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  • A leak of the fluid that protects and supports the brain can cause “brain sagging,” which is associated with the same behavioral symptoms as a less common form of dementia.
  • A new study suggests that surgically fixing such leaks can reverse the symptoms.
  • However, the research also found that it is not always possible to identify the source of the leaks.
  • In these cases, alternative treatments for brain sagging often fail to improve dementia symptoms.

Damage to neurons in the frontal and temporal lobes of the brain can result in early-onset dementia, known as frontotemporal dementia or FTD.

FTD is relatively rare in older people compared with other types of dementia but is the most common cause of the condition in people aged up to 60.

A subset of patients have behavioral FTD or bvFTD, which involves progressive changes in behavior, personality, and thinking skills.

For example, people with bvFTD often fail to empathize with others and can lose their former inhibitions, which can result in inappropriate behavior.

The memory problems that usually characterize dementia only occur later in the course of bvFTD.

A new study by researchers at Cedars Sinai Medical Center in Los Angeles, CA, adds to evidence that cerebrospinal fluid leakage can cause the symptoms of bvFTD.

The good news from the study is that a specialist imaging technique can often identify the source of the leaks, which surgeons can then fix, effecting a complete cure of patients’ symptoms.

“Many of these patients experience cognitive, behavioral, and personality changes so severe that they are arrested or placed in nursing homes,” said Dr. Wouter Schievink, director of the Cerebrospinal Fluid Leak and Microvascular Neurosurgery Program and professor of neurosurgery at Cedars-Sinai.

“If they have behavioral-variant frontotemporal dementia with an unknown cause, then no treatment is available,” said Dr. Schievink, who led the research.

“But our study shows that patients with cerebrospinal fluid leaks can be cured if we can find the source of the leak,” he added.

Normally, cerebrospinal fluid (CSF) provides buoyancy to the brain and acts as a shock absorber. If the fluid leaks, the pressure falls inside the skull, and the brain sags, disrupting its operation.

Some telltale signs of CSF leakage include severe headaches that improve when the patient lies down and significant daytime sleepiness even after a good night’s sleep.

An MRI (magnetic resonance imaging) brain scan can reveal brain sagging, says Dr. Schievink, but doctors often mistake it for a condition known as a Chiari brain malformation, in which brain tissue protrudes into the spinal canal.

Even if a neurologist correctly identifies brain sagging, finding the source of the CSF leak can be challenging.

An imaging technique called a CT myelogram can pinpoint a tear or cyst in the membrane that encloses the CSF.

But Schievink and his colleagues recently discovered that CSF could also leak from the spine into a vein through a hole or “fistula,” which is almost invisible on an ordinary CT myelogram.

To detect these leaks, known as CSF-venous fistulas, requires a more specialized CT scan called a digital subtraction myelogram or DSM. This method involves injecting a fluorescent material into the CSF and tracking its movement.

For the new study, the researchers used DSM to image the spinal cords of 21 patients with bvFTD due to brain sagging.

They discovered a CSF-venous fistula in nine (42.8%) patients. Surgery to close up the fistula reversed the brain sagging in all nine subjects and reversed their dementia symptoms.

They treated the remaining 12 patients, whose leaks could not be located, with therapies designed to relieve brain sagging, such as infusions of CSF into the spine. However, the treatment relieved the symptoms of only three of these patients.

“Great efforts need to be made to improve the detection rate of CSF leak in these patients,” says Dr. Schievink.

“We have developed non-targeted treatments for patients where no leak can be detected, but as our study shows, these treatments are much less effective than targeted, surgical correction of the leak,” he adds.

The study appears in Alzheimer’s & Dementia: Translational Research & Clinical Innovations.

The authors conclude:

“[P]ursuing the detection of CSF-venous fistulas is worthwhile because treatment of the fistula is effective and associated with low risk, while there are no disease-modifying treatments available for the devastating symptoms of bvFTD.”

Dr. Per Kristian Eide, Ph.D., a senior consultant neurosurgeon at Oslo University Hospital – Rikshospitalet, Norway, recently co-authored a review of the diagnosis and treatment of “brain sagging dementia.” He also co-authored the first case report of a cranial leak that caused this type of dementia.

Dr. Eide told MNT that the availability of DSM, which researchers in the new study used to locate CSF leaks, was not the main obstacle to the successful diagnosis of the condition.

“The imaging technique is widely distributed and available so the extent of misdiagnosed cases are primarily due to the lack of awareness among physicians,” said Dr. Eide, who was not involved in the study.

“[C]linicians need to become aware of this disease since symptoms may be reversible by correct treatment, while left untreated the condition may even be fatal,” he added.

The new study’s authors emphasize that their subjects were a highly selected group of patients who had been referred to a specialist treatment center.

They write that their findings may not be widely applicable to other patients with this kind of dementia.

In addition, the total number of patients in the study was relatively low.