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Combined study of somatosensory (SEP) and auditory (BAEP) evoked potentials in patients with brainstem tumors
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F34 THE LOCALIZATION OF UNILATERAL HEMISPHERICAL LESIONS BY SOMATO-SENSORY EVOKED POTENTIALS (SEP) U.W. BUETTNER, M. ST~HR, J. DICHGANS, K. VOIGT, Neurologische U n i v e r s i t ~ t s k l i n i k , LiebermeisterstraBe 18-20, D-7400 TUbingen, FRG T h i r t y patients presenting with a somatosensory d e f i c i t (mainly disturbances of kinesthesia and stereoaesthesia) and a circumscribed u n i l a t e r a l c o r t i c a l and/or subcortical lesion as determined by computertomography were i n v e s t i g a t ed. SEP recordings f o l l o w i n g stimulation of the median nerve at the w r is t were simultaneously obtained from Erb's point, the spinal processes C7 and C2 as well as C'3/C 4" Four types of abnormality could be correlated with specific sites of the l e s i o ~ Type I - Pathology from P 15 on ( a f t e r a normal P 13/14 complex with ear- or extracephalic reference) is found with lesions of the thalamus, the inner capsule, and the centrum semiovale. Type I I with loss or attenuation of N 20 and subsequent components or Type I I a ~ of N 20, but preserved subsequent components) occurred with lesions of the postcentral gyrus. Type I l l - Preserved primary c o r t i c a l , but loss of a l l subsequent potentia]s presumably relates to lesions of the p a r i e t a l association cortex. Type IV observed in only one p a t i e n t with i n f a r c t i o n of area 39 exhibited pathological features from N 55 on. The results suggest generation of P 15 in the thalamus and N 20 in the postcentral cortex. Loss of kinesthesia occurs a f t e r lesions of S I and i f S I is preserved a f t e r lesions of the p a r i e t a l somatosensory association cortex. i
F35 COMBINEDSTUDY OF SOMATOSENSORY(SEP) AND AUDITORY (BAEP) EVOKED POTENTIALS IN PATIENTS WITH BRAINSTEM TUMORS BUETTNER UW, STUHR M, RIFFEL B, POREMBAM~ Neurologische U n i v e r s i t ~ t s k l i n i k , LiebermeisterstraBe 18-20, D-7400 TUbingen, FRG The generator sites of the peaks N13 and N14/P14 of evoked p o t e n t i a l s recorded from above the spinal cord at C2 and C7 (stimulation of median or ulnar nerves) are not e n t i r e l y clear. We therefore investigated these potent i a l s in six patients with brainstem tumors (an ependymomaof the l e f t medulla oblongata, an astrocytoma compressing the IV. v e n t r i c l e , a metastasis of the pons and a metastasis within the cerebello-pontine angle, a medulloblastoma of the IV. v e n t r i c l e and a suspected glioma of the pons) defined by c l i n i c a l t e s t i n g and CT. To aid l o c a l i z a t i o n we a d d i t i o n a l l y recorded BAEPs. The patients e x h i b i t e d pathological SEPs in six cases and BAEPs in f i v e cases (not a v a i l a b l e in one case). In four cases the SEP abnormality mainly consisted in absence, amplitude reduction or delay of P15/N20, whereas spinal p o t e n t i a l s were normal or only s l i g h t l y d i s t o r t e d . In the two cases with a medullary lesion spinal p o t e n t i a l s were abnormal. Intact spinal SEPs and pathological P15/N20 point to a lesion r o st r a l to the medulla which eventually can f u r t h e r be l o c a l i z e d by BAEP recordings. A clear dissociation between p o t e n t i a l s recorded from C7 (normal) and C2 (delayed) may be observed in patients with a medullary lesion and suggests d i f f e r e n t generators of N13 and N14/P14 at C2 and C7, r e s p e c t i v e l y .
F34 THE LOCALIZATION OF UNILATERAL HEMISPHERICAL LESIONS BY SOMATO-SENSORY EVOKED POTENTIALS (SEP) U.W. BUETTNER, M. ST~HR, J. DICHGANS, K. VOIGT, Neurologische U n i v e r s i t ~ t s k l i n i k , LiebermeisterstraBe 18-20, D-7400 TUbingen, FRG T h i r t y patients presenting with a somatosensory d e f i c i t (mainly disturbances of kinesthesia and stereoaesthesia) and a circumscribed u n i l a t e r a l c o r t i c a l and/or subcortical lesion as determined by computertomography were i n v e s t i g a t ed. SEP recordings f o l l o w i n g stimulation of the median nerve at the w r is t were simultaneously obtained from Erb's point, the spinal processes C7 and C2 as well as C'3/C 4" Four types of abnormality could be correlated with specific sites of the l e s i o ~ Type I - Pathology from P 15 on ( a f t e r a normal P 13/14 complex with ear- or extracephalic reference) is found with lesions of the thalamus, the inner capsule, and the centrum semiovale. Type I I with loss or attenuation of N 20 and subsequent components or Type I I a ~ of N 20, but preserved subsequent components) occurred with lesions of the postcentral gyrus. Type I l l - Preserved primary c o r t i c a l , but loss of a l l subsequent potentia]s presumably relates to lesions of the p a r i e t a l association cortex. Type IV observed in only one p a t i e n t with i n f a r c t i o n of area 39 exhibited pathological features from N 55 on. The results suggest generation of P 15 in the thalamus and N 20 in the postcentral cortex. Loss of kinesthesia occurs a f t e r lesions of S I and i f S I is preserved a f t e r lesions of the p a r i e t a l somatosensory association cortex. i
F35 COMBINEDSTUDY OF SOMATOSENSORY(SEP) AND AUDITORY (BAEP) EVOKED POTENTIALS IN PATIENTS WITH BRAINSTEM TUMORS BUETTNER UW, STUHR M, RIFFEL B, POREMBAM~ Neurologische U n i v e r s i t ~ t s k l i n i k , LiebermeisterstraBe 18-20, D-7400 TUbingen, FRG The generator sites of the peaks N13 and N14/P14 of evoked p o t e n t i a l s recorded from above the spinal cord at C2 and C7 (stimulation of median or ulnar nerves) are not e n t i r e l y clear. We therefore investigated these potent i a l s in six patients with brainstem tumors (an ependymomaof the l e f t medulla oblongata, an astrocytoma compressing the IV. v e n t r i c l e , a metastasis of the pons and a metastasis within the cerebello-pontine angle, a medulloblastoma of the IV. v e n t r i c l e and a suspected glioma of the pons) defined by c l i n i c a l t e s t i n g and CT. To aid l o c a l i z a t i o n we a d d i t i o n a l l y recorded BAEPs. The patients e x h i b i t e d pathological SEPs in six cases and BAEPs in f i v e cases (not a v a i l a b l e in one case). In four cases the SEP abnormality mainly consisted in absence, amplitude reduction or delay of P15/N20, whereas spinal p o t e n t i a l s were normal or only s l i g h t l y d i s t o r t e d . In the two cases with a medullary lesion spinal p o t e n t i a l s were abnormal. Intact spinal SEPs and pathological P15/N20 point to a lesion r o st r a l to the medulla which eventually can f u r t h e r be l o c a l i z e d by BAEP recordings. A clear dissociation between p o t e n t i a l s recorded from C7 (normal) and C2 (delayed) may be observed in patients with a medullary lesion and suggests d i f f e r e n t generators of N13 and N14/P14 at C2 and C7, r e s p e c t i v e l y .