Topodiagnostical value of brainstem reflexes and evoked potentials in chronic space-occupying lesions at the cranio-spinal junction

Thirty-three patients with chronically space-occupying lesions at the crani o-spinal region were examined by determining the blink reflex (BR) glabella reflex (GR), jaw reflex (MR), the acoustic (BAEP), somatosensory (derived via median nerve stimulation) (M-SSEP) and visual (VEP) evoked potentials. The aim of this study was to find out whether the brainstem reflexes (BSR) and the evoked potentials (EP) have topodiagnostical validity in such cases . While the early response (R1) of the BR was pathologically relatively rar e (36%), and then only slightly, in these patients, the late response (R2 a nd R2 C) showed extensive and severe bilateral changes in most patients (85 %). The changes in R1 and R2 of the GR were seen less often (21% and 61% re speclively) and were less extensively developed as in BR. The MR was slight ly changed in almost half of the patients (45%). In most patients (79%) the BAEP was clearly pathological. Predominantly, acoustic nerve response and the response of the caudal-pontine part of the auditory path (latency of wa ve I, interpeak latency I-III, amplitude of wave III) was usually markedly, occasionally extensively, changed. The VEP was mostly (61%) normal or only slightly pathiological bilaterally, while the M-SSEP proved to be extensiv ely changed in most (94%) of the investigated persons. Here the pathologies were in the central conduction time (CCT), the cortical (N20), and the cra nio-cervical (N14) registered signal. In cases of extensive neurological sy mptoms and most of all when intra-axial tumours were present, the N14-signa l was severely pathological. This experience seems to indicate that BSR and EP allow to verify the origin of the neurological deficit (location of the lesion) via the verification of bulbo-pontine dysfunctions in lesions at t he cranio-spinal junction. These methods are then also capable to ascertain whether or not accompanying illnesses contribute to the observed symptoms.