Original articles Multiple cerebral de nova aneurysms H.A.M. van Alphen, and Gao Yong-Thong*

Introduction Summary

The incidence and the description of newly developed or so-called de izo~o aneurysms are not unique. Since Graf and Hamby presented the first report on a previously undemonstrated aneurysm in an adult in 1964’, 23 well-documented cases have been published. Miller, et al. reported the largest series of seven cases.’ They estimated the incidence at a minimum of 100 cases per l~,OOO per year in patients known to have intracranial aneurysms. Recently, Pelissou, et al. reviewed the cases reported in the literature.’ Misra, et al. and Dyste, et al. have added another three cases to these.4s5 Nevertheless, the demonstration of newly found cases of de nova aneurysms can still be very instructive and contributes considerably to our understanding of the pathogenesis of cerebral aneurysms in general. This is the reason why we are presenting two patients with multiple de nova aneurysms with an extraordinary appearance. On the basis of the findings in these patients, the pathogenesis will be discussed. Case reports Case 1

A 37-year-old, right-handed woman has a sudden, severe headache on March 5,1979. She was admitted to a local hospital. Before this ictus she

The new development of two remarkable cerebral mirror aneurysms is described in two female patients, who had been surgically treated for a mid-line aneurysm several years previously. The phenomenon of mirror aneurysms makes it likely that an inborn weakness of the vessel wall is one of the underlying causes of cerebral aneurysms. Acquired alterations of the vessel wall and hemodynamic forces, on the other hand, also play an important role in the genesis of aneurysms. Key words: Mirror aneurysms - multiple aneurysms _ de novo aneurysms - aneurysm development

was in good health, except for a moderate hypertension. She smoked 25 cigarettes a day and was using oral contraceptive medication. On admission, she was awake with a G.C.S. score of 15. Her blood pressure was 170/100 mm Hg.; her pulse was 88 per minute. There was stiffness of the neck, but no focal neurological signs. The diagnosis of subarachnoid hemorrhage was confirmed by lumbar puncture. Four-vessel angiography showed a 12x8 mm aneurysm on top of the basilar artery (Fig. 1 A). On the bifurcation of the left middle cerebral artery a small sessible ‘bleb’ was visualized. The right carotid circulation was normal (Fig. 1 C, D). On March 21,

* Department of Neurosurger.y, Free University Hospital, Amsterdam,

The Netherlands

Address for correspondence and reprint requests: H.A. M. van Alphen, Department of Neurosurgery. De Boelelaan I I1 7, IO81 HV Amsterdam, The Netherlands.

Free University Hospital,

Accepted 21.3.90 Clin Neurol Neurosurg

1991. Vof. 93-1

13

Fig. I. Case i .A i’crtebral angiogram, anteroposterior view, showing aneurysm ariaing from the top of the basrlar artery (small arrou-l. H. Postoperative vertebral angiogram. aneurysm clipped. C. Right carotid angiogram and D. Left carotid angiogram at the time of the first subarachnoid bleeding from the basilar aneurysm. Note small hleh on the bifurcation of thr laft middle cerebral artery (arrow). E. Right carotid angiogram and F. Left carotid angiogram, 8 years later, showing mirror aneurysma on the middle cerebral arteries and fusiform aneurysm on the right internal carotid artery.

1979 she was transferred to the Department of Neurosurgery. Two days later the aneurysm was clipped via a right sylvian approach. Postoperatively, the patient had a slight right-sided oculomotor paresis, due to dissection of the nerve out of the adhesions. This improved in a few weeks. Otherwise she made a good and uneventful recovery. Control vertebral angiography revealed a good position of the clip and no filling of the aneurysm (Fig. 1 B). On April 18, 1987 she was re-admitted to the 14

local hospital, because of severe headache and decrease of consciousness. It was reported that she had had a I-week episode of acute headache one year previously, which had disappeared spontaneously. Since that time, she had been behaving in an unusual way and remained in seclusion. Two weeks prior to admi~ion she had a sudden ictus of headache and neck pain, while reading the newspaper. This remained despite the use of analgetics. In the morning before admission she had a severe relapse of headache

