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 »  Abstract
 »  Introduction
 »  Case reports
 »  Discussion
 »  References

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Year : 2001  |  Volume : 49  |  Issue : 4  |  Page : 391-4

Dissecting intracranial vertebral artery aneurysms.


Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum - 695011, India.

Correspondence Address:
Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum - 695011, India.
[email protected]

  »  Abstract

Dissecting aneurysms of the intracranial arteries are exceedingly rare vascular lesions that can produce acute cerebral or brain stem infarction in young healthy adults. They carry a high mortality rate. Two cases of dissecting vertebral artery aneurysms that presented with bleed, were successfully operated by trapping and excision of the dissecting segment. Both dissecting aneurysms were located distal to PICA origin. Both the patients developed post operative lower cranial nerve paresis and one developed lateral medullary syndrome, which improved subsequently. Dissecting aneurysms presenting with bleed should be surgically managed by trapping and excising the involved segment sparing the PICA origin or by interventional radiological techniques. Revascularisation procedures should be considered in addition to trapping of the main vertebral segment if PICA is involved in the trapped segment. The diagnostic and therapeutic difficulties associated with dissecting vertebral artery aneurysms and the controversies regarding their management have been reviewed.

How to cite this article:
Bhattacharya R N, Menon G, Nair S. Dissecting intracranial vertebral artery aneurysms. Neurol India 2001;49:391


How to cite this URL:
Bhattacharya R N, Menon G, Nair S. Dissecting intracranial vertebral artery aneurysms. Neurol India [serial online] 2001 [cited 2020 Oct 24];49:391. Available from: https://www.neurologyindia.com/text.asp?2001/49/4/391/1214




   »   Introduction Top

Intracranial dissecting aneurysms arising from the vertebrobasilar complex are being reported with increasing frequency and are now recognised as a common cause of stroke. The issue of management of ruptured dissecting aneurysms in the vertebral artery (VA) is still unsettled.[1],[2] Generally, the dissection occurs between the internal elastic lamina and media and an intramural haematoma occludes the lumen, resulting in a stroke like presentation. In rare instances, when the plane of dissection lies within the media or between the media and the adventitia and sub arachnoid haemorrhage may occur. Most of the previous cases have been treated by vertebral artery ligation.[3] Two cases of dissecting vertebral artery aneurysms were successfully operated in our institute by trapping and excision of the dissected segment. We report these two cases and review the literature of this rare and difficult surgical problem.



   »   Case reports Top

Case 1 : A 50 year old male, who had subarachnoid haemorrhage six days prior to admission in the hospital, had a left abducens paresis. CT scan was essentially normal. DSA revealed a left vertebral string sign distal to PICA, with filling persisting in the venous phase. He underwent left lateral suboccipital craniectomy and the aneurysm was identified. The vertebral artery distal to PICA appeared bluish black in colour and the aneurysmal dilatation extended just proximal to the VA union. On clip application just distal to PICA there was back bleeding. Another clip was applied proximal to VA union and the segment was excised. The whole dissection was carried out in between the lower cranial nerve rootlets. The patient had lower cranial nerve paresis, which persisted for six weeks. He was off ryles tube later, on follow up. Check angiogram revealed no filling of the aneurysmal segment.
Case 2 : A 41 year old lady presented with doubtful history of seizure on a background history of headache. MRI and MR angio revealed left distal vertebral artery aneurysm with bleed into left cerebello medullary and cerebello-pontine cisterns. Angiogram showed a totally ectatic vertebrobasilar system with fusiform dilatation of the vertebral artery distal to PICA. Diagnosis of dissection was not entertained on angiogram and surgery was carried out for a fusiform aneurysm. Through a left retromastoid craniectomy, the involved segment was exposed and the lesion was tackled similar to the first case. Post operatively she had paraparesis, which improved subsequently.


