Spontaneous intracranial hypotension (SIH) most commonly results from CSF leaks in the cervical and thoracic spine 4, and leads to alterations in the equilibrium between the volumes of intracranial blood, CSF, and brain tissue (Monro - Kellie hypothesis). A decrease in CSF volume leads to compensatory dilatation of the vascular spaces, mostly venous side due to its higher compliance.
It is identical to CSF leaks that occur following lumbar puncture, surgery or trauma, connective tissue disorders like Marfan's Syndrome.
The condition often presents as a positional headache which is relieved by a recumbent position. It is confirmed by assessing opening pressure on LP (less than 7 cm CSF) 2. Note that when this is done fluoroscopically, it should be performed in lateral position to allow for accurate measurement of pressure.
Occasionally presentation is more sinister, with even decreased level of consciousness and coma reported 3.
Described features include
- sub-dural collection
- cerebellar tonsillar herniation into the foramen magnum (acquired Chiari I malformation)
- dural venous sinus distention
Myelography is useful in identifying the location of CSF leak. Ideally the lumbar puncture is performed on the CT table. 10 mls of myelographic contrast is slowly introduced into the thecal space. Following removal of the needle the patient is asked to roll once and is immediately scanned. It is important to scan early as contrast will track a long way from the leak in a relatively short time.
- diffuse brain swelling 3
- sagging brainstem
- droopy penis sign : perhaps only an Australianism to denote the shape of the downward drooping splenium of the corpus callosum
- subdural effusions
- Increased fluid around optic nerves
- Bulbous dilatation of sheath behind globes
- rounding of the cross-section of the dural venous sinuses (venous distension sign)
- contrast-enhanced MR imaging demonstrates
- venous sinus engorgement
- pachymeningeal enhancement (infra- and supra-tentorial)
- enlargement of the pituitary gland
Treatment and prognosis
Epidural blood patch ideally at the sight of CSF leak is the treatment of choice.
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- 1. Paldino M, Mogilner AY, Tenner MS. Intracranial hypotension syndrome: a comprehensive review. Neurosurg Focus. 2003;15 (6): ECP2. Pubmed citation
- 2. Jacobs MB, Wasserstein PH. Spontaneous intracranial hypotension. An uncommon and underrecognized cause of headache. West. J. Med. 1991;155 (2): 178-80. Free text at pubmed - Pubmed citation
- 3. Savoiardo M, Minati L, Farina L et-al. Spontaneous intracranial hypotension with deep brain swelling. Brain. 2007;130 (Pt): 1884-93. doi:10.1093/brain/awm101 - Pubmed citation
- 4. Rai A, Rosen C, Carpenter J et-al. Epidural blood patch at C2: diagnosis and treatment of spontaneous intracranial hypotension. AJNR Am J Neuroradiol. 26 (10): 2663-6. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 5. Farb RI, Forghani R, Lee SK et-al. The venous distension sign: a diagnostic sign of intracranial hypotension at MR imaging of the brain. AJNR Am J Neuroradiol. 2007;28 (8): 1489-93. doi:10.3174/ajnr.A0621 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Benign intracranial hypotension||✗|
|Benign intracranial hypotension (BIH)||✗|