Ocular Palatal Tremor With Face "Twitches"

The syndrome of ocular palatal tremor (OPT) is a unique manifestation of a breach in the Guillain-Mollaret (1) triangle because of a lesion affecting the projections of the deep cerebellar nuclei of the central tegmental tract.

Clinical Correspondence Section Editors: Robert Avery, DO Karl C. Golnik, MD Caroline Froment, MD, PhD An-Guor Wang, MD Ocular Palatal Tremor With Face “Twitches” Mohamed ElKasaby, MD, Abdullah Alqahtani, MD, Fatema F. Ghasia, MD, Aasef G. Shaikh, MD, PhD T he syndrome of ocular palatal tremor (OPT) is a unique manifestation of a breach in the Guillain– Mollaret (1) triangle because of a lesion affecting the projections of the deep cerebellar nuclei of the central tegmental tract. The breach leads to disinhibition and pseudohypertrophy of the inferior olive and consequent spontaneous rhythmic discharges (2). The rhythm is then propagated through the inferior cerebellar peduncle to the contralateral cerebellum triggering maladaptive learning leading to coarse and irregular oscillations (3). Progressive ataxia palatal syndrome and OPT plus dystonia (OPT-D) are 2 of the known OPT variants (4,5). Here, we describe a novel OPT variant in a series of patients who had classic manifestations of OPT. Besides, they also had involuntary twitches of face muscles innervated by the VIIth cranial nerve. Six OPT patients who also had face muscle twitches were studied. The subjects signed an ethics committee– approved informed consent form. We videotaped the neurological examination and eye movements in these patients (See Supplemental Digital Content, Video E1, http:// links.lww.com/WNO/A489). Recorded examinations were independently rated by at least 2 of the authors finding mutually consistent observations. All patients had MRI findings of the enlarged inferior olive. Each patient had a distinct primary etiology that led to pseudohypertrophy of the Guillain–Mollaret triangle as Ophthalmology Department, Capital and Coast District Health Board, Wellington, New Zealand. Supported by the American Academy of Neurology Career Development Award (A. G. Shaikh), American Parkinson’s Disease Association Cotzias fellowship (A. G. Shaikh), Dystonia Medical Research Foundation research grant (A. G. Shaikh), Department of Veterans Affairs Merit Review (A. G. Shaikh), philanthropic support to the Department of Neurology at the University Hospitals (Allan Woll Fund and Fox family fund), Blind Children’s Foundation grant (F. F. Ghasia), and Research to Prevent Blindness Disney Award (F. F. Ghasia). A. G. Shaikh is the recipient of Penni and Stephen Weinberg Chair in Brain Health at the University Hospitals. The authors report no conflicts of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www. jneuro-ophthalmology.com). Address correspondence to Aasef G. Shaikh, MD, PhD, Department of Neurology, University Hospitals, 11100 Euclid Avenue, Cleveland, OH 44110; E-mail: [e-mail] ElKasaby et al: J Neuro-Ophthalmol 2022; 42: e581-e582 outlined in the Supplemental Digital Content (see Table E1, http://links.lww.com/WNO/A488). Clinical examination in all patients revealed irregular and disconjugate oscillations of the eyes. The eye oscillation frequency ranged between 2 and 3 Hz. All patients had jerky and irregular palate oscillations. The facial nerve innervated muscle twitches idiosyncratically varied among different patients. One patient had twitches affecting bilateral eyelids, upper lip, and tongue; orbicularis oculi, orbicularis oris, and the tongue’s longitudinal muscle were involved in this patient. Two patients had left eyebrow twitches; frontalis muscle was affected in these patients. One patient had twitches of the chin, that is, involvement of the mentalis. Platysma was involved in 2 patients; one of these patients also had the involvement of bilateral levator anguli oris. The frequency of facial muscle twitches ranged between 1 and 3 Hz with a mean of 1.5 Hz. In 4 patients, the facial twitches were unilateral. In 2 patients, the twitches were rhythmic. The face twitches and eye oscillations were asynchronous and often had different baseline frequencies. One patient with face twitches did not have eye oscillations. Differences in semiology between ocular and palatal oscillations and facial muscle twitches suggested that the latter were not compensatory or secondary to the eye or palate oscillations. Supplemental Digital Content (see Table E1, http://links.lww. com/WNO/A488) depicts additional features in the patients’ clinical phenomenology. The supplementary material also depicts 2 exemplary videos. In addition to the classic manifestations, that is, eye and palatal oscillations, OPT may have symptoms consistent with the primary lesion location. Symptoms independent of the primary lesion location are also possible. For example, it was suggested that hyperactive inferior olive and its connection with the cerebellar cortex cause conditioned learning of aberrant inferior olive discharge and maladaptive plasticity (3). The maladaptation leads to dystonic jerky movements, that is, OPT-D (5). We believe that face twitches described in the present series of patients were also independent of the primary etiology. We speculate 2 pathophysiological theories. One explanation is based on the involvement of the facial nucleus or postnuclear portion of the facial nerve to describe coexisting OPT and face muscle twitches (6). This theory, in our patients, however, requires 2 spatially and physiologically distinct deficits, one causing OPT and another leading to e581 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Correspondence involvement of the face muscles (2,7). Such dual deficits were not seen in our patients. The second speculation involves dual-mechanism theory for OPT entailing maladaptive cerebellar learning of synchronous inferior olive discharge. The maladaptive inferior olive and cerebellar discharge could lead to movements that could appear like dystonia (5). It is possible that maladaptive discharge could cause face muscle twitches through the same mechanism that also causes dystonia. In summary, we report a variant of OPT presenting with face muscle twitches in the myotomic distribution of the VIIth nerve. The face muscle twitches seemed temporally independent of eye oscillations. We cannot be certain about the physiological underpinning of such muscle twitches, but it is speculated that they could be due to maladaptation in inferior olive cerebellar network. e582 REFERENCES 1. Guillain G, Mollaret P. Both syncronous and myoclonus rhythms of Larynx-pharynx-eye-diaphragm. Rev Neurol. 1931;2:545–566. 2. Herrmann CJ, Brown JW. Palatal myoclonus: a reappraisal. J Neurol Sci. 1966;3:473–492. 3. Shaikh AG, Hong S, Liao K, Tian J, Solomon D, Zee DS, Leigh RJ, Optican LM. Oculopalatal tremor explained by a model of inferior olivary hypertrophy and cerebellar plasticity. Brain. 2010;133:923–940. 4. Samuel M, Torun N, Sharpe JA, Lang AE. Progressive ataxia and palatal tremor (PAPT): clinical and MRI assessment with review of palatal tremors. Brain. 2004;127:1252–1268. 5. Shaikh AG, Ghasia FF, DeLong MR, Jinnah HA, Freeman A, Factor SA. Ocular palatal tremor plus dystonia: new syndromic association. Mov Disord Clin Pract. 2015;2:267–270. 6. 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