while defaecating. She suffered a disturbance of memory and of equilibrium. In the period since her operation she has shown variable hypertension, which had been poorly controlled by irregular use of antihypertensive medication. She was still using oral contraceptives and smoking 25 cigarettes a day. Clinical examination on admission revealed a G.C.S. score of 12. There was marked meningismus. Her blood pressure was 160/85 mm Hg.; her pulse was 80 per minute. Both eyes showed some signs of retinal bleeding and there was a slight oculomotor paresis on the right. CT-scan of the brain showed blood in the basal cisterns and in the fourth ventricle. Angiography showed an extensive fusiform aneurysm of the intracranial segment of the right internal carotid artery and large remarkable mirror aneurysms of the bifurcations of the middle cerebral arteries. There was some vasospasm on the left side (Fig. 1 E, F). In the next few days the patient’s condition remained fairly stable. But she expired suddenly on April 24, 1987. Post-mortem examination was not permitted.

A Fig. 2. Case 2. A. Right carotid angiogram rotid

and B. Left ca-

angiogram,

anteropos-

tcrior view, showing an anterior

communicating

aneurysm

artery

(small

arrow). Small bleb on the left middle

cerebral C.

artery (large arrow).

Right

carotid

angiogram

and D. Left carotid angiogram, 18 years later, showing mirror

aneurysms

on the Ml

segment of both middle cerebral arteries.

Case 2 A 27-year-old, right-handed woman suffered a subarachnoid hemorrhage, confirmed by lumbar puncture in August 1968. Clinical examination revealed a meningismus and a left-sided hemiparesis. Carotid angiography demonstrated a 6x6 mm aneurysm of the Al segment of the left anterior cerebral artery near the junction with the anterior communicating artery. There was some vasospasm of the transition of Al into the A2 segment. On the left Ml segment of the middle cerebral artery a small ‘bleb’ was seen at the origin of the lenticulostriate arteries. On the right Ml segment at this site the origin of the anterior temporal artery was seen. (Fig. 2 A, B). On August 15.1968 the aneurysm was clipped via a frontobasal approach, without opening the sylvian fissure on either side. The postoperative course was uneventful. Control angiography after 2.5 weeks showed the clip to be in a good position, no filling of the aneurysm and some increased vasospasm of the left anterior cerebral artery. Also the ‘bleb’ on

the left Ml segment was still visible in the same extent. In the period following the operation the hemiparesis improved and the patient was without complaints for many years. In 1985 she started to complain of dizziness and headache. She had been suffering from hypertension for 10 years, and had used antihypertensive medication. Clinical examination revealed a blood pressure of 170/110 mm Hg. There were no focal neurological signs. A contrast enhanced CT-scan showed a hyperdense lesion on both sides in the sylvian fissure. Fourvessel angiography, performed in November 1986, demonstrated striking mirror aneurysms at the Ml segment of the middle cerebral artery on either side (Fig. 2 C, D). These aneu~sms were so much more striking because they were not located, as usual, at the apex of the bifurcation of the internal carotid artery, but somewhat more laterally on the middle cerebral artery, where, on one side, no major bifurcation was present. It was on this side that an originating aneurysm could already be seen on the initial angiograms 18 years previously. Both aneurysms were clipped successfully with a time interval of 2 weeks. After the second procedure, the patient had a moderate aphasia and right hemiparesis, which improved gradually. Three weeks postoperatively, she suddenly expired, probably due to pulmonary embolism. Postmortem examination was not permitted. Discussion In these case reports, two female patients are described, presenting with remarkable mirror aneurysms, which had not been visualized on angiograms 8 and 18 years previously. In both cases, however, the initial angiograms revealed an indication of an aneurysm in statu nascendi on one side at the location involved. One patient also showed a fusiform aneurysm of the distal extension of the internal carotid artery, which again was not visible on the first angiograms. In both patients, some factors were present, which are assumed to influence the generation and growth of aneurysms, such as arterial hypertension, the use of oral contraceptive medication and cigarette smoking.h,7 Miller, et al. proposed that a de novo aneurysm might be considered a special case of mul16

