Objective: To assess somatoform disorder (SFMD) prevalence and impact in Parkinson disease (PD) and dementia with Lewy bodies (DLB).
Methods: SFMD were assessed by direct observation of symptoms in the year coincident (+/-6 months) with definite diagnosis of PD, DLB, Alzheimer disease, multiple system atrophy, progressive supranuclear palsy, or frontotemporal dementia, and by interviews with patients, caregivers, and general practitioners, and reviews of prior hospital admissions, in a cohort of 942 patients with neurodegenerative disorders. Matched groups of patients with PD and patients with DLB without vs with SFMD were selected for comparisons and followed up over 4 years.
Results: The frequency of SFMD was higher in DLB (15 patients, 12%) and PD (29 patients, 7%) than in other neurodegenerative diseases (0%-3%). SFMD consisted of conversion motor or sensory disorders, often accompanied by delusional thought content; in one patient catatonic symptoms were observed concomitantly with PD diagnosis. Evidence of SFMD symptoms, preceding diagnosis by 6 months-10 years, was obtained in 28 patients with PD and all patients with DLB. A total of 22 patients with PD and all patients with DLB could be followed for 4 years. SFMD symptoms recurred during follow-up, with catatonic signs developing in 9 patients with PD and 8 patients with DLB. Most baseline demographic and clinical features did not differ between subjects with or without SFMD. Decline of cognitive function was greater in PD-SFMD patients than in those without SFMD (p < 0.01); it was comparable to that observed in DLB.
Conclusions: The frequency of somatoform disorder (SFMD) (with catatonic signs) in Parkinson disease and dementia with Lewy bodies suggests that SFMD are part of the spectrum of Lewy body diseases.