Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 51, Num. 1, 2003, pp. 84-86

Neurology India, Vol. 51, No. 1, Jan-Mar, 2003, pp. 84-86

Case Report

Giant vertebrobasilar junction aneurysms: Unusual cases

A. Suri, V. S. Mehta

Department of Neurosurgery, Neurosciences Center, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, India.
Dr. V. S. Mehta, Department of Neurosurgery Neurosciences Center, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, India. E-mail: mehtavs@medinst.ernet.in

Accepted on 31.08.2001.

Code Number: ni03023

Giant vertebrobasilar (VB) junction aneurysms are uncommon aneurysms, especially those associated with multiple aneurysms of the posterior circulation. We report two cases, one with a small and a giant aneurysm of the VB junction which were surgically clipped; and the other with a small left anterior inferior cerebellar artery (AICA) aneurysm which resolved spontaneously. The patient, however, developed a de-novo giant VB junction aneurysm, which was detected on a follow-up angiogram. This aneurysm was treated by surgical clipping. The clinical features, angiographic considerations and surgical treatment of such rare conditions are discussed and the relevant literature reviewed.

Key Words: Vertebrobasilar aneurysm, Posterior circulation aneurysm, Giant aneurysm, Multiple intracranial aneurysm.

Posterior circulation aneurysms account for approximately 15% of all intracranial aneurysms.¹ Vertebrobasilar (VB) junction aneurysms are uncommon, comprising only 3-4% of the aneurysms of the posterior circulation.¹ At the All India Institute of Medical Sciences, New Delhi, India, 42 (6.4%) posterior circulation aneurysms were operated of a total of 654 intracranial aneurysms, from January 1996 to October 2000.² VB junction aneurysms are uncommon; however, we have encountered two patients with unusual presentations.

Multiple aneurysms of the VB junction associated with a giant aneurysm have not been reported till date. We report a case with a giant as well as a small aneurysm at the VB junction who underwent successful surgical clipping. The other case is one of a small anterior inferior cerebellar artery (AICA) aneurysm which underwent spontaneous resolution, and formation of a de-novo giant VB junction aneurysm which was successfully clipped. This unusual feature of the spontaneous regression of the AICA aneurysm and de novo formation of another at the VB junction, which attained a giant size, has not been reported so far. The clinical features, angiographic considerations, surgical treatment and pathogenesis of these unusual conditions are discussed and the relevant literature reviewed.

Case Report

Case 1: A 60-year-old lady presented with history of sudden onset severe excruciating headache followed by transient loss of conciousness. She also complained of impairment of vision in the right eye and she had neck stiffness. She was a known hypertensive for four years and was on irregular treatment. Clinical examination revealed an alert and oriented individual. She had neck stiffness. Visual acuity was normal in the left eye while there was only perception of light in the right eye, which also showed subhyaloid hemorrhages. A clinical diagnosis of subarachnoid hemorrhage (SAH), Hunt and Hess grade³-II was made. Computerized Tomography (C.T.) scan of the head showed diffuse SAH with intraventricular extension without any evidence of ventriculomegaly. A digital subtraction angiography (DSA) revealed giant and small vertebrobasilar junction aneurysms (Figure 1). She underwent clipping of both aneurysms through a left, far lateral, transcondylar suboccipital approach.^2,4 She had a stormy postoperative course, which included drainage of subdural hygroma, multiple shunt revisions due to recurrent blockade and chest infection. She improved gradually and was discharged with mild residual impairment of lower cranial nerves and left cerebellar signs. These signs became near normal over the next six months. Check angiogram revealed well clipped aneurysms.

