ACCURACY OF FLUOROPROPYL‐2β‐CARBOMETHOXY‐3β‐(4‐ IODOPHENYL) NORTROPANE DATSCAN FOR THE DIAGNOSIS OF LEWY BODY DEMENTIA

Abstract

To the Editor: Dementia with Lewy bodies (DLB), the second main cause of dementia after Alzheimer's disease, is responsible for 15% to 25% of neurodegenerative dementia. Diagnosis at an early stage is sometimes difficult. Diagnostic criteria have been established and reviewed to facilitate diagnosis.1 Evaluation of dopamine transporter with fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (single photon emission computed tomography (SPECT)), referred to as DaTSCAN (General Electric Health Care, Chalfont St. Giles, UK), appears useful in differentiating Alzheimer's disease from DLB. An 84-year-old woman presented with a 2-year fluctuating cognitive decline associated with recurrent visual hallucinations. Her neurological examination was normal. Her past medical history included chronic atrial fibrillation and hypertension. The first suspected diagnosis was Alzheimer's disease because of the progressive evolution and the neuropsychological test showing altered episodic memory. Her Mini-Mental State Examination score was 25. Her brain computed tomography (CT) scan showed global atrophy. Treatment with a neuroleptic drug was started to reduce hallucinations but was stopped because of worsening cognitive decline. The patient was transferred to the Geriatrics Department at CHU La Miletrie, Poitiers, France. Clinical examination did not show any parkinsonism. Daily visual hallucinations continued. The patient exhibited a misidentification delusion (Capgras syndrome), because she believed she saw her son's double. Biological blood testing was normal. Electroencephalography was requested because of suspected temporal lobe epilepsy, but no evidence was found. Cerebral perfusion SPECT was performed that showed a distinct reduction of cortical perfusion with occipital affect, which is uncommon in Alzheimer's disease. The association between fluctuating cognitive decline and recurrent visual hallucinations suggested DLB, despite the absence of parkinsonian syndrome. DaTSCAN was performed and showed distinct dopamine transporter asymmetry at the expense of the right striatum (Figure 1), which strengthened the diagnostic hypothesis. Treatment with an acetylcholinesterase inhibitor resulted in rapid cognitive improvement and reduced hallucinations. After 36 months of follow-up, the patient was free of clinical parkinsonian syndrome. DaTSCAN shows distinct dopamine transporter asymmetry with lack of binding in the right putamen. This case report confirms the usefulness of SPECT imaging with DaTSCAN to facilitate the diagnosis of dementia. A European, multicenter, prospective, longitudinal study reported a mean sensitivity of 78% and specificity of 97% with the use of DaTSCAN to ascertain the diagnosis of Parkinson's disease.2 DaTSCAN is also helpful for patients with hallucinations.3 This case underscores the accuracy of DaTSCAN SPECT to optimize the diagnosis in patients with uncertain degenerative disease. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Odile Bouverie: study concept and design, acquisition of subjects and data, analysis and interpretation of data, and preparation of letter. Rémi Coudroy and François Salmon:and Roger Gil analysis and interpretation of data and preparation of manuscript. Isabelle Merlet-Chicoine and Roger Gil: analysis and interpretation of data. Marc Paccalin: study concept and design, analysis and interpretation of data, and preparation of manuscript. Sponsor's Role: No sponsor's role.