Spontaneous Intracranial Hypotension

Spontaneous intracranial hypotension is a secondary headache due to cerebrospinal fluid leak or CSF venous fistula of a nerve root sheath.
== Clinical Features ==
The classic symptom is the daily orthostatic headache. The headache worsens with upright positioning, and improves when supine. It often starts abruptly. The pain may be felt in the entire head, or more localised in the bifrontal, occipital, or upper cervical regions. A significant minority of patients do not have an orthostatic headache. Associated symptoms include tinnitus, photophobia, phonophobia, dizziness, nausea and vomiting, and difficulty hearing. The condition is sometimes described in association with migraine, POTS, and Ehlers-Danlos Syndrome. Grief et al. Spontaneous intracranial hypotension. Practical Neurology. May 2020. Full Text
There are three subtypes making up three quarters of causes. The remaining one quarter are indeterminate. The three types are
*Dural tear often from a ventral osteophyte that leads to an extradural CSF collection
*Nerve root diverticulum that leaks causing extradural fluid collection
*Fistula connecting the CSF to the venous system without extradural fluid collection.
As part of the assessment one should check for hypermobility using the Beighton scoring system. 
== Investigations ==
=== Opening Pressure ===
Measure the opening pressure, but only 34% with confirmed spinal CSF leaks were found to have a CSF pressure of ≤60 mm H2O. 
=== MRI ===
MRI imaging of the brain will show findings in most cases, but may be normal in chronic leaks. The most well known finding is low lying cerebellar tonsils, however this can also occur with Chiari 1 and is not discriminatory. Dobrocky and colleagues looked at six most relevant brain MRI findings and developed a scoring system with major and minor findings.
Imaging signs with weighted scoring.
Characteristic 	Coefficient (95% CI)	Odds Ratio (95% CI) 	P Value	Score Points
Venous sinus engorgement 	2.95 (1.18-4.72) 	19.12 (3.26-112.30) 	.001 	2
Pachymeningeal enhancement 	4.04 (2.50-5.59) 	57.01 (12.18-266.78)	<.001 	2
Subdural fluid collection 	1.54 (−0.10 to 3.17)	4.65 (0.90-23.92) 	.07 	1
Suprasellar cistern effacementᵃ 	3.48 (2.36-4.60) 	32.32 (10.55-99.02) 	<.001 	2
Prepontine cistern effacementᵇ 	1.47 (0.41-2.52) 	4.34 (1.51-12.47) 	.007 	1
Mamillopontine distance reductionᶜ	1.13 (0.07-2.19) 	3.08 (1.07-8.90) 	.04 	1
ᵃ ≤4 mm. ᵇ≤5 mm. ᶜ≤6.5 mm.
≤ 2 = low probability3-4 = intermediate probability≥ 5 = high probability (>90% sensitive and specific)	ᵃ ≤4 mm. ᵇ≤5 mm. ᶜ≤6.5 mm.
≤ 2 = low probability3-4 = intermediate probability≥ 5 = high probability (>90% sensitive and specific)	ᵃ ≤4 mm. ᵇ≤5 mm. ᶜ≤6.5 mm.
≤ 2 = low probability3-4 = intermediate probability≥ 5 = high probability (>90% sensitive and specific)	ᵃ ≤4 mm. ᵇ≤5 mm. ᶜ≤6.5 mm.
≤ 2 = low probability3-4 = intermediate probability≥ 5 = high probability (>90% sensitive and specific)	ᵃ ≤4 mm. ᵇ≤5 mm. ᶜ≤6.5 mm.
≤ 2 = low probability3-4 = intermediate probability≥ 5 = high probability (>90% sensitive and specific)
== Treatment ==
The epidural blood patch is the mainstay of treatment. This can be targeted or untargeted.
* Untargeted: Typically large volume >30mL at two sites
* Targeted: Lower volume <5mL unilateral or bilateral. (preferred)
The benefits may take days or weeks .
Surgery is a second line treatment if the site of the leak has been identified.
One quarter of cases will have rebound intracranial hypertension post treatment usually within 24 hours. This can be transient but may last several months. Treatment options include acetazolamide and topiramate.
== Resources ==
Tweetorial: https://twitter.com/teachplaygrub/status/1531409490708312064
== References ==
Category:Neurology
Category:Head and Jaw Conditions