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Despite increasing awareness of the high prevalence of functional neurological symptoms, there has been only one recent clinical evaluation of functional eye movement disorders, but this study reported only functional (psychogenic) oculogyric crises, opsoclonus and flutter.1 The aim of this retrospective study was to examine the clinical phenotype and range of functional eye movement disorders, and to report their prevalence across two neuro-otology outpatient clinics.
We performed a systematic retrospective search of the hospital's electronic patient database for patients attending a neurologist-led (AMB) neuro-otology outpatient clinic at Charing Cross Hospital, London, from August 2013 to August 2015 (Clinic 1), and at the National Hospital for Neurology and Neurosurgery, London, from August 2014 to August 2015 (Clinic 2). The terms ‘functional’ or ‘non-organic’ or ‘psychogenic’ or ‘psychosomatic’ or ‘somatoform’ or ‘conversion’ and ‘ocular’ or ‘eyes’ or ‘accommodation’ or ‘near reflex’ or ‘voluntary nystagmus’ or ‘convergence spasm’ or ‘convergent spasm’ or ‘spasm of the near reflex’ or ‘convergence’ were searched for.
From those clinic letters identified from the above searches, patients were included in the study when clinical signs on eye movement examination were deemed to be functional (psychogenic) by the senior clinician (AMB), using chart and video reviews. Table 1 shows the diagnostic categories used.
Six patients out of a total of 147 were found to have a functional eye movement disorder in clinic 1 (4%), and 9 of 670 patients in clinic 2 (1%). The clinical and demographic features of all 15 patients are shown in table 2.
The average age of the 15 patients in the study was 48 years (range 18–73 years). Of the 15 patients, 11 were females and 4 were males. Eight patients (53%) showed evidence of convergence spasm, 6 patients (40%) had functional gaze limitation (see online supplementary video 1) and 1 patient (7%) had functional saccadic oscillations. Eight patients (53%) in the study also presented with other neurological functional signs, most commonly a functional gait disorder. Eight patients (53%) presented with ocular symptoms (diplopia, ‘blurred’ or ‘wobbly’ vision, or visual vertigo), most commonly in the context of convergence spasm (table 2).
A magnetic resonance brain scan was performed in 10 of the 15 patients, all of which were performed prior to referral to our clinics. The scans were normal in all patients except one (patient 5) where an incidental vestibular schwanoma (<5 mm) was identified.
We highlight two findings of clinical relevance: first, functional eye movement disorders are common and occur in 1–4% of patients attending neuro-otology clinics. This is lower than that reported in movement disorder clinics, where the reported functional eye movement disorders were psychogenic oculogyric crises, ‘psychogenic opsoclonus’, and ‘functional saccadic oscillations’.1 Second, identifying functional eye movement disorders during examination may lend weight to a suspected functional disorder as almost half the patients with a functional eye movement disorder in our cohort had an associated functional movement disorder (most commonly a functional gait disorder). We now discuss the different types of functional eye movements observed in our cohorts.
Convergence spasm (CS) was the commonest type of functional eye movement disorder observed. It consists of intermittent brief episodes of convergence, accommodative spasm and miosis. Most patients will report visual disturbance during the spasm (table 2), but not always diplopia. Pupillary constriction is a useful diagnostic sign suggestive of accommodative effort rather than failure of eye abduction. Where miosis is difficult to observe clinically (eg, dark iris), the use of videonystagmography where available might allow pupillary examination in low light conditions. Even if miosis is technically difficult to see during the spasm, a diagnosis of convergence spasm can nevertheless be made when convergence is not sustained and full abduction of the affected eye(s) is observed with distraction or during reflexive eye movements. Although most patients reported CS when fatigued or during tasks requiring high levels of concentration, CS could be triggered during the eye examination with sustained gaze (vertical or horizontal), startle or by positional manoeuvres.
Functional gaze limitation
We found a high proportion of functional limitation of gaze during the clinical evaluation of patients presenting to neuro-otology clinics. The apparent inability to move the eyes is typically transient and intermittent. Improved range of eye movements was observed in all patients during the informal observation of the patient's eye movements during, for example, history taking (the ‘casual’ examination’,3) and either using the dolls-head eye manoeuvre, with verbal encouragement, or reflexive eye movements (see online supplementary video 1). In patients with upward gaze limitation, we observed a lack of eyebrow elevation and a lack of frontalis muscle corrugation, which has previously been reported in a single patient.5
When voluntary nystagmus is experienced as involuntary, this is best referred to as ‘functional’ or ‘psychogenic’.3 The term nystagmus is strictly speaking incorrect, given that these movements consist of low amplitude (∼4°), high-frequency (∼10 Hz) saccadic oscillations that are mostly horizontal; the term ‘psychogenic/functional saccadic oscillations’ has been proposed instead.1 There is often a convergent effort at the onset of the movement, and each episode lasts 5–20 s. There may be accompanying lid flutter as was present in our patient (patient 15). Our patient with functional nystagmus reported that symptoms would occur when she was fatigued, or anxious, and that the frequency of these episodes had increased when she was originally referred to our unit, suggesting perhaps a role for hypervigilance and abnormal attention.
Convergence spasm and functional gaze limitation are the commonest functional eye movements seen in our specialist clinics, and their identification lends weight to a suspected functional movement disorder. Our findings are placed in the context of a neurologically oriented clinical setting, and we suspect that the presence of functional eye movements may be under-recognised. A lack of awareness of the functional nature of these disorders may reinforce patient anxieties about their condition, and lead to invasive investigations and unnecessary treatments.
Contributors VP performed the patient searches, compiled the table and assisted in drafting the manuscript. DK performed patient searches, compiled tables and figures, reviewed clinical data and compiled the manuscript. AMB reviewed all patient data, compiled the manuscript and approved its final version.
Competing interests None declared.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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