Functional Opsoclonus: Mimicry of a Rare Ocular Phenomenon
Amanda Lin1, Aishwarya Koppanatham2, Alberto Espay1
1James J. and Joan A. Gardner Family Center for Parkinson's Disease and Movement Disorders, University of Cincinnati., 2Andhra Medical College
Objective:
To present a case of functional saccadic oscillations reaching, at times, the category of opsoclonus, in a young woman with recurrent visual disturbances.
Background:

Functional neurological disorders (FND) are a group of disorders that can manifest as a variety of neurological symptoms, including weakness, tremor, and sensory loss. Although phenotypically heterogeneous, FND can be diagnosed when examination reveals variability, inconsistency, and distractibility of the symptoms. Presentations of FND involving eye movement abnormalities are uncommon and diagnostically challenging, which likely contributes to their under diagnosis and underreporting in the literature.


Design/Methods:
N/A
Results:

A 31-year-old woman with a past medical history of depression, obsessive-compulsive disorder, eating disorder, and migraines presented with sudden-onset episodes of visual disturbance following recovery from viral conjunctivitis. The episodes were variable in nature, consisting of transient left hemifield vision loss, photopsias, spatial disorientation, and associated with imbalance. They occurred multiple times per day and typically lasted 30–45 minutes. 

Neurological examination revealed frequent saccadic intrusions during smooth pursuit and primary gaze. At times, when attempting vertical gaze during examination, multidirectional saccades were observed without an intersaccadic pause, thus meeting the criteria for opsoclonus. The ocular oscillations varied in frequency, direction, and amplitude, worsening with attention and disappearing with distraction. Other elements of the neurological examination included an inconsistent T10 sensory level and an exaggerated response to the pull test. The rest of the neurological examination was normal.

She was diagnosed with FND expressed as functional oculomotor impairment and functional sensory loss. 

Conclusions:
Functional saccadic oscillations are a rare ocular manifestation of FND, with episodes of opsoclonus not previously reported. As with other functional disorders, diagnosis relies on demonstrating inconsistency, variability, and distractibility. Recognition of this presentation is crucial to prevent unnecessary investigations and to inform appropriate management. Patient education, cognitive-behavioral therapy, and attention-modulation strategies are key components of care.
10.1212/WNL.0000000000212914
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