3-Dimensional Analyses of Eye Motion in Oculopalatal Tremor

ABSTRACT

BACKGROUND: Oculopalatal tremor (OPT) is a delayed complication of damage to the dentato-rubro-olivary pathway (Guillain-Mollaret triangle) and subsequent hypertrophic olivary degeneration. Mixed torsional-vertical pendular nystagmus in OPT has been considered to signify unilateral brainstem damage while symmetrical vertical nystagmus has been regarded to indicate bilateral disease. However, 3-dimensional oculographic analysis of OPT has been sparse. METHODS: In 8 patients with OPT; binocular 3-dimensional analyses of ocular oscillations were performed by using a magnetic search coil technique. Lateralization of the lesions was determined by the imaged olivary hypertrophy in the MRI. RESULTS: One patient had conjugate vertical pendular nystagmus and four showed mixed torsional-vertical pendular nystagmus. Two patients showed mixed horizontal-torsional-vertical nystagmus. One patient had predominantly horizontal pendular nystagmus. MRI demonstrated increased signal or hypertrophy of the inferior olivary nucleus, unilateral in six and bilateral in two. Unilateral olivary changes were associated with mixed torsional-vertical nystagmus in three patients, mixed horizontal-torsional-vertical nystagmus in another two patients, and predominantly horizontal pendular nystagmus in the remaining one patient. Bilateral olivary changes were visible in one patient with conjugate vertical pendular nystagmus and in the other patient with mixed torsional-vertical nystagmus. Palatal tremor appeared to be symmetrical in all patients. CONCLUSIONS: Three-dimensional analyses of OPT indicate that conjugate vertical and mixed torsional-vertical pendular nystagmus do not correspond to the laterality of signal changes in the inferior olivary nucleus. Ocular oscillations often have all the vertical, horizontal and torsional components.