Intracranial hypotension

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Intracranial hypotension is a condition in which there is negative pressure within the brain cavity.[1]

Monro-Kellie Hypothesis[edit | edit source]

The Monro-Kellie hypothesis or doctrine holds that the skull is a closed space and that the volume of the brain, blood, and cerebrospinal fluid together is a fixed amount. "An increase in one should cause a decrease in one or both of the remaining two."[2] In intracranial hypotension, the loss of pressure affecting the amount of cerebral spinal fluid in the cavity can in turn cause cerebral abnormalities, often seen in imaging.

In other words, decreased cerebrospinal fluid volume in intracranial hypotension is compensated for by increased blood volume and why intracranial hypotension is characterized by dilated blood vessels in the brain.

Signs and symptoms[edit | edit source]

Cranial cerebrospinal fluid leaks[edit | edit source]

According to Cedars-Sinai[3], symptoms include:

  • CSF rhinorrhea, a "runny nose" where the drainage is cerebrospinal fluid
  • otorrhea, drainage from the ear
  • salty or metallic taste in the mouth
  • drainage down the back of the throat
  • Cutaneous sinus tract drainage
  • loss of sense of smell
  • change in hearing or ringing in the ears
  • "Less frequently, patients with cranial CSF leaks experience cognitive changes."[4]

Cerebrospinal fluid leaks located in the spine[edit | edit source]

  • positional or orthostatic headache, which may be intense
The headaches are worse when upright and get better lying down. "The headache usually is in the back of the head or base of the skull, but can also occur in the front, sides or all over the head. It is rarely on just one side of the head, and often is described as a 'pulling sensation' from the head to the neck. The severity of the headache can range from mild to very severe and disabling."[5]
  • migraine
  • new daily persistent headache (NDPH)[6]
  • nausea
  • blurred vision
  • dementia––"[b]ehavioral variant frontotemporal dementia (bvFTD)
This is a devastating early onset dementia[,]... and in spontaneous intracranial hypotension, is rare and associated with brain sagging and hypersomnolence"[7]

Diagnosis[edit | edit source]

Diagnosing a cranial cerebrospinal fluid leak[edit | edit source]

Doctors may use a pledget test to determine if a patient has a cranial CSF leak. Imaging would be required to determine where the leak(s) are located. [9]

Diagnostic criteria for spontaneous intracranial hypotension with spinal CSF leaks[10][edit | edit source]

  • orthostatic headache
  • no recent history of dural puncture
  • not attributable to another disorder
  • the presence of at least 1 of:
    • low opening pressure (less than or equal to 60 mm of H20)
    • sustained improvement of symptoms after epidural blood patching
    • demonstration of an active spinal CSF leak
    • cranial MRI changes of intracranial hypotension (e.g. brain sagging or pachymeningeal enhancement)

Imaging signs[edit | edit source]

  • pachymeningeal enhancement[11]
  • brain "sagging" or "sinking"
    • low cerebellar tonsils
    • brainstem distortion
    • Pontine enlargement
    • crowding of the posterior fossa
    • flattening of the optic chasm
  • subdural hygromas (cerebrospinal fluid-filled cysts) and/or subdural hematomas (blood leaking from vessels)
  • engorged venous sinuses
  • pituitary hyperemia

Radiologists' mnemonic for spinal CSF leaks: SEEPS[edit | edit source]

Radiologists use the mnemonic, SEEPS, to describe and remember the signs seen in imaging for CSF leaks located in the spine (not cranial CSF leaks):

Subdural fluid collection

Enhancement of pachymeninges (dura)

Enlargement of veins

Pituitary hyperemia (engorged pituitary)

Sagging of brain (including not limited to saggy tonsils)

Causes[edit | edit source]

Causes of intracranial hypotension are grouped into 3 kinds of cerebrospinal fluid leaks:

iatrogenic, which is caused by a medical procedure;

traumatic, which is the result of an injury; and

spontaneous (idiopathic), which is "occurring with minimal or no clear precipitant".[12]

Iatrogenic causes of intracranial hypotension and spinal CSF leaks[edit | edit source]

  • lumbar puncture (spinal tap). Spinal CSF leaks can develop after a lumbar puncture. Headaches that can develop are "often known as Post Dural Puncture Headache = PDPH. This is the most common cause of a spinal CSF leak."[12]
  • epidural injections
  • spine surgery

Traumatic causes of intracranial hypotension and spinal CSF leaks[12][edit | edit source]

  • brachial plexus injuries (nerves extending from the spinal cord)
  • spinal injuries
  • sports injuries
  • falls

Spontaneous (idiopathic) intracranial hypotension and spinal CSF leaks[edit | edit source]

Potential causes may include: "lifting small or large items, straining, stretching, positional changes, sporting activities, roller coaster rides and falls. Some of these might be categorized as traumatic.

  • Spontaneous spinal CSF leaks may be associated with spinal pathology such as calcified disc material or bone spurs. These leaks are usually ventral or in front of the spinal cord.
  • There is a growing evidence base suggesting that a significant proportion of spontaneous spinal CSF leaks occur as a result of preexisting weakness of the dura mater. A range of dural defects have been reported at surgery. Electron microscopy of dura has revealed abnormalities in a substantial proportion of cases. Heritable Disorders of Connective Tissue (HDCT) occur at a higher frequency in affected individuals; intracranial hypotension may be the first noted manifestation. Marfan syndrome, Ehlers-Danlos syndrome (both classic and hypermobility type) and Unspecified Heritable Disorders of Connective Tissue have been reported. Patients with spontaneous spinal CSF leaks have been shown to have higher risk of intracranial aneurysms, bicuspid aortic valve and thoracic aortic aneurysms and should be evaluated for HDCT.

