Pendular Oscillations

Pendular Horizontal Oscillations; Left Beating Nystagmus; Obtrusive Saccades; Bilateral Gaze Evoked Nystagmus; Saccadic DysmetriaBlurred Vision OscillopsiaThis 37 year old woman has had progressive multiple sclerosis (MS) affecting the cerebellum and brainstem for 6 years. Neurological examination: Titubation Dysarthria Incoordination of the extremities Ataxic gait Spastic paraparesis with generalized hyperreflexia and extensor plantar responses. Neuro-ophthalmological examination: Visual acuity (VA) 20/30 OU Visual fields, pupils and fundi normal Ocular Motility: Head turn to the right to place her eyes in a stable straight ahead position. Pendular horizontal oscillations Left beating nystagmus Superimposed obtrusive saccades Large amplitude gaze evoked nystagmus OU on gaze left Small amplitude gaze evoked nystagmus OU on gaze right Saccadic dysmetria: Right gaze to center hypermetric Left gaze to center hypermetric (consistent with a lesion of the fastigial nuclei) Normal convergence Full vertical gaze no nystagmus Smooth pursuit eye movements No suppression of pendular horizontal oscillations following a saccade.This patient with MS had: • A head turn to the right to place her eyes in a stable straight ahead position • Primary position pendular horizontal oscillations (PHO) • Left beating nystagmus • Occasional superimposed obtrusive saccades • Large amplitude gaze evoked nystagmus OU on gaze left • Small amplitude gaze evoked nystagmus OU on gaze right • Saccadic dysmetria Right gaze to center hypermetric Left gaze to center hypermetric (consistent with a lesion of the fastigial nuclei) • Normal convergence • Full vertical gaze no nystagmus • Smooth pursuit eye movements • No transient suppression of PHOs following a saccade. Systematic comparison of the oscillations prior to, and following a saccade, has demonstrated that the oscillations are phase-shifted (reset) and that larger saccades have a greater effect than small saccades. This observation led Leigh and Zee to hypothesize that the oscillations of acquired pendular nystagmus in MS patients arise in the neural integrator for eye movements, and that large saccades affect the timing of the oscillations by "resetting" the integrator with the large pulse of neural activity. Other structures that may play a role are the nucleus prepositus hyperglossi and the medial vestibular nucleus which are important components of the neural intergrator. Box 10-10 Clinical Features of Acquired Pendular Nystagmus Pg 506 (8) Oscillopsia, an illusion of movement of the visual world, is a common presenting symptom of INO. Horizontal oscillopsia usually occurs from either the adduction lag or the abducting nystagmus. Vertical oscillopsia occurs during head movements and is caused by a deficient vertical VOR or, as in this case, by pendular vertical oscillations. For full discussion of oscillopsia review ID923-2 an MS patient with Pendular Vertical Oscillations and Oscillopsia.Review (8)Review (3)1. Averbuch-Heller L, Kori AA, Rottach KG, Dell'Osso LF, Remler BF, Leigh RJ. Dysfunction of pontine omnipause neurons causes impaired fixation: macrosaccadic oscillations with a unilateral pontine lesion. Neuroophthalmol 1996;16:99-106. http://www.ncbi.nlm.nih.gov/pubmed/11539873 2. Averbuch-Heller L, Tusa RJ, Fubry L, Rottach KG, Ganser GL, Heide W, Büttner U, Leigh RJ. A double-blind controlled study of gabapentin and baclofen as treatment for acquired nystagmus. Ann Neurol 1997;41:818-25. http://www.ncbi.nlm.nih.gov/pubmed/9189045 3. Averbuch-Heller L, Zivotofsky AZ, Das VE, DiScenna AO, Leigh RJ. Investigations of the pathogenesis of acquired pendular nystagmus. Brain 1995;188:369-378. http://www.ncbi.nlm.nih.gov/pubmed/7735879 4. Barton JJ, Cox TA. Acquired pendular nystagmus in multiple sclerosis: clinical observations and the role of optic neuropathy. J Neurol Neurosurg Psychiatry. 1993;56:262-267. http://www.ncbi.nlm.nih.gov/pubmed/8459242 5. Barton JJ, Cox TA, Digre KB. Acquired convergence-evoked pendular nystagmus in multiple sclerosis. J Neuroophthalmol 1999;19:34-38. http://www.ncbi.nlm.nih.gov/pubmed/1009854