Using striatal dopamine transporter single photon emission computed tomography imaging to rule out Dementia with Lewy Bodies in elderly patients with antipsychotic‐induced parkinsonism

Abstract

The persistence of antipsychotic-induced parkinsonism (AIP) after antipsychotic withdrawal in elderly patients requires particular attention. A Dementia with Lewy bodies (DLB) could underlie this phenomenon, since DLB is the second most common type of dementia and severe extra-pyramidal reactions are shown in 53% of DLB patients treated with antipsychotics.1 Moreover, the early detection of DLB is important for therapeutic and prognostic management.2 The authors report the use of striatal dopamine transporter (DAT) with single photon emission computed tomography (SPECT) in ruling out DLB in an elderly patient with severe AIP, hallucinations and cognitive symptoms. DAT are dopamine re-uptake proteins located on the presynaptic terminals of dopaminergic neurons, which can be evaluated in vivo by using DAT transported molecules such as [123I]-FP-CIT, that is, iodine I123 radiolabeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropan and SPECT.3 A significant reduction in striatal uptake of [123I]-FP-CIT has been found in DLB, therefore, showing the degeneration of nigrostriatal dopaminergic presynaptic neurons.4 Striatal uptake of [123I]-FP-CIT remains normal in AIP because antipsychotics have a postsynaptic mechanism of action.5 A 75-year-old woman with progressive cognitive decline during the past several months was hospitalized for a major depressive episode with auditory hallucinations. No parkinsonism was detected at the time of admission. She received venlafaxine (150 mg/d) and haloperidol (5 mg/d). On day 8 after the initiation of treatment, she developed severe parkinsonism, which remained unchanged despite central anticholinergic treatment (tropatepine 20 mg/d) and haloperidol discontinuation on day 19. On day 60, depressive symptoms improved markedly, but parkinsonism persisted with a Mini Mental State score of 21. A positive history of severe antipsychotic sensitivity is strongly suggestive of DLB. This suggestive feature is considered sufficient to warrant a diagnosis of possible DLB.6 However, DAT SPECT showed normal uptake and absence of an underlying dopamine deficit, therefore, arguing against the diagnosis of DLB and establishing the diagnosis of AIP. A 2-year clinical follow up further confirmed the diagnosis. [123I]-FP-CIT DAT SPECT is recommended for early detection of dementia with Lewy bodies in elderly patients with severe AIP, hallucinations and cognitive symptoms.