Diplopia in Parkinson's disease: Indication of a cortical phenotype with cognitive dysfunction?

BACKGROUND: Visual disturbances are increasingly recognized as common non-motor symptoms in Parkinson's disease (PD). In PD patients, intermittent diplopia has been found to be associated with the presence of visual hallucinations and the Parkinson's psychosis spectrum. Here, we investigated whether diplopia in PD is associated with other non-motor traits and cognitive impairment. METHODS: We investigated 50 non-demented PD patients with and without intermittent diplopia and 24 healthy controls for visual disturbances, as well as motor and non-motor symptoms. All participants underwent a neuropsychological test battery; visuospatial abilities were further evaluated with subtests of the Visual Object and Space Perception Battery (VOSP). The two PD patient groups did not differ significantly in age, symptom duration, motor symptom severity, frequency of visual hallucinations, or visual sensory efficiency. RESULTS: PD patients with diplopia reported more frequent non-motor symptoms including more subjective cognitive problems and apathy without changes in global cognition measures compared to those without diplopia. PD patients with diplopia had greater impairment in several tests of visuospatial function (pentagon copying p = .002; number location p = .001; cube analysis p < .02) and object perception (p < .001) compared to PD patients without diplopia and healthy controls. By contrast, no consistent group differences were observed in executive function, memory, or language. CONCLUSIONS: PD patients with diplopia have a greater non-motor symptom burden and deficits in visuospatial function compared to PD patients without diplopia. PD patients with diplopia might be prone to a cortical phenotype with cognitive decline and apathy associated with worse prognosis.

Characterization of diplopia in non-demented patients with Parkinson's disease.

INTRODUCTION: Although diplopia is considered a frequent symptom of Parkinson's disease (PD), little is known about its clinical manifestation, associated mechanisms and treatment. Here we characterized binocular diplopia in non-demented PD patients in an interdisciplinary setting. METHODS: PD patients were prospectively screened for diplopia, visual hallucinations, problems with spatial perception, contrast sensitivity, presence of blurred vision, and history of ophthalmological comorbidities via interview. Two groups of PD patients, one with and one without diplopia, underwent clinical and ophthalmological assessment to characterize diplopia in these patients. Clinical features were investigated using the Unified Parkinson's Disease Rating Scale and the Non-Motor Symptoms Scale. RESULTS: The frequency of binocular diplopia was 29.6% (n = 37) in our cohort of 125 Parkinson's disease patients. Related mechanisms were heterogeneous including convergence insufficiency, strabismus, and motor fluctuations, as well as symptoms related to visual hallucinations. Diplopia was associated with other visual disturbances like visual hallucinations, blurred vision and problems with spatial perception. Beyond that, diplopia was found to be a predictive factor (3.2, odds ratio) for the occurrence of visual hallucinations in PD. CONCLUSION: Binocular diplopia represents a frequent and relevant symptom in PD patients. Different subtypes should be considered due to different associated mechanisms including ophthalmic pathology and motor fluctuation, as well as intermediate to higher level visual processes. Diplopia seems to be part of a continuous spectrum of positive visual symptoms in Parkinson's disease.