Spontaneous spinal CSF leaks are uncommon, but not rare. One estimate of annual incidence is 5 in 100,000, however this has not been well-studied. Unfortunately, misdiagnoses and delayed diagnoses are common in this subset."[12]

Treatment[edit | edit source]

Treatment for cranial CSF leaks and intracranial hypotension[edit | edit source]

One newer kind of surgery for repair of cranial CSF leaks is called TONES or transorbital neuroendoscopic surgery.[13][14][15]

Treatment for spinal CSF leaks and intracranial hypotension[edit | edit source]

According to the Spinal CSF leak foundation, conservative treatment includes "bedrest, oral and IV fluids, oral and IV caffeine" in the absence of severe symptoms.[16]

Epidural blood patch

Epidural patch with fibrin glue +/- blood


Notable studies[edit | edit source]

2019, Intracranial Hypotension and Cerebrospinal Fluid Leak.[17] (Abstract)

2016, Imaging Signs in Spontaneous Intracranial Hypotension: Prevalence and Relationship to CSF Pressure.[10] ((Full text))

See also[edit | edit source]

References[edit | edit source]

  1. "Intracranial Hypotension - UCLA Neurosurgery, Los Angeles, CA". Retrieved August 27, 2019.
  2. Mokri, B. (June 26, 2001). "The Monro-Kellie hypothesis: applications in CSF volume depletion". Neurology. 56 (12): 1746–1748. doi:10.1212/wnl.56.12.1746. ISSN 0028-3878. PMID 11425944.
  3. "Articles". Cedars-Sinai. Retrieved August 28, 2019.
  4. "Articles". Cedars-Sinai. Retrieved September 1, 2019.
  5. "CSF Leak: A Curable Cause of Headache". Cedars-Sinai. Retrieved August 28, 2019.
  6. "American Headache Society's handout on new daily persistent headache" (PDF). American Headache Society. Retrieved August 31, 2019.
  7. Schievink, Wouter I.; Maya, M. Marcel; Barnard, Zachary R.; Moser, Franklin G.; Jean-Pierre, Stacey; Waxman, AlanD.; Nuño, Miriam (November 1, 2018). "Behavioral Variant Frontotemporal Dementia as a Serious Complication of Spontaneous Intracranial Hypotension". Operative Neurosurgery (Hagerstown, Md.). 15 (5): 505–515. doi:10.1093/ons/opy029. ISSN 2332-4260. PMID 29534203.
  8. Chan, Stephen M.; Chodakiewitz, Yosef G.; Maya, Marcel M.; Schievink, Wouter I.; Moser, Franklin G. (May 2019). "Intracranial Hypotension and Cerebrospinal Fluid Leak". Neuroimaging Clinics of North America. 29 (2): 213–226. doi:10.1016/j.nic.2019.01.002. ISSN 1557-9867. PMID 30926112.
  9. "Articles". Cedars-Sinai. Retrieved September 1, 2019.
  10. 10.0 10.1 Kranz, P.G. (July 2016). "Imaging Signs in Spontaneous Intracranial Hypotension: Prevalence and Relationship to CSF Pressure" (PDF). American Journal of Neuroradiology. Retrieved August 28, 2019.
  11. Antony, Joyce; Hacking, Craig; Jeffree, Rosalind L. (November 2015). "Pachymeningeal enhancement-a comprehensive review of literature". Neurosurgical Review. 38 (4): 649–659. doi:10.1007/s10143-015-0646-y. ISSN 1437-2320. PMID 26264063.
  12. 12.0 12.1 12.2 12.3 "Causes". Spinal CSF Leak Foundation. November 20, 2016. Retrieved August 27, 2019.
  13. Ramakrishna, Rohan; Kim, Louis J.; Bly, Randall A.; Moe, Kris; Ferreira, Manuel (February 2016). "Transorbital neuroendoscopic surgery for the treatment of skull base lesions". Journal of Clinical Neuroscience: Official Journal of the Neurosurgical Society of Australasia. 24: 99–104. doi:10.1016/j.jocn.2015.07.021. ISSN 1532-2653. PMC 5955706. PMID 26563603.
  14. Moe, Kris S.; Kim, Louis J.; Bergeron, Chris M. (January 2011). "Transorbital endoscopic repair of cerebrospinal fluid leaks". The Laryngoscope. 121 (1): 13–30. doi:10.1002/lary.21280. ISSN 1531-4995. PMID 21181981.
  15. Moe, Kris S.; Bergeron, Chris M.; Ellenbogen, Richard G. (September 2010). "Transorbital neuroendoscopic surgery". Neurosurgery. 67 (3 Suppl Operative): ons16–28. doi:10.1227/01.NEU.0000373431.08464.43. ISSN 1524-4040. PMID 20679952.
  16. "Overview". Spinal CSF Leak Foundation. July 14, 2014. Retrieved August 28, 2019.
  17. Moser, Franklin G.; Schievink, Wouter I.; Maya, Marcel M.; Chodakiewitz, Yosef G.; Chan, Stephen M. (May 1, 2019). "Intracranial Hypotension and Cerebrospinal Fluid Leak". Neuroimaging Clinics. 29 (2): 213–226. doi:10.1016/j.nic.2019.01.002. ISSN 1052-5149. PMID 30926112.