Revising a diagnosis of functional neurological disorder—a c
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Functional neurological disorders (FND) are defined by neurological symptoms not explained by identifiable neurological pathology and represent up to one-third of neurology outpatient clinic attendances. There is growing emphasis on diagnosis involving demonstration of positive clinical signs, and a reduced emphasis on the demonstration of precipitating traumatic life-events. FND diagnosis demonstrate high diagnostic stability, with a misdiagnosis rate of 4% according to one systematic review.

A 62-year-old female presented to neuropsychiatry services with a 3-year history of gradually progressive dysphonia, difficulty with keeping her eyes open and falls. Her medical history consisted of chronic obstructive pulmonary disease, type 2 diabetes mellitus, ischaemic heart disease, hypertension, grade 3b chronic kidney disease (secondary to hypertensive disease) and anaemia.

She was referred to otorhinolaryngology 1 year after the development of vocal symptoms. At the time, there was no associated odynophagia or dysphagia, but she had described all-over-body pain and difficulty with handwriting. She started experiencing difficulty keeping her eyes open voluntarily and found wearing sunglasses helped with this. Laryngoscopy revealed slowed movements of the hypopharynx and larynx. Speech and language therapy (SALT) assessment reported normal orofacial muscle function with effortful and delayed vocal production. Communication was often supplemented with hand gestures.

Vocal output was variable, at times able to produce complete words audibly, at other times being unable to phonate or imitate sounds to command. She was able to cough and swallowing was preserved. A diagnosis of functional voice disorder was made, and she was referred to an inpatient rehabilitation programme for patients with FND.

Neuropsychiatric review (3 years after symptom onset) revealed that she had started falling and stopped cooking or going outdoors. Montreal Cognitive Assessment revealed a score of 22/30. Neurological examination demonstrated aphonia, eyelid apraxia and blepharospasm, near-constant use of sunglasses indoors and frequent touching of the corner of her eyes (a sensory geste).

MRI showed hypointense signal within the substantia nigra, red nuclei and globus pallidus on susceptibility-weighted imaging (SWI), suggestive of iron deposition. The diagnosis was then revised from FND to an atypical akinetic rigid syndrome. Gait speed and efficiency had improved at the point of discharge from the rehabilitation programme, which was felt to be a non-specific effect of physiotherapy.

Her care was then transferred to neurology. Clinical examination revealed aphonia and apraxia of eyelid opening, mild limitation of upgaze, hypometric vertical saccades and frontalis overactivity. Bilateral bradykinesia, right-sided rigidity and right foot dystonia also were noted. A clinical diagnosis of progressive supranuclear palsy was made, and she received ongoing botulinum toxin treatment and SALT input.