RESUMO
BACKGROUND: The mechanisms of pendular seesaw nystagmus (SSN) remain unknown. METHODS: We evaluated modulation of pendular SSN by removal of visual fixation, convergence, and positional changes in 2 patients, one with bitemporal hemianopia due to a traumatic damage of the optic chiasm and the other with platybasia compressing the medulla and lower cerebellum. RESULTS: In both patients, the pendular SSN markedly decreased or disappeared with convergence, without visual fixation in darkness, during static head tilt toward each shoulder while sitting and while supine. CONCLUSIONS: The similar patterns of nystagmus modulation observed in our patients with a different etiology indicate a common role of both visual and otolithic inputs in generating pendular SSN.
Assuntos
Convergência Ocular/fisiologia , Fixação Ocular/fisiologia , Nistagmo Patológico/fisiopatologia , Percepção Visual/fisiologia , Medições dos Movimentos Oculares , Feminino , Hemianopsia/diagnóstico , Hemianopsia/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Oftalmoscopia , Atrofia Óptica/diagnóstico , Atrofia Óptica/fisiopatologia , Platibasia/diagnóstico , Platibasia/fisiopatologia , Testes de Campo Visual , Adulto JovemRESUMO
A 43-year-old man with a high-grade glioma involving the cerebellar nodulus showed a near-complete suppression of periodic alternating nystagmus (PAN) in the lateral decubitus position to either side. This positional modulation of PAN is consistent with suppression of the velocity storage mechanism by head position changes (tilt dumping) and is supportive of the role of the velocity storage mechanism in generating PAN.
Assuntos
Neoplasias Encefálicas/complicações , Glioma/complicações , Nistagmo Patológico/etiologia , Adulto , Humanos , Imageamento por Ressonância Magnética , Masculino , Tomografia por Emissão de PósitronsRESUMO
A 27-year-old man with MELAS 3243 mutation developed a right homonymous hemianopia, left beating nystagmus, and impaired smooth pursuit (SP) to the left. Intermittently, the left beating nystagmus changed to right beating with rightward eye and head deviation and associated altered mental status. Each episode lasted several minutes. MRI revealed restricted diffusion in left parieto-temporo-occipital cortices. During the ictus, electroencephalogram showed epileptic discharges in the left temporo-occipital region, and single photon emission computed tomography demonstrated hyperperfusion in the same area. The interictal left beating nystagmus may be ascribed to contralesional bias of SP imbalance since the parieto-temporo-occipital region is involved in the generation of SP. The ictal right beating nystagmus and rightward head and eye deviation indicate coactivation of the SP areas and parietal eye field. This report documents the novel co-occurrence of pursuit-paretic and epileptic nystagmus.
