Cerebral evoked potentials in the chronic vertebrobasilar insufficiency.

The syndrome of chronic vertebrobasilar insufficiency (VBI) consists in a complex of symptoms, often mild and transient, and lacks a complementary system of objective paraclinical investigations able to certify its existence. The study of somato-sensory, auditory and visual evoked potentials in VBI showed the occurrence of changes regardless of the symptom importance both in disorders due to extrinsic causes: a) compression by a damage of the cervical column (92.9%, 50% and 63.9%, respectively; b) diseases of the cervical spinal cord (92.9% and 46.6%, respectively) and in disorders due to some intrinsic vascular causes such as atherosclerosis (62.5%, 88.8% and 87.5%, respectively). We described: a) local and far field modifications for the somesthetic evoked potentials (SEPs); b) modifications due to brain stem hypoxia (vestibular and auditory centres) or of the internal ear for the early and middle auditory potentials (AEPs); c) modifications due to lower perfusion of the occipital lobes and of the nonspecific centres in the brain stem for the visual evoked potentials (VEPs). The N0-P0-Na component of the middle auditory response was considered to represent a vestibular response and it was significantly affected in cases with VBI and clinical manifestations like: equilibrium disorders, nystagmus and vertigo. Typical images of the sensory evoked responses affected by VBI are reproduced considering their evidence as an elective method in the paraclinical examination of this syndrome.