Oculogyric Crisis Phenotype of Levodopa‐Induced Ocular Dyskinesia

Ocular dyskinesia (OD) is an uncommon form of the levodopa induced dyskinesia (LIOD) characterized by short-lasting horizontal or upward conjugate gaze deviation. More sustained deviations resembling oculogyric crises (OGC) are distinctly uncommon.1-4 A 62-yr-old man with a 10-yr history of Parkinson's disease (PD) presented florid ocular dyskinesia mimicking OGC. Levodopa introduction caused increased blinking, up rolling of the eyeballs and dose-dependent restlessness lasting 48 hr with a single dose of 300 mg. Amantadine, safinamide, clonazepam, and dopamine agonists were without benefit, and he stayed off medication for 3 yr. The symptoms recurred after restarting levodopa at age 61. There was no relevant tic, dopamine blocker, encephalitis, or family history. His OFF-UPDRS-III score was 78 (Video 1). Within 10–15 min of levodopa 100 mg increased eyeblink, blepharospasm, right-sided horizontal/upward conjugate eye movements, buccolingual and peribuccal dyskinesia were noted (Video 2). Apomorphine (4 mg) resulted in similar ocular features. MRI brain was normal. Whole-exome sequencing showed variants of unknown significance in GBA p.Arg170His (also in his asymptomatic older sister) and LRRK2 p.Arg1943Trp genes. OD and OGC are two different entities with overlapping features (Table 1). Our patient fulfilled all major proposed criteria for OGC (tonic conjugate eye deviation/lasting minutes-hrs/preserved consciousness), and 2/4 supportive criteria (anxiety, discomfort preceding symptoms/ bothersome symptoms).5 Two (dystonia, low dopamine state improved by anticholinergics/dopaminergic medication) were not met.5 LIOD has been described in 17 patients (Table 2).1-4, 6 All patients presented after ≥3 yr of levodopa and in all but one and ours, the OD was preceded by other dyskinesia. While our patient did not have limb dyskinesia, there were buccolingual dyskinesias present (not present before levodopa therapy). Most patients were unaware of symptoms.1-4, 6 Ocular movements tended to worsen during speaking/performing mental tasks/voluntary limb movements and were temporarily suppressed by will/reading/visual fixation.1-4, 6 In over half (6/9), where gaze deviation details were provided, the deviation occurred towards the more affected by PD body-side (unlike in our patient).1-4, 6 LIOD may be more common than appreciated (e.g., detected in 8/10 patients examined by electrooculography and the remaining two were not assessed at peak levodopa levels).3 Not present Levodopa responsiveness is common in other causes of OGC. In contrast, in addition to our patient there are only two reports of OGC precipitated by levodopa use in patients with parkinsonism.7, 8 The sole report in another patient with presumed PD related to the addition of rasagiline to levodopa (for 10 yr, dose 1000 mg/day).9 Symptoms lasted for 6.5 hr, but in contrast to our case, the patient was also unable to respond, had retrocollis, and foot dystonia.9 The nature of the eye movements in LIOD was proposed to be similar to those generating pursuits or slow phases of nystagmus.3 A role of frontal eye fields, substantia nigra reticulata (SNr), and brainstem nuclei linked with the caudate nucleus was also suggested.1 Recent animal studies demonstrated that selective optical stimulation of caudate tail inhibits SNr neurons projecting to the intermediate superior colliculus layer and leads to prolonged visual-saccadic neuronal excitation and induction of contralateral saccades.6 One hypothesis is that the abnormalities are initially more pronounced in the posterior putamen than in the caudate (oculomotor circuit); therefore, LID spreads from the foot depending on the denervation pattern.1-4 This would explain why LIOD occurs in more advanced PD (when caudate is affected), and with pre-existing dyskinesia. However, this would not explain the symptoms seen in our patient and one other isolated LIOD case, suggesting a different pathogenesis.1-4Further, although amantadine has been recently reported to improve LIOD this was not the case in our patient and these further questions the pathogenic relationship between these rare examples of OGC and more typical examples of LIOD.6 1. Research project: A. Conception, B. Organization, C. Execution; 2. Statistical Analysis: A. Design, B. Execution, C. Review and Critique; 3. Manuscript Preparation: A. Writing of the first draft, B. Review and Critique. D.A.O.: 1A, 1B, 1C, 3A R.S.: 1B, 3B T.S.G.: 1B, 3B V.L.R.: 1B, 3B A.E.L.: 1A, 1B, 1C, 3B L.K.P.: 1A, 1B, 1C, 3B The authors confirm that the approval of an institutional review board was not required for this work. Written informed patient consent was obtained for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. The authors declare that there are no funding sources or conflicts of interest relevant to this work. The authors declare that there are no additional disclosures to report.

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