Congenital cyclic oculomotor palsy and spasms: a review of the literature and presentation of two new cases

Background: Cyclic oculomotor palsy and spasms (COPS) is a rare neurological syndrome characterized by alternating involuntary phases of paresis and spasm of muscles supplied by the oculomotor nerve. Its etiology, management, and long-term prognosis are poorly understood. The purpose of this study was to provide a systematic review of the published literature and present 2 new cases. Methods: We systematically reviewed the literature on congenital COPS following PRISMA guidelines (PROSPERO CRD42021286740). Searches were conducted in MEDLINE, EMBASE, Web of Science, KoreaMed, KMBase, KISS, KCI, CiNii, ICHUSHI, CNKI, CQVIP, African Index Medicus, African Journals Online, LILACS through September 1, 2024. Results: In total, 124 congenital COPS cases were identified. Most cases developed oculomotor palsy during infancy (mean, <1 year) before later developing the cycling syndrome (range, 2 months-22 years) involving the pupil (99%), levator (86%), and extraocular muscles (57%). The results of neuroimaging were typically normal. Amblyopia was common (72%), and surgical correction of ptosis/exotropia for cosmesis had variable success and did not abolish cycling. Oral carbamazepine successfully abolished cycling in one case with no recurrences during 5 years’ follow-up. Conclusions: Based on our review, we recommend a standardized nomenclature and definition of COPS. Neuroimaging is not required for diagnosis but may be indicated in cases with associated neurological morbidities or acquired cases with no clear precedent. There are similarities between COPS and other ephaptic disorders, and further research is warranted to assess the efficacy of carbamazepine in its management.