The aim of this study is to determine whether saccadic eye movement recording may help in the discrimination between Lewy body dementia and Alzheimer disease, in the early stages of the disease.

Study type: Interventional Study design: Intervention Model: Single group assignment Primary purpose: Diagnostic

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia. In its early stages, the differential diagnosis of DLB and Alzheimer's disease (AD) can be challenging. The differential diagnosis is particularly important given that patients with DLB respond well to cholinesterase inhibitors but show sensitivity to neuroleptic medications which are contraindicated in DLB. DLB tends to progress more quickly than Alzheimer's disease. Diagnostic accuracy may be improved. Oculomotor recording, easy to perform could be helpful in order to identify and reliably assess fluctuating attention performance in DLB patients.

Main objective:

- to improve differential diagnosis between DLB and AD in the early stages of the disease with oculomotor measurements

Secondary objectives:

• to examine the association between the oculomotor records and neuropsychological examination assessing attention abilities and their fluctuations
• to evaluate the benefit of complementary neuropsychological tests in the distinction between DLB and AD cases
• to examine the relationship between hippocampal volume and neuropsychological examination in DLB cases
• to examine the diagnostic performance of MRI (Support Vector Machine) between DLB and AD
• to examine the interest of CSF alpha synuclein concentration to discriminate DLB from AD
• to assess at one year variations in oculomotor test scores and neuropsychological test scores Method and design Longitudinal multicenter study including 100 patients with a DLB or AD diagnosis. Clinical examination at one year.

Inclusion Criteria:

• Patients aged 65 and over
• Patients with a diagnosis of probable DLB or AD according to the Consortium on DLB criteria (McKeith et al 2005) for Lewy bodies dementia and according to DSM IV and NINCDS- ADRDA criteria for AD or patients in whom there is diagnostic uncertainty between DLB and AD
• No major sensory deficits
• MMSE > 20
• Having signed an informed consent form

Exclusion Criteria:

• Parkinson syndrome progressing for more than one year regarding cognitive impairment
• Use of AchEIs medication
• Taking or having taken anti Parkinson drugs
• Neuroleptic drugs over the previous three months
• Contraindication for lumbar puncture (i.e. anticoagulant agents)
• Patients with Geriatric Depression Scale (GDS) > 10
• Taking medication that could impact dopamine transporter's measurement
• Contraindication for MRI examination
• Diseases involving the short-term survival (shorter than one year)
• Not fluent in French
• Major sensory deficits that could interfere with cognitive assessment (visual and auditory)
• Being under guardianship
• Absence of caregiver/informant to sign informed consent form
• Non health insurance affiliation