Frontotemporal brain sagging syndrome: an SIH-like presentation mimicking FTD

Abstract

Background: Behavioral variant frontotemporal dementia (bvFTD) is a relatively well-defined clinical syndrome. It is associated with frontal and temporal lobe structural/metabolic changes and pathologic findings of a neurodegenerative disease. We have been evaluating patients with clinical and imaging features partially consistent with bvFTD but with evidence also suggestive of brain sagging, which we refer to as frontotemporal brain sagging syndrome (FBSS).

Methods: Retrospective medical chart review to identify all patients seen at our institution between 1996 and 2010, who had a clinical diagnosis of FTD and imaging evidence of brain sag.

Results: Eight patients, 7 male and 1 female, were diagnosed with FBSS. The median age at symptom onset was 53 years. All patients had insidious onset and slow progression of behavioral and cognitive dysfunction accompanied by daytime somnolence and headache. Of the 5 patients with functional imaging, all showed evidence of hypometabolism of the frontotemporal regions. On brain MRI, all patients had evidence of brain sagging with distortion of the brainstem; 3 patients had diffuse pachymeningeal enhancement. CSF opening pressure was varied and CSF protein was mildly elevated. A definite site of CSF leak was not identified by myelogram or cisternography, except in one patient with a site highly suggestive of leak who subsequently underwent surgery confirming a CSF leak. In 2 patients with a neuropathologic examination, there was no evidence of a neurodegenerative disease.

Conclusions: This case series demonstrates that FBSS may mimic typical bvFTD but should be recognized as an unusual presentation that is potentially treatable.

Figure 1. Brain MRI in patients with frontotemporal brain sagging syndrome (FBSS)

Midline sagittal, T1-weighted brain MRI of 8 patients with FBSS demonstrating the characteristic sagging brain with downward displacement of the cerebellar tonsils, swelling of the midbrain, and flattening of the ventral pons with effacement of the basal cisterns. Gadolinium-enhanced images of patient 8 also demonstrate intense pachymeningeal enhancement and subdural fluid collections with the arrow showing an engorged pituitary gland with mild enlargement. The arrow in patient 1 shows the swollen midbrain and compressed interpeduncular cistern common to each patient while the arrow in patient 5 shows the flattening of the ventral pons. The arrow in patient 6 shows downward displacement of the splenium of the corpus callosum, which is also seen in patients 3, 4, 5, and 8.

Figure 2. FDG-PET in patients with frontotemporal brain sagging syndrome

Decreased metabolism in medial frontal and anterior medial and lateral temporal lobes was observed in patient 4 (A) while asymmetrically decreased metabolism of the left > right frontal and anterior medial and lateral temporal lobes and bilateral cerebellum was observed in patient 5 (B).