Case No. :	57
Month :	September
Year :	2003
Contributor :	Dr. Vyankatesh Kansatwad

Other Cases

A 20-year-man presented with the complaints of severe headaches since three months - mostly in the occipital region. There was history of nasal regurgitation, blurring of vision and gait disturbance with feeling of falling to either side.

On examination, motor power was IV /V in lower limbs, rhomberg sign was positive with no sensorineural loss. The rest of the CNS examination was normal.

A plain and contrast enhanced CT scan of the brain was done. This revealed iso to hyper dense, poorly enhancing, two centimeter mass lesion in lower pons without perifocal edema. The lesion was thought to be a cavernous angioma with hemorrhage. (Figs. 1, 2)

Fig.1	Fig.2

A plain and contrast examination of the brain however, clearly showed the lesion to be extra-axial. It was 2.8 x2.6x1.8 centimeter sized well marginated, hyperintense mass lesion on T1 weighted images situated in the premedullary cistern at the junction of the pons and the medulla. (Figs.3,4,5)

Fig.3	Fig.4
Fig.5

This lesion appeared relatively hypointense on T2 weighted images (Fig.6).

Fig.6

The vertebral arteries were seen to course along the anterior margin of the lesion .

On MRI, the lesion was thought to be a thrombosed aneurysm. However, an extra-axial neoplasm with paramagnetic substance deposition with hemorrhage or calcification within like nerve sheath tumour was considered remotely possible.

A four vessel cerebral angiogram revealed a large, fusiform, partially thrombosed dissecting aneurysm involving the distal vertebral artery (V4 segment) on the left with sparing of the vertebro-basilar junction and the left poster inferior cerebellar artery(Fig.7)

Fig.7

The lesion was treated by the endovascular route. The aneurysm was packed with GDC coils and the left vertebral artery occluded distal to the posterior inferior cerebellar artery. The post embolization vertebral angiogram showed occlusion of left vertebral artery distal to posterior inferior cerebellar artery with good opacification of posterior inferior cerebellar artery and its branches. The rest of the posterior fossa circulation was fed by the right vertebral artery.

The patient tolerated the procedure well and is doing well with relief in headache,vision and gait disturbance.


DISCUSSION:

About 10 % of all intracranial aneurysms arise on posterior that is vertebro-basilar circulation. Five percent arise from the basilar artery bifurcation and the remaining 1 to 5 % arise from other posterior fossa vessels. Very few aneurysms develop on vertebral artery without involving the VA -PICA junction or the vertebro-basilar union. Common posterior fossa sites include the superior cerebellar artery and the vertebral artery at the origin of the posterior inferior cerebellar artery. Most aneurysms are asymptomatic until they rupture; when they do so, are associated with significant morbidity and mortality. The most common presentation of intracranial aneurysm is subarachnoid hemorrhage. Some intracranial aneurysms produce cranial neuropathies, the best example is third nerve palsy secondary to posterior communicating artery aneurysm. Guglielmi detachable coils have become a popular alternative to surgery for the treatment of intracranial aneurysms. Complete angiographic occlusion can be obtained in up to 85 % of aneurysms with neck less than 4 mm. in diameter, but in less than 15 % of patients with wider aneurysmal necks. Difficulties in coiling of large aneurysms occur at the base of neck if neck is wider than dome height .It is very difficult to prevent egress of coils in to the parent artery in these situations with attendant risk of thrombus formation, distal emboli or vessel occlusion.

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