Slow saccades due to unilateral paramedian pontine reticular formation (PPRF) injury with preserved movements using the vestibulo-ocular reflex

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Identifier Unilateral_PPRF_saccades_and_HIT
Title Slow saccades due to unilateral paramedian pontine reticular formation (PPRF) injury with preserved movements using the vestibulo-ocular reflex
Subject Abnormal Saccades, Pons OMS, Sixth Abducens Nerve, Abnormal VOR, Vestibulocochlear Nerve, Horizontal Gaze Palsy
Creator Tony Brune, DO, Departments of Neurology, The Johns Hopkins School of Medicine; Daniel R. Gold, DO, Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, The Johns Hopkins School of Medicine
Description This is a 60-year-old man who presented for imbalance and oscillopsia 10 months after surgery and 8 months after radiation for Merkel cell carcinoma of the neck. He developed imbalance after surgery and diplopia and oscillopsia 6 months prior to our evaluation. MRI showed enhancement of both 6th nerves, as well as the left 9th, 10th, 11th and ascending portions of the 12th cranial nerve. There was a mild left lower motor neuron facial palsy as well. Exam demonstrated mild right adduction and bilateral abduction deficits, without clear evidence of a right partial 3rd nerve palsy otherwise. Convergence was relatively spared compared to adduction OD. Saccades to the left were very slow, seemingly out of proportion to his mild motility deficits. Pursuit appeared normal vertically and horizontally. There was a right hypertropia due to a skew deviation with a left head tilt, and ocular counterroll with top poles deviated toward the left ear (i.e., a leftward ocular tilt reaction). There was very mild vertical-torsionalpendular nystagmus OS>OD, seen best with the ophthalmoscope (unable to appreciate in this video because it was so subtle). ; To an optokinetic stimulus moved to the right, there were no leftward fast phases. With head impulse testing to the left, there was were abnormal catch-up saccades suggesting unilateral vestibular loss on the left. Given the fact that leftward saccades were so slow, with head impulses to the right, leftward movements were very normal appearing -if slow leftward saccades were due to nuclear(left 6th nucleus)/infranuclear motility deficits, leftward movements with the vestibulo-ocular reflex (VOR) should look just as slow. In this case, the VOR resulted in much faster movements, which strongly suggests a supranuclear mechanism (in addition to the fact that his right adduction deficit improved with convergence); therefore, it was felt that the left paramedian pontine reticular formation (PPRF) had been preferentially affected as well. Additionally, there was no impairment of smooth pursuit to the left. A left dorsal pontine localization was also supported by pendular nystagmus that had the appearance of oculopalatal tremor, which is commonly related to pathology in the vicinity of the descending central tegmental tract in the pons (in his case without palatal tremor or inferior olivary hypertrophy on MRI -perhaps full-blown ‘oculopalatal tremor' was evolving), and a left lower motor neuron (LMN) facial palsy, which if ‘central', would also support a left pontine localization. However, in his case, a left peripheral LMN facial palsy was entirely possible. The skew deviation (right hypertropia) could theoretically relate to damage just caudal to the decussation involving the utricule-ocular motor fibers at the left pontomedullary junction, although since his disease was so multi-focal and given otherwise unremarkable imaging of the cerebellum and brainstem, it was difficult to localize all of his deficits.
Publisher Spencer S. Eccles Health Sciences Library, University of Utah
Date 2018-04
Format video/mp4
Rights Management Copyright 2018. For further information regarding the rights to this collection, please visit: https://NOVEL.utah.edu/about/copyright
Collection Neuro-ophthalmology Virtual Education Library: NOVEL http://NOVEL.utah.edu
Language eng
ARK ark:/87278/s6n058z5
Setname ehsl_novel_gold
Date Created 2018-04-26
Date Modified 2018-08-01
ID 1316081
Reference URL https://collections.lib.utah.edu/ark:/87278/s6n058z5
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