Aneurysms of the Vertebral Artery (VA)

The late Dr. C. G. Drake (with his enormous, never-to-be-repeated surgical experience of having treated 1 767 vertebrobasilar artery aneurysms [VBAAs]) quoted Francis Bacon (1561-1626) in his book on vertebrobasilar aneurysms (VBAAs): “Every man owes it as a debt to his profession to put on record whatever he has done that might be of use to others” [1]. We read with great interest the excellent technical article by Sandalcioglu et al. on 28 vertebral PICA aneurysms [8]. Actually, the total number of patients was 32, but only those cases that could be treated were reported as a series: 2 patients died, and 2 refused any treatment. It is our policy that all patients should be included in the series, and when calculating the outcome of the treatment [4]. Furthermore, we always are standing on the shoulders of pioneering giants and feel that their techniques and their results as gold standards should be carefully scrutinized. As the series of 9 surgically treated patients by Sandalcioglu et al. remains small; we would like to add some more, mainly unpublished, information on vertebral PICA aneurysms, that might be useful for those attacking these deadly lesions of vertebral artery, endo- or exovascularly.

Our comment is based on a collaborative database with Drs. Drake and Peerless based on their surgical interventions in 1 767 patients with VBAAs, with one-eighth (221 patients) or 12.5 % presenting with vertebral artery (VA) or PICA aneurysms [1] and on an unpublished and a published article with Drs. Drake and Peerless on the same patients [2] [7]. Our comment is supported by a total experience of more than 420 vertebrobasilar aneurysms out of an unselected patient material of 2 463 patients with cerebral aneurysm treated in Eastern Finland in Kuopio in the years 1977-2000 [3] [4], and of more then 2 000 patients with cerebral aneurysms treated in Helsinki, Finland in senior author (JH) 8 years' experience since 1997. The frequency of vertebral aneurysms in these more than 4 500 Finnish patients with cerebral aneurysms is 3 %. Of the 150 Finnish patients with vertebral aneurysms, half of the patients had vertebral PICA aneurysms, 30 % had PICA aneurysms (proximal or distal) and the remaining 20 % had other vertebral aneurysms. We will report our Finnish experience elsewhere, but here we report on the classic experience of Drake and Peerless, adding some of our recent experience.

Based on a scrutiny of the angiographic tracings, operative findings and surgical techniques of the London, Ontario experience, 221 vertebral aneurysms were classified by Drake, Peerless and Hernesniemi as follows [1] [2] [7]:

Proximal vertebral artery aneurysms. These arise extra- or intradurally, or both; all four cases found were of giant size. Vertebral PICA aneurysms (150). These aneurysms arise near the origin of the PICA, and can be subdivided as follows:- Vertebral prePICA aneurysms (10). Three saccular vertebral aneurysms arose from the proximal aspect of the origin of the posterior inferior cerebellar artery (prePICA), six dissecting and one traumatic aneurysm originated at the same site.- Vertebral postPICA aneurysms (121). The most common aneurysm site is at the distal side of the PICA at its origin from the vertebral artery, the classical vertebral PICA aneurysm. All except four (three dissecting and one fusiform aneurysm) were saccular.- Vertebral PICA giant aneurysms (19). These aneurysms are of giant size, located in close proximity to the PICA, but due to their size the exact site of origin (prePICA or postPICA) cannot be determined. Sixteen were saccular aneurysms, two fusiform and one atherosclerotic. Distal vertebral artery aneurysms (41). An important group of aneurysms arose between the origin of the PICA and the vertebrobasilar junction, usually well under the medulla, if saccular possibly at the site of origin of the anterior spinal artery or a smaller, unnamed perforating branch. Eleven were saccular, 13 fusiform, 14 dissecting and three were atherosclerotic aneurysms. PICA aneurysms (26).- Proximal PICA aneurysms (10). These aneurysms have their origin from the PICA usually within a centimeter or so from its origin. Seven were saccular, two were dissecting and one was fusiform.- Distal PICA aneurysms (16). These are clearly located more distally; 12 were saccular, one fusiform, and three were fistulas with giant sacs associated with AVM.