tiple aneurysms in which the lesions appear in series rather than in parallel.’ Our two cases favour this hypothesis. The different stages of the series can be observed on the subsequent angiograms. On the initial angiograms, not only a mature mid-line aneurysm was present, but also a small, sessile bleb on one side more laterally, which was apparently the origin of one of the mirror aneurysms, and which, after an interval of several years, presented as a fullygrown aneurysms. These aneurysms in statu nascendi have been observed on angiograms as well as during surgery and at autopsy and have been shown to develop into adult aneurysms by several aUthorS.“.X,~,“‘.“.‘:On the contralateral side such an originating aneurysm was not yet visible at the time of the first angiogram. But in the end, real, symmetrical mirror aneurysms are present in both cases. It it obvious, therefore, that the bleb has to be considered as an early stage of the de now aneurysm and that it depends on when the patient presents with the first bleeding or when the first angiogram is taken, whether we witness the development of a de now aneurysm or discover multiple aneurysms. According to this line of reasoning, newly-detected aneurysms are not necessarily a result of ‘false-negative’ angiograms or of ‘missed’ aneurysms,‘“,‘4 but they may, indeed, develop as an acquired vascular lesion. The occurrence and the almost simultaneous origin and growth of aneurysms at symmetrical locations in the cerebral arterial system, might be an indication that these locations are a locus minoris resistentiae of the vessel wall, which are inborn rather than acquired.’ Another argument for this might be the familiar incidence of aneurysms on exactly the same site in the circle of Willis, as we have seen in some of our patients. This in no way excludes some external or acquired, additional stimuli, which generate the origin of an aneurysm.‘” At the predisposed, weak spots, the usual, probably partly age-defined alterations of the vessel wall may lead to smalt defects. Especially defects of the internal elastic lamina are of aetiological importance for the development of aneurysms, rather than the more common defects of the tunica media, as believed by many investigators.h.‘s.‘h.‘7.‘XI4 This essential role of the internal elastic lamina could be estab-

lished by us in an experimental model.‘“~“.?’ The media and adventitia will expand through this small defect in the internal elastic lamina, initially causing a bleb in the vessel wall. Subsequently, this bleb will develop into a mature aneurysm, probably influenced by hemodynamic forces. Under rare circumstances a larger defect or a crack in the internal elastic lamina occurs. which might give rise to a fusiform aneurysm, as seen in our first patient. Ferguson and others have suggested that the impingement of the central streams of the blood at the apex of intracranial bifurcations might be the initiating cause of a localized degeneration of the internal elastic membrane, which should lead to destruction and to outpouching of the vessel wall.h~‘h~‘7~‘y~~” However, although not as common, aneurysms may also occur at sites in the circle of Willis, other than the apices of major bifurcations, as shown in our second patient. Here, the role of impingement is much less likely. The hemodynamic forces were also considered as a causal aetiological factor in the earliest reports on de nova aneurysms. The development of a new contralateral mirror aneurysm, mostly on the posterior communicating artery, was attributed to the ligation of the other carotid artery for a first aneurysm on that side with subsequent hemodynamic changes.1.5.“.‘-5.‘h.‘7.LX In our cases, however, no vessels were occluded, giving rise to hemodynamic alterations. Moreover, in these cases the aneurysms developed symmetrically and simultaneously on both sides. Therefore, it is more likely that also in the case of carotid ligation. an inborn locus minoris resisterhe at symmetrical places of the carotid arteries was present, where acquired alterations of the vessel wall and the changes in hemodynamics, due to carotid ligation, are given the opportunity to generate the growth of an aneurysm. rather than to consider carotid ligation and the subsequent hemodynamic alterations as a primary causal factor of aneurysmal formation. Both our patients were female. The preponderance of females amongst cases of cerebral aneurysms has been noticed by many authors. 1.14.24~29.30 For multiple aneurysms, which occur in about 30% of the patients with confirmed aneurysms, this female preponderance is

