Intracranial hypotension

Intracranial hypotension is a condition in which there is negative pressure within the brain cavity.

Signs and symptoms

 * positional or orthostatic headache
 * migraine
 * nausea
 * blurred vision
 * dementia––"[b]ehavioral variant frontotemporal dementia (bvFTD) is a devastating early onset dementia[,]... and in spontaneous intracranial hypotension, is rare and associated with brain sagging and hypersomnolence"
 * coma

Imaging signs

 * pachymeningeal enhancement
 * brain "sagging" or "sinking"
 * low cerebellar tonsils
 * brainstem distortion
 * Pontine enlargement
 * crowding of the posterior fossa
 * flattening of the optic chasm
 * subdural hygromas/hematomas
 * engorged venous sinuses
 * pituitary hyperemia

Radiologists' mnemonic: SEEPS
Radiologists use the mnemonic, SEEPS, to describe and remember the signs seen in imaging for CSF leaks located in the spine (not cranial CSF leaks):"Subdural fluid collection""Enhancement of pachymeninges (dura)""Enlargement of veins""Pituitary hyperemia (engorged pituitary)""Sagging of brain (including not limited to saggy tonsils)"

Causes
Causes of intracranial hypotension are grouped into 3 kinds of cerebrospinal fluid leaks:

iatrogenic, which is caused by a medical procedure;

traumatic, which is the result of an injury; and

spontaneous (idiopathic), which is "occurring with minimal or no clear precipitant".

Monro-Kellie Hypothesis
The Monro-Kellie hypothesis or doctrine holds that the skull is a closed space, that the volume of the brain, blood, and cerebral spinal fluid together is a fixed amount. "An increase in one should cause a decrease in one or both of the remaining two." In intracranial hypotension, the loss of pressure affecting the amount of cerebral spinal fluid in the cavity can in turn cause cerebral abnormalities, often seen in imaging.

In other words, decreased cerebrospinal fluid volume in intracranial hypotension is compensated for by increased blood volume and why intracranial hypotension is characterized by dilated blood vessels in the brain.

Treatment
According to the Spinal CSF leak foundation, conservative treatment includes bed rest, fluids, and caffeine in the absence of severe symptoms.

Epidural blood patch

Epidural patch with fibrin glue +/- blood

Surgery

Notable Studies
2019, Intracranial Hypotension and Cerebrospinal Fluid Leak. (Abstract)