Introduction 

   Moyamoya disease is associated with intracranial aneurysms in 3~15% of patients.^7)8)12) Direct surgical intervention has been used for the treatment of such aneurysms.¹⁹⁾²⁰⁾ However, clipping is often difficult because the operative field is disturbed by interlaced abnormal vessel.¹⁾¹⁹⁾ We describe a patient with moyamoya disease and a ruptured superior cerebellar artery aneurysm presenting as subarachnoid hemorrhage, which we treated with coil embolization. 

Case Report 

History 
   A 53-year-old man with sudden onset severe headache and altered mental status was referred to our hospital on November 24, 2007. A computed tomography (CT) at an outside hospital revealed SAH. His neurological examination revealed drowsy mental status without focal signs. 

Examination 
   CT demonstrated hemorrhage in the basal cistern, both sylvian fissures, the inter-hemispheric fissure, and both lateral ventricles (Fig. 1). Brain CT angiography revealed a 7 mm sized saccular aneurysm at the origin of the right superior cerebellar artery (SCA). There was poor visualization of both the anterior (ACA) and middle cerebral arteries (MCA), suggesting severe stenosis (Fig. 2). For further evaluation of anatomical structures, trans-femoral cerebral angiography was performed. This revealed evidence of severe stenosis of supraclinoid internal cerebral artery (ICA) with rich collateral vessels in the right MCA territory (Fig. 3). The circulation of both the ACA and MCA territories was preserved via both PCAs. Seven mm sized saccular aneurysm was detected at the origin of right SCA (Fig. 4). We concluded that the patient had moyamoya disease (MMD) with SAH due to rupture of a right SCA aneurysm. 

Operation 
   Coil embolization was performed under general anesthesia. A microcatheter was introduced through the intracranial vertebral and basilar arteries and finally into the aneurysm lumen. Five microcoils with a total length of 45 cm were packed in the aneurysm. After embolization, angiography showed that the aneurysm was nearly completely occluded. The PCAs and SCAs were preserved bilaterally (Fig. 5). 

Postoperative Course 
   Five days after embolization, the patient had decreased consciousness with left hemiparesis (Gr IV+). After hypertensive dynamic fluid therapy was started, the patient's mental status and motor weakness fully recovered. It was thought that vasospasm or hemodynamic hypoperfusion ischemia may occured. 
   Four months after embolization, Diamox brain SPECT (single photon emission computed tomography) revealed a significant decrease in cerebrovascular reserve in the left MCA territories (Fig. 6). Extracranial-intracranial arterial bypass surgery is currently being considered. 

