Superior oblique myokymia: diagnostic criteria and long-term outcome

BACKGROUND: Superior oblique myokymia (SOM) is a rare disorder characterized by brief episodes of high-frequency, low-amplitude monocular nystagmus frequently caused by vascular contact with the trochlear nerve. Comprehensive analyses of SOM symptomatology and long-term progression are limited. No diagnostic criteria are available. METHODS: Adult patients who were diagnosed with SOM between 2008 and 2024 were asked to complete a detailed questionnaire on disease symptomatology, time course, and medication. The impact of the disease on patient-reported functioning was assessed using a Likert scale. In addition, medical records were screened in all patients. RESULTS: A total of 35 patients with SOM were identified (21 females; mean age at symptom onset 42.8 ± 15.0 years). 30 patients experienced visuo-perceptual symptoms (i.e., diplopia or oscillopsia, 85.7%), 22 patients ocular motor symptoms (i.e., noticeable "eye-twitching", 62.9%), and 15 patients dizziness or gait instability (42.9%). Of 22 patients analyzed for their long-term therapeutic outcome, 13 described symptom improvement with pharmacotherapy, and six without pharmacotherapy. Patients experienced a moderate to high impact of the disease on their daily private and professional lives. Based on these findings, specific diagnostic criteria for SOM were proposed. CONCLUSIONS: SOM can substantially impair patients' quality of life and daily functioning. The long-term course appears favorable, with most patients experiencing either complete remission or significant symptom reduction over time. Pharmaceutical treatment proved effective in nearly 90% of patients, and spontaneous remission was also observed. Further research should focus on larger patient cohorts defined by clear diagnostic criteria to enhance understanding of SOM's natural history and treatment outcomes.