Visual hallucinations in dementia with Lewy bodies: transcranial magnetic stimulation study.
BACKGROUND
The aetiology of visual hallucinations is poorly understood in dementia with Lewy bodies. Pathological alterations in visual cortical excitability may be one contributory mechanism.


OBJECTIVE
To determine visual cortical excitability in people with dementia with Lewy bodies compared with aged-matched controls and also the relationship between visual cortical excitability and visual hallucinations in dementia with Lewy bodies.


METHODS
Visual cortical excitability was determined by using transcranial magnetic stimulation (TMS) applied to the occiput to elicit phosphenes (transient subjective visual responses) in 21 patients with dementia with Lewy bodies and 19 age-matched controls.


RESULTS
Phosphene parameters were similar between both groups. However, in the patients with dementia with Lewy bodies, TMS measures of visual cortical excitability correlated strongly with the severity of visual hallucinations (P = 0.005). Six patients with dementia with Lewy bodies experienced visual hallucination-like phosphenes (for example, seeing people or figures on stimulation) compared with none of the controls (P = 0.02).


CONCLUSIONS
Increased visual cortical excitability in dementia with Lewy bodies does not appear to explain visual hallucinations but it may be a marker for their severity.
Institute for Ageing and Health, Newcastle University, Wolfson Research Centre, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK. john-paul.taylor@ncl.ac.uk
John-Paul
JP
Taylor
Michael
M
Firbank
Nicola
N
Barnett
Sarah
S
Pearce
Anthea
A
Livingstone
Urs
U
Mosimann
Janet
J
Eyre
Ian G
IG
McKeith
John T
JT
O'Brien
D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping; D016022:Case-Control Studies; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003704:Dementia / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D006212:Hallucinations / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D016631:Lewy Bodies / Q000378:metabolism*; D020961:Lewy Body Disease / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010300:Parkinson Disease / Q000378:metabolism / Q000503:physiopathology; D010719:Phosphenes / Q000187:drug effects / Q000502:physiology; D012684:Sensory Thresholds; D012720:Severity of Illness Index; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014793:Visual Cortex / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*
D002800:Cholinesterase Inhibitors