Journal Article

Functional involvement of central cholinergic circuits and visual hallucinations in Parkinson's disease

Fiore Manganelli, Carmine Vitale, Gabriella Santangelo, Chiara Pisciotta, Rosa Iodice, Autilia Cozzolino, Raffaele Dubbioso, Marina Picillo, Paolo Barone and Lucio Santoro

in Brain

Published on behalf of The Guarantors of Brain

Volume 132, issue 9, pages 2350-2355
Published in print September 2009 | ISSN: 0006-8950
Published online July 2009 | e-ISSN: 1460-2156 | DOI: http://dx.doi.org/10.1093/brain/awp166
Functional involvement of central cholinergic circuits and visual hallucinations in Parkinson's disease

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Visual hallucinations (VHs) represent a frequent and disturbing complication of Parkinson's disease. Evidence suggests that VH can be related to central cholinergic dysfunction. Short-latency afferent inhibition (SAI) technique gives the opportunity to test an inhibitory cholinergic circuit in the human cerebral motor cortex. This inhibition of motor-evoked potentials can be observed when transcranial magnetic stimulation is delivered with a delay ranging from 2 to 8 ms, after a peripheral nerve afferent input has reached the somatosensory cortex. We applied SAI technique in 10 non-demented patients with Parkinson's disease with VHs, in 12 non-demented patients with Parkinson's disease without VHs (NVH-pts) and in 11 age-matched normal controls. All patients with Parkinson's disease underwent a battery of neuropsychological tests to assess frontal and visuospatial functions, memory and attention. SAI was significantly reduced in patients with VHs compared with controls and patients without VHs. Neuropsychological examination showed a mild cognitive impairment in 16 out of 22 patients with Parkinson's disease. In addition, we found that in our patients with VHs, performance of some tasks evaluating visuospatial functions and attentional/frontal lobe functions was significantly more impaired than in patients without VHs. SAI abnormalities, presence of VH and neuropsychological results strongly support the hypothesis of cholinergic dysfunction in some patients with Parkinson's disease, who will probably develop a dementia. A follow-up study of our patients is required to verify whether SAI abnormalities can predict a future severe cognitive decline. Moreover, SAI can also be very useful to follow-up the efficacy of anti-cholinesterase therapies.

Keywords: Parkinson's disease; TMS; short-latency afferent inhibition; cognitive deficits; visual hallucinations

Journal Article.  3772 words. 

Subjects: Neurology ; Neuroscience

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