   »   Discussion Top

Although dissecting aneurysms of the vertebral artery producing subarachnoid haemorrhage have been reported more frequently in recent years, their true incidence is unclear[1],[4],[5],[6],[7] and seems to be much higher than previously assumed.[5],[6] The difficulty in diagnosing these lesions may have obscured the true incidence. These lesions often simulate cerebral thrombosis and can be overlooked in the evaluation of a patient with cerebral vascular insufficiency of sudden onset.
It is of interest to note that the majority of ruptured vertebral artery dissecting aneurysms have been reported from Japan.[2],[4],[5],[8],[9] In contrast to the female dominance in vertebral saccular aneurysms, dissecting aneurysms showed a male predominance. Manz and Luessenhop[10] reported a right sided dominance. These aneurysms can be divided clearly into two groups.[1] While in the first group (Group I) the dissection remains confined to the vertebral artery , in the second it extends into the basilar artery. In vertebral artery dissection the plane of dissection differed between the two groups. In group I the intramural haematoma predominantly lies in the media or between the media and the adventitia. Arterial layers usually get destroyed in most cases. In Group II, the plane of dissection is mainly subintimal, subadventitial, intratmedial or intramural. Clinical presentations appear to be largely determined by the plane of dissection. Patients in group I present with subarachnold haemorrhage whereas those in group II present with brain stem ischaemia.[11],[12]
The causative factors in vertebral artery dissection include various combinations of hypertension, congenital or degenerative changes in the vessel wall and anatomical and pathological characteristics of the artery. Whether the defect in the elastic layer is congenital or acquired is not known. Fusiform aneurysms quite often occur as sequelae of dissection. When a fusiform vertebrobasilar aneurysm without elongation or tortuosity of the parent vessel is seen, especially in young patients, dissection should be considered as a likely cause.[1],[4],[13],[14] It is suspected that destruction of the internal elastica or the lamina muscularis by intramural haemorrhage causes weakness of the arterial wall and fusiform dilatation.
The most characteristic operative finding was a fusiform or tubular enlargement of the affected artery and discolouration due to intramural haematoma. After a certain period, the wall of the dissecting aneurysm becomes whitish gray and firm, probably due to organised intramural clot. Other interesting observations include a neurovascular pattern in the outer wall of aneurysms and serous fluid beneath the adventitia (resolution of intramural haematoma).
The string sign of occlusion, rosette, intimal flap, proximal and/or distal dilatation, double lumen, retention of contrast medium in the late venous phase and intramural pooling of the contrast are the angiographic features suggestive of dissection.[5],[15],[16] The sole pathognomonic sign of a dissecting aneurysm is a double lumen (true lumen and intramural dissection). Angiographic identification of the double lumina consisting of a true vessel lumen and the subintimal false lumen seems necessary for a decisive diagnosis. The dynamic nature of this pathology is demonstrated by angiography, which probably reflects the healing process in the affected vessel. The angiographic dynamic period seems to last as long as 2 or 3 months after onset, resulting in angiographic cure. Both the ectatic and stenotic changes in the affected vessel resolve over time.
Management
The first surgical procedure for dissecting aneurysm was performed by Yonas in 1977. The indications for surgical treatment of the vertebral dissecting aneurysms remain controversial. Three points need to be considered in management of dissecting aneurysms of the vertebral artery.[17] The first concerns the risk of rerupture if the dissecting aneurysm is not treated surgically. A ruptured dissecting aneurysm in the vertebral artery is at risk of rebleeding during the acute stage, similar to a saccular aneurysm in the same location; hence the need for early active intervention. The second issue invloves the selection surgical procedure of likely to prevent rerupture. The third issue deals with prevention of ischaemic complications, if the vertebral artery is occluded or the aneurysm trapped. Although analysis of literature shows that surgical treatment, if the patients condition allows, is necessary for those presenting with SAH; patients presenting without SAH can be treated nonsurgically. Surgery is being now considered even for cases with ischaemia to prevent further extension of the dissection.
Most of the previous cases have been treated by vertebral artery ligation,[19],[20],[21] however ligation does not guarantee prevention of rebleeding. A proximal clip occlusion of the affected artery was carried out when the size of the opposite vertebral artery was equal to or larger than the affected artery. Wrapping of the lesion was the method of choice, when the vertebral was dominant. Unfortunately trapping an aneurysm with the PICA included in the trapped segment carries a substantial risk of morbidity. Previous reports on trapping of vertebral artery aneurysms describe a number of resultant neurological deficits, most frequently lateral medullary syndrome.[6],[21] When the PICA is involved in the trapped segment, revascularisation procedures such as occipital artery - PICA anastomosis and side to side OCA anastomosis should be considered in addition to trapping of the main vertebral segment and clipping of the proximal PICA.[21] This technique will prevent both recurrent haemorrhage and potential vertebral artery - PICA syndrome. Vertebral artery dissection proximal to the the origin of the PICA should be trapped intracranially to prevent collateral flow from cervical muscular branches; if the dissection originates extradurally a high cervical ligation can be performed as apart of trapping procedure.
Recent reports have revealed that conservative treatment of these dissections has resulted in successful resolution. Control of the blood pressure and bed rest prevent further progression of the dissection. Use of antiplatelet or anticoagulant drugs is controversial. The optimum angiographic follow up period is considered to be 2 or 3 months after which changes are less likely to occur. Intraoperative observations suggest that a ruptured dissecting aneurysm becomes a firm whitish gray mass probably due to organised intramural clot, approximately one month after the ictus and rebleeding is less likely to occur at this stage.
Surgical indications for unruptured vertebral artery dissections would be limited to the following two situations, observed on serial angiography : i) a persistent double lumen sign or retention of contrast material ii) fusiforin aneurysms occurring as sequela of dissection.