The baseline characteristics as related to the site in 221 patients with vertebral and PICA aneurysms can be seen in Table [1]. A preponderance of female patients is peculiar to vertebral aneurysms and it can be seen at all sites except the proximal PICA. Of the 221 patients with vertebral aneurysms, 170 (77 %) were females. The female preponderance was even more notable in saccular aneurysms (142 : 25 = 85 %). The majority of the aneurysms 167 (81 %) were saccular. There were 154 (70 %) small aneurysms (< 12 mm), 27 large aneurysms (13-24 mm) and 40 giant (25 mm or more) aneurysms. A left sided origin (122 patients = 55 %) is more common and this is probably due to the more common predominance of the left vertebral artery. Forty-three aneurysms were unruptured. Twenty-six of the 40 giant aneurysms had mass effect only, with varying degrees of bulbar paresis and ataxia (18), often with mild (14) hemiparesis, hemisensory loss and limb dysmetria.

Table 1 Baseline characteristics as related to the site in 221 patients with vertebral and PICA aneurysms 1 2 7 variable aneurysm sitevertebralproximal vertebralPICA vertebraldistal PICA total no. of patients 4 150 41 26 221 female/male 3/1 130/20 22/19 15/11 170/51 mean age yearsage range 53.840-62 50.7 34-70 45.216-66 47.3 3-70 49.3 3-70 ruptured/nonruptured aneurysm 0/4 131/19 26/15 21/5 178/43 multiple bleeds (% of ruptured) - 31 % 46 % 33 % 34 % right 3 56 18 8 85 left 1 87 18 16 122 midline 7 5 2 14

Curiously, lower cranial nerve paresis is not more common with rupture of a vertebral aneurysm, as these nerves must frequently be subject to a jet of blood under tension from the aneurysm or clot after rupture. Surprisingly, hemorrhage causing coma was not more common than in other VBAA sites in spite of the earlier clinical impressions, but as one might expect, dramatic cardiac respiratory arrests with recovery were seen more frequently in the patients with ruptured vertebral aneurysms.

Sixth nerve palsy was the most frequent preoperative cranial nerve dysfunction. It was often bilateral and it was nearly always, in 23 of the 26 patients, associated with subarachnoid hemorrhage (SAH). In 20 of 26 it was the only preoperative cranial nerve paresis. In three fourths of patient recovery was complete and paresis never remained bilateral. One patient in poor condition after six bleeds from a small vertebral PICA aneurysm had oculomotor nerve palsy. Another had a trochlear nerve palsy preoperatively. Other preoperative cranial nerve pareses were more frequently associated with giant aneurysms (Table [2]).

Table 2 Cranial nerve deficit preoperatively, postoperatively and at follow-up in 221 patients with vertebral artery and PICA aneurysms 1 2 7. Unilat = unilateral cranial nerve paresis, bilat = bilateral cranial nerve paresis cranial nerve paresis preoperative unilat-bilat postoperative unilat-bilat follow-up unilat-bilat III 1-0 2-1 0-0 IV 1-0 1-0 0-0 V 13-1 15-1 5-0 VI 12-14 20-15 5-0 VII 13-3 21-4 5-1 VIII 8-1 13-1 8-0 IX-X 16-7 39-11 13-4 XI 2-1 6-1 6-1 XII 5-2 21-4 4-1 patients with cranial nerve deficits (%) 61 (28 %) 103 (47 %) 48 (23 %)

When vasospasm was associated with a poor grade, the outcome after surgery was poor. It appears to be advisable to delay surgery in these cases, whereas good grade patients can be operated on early. The rebleeding frequency was the same as that in other VBAA sites except in the rare locations of prePICA, proximal PICA and distal vertebral aneurysms. Dissecting aneurysms in these locations rebleed more easily (in more than half of the cases) - and therefore would represent one indication for early surgery, either open or endovascular. Unfortunately, the vertebral ligation is less well tolerated in the acute phase, and should be delayed, but nowadays stenting might be the treatment of choice.

The operative methods and outcomes are described in the book [1]. Although the clinical impression of frequent multiple bleedings in saccular aneurysms proved to be unfounded, early surgery can be recommended in good grade patients, as 16 of 19 patients operated on in the first 3 days made good recoveries [7]. Acute and early surgery has been our policy since 20 years for all aneurysmal sites. There were 7 bad outcomes in 142 good condition patients (5 %) with small aneurysms. There were only two poor outcomes in 27 large aneurysms, both in poor grade patients (grades 3 and 4) and no deaths. Of the seven poor results in 40 giant aneurysms, five were in poor condition preoperatively. In Helsinki, we operate all cases with reacting pupils nowadays acutely, with the exception, of course, of moribund cases with fixed dilated pupils. Intraparenchymal hematomas in the posterior fossa do not actually exist [1] , but acute hydrocephalus often needs acute drainage.

