Uplifting news for frontotemporal dementia: The sagging brain syndrome.

Neurology 2011;76:1370–1371 In this issue of Neurology, Wicklund et al.1 report and discuss an extraordinary series of individuals with clinical features of behavior variant frontotemporal dementia (bvFTD)2 caused by frontotemporal brain sagging syndrome (FBSS) (spontaneous intracranial hypotension). In FBSS, structural imaging shows downward displacement or “sagging” of the brain,3 which may have an iatrogenic or traumatic etiology, or occur spontaneously.4 Some cases of spontaneous FBSS may occur with dural rupture and CSF leakage along nerve root sleeves.5 Other times, however, CSF leakage is not demonstrated. The precise mechanism thus remains to be established. This syndrome nevertheless is of interest to clinicians because there are specific treatments available for some forms of FBSS such as spontaneous intracranial hypotension, as opposed to the symptomatic management strategies that are used in the more common form of bvFTD due to neurodegenerative disease. Although this is not the first report of FBSS with features of bvFTD,6–8 the article by Wicklund et al. is important as it brings visibility to the notion that postural intracranial hypotension may present in unusual ways, such as with an bvFTD, instead of with the classic postural headache.9 With respect to clinical care, Wicklund et al. note that FBSS should be considered, especially when bvFTD occurs in the presence of brainstem features and headache. Although degenerative forms of bvFTD are not typically associated with headache, some degenerative syndromes exhibit the bvFTD phenotype, such as corticobasal degeneration, progressive supranuclear palsy, and motor neuron disease with dementia. Furthermore, some individuals with abnormalities of the microtubuleassociated protein tau (MAPT) gene typically have brainstem symptoms and signs.2 In addition to MRI evidence of FBSS, the absence of lobar (frontotemporal) atrophy is consistent with the diagnosis of FBSS. However, patients with bvFTD may lack lobar atrophy10 so the presence of lobar atrophy should be considered evidence against FBSS. One is left wondering how many patients have bvFTD syndrome due to FBSS but lack the headache and brainstem features,10 how many patients have FBSS without an bvFTD syndrome, and if there are medical conditions that predispose to the development of FBSS.5 Wicklund et al. hypothesize that the frontotemporal features are due to mechanical forces but do not provide direct evidence to support this theory. Future research might include a follow-up series with before-and-after functional imaging data to determine whether impaired brain metabolism returns to normal in cases where the condition is treated surgically, normalizing the forces of brain traction. It would also have been interesting for Wicklund et al. to document clinical features, rate of progression, and structural/functional brain changes using quantitative techniques such as voxel-based morphometry to more clearly document the frequency and severity of temporal lobe and cerebellar tonsil herniation. From the perspective of our sagging health care economy, skeptical physicians wonder if it is costeffective to perform neuroimaging studies on patients with dementia, especially if the cognitive testing suggests an established degenerative pattern of impairment. If nothing else, the work of Wicklund et al. helps to justify the continued use of neuroimaging assessments in individuals with cognitive decline even if the symptoms mimic aspects of degenerative bvFTD or other syndromes of degenerative dementias.