Electrophysiological investigations of the brainstem in the vertebrobasilar reversible attacks

Evaluation of vertigo by auditory brain stem response

The authors examined the hypothesis that abnormal patterns of the auditory brain stem response (ABR) could supplement the neuro-otological evaluation and assist in localizing the site of vestibulocerebellar dysfunction. This project is based upon the fact that the sources of waves I through V have been regionally identified. Absent or delayed patterns can be referenced to the normal data, and the site of a lesion generating vertigo can be established. We found absence of waves or prolonged interpeak latencies in 25% of the vertiginous subjects with normal hearing and magnetic resonance images of the brain. We conclude that in selected cases, lesions affecting the vestibular system can influence the ABR, and the electrophysiological tests of audition may suggest regionalization of the dysfunction in the hindbrain and midbrain.

ABR findings in brainstem ischemia: occlusion of the left anterior inferior cerebellar artery

ABR was measured ipsilaterally following permanent left anterior inferior cerebellar artery (AICA) occlusion to assess the discrepancy in recovery between blood flow and function in the rat brainstem. Three types of wave patterns were classified: in type 1, all components disappeared: in type 2, all components disappeared transiently, then re-appeared; and in type 3, only a significant increase in the latency difference between components I-IV was noted. In type 2, we suggest that all components re-appeared because cochlear blood flow was re-established quickly by collateral circulation.

The late waves of brainstem auditory evoked potentials in children with cerebrovascular diseases

We examined brainstem auditory evoked potentials (BAEPs) in 28 children with cerebrovascular diseases and 38 normal control subjects and investigated the neuroanatomic correlations of the late waves (VI and VII) of the BAEPs. The patients included 19 patients with moyamoya disease and 9 with other cerebrovascular accidents. Wave VI was more consistently seen (only missing in 2 cases, 5%-2 ears, 3%) than wave VII (missing in 26 cases, 68%-40 ears, 53%) in the control group. Absent, depressed or prolonged wave VI correlated well with cerebral lesions involving internal capsule and basal ganglia, while wave VII had a less significant correlation with any cerebral lesions in children with cerebrovascular diseases.

Neuroradiological, neurophysiological and anatomopathological study of a case of locked-in syndrome

We report an anatomoclinical case of locked-in syndrome together with the neuroradiological and neurophysiological findings. MRI confirmed its value in the diagnosis of posterior cranial fossa pathology while the neurophysiological work-up (BAEPs, SEPs, MAPs and TEPs) revealed that the lesion may have broader functional implications than may be gauged from the neuroradiological and pathological evidence. Evoked potentials may therefore be of considerable importance in pinpointing brainstem lesions.

ABR findings in vertebrobasilar ischemia

Auditory brainstem response (ABR) changes in the ischemic brainstem condition and the correlation between ABR and blood flow of the auditory pathway are not clear. In this study, ABR changes in two cases with brainstem ischemia are reported. In order to clarify the correlation between ABR changes and cochlear blood flow, experimental studies on guinea pigs with brain ischemia were performed. Changes of ABR in the human brainstem ischemic condition consisted of a decrease of the amplitudes of all waves and a delay in wave latencies. Even if ABR showed no response, it turned to normal when the blood flow was recovered. In the experimental study, the same changing patterns in ABR occurred in parallel with a decrease of the cochlear blood flow, and the cochlear blood flow was not zero when ABR became non-responsive. This suggests that ABR changes reflect the degree of ischemia in the auditory pathway, and that non-responsive ABR does not imply irreversible ischemic condition.

Auditory evoked potentials in vertebrobasilar transient ischemic attacks

Brainstem auditory evoked potentials (BAEPs) are affected by stroke or migraine in the vertebrobasilar arterial system. Some studies have reported BAEP changes in vertebrobasilar transient ischemic attacks (TIAs), but others have shown no alterations. We recorded BAEPs in 35 patients with TIAs in the vertebrobasilar system who did not have a stroke, other neurologic disease or significant hearing loss. Thirty patients were recorded after resolution of symptoms, while five individuals still had some resolving signs or symptoms. TIA patients as a group had longer interpeak latencies, but I-III, III-V, and I-V latencies were not significantly longer than in controls. Wave V was significantly longer in latency and lower in amplitude in TIA patients, however. The patients whose TIAs had resolved at absolute and interpeak latencies were within normal limits, but three of five had interpeak latencies at or above three standard deviations beyond the normal mean in the still symptomatic group. One of these was later tested and found to be within normal limits. BAEPs after subsidence of symptoms may add little to the evaluation of vertebrobasilar ischemia, but further AEP analysis may show more definitive differences of diagnostic use. The occasional BAEP abnormality during the resolving transient ischemia supports the recently suggested continuum between ischemia and infarction in the vertebrobasilar territory.

Repeatedly reversible alteration of acoustic-evoked brainstem responses with a cystic craniopharyngioma

The case of a cystic craniopharyngioma in a young patient, in which the tumor extended in the parasellar and retrosellar region down to the left cerebellopontine angle, is described. The postoperative reversibility of alterations in the acoustic-evoked brainstem responses after repeated surgical intervention and refilling of the cyst is described. The correlations between clinical and CT findings and the repeated alterations in the evoked responses are presented. The evoked responses were instrumental in following the postoperative course and timing CT controls. It is stressed that alterations in evoked responses were used as a reliable indication to evacuate cyst fluid via a Rickham-reservoir, although hearing was still intact, thus keeping the number of repeated CT scans lower.

Visual evoked potentials and brainstem auditory evoked potentials in migraine and transient ischemic attacks

A study of brainstem auditory evoked potentials (BAEPs) and pattern reversal visual evoked potentials (VEPs), recorded in intercritical phase, was carried out in 20 subjects (10 suffering from common migraine and 10 suffering from vertebrobasilar TIA) in order to obtain a comparative evaluation of cortical-subcortical functions. The data we obtained demonstrate the presence of BAEPs alterations in patients with previous vertebrobasilar TIA: no abnormalities were found in the migraine group. VEPs parameters are normal in both groups. Our data show that the study of the so-called "stimulus-related" potentials, such as BAEPs and pattern reversal VEPs, is useful in evaluating the damage produced by any noxa, while it cannot clearly emphasize individual factors predisposing to a specific pathology, as the absence of specific alterations in migraine patients demonstrates.