Intra- and postoperative complicating factors in 221 patients with vertebral or PICA aneurysms are listed in Table [3]. Lower cranial nerve deficits are common in the immediate postoperative period even when carefully handled intraoperatively: more than one-fifth of the patients had postoperatively IX-X nerve deficits (Table [2]), two thirds of them were transient but in follow-up four patients had severe dysphagia requiring prolonged tracheostomy. A temporary tracheotomy should be done without delay in the presence of lower cranial nerve deficits, even when only a suspicion exists. Aspiration pneumonia is still one of the most dangerous postoperative complications. Septicemia complications were more common than at other vertebrobasilar aneurysm locations (13 patients = 6 %) as were also meningitis (8 patients = 4 %), maybe due to mastoid air cells opening.

Table 3 Intra- and postoperative complicating factors in 221 patients with vertebral or PICA aneurysms 1 2 7 complication patients poor dead intraoperative aneurysm rupture 16 1 4 perforator injury 2 1 1 inadvertent arterial occlusion 10 2 1 deep arterial hypotension during surgery 1 0 1 postoperative hematoma 10 2 3 postoperative significant spasm 8 1 2 rebleeding from treated aneurysm 4 0 3 septicemia 13 3 0 meningitis 8 0 1 respiratory complication 8 1 2 bleeding diathesis 1 0 1 pulmonary embolus 2 0 1 multiple medical complications 13 3 5 total no. of patients 66 pts 13 pts 10 pts

In large and giant aneurysms VA occlusion at the clip site by thrombosis may occur; fortunately this is well tolerated. Trapping procedures should be used cautiously. Blood flow to vital medullary perforators may be compromised and this can be fatal or lead to a poor outcome. Intraoperative aneurysm rupture (7 %) was rare but dangerous: out of 16 patients, 4 died and 1 is severely disabled.

References

• 1 Drake C G, Peerless S J, Hernesniemi J A. Surgery of Vertebrobasilar Aneurysms. London, Ontario Experience on 1 767 patients. Springer-Verlag, Vienna 1996
• 2 Drake C G, Hernesniemi J A, Peerless S J. Aneurysms of the vertebral and posterior inferior cerebellar artery. An analysis of 221 patients with surgical treatment. Unpublished, written 1993
• 3 Hernesniemi J A, Vapalahti M P, Niskanen M, Kari A. Management outcome in vertebrobasilar artery aneurysms by early surgery.  Neurosurgery. 1992;  31 857-862
• 4 Hernesniemi J, Vapalahti M, Niskanen M. et al . One-year outcome in early aneurysm surgery: a 14 years experience.  Acta Neurochir (Wien). 1993;  122 1-10
• 5 Horowitz M, Kopitnik T, Landreneau F, Krummerman J, Batjer H H, Thomas G, Samson D. Posteroinferior cerebellar artery aneurysms: surgical results for 38 patients.  Neurosurgery. 1998;  43 1026-1032
• 6 Kivisaari R P, Porras M, Öhman J, Siironen J, Ishii K, Hernesniemi J. Routine cerebral angiography after surgery for saccular aneurysms: Is it worth it?.  Neurosurgery. 2004;  55 1015-1022
• 7 Peerless S J, Hernesniemi J A, Gutman F B, Drake C G. Early surgery for ruptured vertebrobasilar aneurysms.  J Neurosurg. 1994;  80 643-649
• 8 Sandalcioglu I E, Wanke I, Schoch B, Gasser T, Regel J P, Doerfler A, Forsting M, Stolke D. Endovascularly or surgically treated vertebral artery and posterior inferior cerebellar artery aneurysms: clinical analysis and results.  Zentralbl Neurochir. 2005;  66 9-16
• 9 Streefkerk H J, Wolfs J F, Sorteberg W, Sorteberg A G, Tulleken C A. The ELANA technique: constructing a high flow bypass using a non-occlusive anastomosis on the ICA and a conventional anastomosis on the SCA in the treatment of a fusiform giant basilar trunk aneurysm.  Acta Neurochir (Wien). 2004;  146 1009-1019
• 10 Yasargil M G. Vertebrobasilar aneurysms. In: Yasargil MG. Microneurosurgery in 4 Volumes, Vol II. Georg Thieme Verlag, Stuttgart, New York 1986; 232-295
• 11 Yasargil M G. A legacy of microneurosurgery: memoirs, lessons, and axioms.  Neurosurgery. 1999;  45 1025-1092