Written by Clay Smith
This is an update on the presentation, diagnosis, and management of spontaneous intracranial hypotension.
Why does this matter?
Spontaneous intracranial hypotension (SIH) is a rare headache syndrome you will likely encounter at some point in your career. Here are the need-to-know points for emergency medicine.
Saggy brains hurt
How it works: Normal CSF pressure is 6-25 cm H2O. Rarely (4-5/100,000), a CSF leak occurs, usually in the spinal cord. Spontaneous means no post-procedural reason for the leak. Spontaneous leaks may be from a ventral or posterolateral linear tear in the dura. “Meningeal diverticula (Tarlov cysts) or diffuse dilatations of the dural sac (dural ectasia), as occurs, for example, in ankylosing spondylitis,” may also cause a leak. Or a leak may results from a spinal CSF– venous fistula. Any age may have SIH, but it is more common in women 35-55 years.
How it presents: This is an orthostatic headache, worse when upright, better when supine, which usually occurs within minutes of being upright and is severe. It’s like a post-dural puncture headache. SIH may also present with other symptoms, like vertigo, hearing changes, nausea, neck pain, cognitive slowing, and rarely paresthesias or sixth nerve palsy. Some patients have behavior changes or personality change.
How it is diagnosed: Usually contrast-enhanced MRI of the brain and spine is used and may show subdural fluid collections, enhancement of pachymeninges, or dural abnormalities along the spine. CT myelogram or digital subtraction myelogram (under fluoro) can also be needed for surgical planning in leaks not found on MRI that are refractory to conservative treatment. LP may show low pressure (<6 cm H2O) but could be normal (or even elevated). LP is not necessary for diagnosis per the author, unless there is limited access to imaging.
How it is treated: Conservative bed rest, hydration, and caffeine are a good place to start. Some need a blood patch or two. Worst case, some patients have to have the identified dural leak surgically repaired.
Spontaneous Intracranial Hypotension. N Engl J Med. 2021 Dec 2;385(23):2173-2178. doi: 10.1056/NEJMra2101561