Surg Neurol 1994;41:119-24
Dissecting Aneurysms of the Vertebrobasilar System: Study of 16 Cases Eugenio Pozzati, M.D., Alvaro Andreoli, M.D., Paolo Limoni, M.D., and Mario Casmiro, M.D. Division of Neurosurgery, Bellaria Hospital, Bologna, Italy, and Division of Neurology, Faenza, Italy
Pozzati E, Andreoli A, Limoni P, Casmiro M. Dissecting aneurysms of the vertebrobasilar system: study of 16 cases. Surg Neurol 1994;41:119-24. In the last 14 years we have encountered 16 patients with spontaneous intracranial dissections of the vertebrobasilar (VB) system (mean age was 46 years and male/female ratio was 10/6). VB dissections presented in eight cases with subarachnoid bleeding and in eight with brainstem, cerebellar, or cerebral ischemia. Three patients had multiple dissections. Ten dissections occurred in the vertebral artery (two extended to the basilar artery), three in the posterior cerebral artery (one bilateral), two in the basilar artery, and one in the posterior inferior cerebellar artery. The angiographic configuration included "string" sign, "pearl and string" sign, fusiform dilation, and double lumen. The following angiographic evolution (available in 11 cases) was that of complete healing (three cases), partial resolution (five cases), progression (one case), and unimproving (two cases). Three patients died (two due to recurrent subarachnoid hemorrhage): two patients were explored surgically (one had further intravascular therapeutic embolization), and the rest were treated conservatively. Not all dissecting aneurysms fared in the same manner, depending either on the location in the VB circulation or on the variable vascular configuration: treatment should be fitted to the timing of diagnosis. KEY WORDS: Cerebral angiography; Dissecting aneurysm; Subarachnoid hemorrhage; Vertebral artery; Vertebrobasilar ischemia
Spontaneous intracranial dissections of the vertebrobasilar (VB) system are being reported with increasing frequency and are becoming more widely appreciated as a cause of subarachnoid hemorrhage (SAH) [ 1 , 4 - 6 , 8,13-15]. Address reprint requests to: E. Pozzati, M.D., Division of Neurosurgery, Bellaria Hospital, Via Altura, 3, 40139 Bologna, Italy. Received October 22, 1992; accepted May 21, 1993.
© 1994 by ElsevierScienceInc.
Diagnosis is often based on the angiographic demonstration o f the typical alternating widening and narrowing with venous pooling in the dissected segment "pearl and string" sign. The vertebral artery is more often involved and the prognosis o f dissecting aneurysms presenting with S A H is considered particularly severe . W e report our experience with 16 patients presenting with protean symptoms (hemorrhagic and ischemic) to better elucidate the clinical profile o f the disease, the radiologic evolution with its changing patterns, and the strategy o f treatment in the light o f a possible benign evolution.
Case Material During the last 14 years we have encountered 16 patients with a total of 18 dissecting aneurysms o f the intracranial vertebrobasilar system. Two patients had bilateral dissecting aneurysms o f the posterior cerebral and vertebral arteries and one had combined carotid and vertebral dissections. The ten men and six women in this group were aged between 34 and 68 years, with a mean age of 46. One patient (no. 5) had previous neck manipulations (Figure 4). Eight patients presented with S A H and eight with ischemia (Table 1). Ten dissections were located along the intracranial vertebral artery (two extended to the basilar artery and one bilateral), two on the basilar artery, three on the posterior cerebral artery (one bilateral), and one on the posterior inferior cerebral artery (PICA) (Figures 1 and 2). Fusiform or sausagelike dilation with proximal or distal narrowing (string and pearl sign) was found at angiography in six cases, double lumen in one (Figure 3), fusiform dilation in four, and string sign in four. One patient (no. 7), had a normal angiogram on admission and a vertebral dissecting aneurysm was found at autopsy 1 week later. Two patients with vertebral dissections had distal embolic occlusions. Repeat angiography was performed in 11 patients: the dissection was found resolved in three cases, improved in five (residual stenosis), unchanged in two, and worsened in one. In 0090-3019/94/$7.00
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Table 1. Summary of 16 Patients with Dissections of the Intracranial Vertebrobasilar System Case
Angiography String pearl Fusiform dilation String sign Fusiform dilation
-1 Month normal
String-pearl sign Extracranial dysplasia String sign
String-pearl sign String sign
Unchanged 6 months Improved
SAH Deep coma Brain stem ischemia Brain stem ischemia Brain stem ischemia Brain stem ischemia Cerebral ischemia
3 Months, healing
Fusiform dilation Double lumen String-pearl sign
Brain stem ischemia Wallenberg's syndrome Brain stem ischemia
3 Months residual stenosis 1 Month and 3 months progressive dilation 2 Months: improved --
-1 Month residual stenosis 1 Year unchanged
-3 Months, irregular prophile 6 Months, normal
Remarks Early rebleeding Bilateral lesions --
Clinical course Death Good Good
Surgical exploration Previous neck manipulation attempted proximal occlus, surgical exploration a --
Good Minor sequelae ventricular dilation
Cervical carotid dissection early rebleeding
Death. autopsy: 2 cm dissecting aneurysm Death Poor
-Previous go-kart racing Previous anticoagulation -Extracranial vertebral dysplasia -Multiple lesions
Recurrent symptoms Poor Good Recurrent symptoms Good
Abbreviations: VA, vertebral artery; PCA, posterior cerebral artery; BA, basilar artery; PICA, posterior inferior cerebellar artery. Intravascular therapeutic embolization was performed in Paris by Dr. Moret.
this last case (no. 5) the dissection started at C1 and progressive luminal dilation at vertebral/PICA junction occurred over 3 months (Figure 4). All SAH patients but one were in the grade 1 or 2 o f H u n t and Hess scale: two o f them died o f recurrent hemorrhage within 10 days. Two patients with dissecting aneurysm o f the vertebral artery were operated on at 3 and 8 weeks after SAH: in both cases a firm, whitish fusiform mass was found and left untouched. In one case (no. 5) balloon occlusion o f the cervical vertebral artery was suspended due to sudden vertigo and clouding o f consciousness. We know that intravascular therapeutic embolization was performed afterwards in Paris by Dr. Moret. Among patients presenting with ischemia, two had major strokes involving the brainstem, three had minor neurologic signs (vertigo, diplopia), one presented with Wallenberg's syndrome, one had occipital ischemia, and one had no localizing signs. One was under anticoagulation for peripheral arterial disease. These patients received
antiplatelets as initial therapy; anticoagulation was never undertaken. All patients survived their strokes, but two remain in p o o r neurologic condition. At the follow-up (mean 3.2 years) one has minor sequelae and three are symptomatic; two had recurrent minor symptoms. Discussion Intracranial dissecting aneurysms o f the VB system are considered dangerous and virulent lesions that carry a high morbidity and mortality rate. H o w e v e r the natural history o f the disease and its clinical profile are poorly understood. Some recent observations emphasize that a favorable course may occur in a relevant n u m b e r o f cases [7,11]. The impression is that not all dissecting aneurysms have the same end result, depending either on the location in the VB circulation or on the variable vascular configuration. Ruptured dissecting aneurysms o f the vertebral artery are more frequent and at risk for
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Figure 1. Vertebral angiogram (lateral and anteroposterior views) 2 weeks after the onset of Wallenberg's syndrome showing multiple dilations of the right PICA (string of pearl sign) (arrow) (case 15).
rebleeding during the acute stage , while this risk drops after 1 month or when located in other arteries of the VB system [11-14]. Intraoperative observations suggest that a ruptured dissecting aneurysm becomes a firm whitish mass approximately i month after the stroke and that rebleeding occurs less frequently at this stage . Preferential involvement of the vertebral artery includes various combinations of predisposing degenerative changes (small fusiform aneurysms due to wall derangement) and anatomic factors (changes in structure
as the vessel pierces the dura) [9,12]. The poor prognosis of ruptured dissecting aneurysms of the vertebral artery is confirmed in our series (six cases): three patients died (two due to acute rebleeding and one due to the original ictus) and one needed intravascular embolization due to progressive aneurysmal dilation. Only two SAH patients did well without treatment: this small number of good results is probably insufficient to justify an expectant policy in the acute phase. In two other patients the
Figure 2. (A) Vertebral angiogram (lateral view) 5 weeks after the stroke showing substantial remodeling of the vesselwith residual luminal dilation. (B) Vertebral angiogram (lateral view) at 3 months showing an almost complete healing of the dissecting aneurysm: only a minimal luminal irregularity may be noted.
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A Figure 3. (A) Right vertebral angiogram showing dilation of the intracranial vertebral artery and a line in the basilar artery representing the double lumen (arrow) (case 14). (B) Left vertebral angiogram shows stenosis/ dilation of the vertebral artery and confirms a faint double lumen of the basilar artery (arrow) related to previous dissection.
dissection extended from the vertebral into the basilar artery; one had bilateral vertebral dissection extending to the basilar artery showing the typical double lumen. Both were young adult males, presented with brain stem ischemia and survived their strokes. In this group of patients brain stem infarction develops resulting from luminal occlusion by subintimal mural hematoma, opposite to pure vertebral artery dissections presenting with S A H from rupture of the arterial wall . Dissecting aneurysms of the basilar artery often present with brain stem infarction and more rarely with SAH: their prognosis is known to be poor even if some rare cases may run a favorable course . In our series both basilar artery dissections presented with brain stem ischemia and resolved spontaneously leaving in one case major neurologic sequelae. Opposite to the vertebral artery the PCA was a rather benign location of arterial dissection: our three cases (two presenting with SAH and one with ischemia) did
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surprisingly well with documented complete or partial angiographic resolution o f the lesion . The only patient with dissecting aneurysm o f the PICA presented with Wallenberg's syndrome and did clinically and angiographically well. Lateral medullary infarction is a c o m m o n r e s u l t - - V B occlusion--and it is generally referred to occlusion o f the PICA or of the terminal vertebral artery. In a recent review o f patients with infarction in the territory o f the PICA, the vascular occlusion was atherosclerotic and embolic in the majority o f cases . However, in 30% o f patients no occlusion was found, suggesting a role o f a previous healed dissection in some cases. In our series precise predisposing or precipitating factors (fibromuscular dysplasia, previous neck manipu-
Figure 4. (A) Vertebral angiogram (anteroposterior view) 24 hours after SAH showing mild stenosis of the intracranial vertebral artery (arrow) and minimal dilation at the vertebral~PICA junction. (B) Vertebral angiogram (lateral view) 1 month later showing dilation and luminal defect (arrow) of the artery at C1 probably representing the proximal limit of the dissection related to previous neck manipulations. (C) Aneurysmal dilation (lateral view) at the vertebral~PICA junction. (D) Three months later progressive "globoid" widening of the dissected segment may be seen. At operation a firm, whitish fusiform aneurysm was found (case 5).
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lation, migraine) were identified in a minority o f cases. H o w e v e r , the multiple vascular involvement in three cases suggests that an occult wall disease should be investigated as the main etiologic factor o f the disease. T h e angiographic features o f intracranial dissection have been described in detail elsewhere [4,6,13,15] and are those found also in our cases (string sign, pearl and string sign, double lumen, fusiform dilation with pooling in the venous phase). H o w e v e r the changing patterns o f a dissecting aneurysm and their temporal evolution are still incompletely understood. The angiographic signs o f a dissection are not always evident in the acute phase: sometimes, these changes are subtle, introducing the p r o b l e m o f "minimal" dissection and o f its further course, particularly in those patients with S A H o f apparently unknown etiology . In case 7, the initial vertebral angiogram was normal, and a huge dissecting vertebral aneurysm ruptured in the brainstem was found 10 days later at autopsy. In case 5, repeat angiograms at 1 week, I and 3 months demonstrated progressive dilation o f the vertebral artery at the site o f an initial segmental narrowing (Figure 4). This angiographic "globoid" evolution in contrast to the fusiform configuration found at surgery permitted an intravacular therapeutic embolization, an unusual treatment o f dissecting aneurysms. Probably a n u m b e r o f dissections with initial angiographic narrowing has been attributed to vasospasm in patients with SAH. These luminal changes early after bleeding must be interpreted with a high degree of suspicion and carefully evaluated in repeat angiograms. Some peculiarities may help in differentiating vasospasm from dissection: appearance on early angiograms, retention of contrast medium, luminal irregularities , and unexpected occlusions o f distal branches resulting from early embolization. In two o f our patients with dissecting aneurysms o f the vertebral artery (one with initial normal angiogram) the presence o f distal occlusions o f the PCA was the m o s t p r o m i n e n t angiographic finding. Spontaneous resolution is sometime observed in occlusive or stenotic dissections [7,11]. Based on these observations, for patients with ischemic stroke, conservative treatment and angiographic follow-up should be planned. A late angiographic residuum (wedge-shaped defects, diffuse luminal stenosis) may be found in relation to the scar occurring in the dissected segment . Conversely, the complete regression o f an aneurysmal dilation is unusual [6,11]. In our series benign outcome and spontaneous healing occurred in two S A H patients with fusiform dissecting aneurysms o f the PCA; these are probably at the better end o f the clinical spectrum and fare better than dissections with other shapes. T h e residual fine wall wrinkling o f the P I C A found in case 15 (Figures 1 and 2) is very similar to some irregular
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configurations often attributed to "arteritis" and should be kept in mind when dealing with intracranial vascular disease. T h e m a n a g e m e n t o f ruptured dissecting aneurysms is suspended between possible self-healing with risk o f rebleeding and surgical occlusion o f the parent vessel [3,6,14] precluding a spontaneous recanalization. T h e subgroup o f patients with dissection o f the intracranial vertebral artery is at high risk o f early rebleeding and should be considered for early operation (proximal clipping or trapping) . After the acute phase, a process o f self-healing may occur and definite indications to surgical treatment depend on the course o f the disease demonstrated by angiography: repeat angiography should be carried out to assess the evolution in all patients who do not undergo early operative management.
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