[Coma and transtentorial herniation syndrome due to acute non-expansive hemispheric lesion].

An 81-year-old woman developed left hemiplegia and coma due to a right hemisphere infarct and died 6 days later. When first seen in coma she had the classical signs of descending central herniation in the diencephalic stage. The CT scan of the third day showed a large hypodense area occupying the superficial and deep territories of the middle and anterior cerebral arteries on the left as well as a frontal cortico-subcortical hypodense area indicative of an older infarct on the opposite hemisphere. No mass effects were apparent. She followed a downhill course with signs of brainstem deterioration. A second CT scan a few hours before death revealed the expected pattern of brain shift and herniations. This case adds to the available evidence showing that the clinical signs of encroachment of supratentorial structures upon the basal forebrain can be reproduced by an acute mono-hemispheral lesion without visible mass effects. It indicates, further, that the role of intracranial displacements in the genesis and short-term prognosis of coma remains an unsettled matter. In at least a few number of cases, diaschisis might play a major role.