even more striking. I4 Moyes reported a female to male ratio for multiple aneurysms of 3: 1.3’ Andrews found a female to male ratio of 7:3 for all patients with multiple aneurysms and of 3:l for patients with three or more aneurysms.” In the series of Nehls et al. these rates were 5: 1 and ll:l, respectively, and in the series of Q)stergaard et al. 2:l and 7:3, respectively.3”,32 Of 25 cases of de nova aneurysms reported in the literature to date, 1.5 occured in females and 10 in males. The reason for this female preponderance in multiple aneurysms. which also increases with increasing number of aneurysms2’. is unclear. A possible explanation might be that female sex hormones are amongst the factors responsible for the probably age-defined alterations in the vessel wall and especially of the internal elastic lamina, as mentioned above. These alterations at the sites of inborn weakness of the vessel wall may give rise to aneurysmal formation. The relatively high frequency of de nova aneurysms in women. on the other hand, might be explained by a greater vulnerability of the aneurysm wall, which may lead to a subarachnoid hemorrhage at an earlier stage, before other (multiple or de nova) aneurysms have developed. Other factors, which may put a premium on the degenerative, age-defined alterations of the vessel wall, are atherosclerosis, oral contraceptives and cigarette smoking.4,‘h.““.“4In our first patient, two of these factors were also present. The final growth of aneurysms, i.e. the distension of the tunica media and tunica adventitia, is probably mainly influenced by hemodynamic forces, such as arterial hypertension and altered flow conditions, e.g. in cases of anomalies of the circle of Willis, carotid ligation, or arteriovenous malformations.h,‘4,” The association between arterial hypertension and the occurrence of intracranial aneurysms has been described by several authors.4.‘y.3”.” Also, our two patients had been suffering from hypertension for many years, although the second patient had no hypertension at the time of her first subarachnoid hemorrhage. Ferguson also mentioned the role of turbulence in the developing sac of the aneurysm on its frlrther growth.” During the growth of the aneurysm a defect of the media, which initially is part of the aneurysm wall, can also occur. This thinning of the wall of 17

the aneurysm most likely increases the risk of rupture and bleeding at these sites. The frequently found medial defects of the vessel wall in themselves are probably of no importance for the development of aneurysms.6”8.‘y*‘” In conclusion, in our concept of the pathogenesis of cerebral aneurysms, the condition of the internal elastic lamina plays a predominant role. Three major aetiological factors are supposed to be important for aneurysmal formation: (i) an inborn locus minoris resistentiaein the arterial wall of the vessels of the circle of Willis, (ii) an acquired, degenerative alteration of the internal elastic lamina, elicited by factors such as age, sex, atherosclerosis, cigarette smoking, and (iii) hemodynamic forces, such as impingement of blood stream, hypertension, and changes in hemodynamics in the circle of Willis, which might influence the growth of the aneurysm. References GRAF CJ, HAMBY BN. Report of a case of cerebral aneurysm in an adult developing apparently de nova. J Neurol Neurosurg Psychiat 1964; 27: 1.53-6. MILLERCA,HILLSA,HUNTWE. ‘DeN0vo’aneurysms.A clinical review. Surg Neurol 1985; 24:173-80. PELISSOU I,SINDOU M,PIERLUCA P, eta/. An6vrysms‘De Novo’. A propos d’un cas op&. Neurochirurgie 1987; 33: 399-404. MISRABK,WHITTLE IR,STEERSAJW,SELLARRI. Denovo saccular aneurysms. Neurosurgery 1988; 23:10-5. DYSTE GN, BECK DW. De novo aneurysm formation following carotid ligation: case report and review of the literature. Neurosurgery 1989; 24:88-92. STEHBENS WE. Intracranial arterial aneurysms. In: Pathology of the Cerebral Blood Vessels, St Louis: C.V. Mosby: 351-470, 1972. SEKHAR LN, HEROS RC. Origin, growth, and rupture of saccular aneurysm: a review. Neurosurgery 1981; 8:24860. BREMER JL.Congenital aneurysms of the cerebral arteries, an embryonic study. Arch Pathol 1943; 35:819-31. FORBUS WD. On the origin of miliary aneurysms of the superficial cerebral arteries. Bull Johns Hopkins Hosp 1930; 47:239-84. YASARGIL MC. Microneurosurgery, Vol 1+2, Stuttgart: Georg Thieme Verlag, 1984. YOSHIMOTO T, SUZUKI J.Eight-year documented study of an aneurysm growth at the origin of the posterior communicating artery. Neurol Surg 1974; 2:571-3. YOUNG B, MEACHAM WF, ALLEN JH. Documented enlargement and rupture of a small arterial sacculation. Case report. J Neurosurg 1971; 34:814-7. MC KISSOCKW,RICHARDSONA,WALSH L,OWENE. Multiple intracranial aneurysms. Lancet 1964; 1:623-6.

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Multiple cerebral de novo aneurysms.

The new development of two remarkable cerebral mirror aneurysms is described in two female patients, who had been surgically treated for a mid-line an...
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