Case 2: A 22-year-old male presented with five episodes of sudden onset, moderately severe headache over two months. The patient did not pay much attention to it till the last episode following which he developed altered sensorium. Clinical examination revealed a stupurose individual with Glasgow Coma Score E2V2M5 with normal pupillary size and reaction, hyperaemic optic discs, left hemiparesis and extensor plantars and with severe neck stiffness. A clinical diagnosis of SAH grade IV was made. CT scan of the head revealed SAH and a thick clot in the prepontine cistern with moderate ventriculomegaly. A medium pressure ventriculoperitoneal shunt was inserted. DSA revealed a small left AICA aneurysm filling from the right vertebral artery; the left vertebral artery being hypoplastic (Figure 2). Definitive surgery was delayed till the patient improved over the next three weeks. A left retromastoid craniectomy was performed; exploration revealed no aneurysm of the AICA or the basilar-AICA junction. A follow-up angiogram after four weeks revealed a giant vertebrobasilar junction aneurysm filling from the right vertebral artery and non-visualization of the left AICA aneurysm (Figure 3). The patient underwent clipping of the giant vertebrobasilar junction aneurysm through a right far lateral transcondylar suboccipital approach.^2,4 He improved gradually over time and was discharged with minimal left hemiparesis which improved at one year follow-up.

Check angiogram after two weeks and nine months revealed well- clipped VB junction aneurysm and no aneurysm at basilar-AICA junction.

Discussion

In 1968 Kenneth Jamieson, one of the pioneers in the surgical treatment of posterior circulation aneurysms, said "It is clear that the posterior circulation is no place for the faint of heart".² Aneurysms of the vertebrobasilar system are a real challenge for neurosurgeons and their treatment undergoes constant change.

Multiple aneurysms in the posterior circulation are an uncommon occurrence. In Drake and Peerless' series of 1767 patients, there were 113 (6.4%) patients with multiple aneurysms of the posterior circulation.⁵ The VB junction was associated with other aneurysms of the posterior circulation in 1.5% of their cases.⁶ None of the 39 giant aneurysms of the VB junction in Drake's series was associated with other aneurysms of the posterior circulation; surgical treatment was associated with 21% mortality and 18% morbidity.⁶ Sporadic reports of multiple posterior circulation aneurysms exist in the literature;^7-10 Konishi et al reported as many as five aneurysms of the vertebrobasilar system in a single patient.⁷ Association of multiple posterior circulation aneurysms with sickle cell disease is reported by Batjer et al¹¹ and reviewed by Preul et al,¹² with polyarteritis nodosa by Oran et al¹³ and with pulseless disease by Masuzawa et al.¹⁴ Our series was not associated with any such coexisting vascular affection. The present case of coexisting small and giant aneurysms at the VB junction is the first case in our review of existing medical literature.

Angiographically confirmed formation of a new cerebral aneurysm (de-novo) is uncommon.^15-19 De-novo aneurysms in the posterior circulation are rare. Miller et al reported two cases of de novo basilar aneurysms and another case of SCA aneurysm.¹⁵ Koeleveld et al have reported a single case of de novo basilar aneurysm. Three cases of de novo aneurysms of the posterior inferior cerebellar artery (PICA) are individually reported.^16-18 Rinne et al series of 13 de novo aneurysms does not contain any posterior circulation aneurysms.¹⁹ The present case is the first report of a de-novo giant aneurysm at the VB junction in the existing medical literature.

The disappearance of the left AICA aneurysm and de-novo appearance of the Rt. vertebrobasilar junction aneurysm are a unique phenomenon. It would be difficult to explain it on the basis of arterial dissection since the characteristic angiographic findings are absent. Its explanation on the basis of a traumatic pseudoaneurysm is also unlikely as exploration of the Lt. AICA-Basilar junction is not likely to cause operative handling and injury at the Rt. Vertebrobasilar junction. Dissecting aneurysms of the vertebrobasilar circulation most commonly involve the vertebral or the basilar arteries and are either spontaneous or are associated with arteriopathy such as fibromuscular dysplasia. Traumatic dissections most commonly involve the extracranial vertebral artery from C2 to the occiput.²⁰ SAH is a rare presentation of dissecting intracranial aneurysms.⁷ Friedman and Drake reviewed 20 cases of dissecting posterior circulation aneurysms which presented as SAH.²¹

The literature contains sporadic cases of angiographically confirmed spontaneous thrombosis or resolution of intracranial aneurysms.^22-26 Maiuri et al postulated their association with severe cerebral vasospasm, giant aneurysms, thrombosis of feeding artery and antifibrinolytic therapy.²⁵ Spontaneous resolution is more commonly seen with aneurysms of the vertebrobasilar system.^10,23 However, spontaneous resolution of the AICA aneurysm has not been reported earlier.

References

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