Case of the Month
Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO
November 2011
Venous Sinus Thrombosis in Spontaneous Intracranial Hypotension
- Intracranial hypotension is a well described cause of new persistent headaches in young and middle aged patients.
- A potentially life threatening complication of intracranial hypotension is dural venous sinus thrombosis. It occurs in approximately 2% of patients with intracranial hypotension.
- Most common presenting symptom is orthostatic headache. Associated symptoms include neck stiffness, nausea and vomiting. Superimposed dural venous sinus thrombosis is difficult to detect clinically as symptoms are nonspecific.
- Intracranial hypotension may be iatrogenic, post traumatic, spontaneous, or secondary to decreased CSF production. Spontaneous intracranial hypotension commonly occurs secondary to a rupture of an arachnoid diverticulum or other etiology predisposing to focal meningeal weakness, such as in Marfan's syndrome and Ehlers-Danlos type 2.
- According to the Monroe-Kellie hypothesis, the intracranial volume is always constant. Therefore, any decrease in CSF volume is compensated by an increase in the blood volume. As the hydrostatic pressure within the dural venous sinuses increases, the meninges become engorged, followed by transudation of fluid into the subdural and subarachnoid space by means of increased hydrostatic gradient. Further decrease in CSF may lead to increased microvascular permeability and result in blood in the subdural space.
- Pathophysiology of dural venous sinus thrombosis in patients with intracranial hypotension is multifactorial. Etiologies include venous stasis, vascular distortion secondary to brain sagging, and CSF depletion leading to increased blood viscosity in the dural venous sinuses.
- Key Diagnostic Features: Venous sinus thrombosis: Hyperdensity within the involved sinuses on CT, loss of flow-void in orthogonal planes on MR, and loss of flow-related signal on TOF MR venogram. Spontaneous intracranial hypotension: MR demonstrates prominent pituitary gland, effacement of the suprasellar cistern, relatively flat orientation of the optic chiasm, loss of midbrain-pons angle, tectal beaking, "sagging" of brain stem, effacement of the 3rd and 4th ventricles, and tonsillar herniation. Pachymeningeal enhancement, prominent epidural venous plexus, and delayed opacification of the subdural and subarachnoid space on contrast-enhanced images are also seen.
- Rx: Uncomplicated intracranial hypotension may be initially treated conservatively with bed rest and caffeine. If conservative treatment fails, if symptoms are severe, or if intracranial hypotension is complicated by dural venous sinus thrombosis, treatment of underlying CSF leak either by blood patch or surgical repair must be performed.
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