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SPONTANEOUS INTRACRANIAL HYPOTENSION

Reviewed by Dr. Danny Adel Monsour, MD, FRCPC

Page last updated: May 2026

Intracranial Hypotension (IH) or Spontaneous intracranial hypotension (SIH) is a highly disabling neurological condition caused by leakage of cerebrospinal fluid (CSF), through the dura mater, the fibrous tissue (the outermost layer of the meninges, surrounding the spinal cord) that contains CSF, either through a tear or defect, ruptured nerve root sleeve, or directly into a paraspinal vein aka a CSF venous fistula (CVF) (See CAUSES).

Symptoms are believed to result from reduced intracranial CSF volume rather than a strict reduction in pressure. CSF is a clear fluid that surrounds and protects the brain and spinal cord, cushioning them from injury. CSF also helps wash out waste from the brain.

The Spinal Cord

Loss of CSF volume causes the brain to sag within the skull, resulting in traction and compression of pain-sensitive structures such as blood vessels and meninges., The hallmark headache is positional or also known as “orthostatic” headache - developing or worsening when upright and improving when lying down. This type of headache is seen in approximately 76-92% of patients. Importantly, the positional pattern may be delayed, lost over time or rarely absent. A CSF leak can also lead to other possible neurological symptoms.  See SYMPTOMS.

Recorded video from the 2nd Canadian SIH Conference: “Introduction to Spontaneous Intracranial Hypotension: Overview, Epidemiology, Risk Factors, Precipitating Factors, Pathogenesis, Clinical presentation and assessment.”

Recorded video from the 2nd Canadian SIH Conference: “Challenges in diagnosis and reasons not to miss a diagnosis of SIH: Challenges in diagnostic criteria, Differential diagnosis, Utility of LP OP, morbidity and disability/QoL, and potential long-term complications.”

Key Notes

  • SIH has a significant impact on patients’ quality of life and financial well-being. Over half of patients (63.2%) with SIH undergoing surgical intervention present with significant depressive symptoms, a figure that decreases to 23% upon successful resolution of the leak 11. Canadian survey data highlights the severity of this burden, with over 81% of respondents reporting financial strain and nearly 90% requiring modified work duties. At the time of the survey, over 40% of Canadian patients were on disability leave, yet only 9% had been offered mental health services as part of their ongoing care.

  • SIH is an underdiagnosed medical condition, resulting in little or no treatment for many individuals who are suffering from this condition.

  • SIH should be considered as a potential cause of New Daily Persistent Headache (NDPH). This is a headache that begins suddenly and becomes continuous within 24 hours.

  • SIH is an important cause of secondary headaches with an estimated incidence of 3.8 - 5 per 100,000 which is comparable to multiple sclerosis. However, the true prevalence is still unknown and likely to be higher given misdiagnosis and lack of awareness of the condition.

  • There is a lack of consistency in managing SIH globally.

  • SIH has historically been reported more commonly in women, though it can affect anyone at any age.

  • A normal opening pressure does not rule out a spinal CSF leak. Intracranial hypotension is now believed to be more of a CSF volume disorder, rather than a CSF pressure disorder. Therefore, a lumbar puncture (“spinal tap”) is NOT recommended as a diagnostic tool for SIH unless other diagnoses need to be ruled out.

  • Research has revealed that despite loss of CSF, and despite the name “intracranial hypotension’’, patients with spinal CSF leak, particularly in chronic leaks, most often will have opening pressures within the normal range. In fact, between 61% and 94% of patients with positive signs of spinal CSF leaks on imaging have normal opening pressures. This is not yet widely recognized by the medical community.

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