Regional cerebral blood flow changes in a patient with delusional parasitosis before and after successful treatment with risperidone: A case report

The pathophysiology and appropriate pharmacological interventions for delusional parasitosis (DP) remain unknown. Here, we present a case of DP following brain infarction of the right temporoparietal region. Pharmacotherapy with risperidone resulted in a dramatic therapeutic response over a short period. In a sequential N-isopropyl-p-[123I]-iodoamphetamine single photon emission computed tomography ([123I]-IMP SPECT) study, post-treatment SPECT images revealed a marked increase of rCBF in the large areas including the bilateral frontal and left temporoparietal regions, the right parietal operculum and the bilateral basal ganglia, in contrast to pre-treatment SPECT images showing a global decrease of rCBF. Our clinical outcome suggests the efficacy and safety of risperidone for treatment of DP and that both dopaminergic and serotonergic dysfunction may play a role in DP. Our sequential SPECT findings suggest that psychiatric improvement of DP is associated with increased rCBF.