EP and brainstem reflexes in patients with large temporal brain tumours

To find possible functional irritation of reflex and sensory neural pathways of the brain and of the brainstem caused by lateralised supratentorial mass shift, 55 patients with large temporal brain tumours were electrophysiological investigated. In this patients the electrical (BR) and mechanical (GR) elicited blinking reflex, the jaw-reflex (MR) were derived as well, as the acoustic (BAEP) the somato-sensory (MSSEP) and the flash elicited visual (f-VEP) evoked potential. The infratentorial generated BR, GR and BAEP showed very frequently (>3/4 of the cases) slight pathological changes (pontine and ponto-bulbar). In contrast to this, the predominantly in tentorial level (mesencephalic) generated MR, and also supratentorial generated cortical MSSEP and the f-VEP indeed showed less frequent but more marked signal changes than the BR, GR and BAEP. On grounds of the constellation of the electrophysiological findings is to assume, that the mass-shift of the brain lead very early to a slight infratentorial brainstem irritation due to an cranio-caudal brainstem displacement and later to a marked irritation of the tentorial and supratentorial signal generators, because for the present there is (supratentorial) more space for unhindered mass-displacement. After the space is occupied the immediateness of the tissue irritation lead to more intensive signal changes than those of the infratentorial generated electrophysiological signals. The last remain for long time unchanged up to the time point of transtentorial and tonsillar herniation.