This new publication describes a patient with frontotemporal dementia with brain sag in whom a spinal cerebrospinal fluid (CSF) leak was not identified, treated successfully with dural reduction surgery. Spinal imaging often fails to identify a suspected spinal CSF leak, yet does not rule it out due to limited sensitivity, so treatment options are limited.
This demonstrates the importance of evaluating patient with frontotemporal dementia for intracranial hypotension in order to offer a potential treatment.

Dural Reduction Surgery: A Treatment Option for Frontotemporal Brain Sagging Syndrome
Mostofi E, Schievink WI, Sim VL.
Can J Neurol Sci. 2016 Mar 14:1-3. [Epub ahead of print]
Frontotemporal brain sagging syndrome is a dementia associated with hypersomnolence, personality changes, and features of intracranial hypotension on magnetic resonance imaging. The literature is sparse with respect to treatment options; many patients simply worsen. We present a case in which this syndrome responded to lumbar dural reduction surgery. Postoperative magnetic resonance imaging indicated normalization of brain sagging and lumbar intrathecal pressure. Although no evidence of cerebrospinal leak was found, extremely thin dura was noted intraoperatively, suggesting that a thin and incompetent dura could result in this low-pressure syndrome. Clinicians who encounter this syndrome should consider dural reduction surgery as a treatment strategy.
PMID: 26972054

In 2011, Mokri et al described a series of 8 patients with a clinical diagnosis of frontotemporal dementia as well as imaging evidence of brain sag. It appears that a subset of patients presenting with frontotemporal dementia may have spontaneous intracranial hypotension which is a treatable condition. Interestingly, the majority of these patients had normal spinal imaging without evidence of CSF leak, even though a CSF leak was suspected.

Frontotemporal brain sagging syndrome: an SIH-like presentation mimicking FTD
Wicklund MR1, Mokri B, Drubach DA, Boeve BF, Parisi JE, Josephs KA.
Neurology. 2011 Apr 19;76(16):1377-82. doi: 10.1212/WNL.0b013e3182166e42.
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).
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.
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.
This case series demonstrates that FBSS may mimic typical bvFTD but should be recognized as an unusual presentation that is potentially treatable.
PMID: 21502595
Full text PMCID: PMC3087405

The surgical procedure, lumbar dural reduction, was first described in this paper:

A novel technique for treatment of intractable spontaneous intracranial hypotension: lumbar dural reduction surgery.
Schievink WI.
Headache. 2009 Jul;49(7):1047-51.
doi: 10.1111/j.1526-4610.2009.01450.x.
Spontaneous intracranial hypotension has become a well-described cause of headache particularly among young and middle-aged individuals. Treatment of the underlying spinal cerebrospinal fluid (CSF) leak is effective in relieving symptoms in the vast majority of patients but symptoms may become refractory. The author describes a novel surgical technique to treat intractable spontaneous intracranial hypotension.
A lumbar laminectomy is performed, a strip of dura is resected, and the dural defect is closed. The resulting decrease in lumbar CSF volume is believed to increase intracranial CSF volume and pressure.
The technique was utilized in a patient who suffered with intractable positional headaches because of a spinal CSF leak for 6 years in spite of numerous surgical and nonsurgical therapies. Significant improvement of symptoms was sustained during a 1-year period of follow-up.
Dural reduction surgery may be considered in carefully selected patients with intracranial hypotension.
PMID: 19473279