Frontotemporal Brain Sagging Syndrome as a Treatable Cause Mimicking Frontotemporal Dementia: A Case Report

Frontotemporal brain sagging syndrome (FBSS) is a progressive disorder characterized by symptoms similar to the behavioral variant of frontotemporal dementia (FTD), with a sagging appearance of the brain on imaging similar to that observed in spontaneous intracranial hypotension (SIH). The onset of behavioral and cognitive symptoms of FBSS is insidious and progressive, similar to those of FTD. Here, we report a case involving a 53-year-old man with progressive hypersomnolence, apathy, forgetfulness, and personality changes but without headache or auditory symptoms. The combination of frontotemporal dysfunction, hypersomnolence, and the appearance of a sagging brain on magnetic resonance imaging suggested a diagnosis of FBSS. Although a definite site of cerebrospinal fluid leakage could not be identified in our case, clinical symptoms and imaging findings were improved after an epidural blood patch. Considering FBSS as a differential diagnosis of FTD is important even in the absence of typical SIH symptoms, such as headache or auditory symptoms.