SPONTANEOUS INTRACRANIAL HYPOTENSION
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.
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.
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.
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.
Dr. Carroll of the Stanford University of Medical Center discusses spontaneous CSF leaks. (shared with permission)
Sources & Suggested Reading
Davidson B, Nassiri F, Mansouri A, Badhiwala J, Witiw C, Peng P, Farb R, et al. Spontaneous intracranial hypotension: A review and introduction of an algorithm for management. World Neurosurgery. 2017;101:343–49.
Tanaka Y, Tosaka M, Fujimaki H, Honda F, Yoshimoto Y. Sex- and age-related differences in the clinical and neuroimaging characteristics of patients with spontaneous intracranial hypotension: a records review. Headache. 2016;56(8):1310–6. doi:10.1111/head. 12887.