Frontotemporal brain sagging syndrome

Frontotemporal brain sagging syndrome (FBSS) is an uncommon presentation of spontaneous intracranial hypotension where the dominant clinical features are neuropsychiatric signs and symptoms that can be mistaken for frontotemporal lobar degeneration.

Clinical presentation

Patients with frontotemporal brain sagging syndrome present slowly, progressively and heterogeneously with a variety of signs and symptoms.

In many, neuropsychiatric and cognitive features occur only after a period of symptoms attributable to untreated intracranial hypotension (e.g. orthostatic headache). Importantly, however, a significant proportion of patients with spontaneous intracranial hypotension do not have headaches ⁴. In these individuals, the diagnosis is harder to make and more closely resembles a neurodegenerative disease.

Signs and symptoms include ^1-4,6:

• headache

  • most often orthostatic

  • often preceded other symptoms but not always present

• frontal dysfunction (e.g. apathy, disinhibition, poor planning)

• cognitive impairment (e.g. memory disturbance)

• reduced conscious state (e.g. somnolence, drowsiness, even coma)

• neck pain

• brainstem/cerebellar dysfunction

  • tremor

  • disequilibrium

  • cranial nerve dysfunction

  • auditory symptoms

• compulsive repetitive flexion (at the waist) with breath-holding

In some patients the neuropsychiatric symptoms are more pronounced later in the day and may improve by lying down ⁴.

Only approximately half of patients will have a low CSF opening pressure (<6 cm H₂O) ⁴.

Intrathecal infusion of preservative-free normal saline can also be performed to determine if symptoms abate ⁴.

Radiographic features

MRI

The MRI brain and spine features are those of spontaneous intracranial hypotension, dominated by ^1,2,4:

• pachymeningeal thickening and enhancement

• venous engorgement

• subdural effusions or subdural hematomas

• sagging of intracranial content

  • acquired cerebellar tonsillar ectopia

  • reduced mamillopontine distance

  • effacement of the basal cisterns

  • slumping of the pons against the clivus

  • downward drooping splenium of the corpus callosum

  • temporal uncal herniation

• spinal longitudinal epidural CSF collection (SLEC)

Features of superficial siderosis of the central nervous system may also be present ⁷. Importantly, frontotemporal atrophy is usually absent ². MRI obtained following treatment will show resolution of the aforementioned features if successful ⁴.

Nuclear medicine

Positron emission tomographic (PET) may show frontotemporal hypometabolism ^2,4.

Treatment and prognosis

Treatment depends on identifying and treating the site of CSF leak (see spontaneous intracranial hypotension). If this is successful then substantial symptomatic improvement can be expected in many patients ⁴.

Unfortunately, a source of leak cannot be identified in all patients. In such cases speculative epidural blood patches can be performed. These frequently result in transient improvements, however, these are not often sustained ^1,2,4. It is likely that in the past, many of these patients with unidentifiable leaks have had CSF-venous fistulas, given it is an underdiagnosed entity ³.

Other treatment options may include:

• wearable epidural spinal infusion systems, may have benefit ⁴

• oral corticosteroids, usually with underwhelming results ^1,2,4

Importantly, posterior fossa decompression as performed in Chiari 1 malformations is generally not helpful as cerebellar tonsillar ectopia is a sequela of the underlying problem rather than being causative ⁴.

History and etymology

The first case of neuropsychiatric presentation of a patient with spontaneous intracranial hypotension was published in 2002 by Hong et al. ⁵, and the term frontotemporal brain sagging syndrome first proposed in 2011 by Wicklund et al. ². An alternative name 'spinal dementia' was proposed in 2024 ⁷.

Differential diagnosis

• frontotemporal dementia

  • frontotemporal atrophy usually present

  • absence of signs of spontaneous intracranial hypotension

  • compulsive repetitive flexion (at the waist) with breath-holding, which can occur in frontotemporal brain sagging syndrome, may be a useful clinical sign to differentiate these patients from those with behavioral variant frontotemporal lobar degeneration ⁶

• Chiari 1 malformation

  • absence of signs of spontaneous intracranial hypotension