Intracranial Hypotension

CSF physiology

• 20ml/hour

• Volume 125-150ml

Aetiology:

• Iatrogenic

• Spontaneous

Types of spontaneous spinal CSF leak:

• Ventral dural tear

o Usually from disc/spur piercing dura

o Leak of intrathecal fluid into epidural space

o Longitudinal CSF fluid collection

• Lateral leaks

o Caused by

- Nerve root sleeve tear

- Rupture/leak of meningeal diverticula

- Disc/spur (as for ventral tear)

o May be circumferential epidural collection

• CSF-venous fistula

o Often associated with venous diverticulum

o More common in thoracic spine (and more common on right side)

Clinical

• Orthostatic headache

• Neck pain

• Auditory symptoms

• Cognitive

• Vertigo

• Visual

o Diplopia – abducens palsy

• Nausea and vomiting

Prognosis

• 80% recover with a couple of weeks-months

o Clinical trial 23% incomplete recovery in steroids group vs 32% in controls

• Presence of incomplete paralysis in first week is the best prognostic sign

• Complications:

o Synkinesis

- Motor

- Autonomic (tears when hungry)

Diagnosis:

• Low CSF pressure on lumbar puncture – often not present at time of measurement

• Imaging of brain

o ‘Brain sag’

- Distortion of brainstem

• Flattened midbrain in sagittal (line across top from optic chiasm should usually slope up posteriorly)

• Mamillary pontine distance narrows

• Flattening of ventral pons

• Narrowing of interpeduncular cistern of midbrain on axial

- Cerebellar tonsillar descent

o Venous distention

- Sinus distention

• Downward convexity of inferior aspect of transverse sinus

• Superior sagittal sinus appears round, rather than bi-concave

- Pituitary expansion

o Dural abnormality

- Diffuse dural thickening and enhancement

- Subdural collections

o Optic nerve sheath – obliterated

o Skull changes (with chronic disease)

- ‘Layer cake’ appearance, smooth

• Supratentorial superficial siderosis

o Associated with friable blood vessels with spinal dural abnormality and associated with some cases of intracranial hypotension.

Localisation of leak

• MRI of spine

o Consider 3D T2 imaging for greater resolution

o Spinal longitudinal epidural collection (SLEC)

• CT

o Look for disc spurs

• Myelography

o CT

- On table prone

• LP, patient lifts and rolls to move contrast around

- Lateral decubitus

• LP, patient lying on one side, have to do one side at a time.

- Ultrafast dynamic CT

• LP, patient prone with head down, then immediate scan/s (may need several runs)

• Useful for fast ventral leaks

o Fluoroscopic

- Digital subtraction myelography

o MRI (rarely used)

DDx:

• Chiari

Management

• Conservative

o Bed rest

o Caffeine

o Hydration

• Gabapentin, hydrocortisone - ?some mild evidence of benefit

• Non-targeted blood patch

o Large volume

o Can trial multi/2 level

o 30-60% response rate

• Targeted management - radiological

o Targets blood patch

o ‘Fibrin glue’ to CSF fistula

o Endovascular

• Targeted management – surgical