Monocular Torsional Oscillopsia in Dentato-olivary Disconnection.

Monocular torsional eye oscillations are a rare form of disconjugate nystagmus and the underlying pathophysiology is not well understood. Here, we present and discuss a case with disabling torsional oscillopsia in one eye only. The patient exhibited (i) spontaneous pendular torsional nystagmus of the left eye and (ii) rhythmic involuntary movements of the soft palate and uvula, consistent with the syndrome of oculopalatal tremor with monocular nystagmus. Brain MRI revealed an infarct of the left dentate nucleus in the cerebellum and, more caudally, a secondary hypertrophic degeneration of the right inferior olivary nucleus. To account for the presence of torsional nystagmus on the eye contralateral to the side of inferior olivary hypertrophy and ipsilateral to the lesioned dentate nucleus, we discuss the hypothesis of a (inferior olivary nucleus-mediated) malfunctioning adaptation of the anterior canal vestibulo-ocular reflex.

Clinical utility of square-wave jerks in neurology and psychiatry.

Human eye fixation is steadily interrupted by small, physiological or abnormal, eye movements. Square-wave jerks (SWJ) are the most common saccadic intrusion which can be readily seen at the bedside and also quantified using oculographic techniques. Various neurological, neuropsychiatric and psychiatric disorders display abnormal fixational eye movement patterns characterized by frequent SWJ. For the clinician, SWJ are particularly important because they can be readily observed at the bedside. Here, we will discuss the pathological conditions that present with SWJ and explore the expanding body of literature suggesting that SWJ may serve as a potential indicator for various clinical conditions.