Changes of brainstem reflexes and evoked potentials in large frontal tumours

Intracranial space occupying lesions seems to influence electrophysiological functions of the brain and brainstem caused by perfusion disturbances due to mass-shift, stretching or/and compression of the corresponding pathways. In this study possible changes of brainstem reflexes and evoked potentials caused by large frontal tumours was examined. In 103 patients with histological different frontal tumours with a diameter >4cm and mostly accompanying oedema the electric elicited blinking-reflex (BR) the jaw-reflex (MR), the acoustic (BAEP), the flash induced visual (f-VEP) and the somatosensory (MSSEP) evoked potentials were derived. In 81% of the cases slight changes of BR were found. In 65% of the cases these changes were bilaterally recorded. The R1-response was frequently unilateral changed in 45% without significant correlation to the tumour side. An amplitude reduction was most frequently found than a prolongation of the R1-latency. The late R2-response was bilateral and mostly symmetrically changed in 55% of the patients. In this cases an increase of R2-duration was most frequently shown than an Amplitude reduction or a prolongation of the R2-latency.Changes of MR were shown in 85% of the cases. MR was mostly pathological changed contralateral than ipsilateral to the tumour. The duration of MR-signal was most frequently changed than the MR-amplitude or MR-latency. In 91% of the cases slight changes in BAEP were found bilaterally. Mostly the IPL-III and the amplitude of wave III were asymmetrical changed without significant correlation to the tumour side. Marked MSSEP-changes were found in 54% of the cases. There were changes of N20-amplitude and latency tumour ipsilaterally. The corresponding central conduction time (CCT) was also clear prolonged. Marked VEP changes were also bilaterally found in 55% of the cases. An amplitude reduction and a latency prolongation of the wave P-100 and of the adjoining negative waves are shown. In eight of the cases the VEP-signal was severe changed. In further two cases a loss of signal was shown. These findings show a frequent marked influence on the supratentorial brain in the vicinity of the tumour and on the anterior and perimesencephalic visual pathways. They also indicate an „early“ slight influence on the brainstem infratentorial due to axial mass shift caused by the large frontal tumours additionally.