Dissociation of frontal and parietal components of somatosensory evoked potentials in severe head injury.
Reports on the topography of SEPs in non-comatose patients have drawn attention to a second thalamo-cortical loop connecting the thalamus with the frontal cortex, which has a close anatomical relation to the fronto-limbic structures frequently damaged in severe head injury (SHI). We studied whether the frontal component (P20/22) of the somatosensory evoked response (SEP), known to be due to a generator different from that of the traditionally analysed parietal SEP component (N20), would be differently affected by SHI. Moreover, we examined whether its analysis would improve the prognostic evaluation in the Glasgow outcome scale (GOS) after 3-6 months. In 50 patients examined within 72 h after the injury we found a dissociated impairment of frontal and parietal components in 24% of the recorded SEPs. When both frontal and parietal components were used as predictors, discriminant analysis correctly classified 94% of the patients into good (GOS good recovery and moderate disability) or poor (GOS severe disability, persistent vegetative state or death) outcome groups. Classification was less accurate and misclassifications grosser when considering parietal or frontal parameters alone. Our results show that (i) the evaluation of frontal components provides information different from that of the parietal SEPs, confirming the presence of different generators, and (ii) a combined analysis of the two components improves the prognostic evaluation with regard to the global outcome.
Gütling
E
E
Department of Neurology, University Hospital, Zurich, Switzerland.
Gonser
A
A
Regard
M
M
Glinz
W
W
Landis
T
T
D000293:Adolescent; D000328:Adult; D006259:Craniocerebral Trauma / Q000503:physiopathology*; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D015600:Glasgow Coma Scale; D006801:Humans; D008875:Middle Aged; D010296:Parietal Lobe / Q000503:physiopathology*; D011379:Prognosis; D012044:Regression Analysis