Functional Cortical lnvolvement in Paramedian Tha/amic (Diencephalic) Syndrome: An Example for Cortico-subcortical Disconnections

Abstract

Background: Paramedian thalamic (diencephalic) syndrome (PTS) has been characterized by hypersomnolence apathy, amnesia and vertical gaze limitation. It is rarely encountered in the neurological practice. Subcortical dementia developes during the disease course in some of these cases. Dementia seen in this syndrome is supposed to be due to disconnection of thalamic dorsomedial nuclei and their cortical connections. Lschemia due to obstruction of the posterior thalamo-subthalamic paramedian artery and rarely hemaorrhagic and tumoral lesions are reported as etiologic causes. In additionto the subcortical dementia, limitation of vertical eye movements, motor abnormalities and hypersomnolant apathia develop.Objective: In this paper, SPECT and neuroradiologic findings of a 42 year old female PTS patient with hypertension and diabetes mellitus are evaluated.Findings: In addition to bilateral thalamic lesions on CT, frontal and temporoparieatal diffuse hypoperfusion were observed on SPECTConclusion: 0ur case,along with the other cases in the literature shows that classical lesion studies by CT may not detect cortico-subcortical relations which can be observed by doing perfusion studies.