Vestibular Epilepsy

Abstract

Vestibular epilepsy is a cortical vertigo syndrome secondary to focal discharges from either the temporal lobe or the parietal association cortex (Foerster 1936; Penfield and Jasper 1954; Schneider et al. 1968), both of which receive bilateral vestibular projections from the ipsilateral thalamus. Results of electrical stimulation in man have shown that the intraparietal sulcus (Foerster 1936) and the posterior part of the superior temporal gyrus (Penfield and Jasper, 1954) form part of the vestibular cortex, and experiments in monkeys have similarly identified the posterior caudal part of the postcentral gyrus (Fredrickson et al. 1966). Fig. 6.1 gives a schematic representation of the vestibular cortex areas. An acute unilateral functional deficit of the vestibular cortex (for example, in medial cerebral artery infarction) does not usually manifest with vertigo, unlike lesions in the vestibular area of the brainstem. It is not the functional loss but the focal discharge that causes central vertigo. This has been repeatedly demonstrated by stimulation experiments. Electrical stimulation of the human thalamus during stereotactic neurosurgical procedures induced sensations of movement in space, most frequently described as horizontal or vertical rotation or sensations of falling or rising (Hawrylyshyn et al. 1978). These sensations were similar to those induced by stimulation of the vestibular cortex (Foerster 1936; Penfield and Jasper 1954).