked potentials in Thais.

Short latency somatosensory evoked potentials (SSEPs) is a new noninvasive electrophysiological technique that is very useful in the assessment of proprioceptive afferent system in man. Limited normative data in Asians were studied in Taiwan and Japan only. As yet there are no normal values for Thais. The latencies and central conduction times of the SSEPs in 112 neurologically normal Thais, aged 18-74 years were reported and the influence of sex difference investigated. The subjects enrolled were 58 males and 54 females with a mean height of 164.31+7.86 cm and 158.89+5.87 cm respectively. the latencies of brachial plexus, cervical cord and somatosensory cortex in males were significantly longer than for females (p<0.05). But the central conduction tines from brachial plexus to cervical cord and somatosensory cortex were not significantly different (p>0.05). However, this latency difference betweem males and females is probably due to height differences (p<0.001).