Amnesia after right frontal subcortical lesion, following removal of a colloid cyst of the septum pellucidum and third ventricle

Amnesia is usually associated with bilateral medial temporal lesions. Only few cases of amnesia associated with isolated frontal white matter lesion are described in literature, while the role of frontal-striatal-thalamic circuit in cognition is still elusive. The aim of this case report was to bring a contribution to the role of frontal-striatal-thalamic pathways in human memory. The authors describe the neuropsychological longitudinal profile of a 40-year-old man that developed amnesia after removal of an asymptomatic colloid cyst of the septum pellucidum and third ventricle that damaged the right frontal subcortical white matter, sparing the fornix and other limbic regions. The patient showed working memory deficit, anterograde amnesia for verbal and non verbal materials and mild frontal executive deficits. A follow-up evaluation 13 months after onset showed only some mild improvements in his memory functions. The authors hypothesize that amnesia may have been caused by impairment of working memory and encoding process as a consequence of a lesion of the dorsolateral prefrontal circuit, that disrupted the projections to the neos-triatum and the thalamus. These observations suggest that the frontal-striatal-thalamic pathways might have a crucial role in working memory and encoding processes, and also that one mechanism for memory impairments in white matter diseases is the discon-nection of this fronto-subcortical connections.