Epileptic discharges triggered by eye convergence

Anomalous cross-modal plasticity following posterior fossa surgery: some speculations on gaze-evoked tinnitus

A unique and intriguing form of subjective tinnitus evoked by eye gaze is reviewed. A new perspective is presented because this condition is sufficiently different from other forms of subjective tinnitus and its manifestation cannot be adequately explained by existing models or conceptual frameworks. Our examination of this topic considers pathophysiologic changes in the central nervous system in the context of deafferentation-induced plasticity. Potential neuroanatomical areas contributing to this effect include a number of distributed and functionally diverse areas in the brainstem and neocortex involved in the auditory control of eye movements. We also consider contemporary psychophysical methods to evaluate the perceptual correlates of this phenomenon and tools for the development of objective tinnitus measurements. Although theoretical and speculative in nature, this article is intended to stimulate interest in, advance knowledge of, and provide a better understanding about this condition.

Language-apparent reflex epilepsy

An adolescent with photosensitive epilepsy had absence seizures reproduced by forced voluntary eye closure in light or in darkness, independent of eyelid immobilization or ocular elevation. Attacks preferably occurred while speaking Spanish, her second language, mediated through brief, strong, automatic closing of the eyes during difficult word retrieval. Complex other multidirectional ocular movements or blinking, cognitive and language tasks were ineffective. Frontorolandic cortical epileptogenesis is seemingly responsible for light-provoked seizures in Papio papio, acting via hyperexcitable neuronal facial aggregates (i.e. Baba and Wada). Since orbicularis oculi muscle fibers mediating strong and weak contractions are differentially innervated by the facial nuclei, we submit that critical threshold tonic activation of specific nuclear aggregates explains this language-apparent reflex epilepsy, triggered by extreme eye closure. A "dopamine connection hypothesis" linking periodic eye closure, effortful memory and photosensitivity, based on its putative evolutive significance, is discussed.

Gaze-evoked involuntary movements

Voluntary gaze may evoke a number of neurological phenomena such as vertigo, tinnitus, blepharoclonus, eyelid nystagmus, "facial nystagmus," involuntary laughter, and seizures. We report two patients in whom eccentric gaze evoked facial twitching and arm movement. Electroencephalograms remained unchanged during these movements. The pathogenesis of these movements is unclear but may involve ephaptic transmission.

Periodic complexes and alternating rotatory nystagmus with cyclic pupillary changes

A 69-year-old male, with a history of a previous subdural hematoma, multistroke dementia and ventricular shunting for hydrocephalus, exhibited while comatose isolated periodic alternating rotatory nystagmus with cyclic pupillary changes and periodic alternating gaze. His simultaneous EEG showed PLEDs and subsequently burst-suppression pattern. The latter abnormality was associated, in addition, to transient eyelid opening, synchronized with the EEG bursts. Complex neuro-ophthalmologic clinical signs, sometimes subtle, may be the sole manifestation of EEG periodic complexes that have potential prognostic and therapeutic implications.

Organic convergence spasm

Convergence spasm has frequently been reported as a hysterical manifestation. A case presenting with this sign and diphenylhydantoin intoxication is described. Other previously reported organic associations are discussed. Convergence spasm may be seen in association with significant organic disease of the nervous system affecting the cerebral hemispheres, the brain-stem, or both.