Spontaneous intracranial hypotension (SIH) is a debilitating and often invisible medical condition resulting from a spontaneous spinal cerebrospinal fluid (CSF) leak.  

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. 

The Spinal Cord

A loss of CSF will usually cause the brain to sag in the skull, 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 Spontenous 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

  • 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.