Definition
- Following features in the absence of trauma or dural puncture
- Low CSF pressure (generally < 6cm H₂O)
- Typically associated with orthostatic headache: dramatically worse when upright, improved in recumbency
- Diffuse pachymeningeal enhancement (cerebral and/or spinal) on MRI
Numbers
- Incidence: 5:100,000
- Prevalence: 1:50,000
- Females>male
- Mean age of presentation in the 40’s
Aetiology
- Spontaneous (we talk about here more)
- Post traumatic (including iatrogenic)
- Collagen disorders
- Dural diverticula
Clinical
- Headaches
- Mainly: Orthostatic headache with sudden onset
- Low pressure headaches, characteristically worse in the upright position and relieved by lying down
- Others
- Thunderclap,
- Non-positional,
- Exertional headaches,
- Headaches at the end of the day,
- Paradoxical headaches with worsening upon lying.
- Atypical presentation
- Without headache or pachymeningeal enhancement on MRI, BUT
- With clinical signs of encephalopathy, cervical myelopathy or parkinsonism
- Extrapyramidal movement disorders
- These might have CSF hypovolemia : Normal ICP, but just low volume
- Altered conscious level
- Galactorrhoea
- Due to ‘reverse Monro- Kellie’ effect;
- Reduction of the CSF volume intracranially → increased vascular perfusion of the intracranial contents, including the pituitary gland → resultant increased prolactin production.
- Altered hearing
- Diplopia
- Spinal pain
Diagnosis
- Diagnostic criteria of headache attributed to low CSF pressure (per IHS Classification (ICHD-III))
- Any headache that developed in temporal relation to low CSF pressure or CSF leakage or has led to its discovery
- Low CSF pressure (< 6cm of water) and/or evidence of CSF leakage on imaging
- Not better accounted for by another ICHD-III
- Radiographic criteria
- Not required for diagnosis
- Since no characteristic findings are seen in 20– 25% of patients.
- Median delay from presentation to diagnosis is 4 months → detrimental to patient outcomes.
- Therefore, brain MRI without and with contrast is recommended in patients with new onset orthostatic headaches.
Pathophysiology
- Due to a
- Spontaneous CSF leak or
- Low CSF volume (CSF hypovolaemia)
- Weakness of the meninges as a contributing factor
- Connective tissue disorders like Marfan syndrome, and Ehlers-Danlos syndrome.
- Spinal diverticula, at the cervicothoracic junction or thoracic spine (thoracic being more common), and excluding lumbosacral perineural cysts, are thought to be the source of CSF leak in most patients.
- Other causes of dural injury are degenerative disc disease, osteophytes and bony spurs.
- No relationship has been found between cranial leaks and SIH.
- The orthostatic headache is believed to be caused by the descent of the brain, causing strain on intracranial structures sensitive to pain.
Evaluation
- Radiographic studies
- Sagging of the brain
- Due to loss of buoyancy from low CSF volume.
- Seen as
- Low-lying cerebellar tonsils (seen in 36% of patients)
- Effacement of perichiasmatic and prepontine cisterns,
- Bowing of the optic chiasm,
- Flattening of pons,
- Ventricular collapse
- Enhancement of the pachymeninges (Dura only),
- Most common finding
- BUT Sparing the leptomeninges,
- Due to dilation of subdural blood vessels
- Refers to a dural and outer layer of arachnoid pattern of enhancement
- Engorgement of veins.
- Rounding of the cross-section of the dural venous sinuses
- Pituitary hyperemia
- Subdural fluid collections seen in 50% of patients.
- Can be hygromas versus hematomas, with hygromas being twice as frequent as hematomas. Occasionally may require intervention
- SWI
- Siderosis of brain surface
- Not as conclusive as MRI but can help identify these changes.
- 11% of SIH patients also have pseudo-SAH finding on CT caused by effacement of basal cisterns due to sagging of the brain
- The apex convexity's sulci are wide compared to the base of the brain
- Subdurals
- Study of choice for diagnosis and localization of a CSF leak.
- Timed images immediately after contrast injection or at delayed intervals after injections can help localize intermittent leaks
- Alternative to CT myelogram.
- Injection of 0.5 ml of gadolinium followed by full spine T1 with fat suppression imaging an hour after injection.
- Contrast remains for 24 hours, hence it can aide in detection of intermittent leaks.
- Evidence
- 1st study: Prospective cohort study localized leak in 67% of patients with SIH.
- 2nd study: MRI 15 minutes after gadolinium injection identified CSF leak in 21% of SIH patients with a negative CT myelogram.
- No side effects were reported, but intrathecal gadolinium is not FDA approved (off-label use)
- May show evidence of CSF leak, but is more likely to help localize extrathecal fluid collections for patients with local symptoms.
- If there is focal spine pain, the leak will often be near this location.
- Other findings include
- Dural enhancement,
- Dilated veins,
- Deformed dural sac,
- Meningeal diverticula,
- Syringomyelia, and
- Retrospinal fluid collections at C1–2.
- Poor resolution
- May leave as many as one third of leaks unidentified.
- Can be used especially if CT myelogram fails
MRI (brain): findings (mnemonic SEEPS)
T1
T1+C
T2
Flair
Gradient Echo
CT (brain)
CT myelogram with iodinated contrast
MRI with intrathecal gadolinium
Spinal MRI
Radioisotope cisternography
- Lumbar puncture
- CSF pressure < 6cm of water is part of the diagnostic criteria.
- Patients have been identified with normal CSF pressure.
- Other CSF findings
- Lymphocytic pleocytosis,
- High protein level, and
- Xanthochromia
- Positive response to Epidural Blood Patch also supports the diagnosis
Treatment
- None of these treatments have been evaluated by randomized clinical trials.
- Conservative medical management
- Bed rest
- Hydration
- Analgesics
- Caffeine
- Abdominal binder
- Other treatment but with limited effect
- Intravenous caffeine
- Steroids
- Theophylline
- Epidural blood patch (EBP)
- Injection of autologous blood (10–20ml) into epidural space.
- Technique
- LP technique
- Before entering canal gently try injecting air with small syringe while advancing
- When the epidural space is entered, resistance to injection disappears, but CSF cannot be aspirated
- Then get blood from vein
- May require >1 EBP
- Respond well and usually immediately.
- If unsuccessful, can repeat blood patch with same or larger amount of blood.
- Positioning the patient in Trendelenberg position after injection aides in movement of blood to cover more segments for increased effectiveness.
- May not be effective in up to 25–33%
- Directed epidural blood patch to leak site
- Indication: If the above fails
- Percutaneous placement of fibrin sealant at site of leak
- Can provide relief in patients that fail to improve with conservative measures and epidural blood patch
- Surgical intervention: Last option
- Indication
- Patients without relief with all the above
- Exact site of the leak has been identified.
- Meningeal diverticula can be ligated with
- Suture
- Aneurysm clips
- Muscle pledget with gel foam and fibrin sealant
- A technique that may also be effective if a dural defect is identified
Outcome
- Clinical improvement and precedes radiographic improvement.
- MRI usually takes days to weeks to normalize.
- Complete resolution of HA was achieved in 70% of patients (usually in days to weeks).
- Good prognostic indicator
- Receiving EBP
- Patients with MRI changes characteristic of SIH and an identifiable focal CSF leak
- Poor prognostic indicator
- Multiple sites of CSF leak.
- Longer interval from symptom onset to diagnosis
- Can recur in approximately 10%
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