Saturday 19 November 2011

CVT and Intracranial hypotension

Coexistence of findings spontaneous intra cranial hypotension and chronic Dural sinus thrombosis.

A 30 yo male with long standing headache. Recurrent of episodes of severe headache with nausea and vomiting.In history of previous hospital admissions headache improves with head low. Now on admission bilateral papillodema. No neuro signs. No history of lumbar puncture.

On admission MRI:

Findings of intra cranial hypotension in this case are:
1. Thin layer of sub dural effusion overlying bilateral cerebral convexity.
2. Medialisation and compression of both the lateral ventricles.
3. Mid brain compressed and antero posterioly elongated.
4. Mid brain and Brain stem sagging down on sagittal sections.
5. Obliteration of supra sellar cistern, pre pontine  and cp angel cistern.
6. Low lying cerebellar tonsils.

Findings of thrombosed dural venous sinus in this case are:
1. Heterogeneous T2 high siginal in the region of Dural venous sinuses namely superior sagittal sinus and left lateral sinuses. Loss normal T2 flow voids,
2. No to poor flow related signal on MR Venogram in the region of sinus.
3. Tiny eccentric T2 flow void in the region of sinus on cross sections which show poor flow related signal on MR Venogram represent partially recanalised channels as a part of chronic sinus thrombosis.

In this case, Idiopathic Intra canial Hypotension (IIH, also known as Spontanous Intracranial hypotension, SIH) is complicated by CVT. Intracranial hypotension is rarely associated with CVT. It is proposed that intracranial hypotension appears as primary event followed by CVT, the engorged dural venous sinuses result in venous stasis and predisposes to Dural sinus thrombosis. So IH may constitute an additional risk factor for CVT and an unusual cause for CVT.

Spontaneous Intracranial Hypotension:
 An important cause of new onset headache, common in young and middle age, in female twice more common than male.
 Often underestimated as the condition is uncommon ( ~1 per 50,000) , lack of knowledge of condition and CT in early cases may be normal.
 Exact cause not known, appears to be caused by CSF leak at base of skull or spine secondary to weak meninges and dural defects. History of previous head injuries in few.
 History of previous lumber puncture to be ruled out fist to label it as spontaneous.
 In an intact bony calvarium the total volume is a sum of volumes of intracranial blood, CSF & cerebral tissue, this remain constant. If due to any cause csf loss occurs is compensated by increased vascular component by vascular congestion or by increased extra axial CSF, effusions or hematoma.
 Subdural hematoma is caused by tearing of bridging veins traversing the subdural space.
 Sagging of brain stem and Low lying cerebellar tonsils caused by loss of CSF buoyancy.

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