title: Median and tibial somatosensory evoked potentials. Changes in short- and long-latency components in patients with lesions of the thalamus and thalamo-cortical radiations.
abstract: Alterations in short- and long-latency components of median and tibial somatosensory evoked potentials (SEPs) were studied in patients with lesions in the thalamus and thalamo-cortical radiations. When the lesions were located primarily in the ventro-posterior thalamus, the SEP changes consisted of the following combination: absence of response; decrease in response amplitude; delay in peak latency; and attenuation of median N20-P25 and tibial P40. The laterally situated ventro-posterior lesions tended to preferentially affect tibial SEPs whereas the medially situated lesions tended to preferentially affect median SEPs. The lateral thalamic lesions affected primarily the long-latency SEP components, whereas the medial thalamic lesions affected primarily the mid-latency or the mid- and long-latency SEP components. Corona radiata infarcts produced SEP changes similar to those with the ventro-posterior thalamic lesions except that absence of evoked responses was not observed. Subcortical infarcts tended to affect the mid- and long-latency SEP components with relative preservation of the short-latency components. The present data indicate that only the lesions involving the primary thalamic relay area affected all SEP components, particularly the short-latency components, and that the lesions in other thalamic areas can also influence the SEPs, particularly the mid- and long-latency components. The present study further demonstrates that a combined use of median and tibial SEPs is useful in delineating the topographic organization of the somatosensory system in the thalamus.
mesh_terms: D000328:Adult; D000368:Aged; D001480:Basal Ganglia Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology; D002543:Cerebral Hemorrhage / Q000000981:diagnostic imaging / Q000503:physiopathology; D002544:Cerebral Infarction / Q000000981:diagnostic imaging / Q000503:physiopathology; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging / Q000503:physiopathology; D004806:Ependymoma / Q000000981:diagnostic imaging / Q000503:physiopathology; D005073:Evoked Potentials, Somatosensory; D006801:Humans; D008475:Median Nerve / Q000503:physiopathology*; D008875:Middle Aged; D011930:Reaction Time; D013786:Thalamic Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013788:Thalamus / Q000503:physiopathology / Q000601:surgery; D013979:Tibial Nerve / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed