Functional (psychogenic) saccadic oscillations and oculogyric crises

Abstract

In their Review in The Lancet Neurology, Diego Kaski and colleagues describe the clinical features of cranial functional (psychogenic) movement disorders, including ocular movement disorders. The authors correctly state that there is no information available regarding the frequency of eye functional movement disorders. We have recently studied a cohort of 182 patients with functional movement disorders and identified 11 (6%) patients with functional (psychogenic) ophthalmological movement disorders. This proportion is lower than those reported in previous series describing other functional (psychogenic) cranial movement disorders. We identifi ed evidence consistent with oculogyric crises in seven cases, opsoclonus in fi ve cases, and ocular fl utter in one case (two patients had two types of psychogenic ophthalmological movement disorders). These patients were not different in terms of sex and other movement disorders compared with those without psychogenic ophthalmological movement disorders. Most of our patients had symptoms including oscillopsia, inability to fixate, and blindness, the latter being related to persistent ocular supraversion and psychogenic blepharospasm, adding to the burden of other psychogenic symptoms. We highlight some clinical features that should make the clinician suspicious of functional (psychogenic) causes for such ocular movements, including suggestibility, inability to voluntarily suppress the ocular movements, prominent distractibi l ity, and temporal correlation with other functional movement disorders. However, such patients could be misdiagnosed as having a disorder with different causes, such as symptoms being druginduced, neoplastic, paraneoplastic, autoimmune, hereditary, or of vascular origin. Kaski and colleagues state that nystagmus has at least one slow phase, which differs from saccadic oscillations in which both phases are rapid. For this reason we do not use the terms psychogenic or functional nystagmus; instead we think that these movements should fall into the category of psychogenic or functional saccadic oscillations and oculogyric crises. In the case of oculogyric crises, the conjugated ocular movements are more sustained. In psychogenic eye flutter, the ability to provoke such movement voluntarily has been reported in 8% of healthy controls. A livelily debate is ongoing about which term should be used to name these movements, psychogenic or functional. Whereas the term psychogenic assumes a purely psychological cause, the term functional lacks specificity and does not address disability, given that these disorders are actually quite dysfunctional rather than functional.