Auditory Brainstem Evoked Potential Responses in Focal Brain Lesions

Brainstem auditory response abnormalities directly reflect disturbance of neural function rather than the underlying anatomic cause of that disturbance. The test has advantage in detecting lesions that alter electrophysiology but do not produce detectable alterations of radiodensity, displace surrounding structures or change vascular supply and permeability. A sequence of seven low-amplitude potentials that occur in the initial 10 msec following click signals can be recorded from scalp electrodes in 44 patient with focal brain lesions using computer averaging techniques. The potentials, termed auditory brainstem responses, are thought to be the far-field reflection of electrical events originating in the auditory pathway during its course through the brainstem. We have studied auditory brainstem evoked potential responses in a variety of focal brain lesions and found them to be of assistance in evaluating the localization of pontomedullary, pons, midbrain, thalamus, subcortical and functional recovery. 1) Distortion of early components (type I) was occured in the brainstem lesions. 2) Distortion of late components (type II) was developed in the diencephalon or subcortical lesions. 3) Distortion of all components (type III) was developed in the brainstem and diffuse brain contusions. 4) Serial recordings provided information about the evolution of brain stem lesions and good functional recovery marker.

Auditory Brainstem Evoked Potential Responses in Focal Brain Lesions

Brainstem auditory response abnormalities directly reflect disturbance of neural function rather than the underlying anatomic cause of that disturbance. The test has advantage in detecting lesions that alter electrophysiology but do not produce detectable alterations of radiodensity, displace surrounding structures or change vascular supply and permeability. A sequence of seven low-amplitude potentials that occur in the initial 10 msec following click signals can be recorded from scalp electrodes in 44 patient with focal brain lesions using computer averaging techniques. The potentials, termed auditory brainstem responses, are thought to be the far-field reflection of electrical events originating in the auditory pathway during its course through the brainstem. We have studied auditory brainstem evoked potential responses in a variety of focal brain lesions and found them to be of assistance in evaluating the localization of pontomedullary, pons, midbrain, thalamus, subcortical and functional recovery. 1) Distortion of early components (type I) was occured in the brainstem lesions. 2) Distortion of late components (type II) was developed in the diencephalon or subcortical lesions. 3) Distortion of all components (type III) was developed in the brainstem and diffuse brain contusions. 4) Serial recordings provided information about the evolution of brain stem lesions and good functional recovery marker.

Somatosensory Evoked Potential Responses in Focal Brain Lesions

Cerebral somatosensory evoked potentials(SEPs) produced by stimulation of peripheral nerves provide a useful diagnostic index of conduction in somatosensory pathways to the cortex. Thus the integrity of both the dorsal column-medial lemniscus pathway and primary sensorimotor area has been considered an essential requirement to record a normal SEP. There are suggestions that SEPs contain several components arising from different neuronal sources, the early short latency potentials corresponding to the lemniscus-mediated responses and the late waves to the diffuse spino-thalamic projections. The present work analyses the influence on SEPs of focal brain lesions, using the computerized tomography in detecting and localizing brain lesions. Somatosensory evoked potentials were recorded in 20 patients with focal brain lesions recognized by computerized tomography. 1) Patients with primary sensorimotor area(PSMA) damages(group I) had a very abnormal of the early component(No, Po, Nl, Pl) in 100% on the lesion side. 2) Patients presented supratentorial lesions, sparing PSMA(group II), 87.5% showing abnormal SEPs in early components and characterized by increment of amplitude in late components. 3) Brainstem damage(group III) produced a distortion of the early components especially N11, N20msec in latency. 4) In incomplete spinal cord injuries, the SEPs is indeed signal of functional recovery, of posterior column, and incorrespondance with clinical improvement.