SPECT FINDINGS IN AN UNUSUAL CASE OF VISUAL HALLUCINOSIS

A 64-year-old right-handed man acutely developed elementary visual hal lucinations (monochromatic, moving geometrical figures), visual illusi ons (distortion of the right side of faces) with achromatopsia and blu rred vision restricted to the left visual hemi-field. CT of the brain before and after administration of contrast medium and a repeat examin ation 2 months later showed no abnormalities, while brain mapping (pow er analysis of EEG) demonstrated theta wave slowing of the curve over the posterior part of the right hemisphere. (TC)-T-99m HMPAO SPECT of the brain, however, demonstrated an area of definite focal hypoperfusi on in the right occipito-temporal region. Echo-Doppler-duplex and cont inuous wave examination of the cervical arterial blood vessels disclos ed bilateral discrete atheromatous plaques that did not affect the blo od flow. Transoesophageal echocardiography demonstrated slight mitral valve insufficiency. Cerebral angiography showed an occlusion of the r ight posterior cerebral artery. After the visual hallucinations had su bsided, SPECT showed partial normalization of the right occipito-tempo ral perfusion, In the absence of CT evidence for a structural lesion i n the clinically suspected areas, only functional imaging revealed an obviously significant lesion. This case furthermore demonstrates that SPECT can contribute to the identification of the pathophysiology unde rlying visual hallucinosis.