 

  »   References Top

1.Osamu Sasaki, Hiroshi Ogawa, Tetsuo Koike et al : A clinicopathological study of dissecting aneurysms of the intracranial vertebral artery. J Neurosurg1991; 75 : 874-882.   Back to cited text no. 1    
2.Chifumi Kitanaka, Jun- lchi Tanaki, Masanori Kuwahara et al : Nonsurgical treatment of unruptured intracranial vertebral artery dissection with serial follow up angiography. J Neurosurg1994; 80 : 667-674.   Back to cited text no. 2    
3.Freidman AH, Drake CG : Subarachnoid haemorrhage from intracranial dissecting aneurysm. J Neurosurg 1984 ; 60 : 325-334.   Back to cited text no. 3    
4.Shimoji T, Bando K , Nakajima K et al : Dissecting aneurysm of the vertebral artery. Report of seven cases and angiographic findings. J Neurosurg1984; 61 : 1038-1046.   Back to cited text no. 4    
5.Yamaura A : Diagnosis and treatment of vertebral aneurysms. J Neurosurg1988; 69 : 345-349.   Back to cited text no. 5    
6.Yonas H, Agamanolis D, Takaoka Y et al : Dissecting intracranial aneurysms. Surg Neurol 1977; 8 : 407-415.   Back to cited text no. 6    
7.Nobuhiko Aoki, Tatsuo Sakai : Rebleeditig from intracranial dissecting aneurysm in the vertebral artery. Stroke1990; 21 : 1628-1631.   Back to cited text no. 7    
8.Chifumi Kitanaka, Tadashi morimoto, Tomio Sasaki et al : Rebleeding from vertebral artery dissection after proximal clipping. J Neurosurg1992; 77 : 466-468.   Back to cited text no. 8    
9.Manz HJ, Luessenhop AJ : Dissecting aneurysm of the intracranial vertebral artery : Case report and review of literature. J Neurol1983; 230 : 25-35.   Back to cited text no. 9    
10.Mitchel S Berger, Charles B Wilson : Intracranial dissecting aneurysms of the posterior circulation. J Neurosurg1984; 61 : 882-894.   Back to cited text no. 10    
11.Stehbens WE : Pathology of the cerebral blood vessels. St Louis : CV Mosby, 1972; 60-68.   Back to cited text no. 11    
12.Adams HP Jr, Aschenbrener CA, Kasssell NF et al : Intracranial haemorrhage produced by spontaneous dissecting intracranial aneurysm. Arch Neurol 1982; 39 : 773-775.   Back to cited text no. 12    
13.Mizutani T, Goldberg HI, Parr J et al : Cerebral dissecting aneurysm and intimal fibroelastic thickening of cerebral arteries. Case report. J Neurosurg 1982; 56 : 571- 576.   Back to cited text no. 13    
14.Caplan LR, Baquis GD, Pessin MS et al : Dissection of the intracranial vertebral artery. Neurology1988; 38 : 868-877.   Back to cited text no. 14    
15.Ojemann RG, Fischer CM, Rich JC : Spontaneous dissecting aneurysm of the internal carotid artery. Stroke1972; 3 : 434-440.   Back to cited text no. 15    
16.Grosman H, Fornasier VL, Bonder D et al : Dissecting aneurysms of the cerebral arteries : Case report. J Neurosurg1980; 53 : 693-697.   Back to cited text no. 16    

 

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