SPONTANEOUS INTRACRANIAL HYPOTENSION

Spontaneous intracranial hypotension (SIH) is a is a debilitating neurological condition caused by leakage of cerebrospinal fluid (CSF) through the dura mater, the fibrous tissue that contains CSF, either through a dural defect, ruptured nerve root sleeve, or directly into a paraspinal vein (CSF venous fistula (CVF)).

CSF is a clear fluid that surrounds and protects the brain and the spinal cord, and cushions it from injury or damage. A CSF leak stems from a tear or abnormality in the dura, the fibrous tissue that covers CSF circulating around the brain and the spinal cord.

A loss of CSF will usually cause the brain to sag in the skull and may cause traction in various brain regions, resulting in a severe headache that is typically positional. This means that the headache is much better lying down compared to being upright. A CSF leak can also lead to other possible neurological symptoms. See SYMPTOMS.

What is Spontaneous Intracranial Hypotension (SIH) ?

There is little awareness of this medical condition among the public and within the medical community. In fact, under-diagnosis and/or misdiagnosis is extremely common, resulting in little or no treatment for many individuals who are suffering from this condition.

Key Notes

SIH is an important cause of secondary headaches with an estimated incidence of 5 per 100,000 persons per year and a prevalence of 1 in 50,000 persons per year.
CSF leaks/ SIH is an under-diagnosed medical condition.
Currently, there is no medical diagnosis code for this disorder in Canada.
Adults are most commonly diagnosed in 40s to 50s, but spinal CSF leaks and the resulting SIH can occur at any age.
Research has revealed that despite loss of CSF, and despite the name “intracranial hypotension’’, patients with CSF leaks most often have normal pressure in the CSF when a so called ‘‘opening pressure’’ is measured. This is not yet widely recognized by the medical community, even among well-educated physicians. A normal opening pressure may cause a physician to erroneously conclude that a CSF leak is unlikely. In fact, many patients with a CSF leak will have opening pressures within the normal range. Intracranial hypotension is now believed to be more of a CSF volume disorder, rather than a CSF pressure disorder.

“The Mystery Headache: CSF Leak” A Fixable Cause of Daily Headache - 2023 update by Dr. Ian Carroll of the Stanford University of Medical Center. (shared with permission)

Dr. Carroll of the Stanford University of Medical Center discusses spontaneous CSF leaks. (shared with permission)

Sources & Suggested Reading