Monocular pendular nystagmus in a patient with sporadic cerebellar ataxia syndrome

Abstract

Dear Editor-in-chief, Pendular nystagmus (PN) corresponds to an enduring toand-fro eye oscillation without resetting quick phases [1]. Multiple sclerosis (MS) and oculopalatal tremor (OPT) are known to be the most common causes of acquired PN. OPT is more frequently associated with lesions in the GuillainMollaret triangle, whereas PN in MS is mainly associated with central (i.e., pontine tegmentum or optic nerve) demyelination [1]. We experienced monocular PN in a patient with progressive cerebellar ataxia but showed no palatal tremor. MRI disclosed diffuse cerebellar atrophy, but the hypertrophic degeneration of the inferior olivary nucleus or a focal lesion involving the Gullain-Mollaret triangle was not observed. Disruption of the cerebellum that influences the gaze-holding neural network in the brainstem may give rise to PN. CaseA 58-year-old man presented with gait disturbance for 4 years. His symptom worsened over the years. He could stand without support but veered to the both sides when walking. From 2 years, he felt dizziness and oscillopsia. There was no family history on progressive gait ataxia. On neurological examination, he had mild dysarthria and PN in the left eye. He showed limb dysmetria on both extremities and gait ataxia but no palatal tremor, postural tremor, or any extrapyramidal signs. In three-dimensional VOG (SMI, Teltow, Germany, resolution of 0.1°, sampling rate of 60 Hz), the peak velocity of PN was 5.5°/s. The frequency and amplitude were 5.5 Hz and 0.5°, respectively, and the horizontal and torsional components were mostly regular (Fig. 1a). The vertical component of oscillation was smaller than the torsional or horizontal component. The nystagmus was not attenuated with visual fixation. The amplitude of horizontal PN was increased on leftward or upward gaze. In the leftward or upward gaze, the amplitude of horizontal PN was 1 degree. Measurement of saccade for 30°target displacement disclosed hypermetria (mean accuracy of first saccade, 115.7 %) of the rightward and downward (mean accuracy of first saccade, 109.4 %) saccades, and slight hypometria of the leftward (mean accuracy of first saccade, 86 %) and upward saccades (mean accuracy of first saccade, 78.3 %) in the both eyes. The Brain MRI showed diffuse atrophy in the cerebellum, but there was no abnormality in other areas including the inferior olivary nucleus (Fig. 1b, c). On ophthalmological examination, visual acuity using Snellen test chart was 0.2 in the both eyes. Funduscopic examination was normal. Pupils were normal without a relative afferent pupillary defect. Motility was full and confrontation visual fields were also full. Visual evoked potential test and optical coherence tomography showed no abnormality. Extensive investigations to exclude other causes including genetic analysis for spinocerebellar ataxia 1, 2, 3, 6, 7 and dentatorubral-pallidoluysian atrophy, and thyroid function test were unremarkable. He was finally diagnosed as having S.-M. Woo and H.-A. Kim equally contributed as co-first authors to this work.

A Case of Anti-Ma2 Encephalitis Presenting with Pendular Torsional Nystagmus

“…Our patient’s nystagmus had a pendular waveform and a predominant conjugate torsional component. Etiology of acquired pendular nystagmus includes visual loss, demyelinating diseases [ 15 – 19 ], oculopalatal tremor (OPT) syndrome [ 20 , 21 ], Whipple’s disease [ 22 ], hypoxic encephalopathy [ 23 ], serotonin syndrome [ 24 ], and sporadic cerebellar ataxia [ 25 ].…”