Discussion 

   Maki and Nakta¹⁵⁾ first reported an intracranial aneurysm associated with MMD in 1965. The overall prevalence of intracranial aneurysms in MMD is 3~15%.^7)8)12) 
   There are two major types of aneurysms in this disease.^{2)4)8)11)16)21)22)} The first is peripheral artery aneurysm, occurring in periventricular area, near or in the abnormal fine network of moyamoya vessels; it may result in intracerebral hemorrhage and intraventricular hemorrhage.¹⁰⁾ This type of aneurysm appears histologically as a pseudoaneurysm and may disappear on follow-up angiography.¹³⁾ For this reason, Kawaguchi et al.⁸⁾ argued that surgical intervention is not recommended for aneurysms found in the basal ganglia or in the collateral vessels. The second aneurysm type is a major artery aneurysm, which develops in the circle of Willis and is likely to grow and rupture without spontaneous resolution.⁶⁾ 
   Even though saccular aneurysms arise more frequently overall in the anterior circulation, those associated with MMD occur more frequently in the posterior circulation.⁹⁾ Vertebrobasilar artery aneurysms represent 43.3% of saccular aneurysms in patients of MMD, compared to 5.3~9.6% in the general population.^14)17)19) Because of occlusive disease of the internal carotid system, increased blood flow through the posterior circulation worse hemodynamic stress on arterial walls and may result in aneurysm formation and rupture.³⁾¹⁸⁾ 
   Direct surgical treatment is thought to be necessary for treating patients with SAH because these aneurysms easily expand and rupture.⁷⁾¹⁹⁾ However, direct surgery is impeded by a variety of restrictions. First, innovative preservation of the transdural anastomosis may be necessary during craniotomy, dural, and arachnoid incisions.¹⁾ Second, patients with MMD have poor tolerance to retraction and ischemia¹⁹⁾ and have low reserve capacity. The carotid artery is so stiff that adequate retraction can not be achieved¹⁶⁾. Excessive brain retraction may cause cerebral blood flow disturbance, resulting in postoperative complications such as cerebral infarction or intracerebral hemorrhage, and may also damage the moyamoya vessels.¹⁹⁾Third, the rich tortuous collateral moyamoya vessels around the aneurysm act as vital collateral pathways and cannot be sacrificed.¹⁹⁾ So, there are less chances to clip the aneurysms. Moreover, intraoperative compression of ischemic cerebral cortex or temporary clipping of the parent artery may result in irreversible brain damage. Finally, direct surgery necessitates general anesthesia, which may cause postoperative aggravation of clinical symptoms or cerebral infarction due to hypocapnia induced by intraoperative hyperventilation.²³⁾ 
   It is important to choose appropriate surgical approach. Subtemporal,⁷⁾⁹⁾ pterional,⁸⁾¹⁹⁾ and orbitozygomatic approaches have been used to reach to basilar artery aneurysms associated MMD. The subtemporal approach avoids moyamoya vessel injury and is better than the other approaches when trying to reach the posterior circulation.⁷⁾ However, the surgical outcome of clipping is worse than that in general population. 
   Because of these complications, only half of patients with moyamoya and intracranial aneurysms undergoes direct surgery. The success rate of aneurysm clipping is very low at 20%.⁸⁾ Some authors suggest that aneurysm clipping should be performed in saccular aneurysms with a few transdural anastomoses-collateral vessels. 
   Endovascular procedures using microcoils have become a viable alternative for treating aneurysms in patients considered ineligible for general anesthesia and for treating aneurysms difficult to reach by craniotomy.⁵⁾ 
   However, the posterior cerebral arteries are the major source of collateral flow to the anterior circulation in moyamoya disease. Rebleeding due to aneurysmal wall perforation during catheter tube and coil insertion is common complication. It results in bad outcomes ; altered mental status, intracerebral hemorrhage, increased intracerebral pressure and death. It is also very fatal to moymoya patients, if dislodging of coils from aneurysm lumen, blood vessel occlusion due to mechanical vasospasm and arterial dissection may occur.¹³⁾ The combined procedural and clinical morbidity of microcoil embolization has dramatically decreased in recent years, because of the better delivery systems and softer coils.⁶⁾ The long-term anatomical results have also been improved by the combined utilization of three-demensional coils, soft coils, and balloon assisted techniques.⁶⁾ There are also several complications associated with coil embolization. Hence, endovascular treatment can restrictively be used for the treatment of posterior circulation aneurysms, especially narrow neck,¹³⁾ in patients with MMD.³⁾ 

Conclusion 

   Endovascular treatment with microcoils appears particularly safe for the treatment of cerebral saccular aneurysms in patients with MMD. Surgical complications such as cerebral ischemia, infarction, intracerebral hemorrhage, and moyamoya vessel injury may be avoided through this approach. Angiographic and clinical follow-up are necessary to determine the long-term efficacy of this embolization technique. 

REFERENCES

1. Adams HP Jr, Kassell NF, Wisoff HS, Drake CG. Intracranial saccular aneurysm and moyamoya disease. Stroke 10:174-9, 1979 

2. Aoki N, Mizutani H. Does moyamoya disease cause subarachnoid hemorrhage?:review of 54 cases with intracranial hemorrhage confirmed by computerized tomography. J Neurosurg 60:348-3, 1984 

3. Arita K, Kurisu K, Ohba S, Shibukawa M, Kiura H, Sakamoto S, et al. Endovascular treatment of basilar tip aneurysms associated with moyamoya disease. Neuroradiology 45:441-4, 2003 

4. Grabel JC, Levine M, Hollis P, Ragland R. Moyamoya-like disease associated with a lenticulostriate region aneurysm: case report. J Neurosurg 70:802-3, 1989 

5. Guglielmi G, Vinuela F, Duckwiler G, Dion J, Lylyk P, Berenstrein A, et al. Endovascular treatment of posterior circulation aneurysms by electrothrombosis using electrically detachable coils. J Neurosurg 77:515-24, 1992 

6. Irie K, Kawanishi M, Nagao S. Endovascular treatment of basilar tip aneurysm associated with moyamoya disease: case report. Neurol Med Chir 40:515-8, 2000 

7. Iwama T, Todaka T, Hashimoto N. Direct surgery for major artery aneurysm associated with moyamoya disease. Clin Neurol Neurosurg 99(Suppl 2):S191-3, 1997 

8. Kawaguchi S, Sakaki T, Morimoto T, Kakizaki T, Kamada K. Characteristics of intracranial aneurysms associated with moyamoya disease: a review of 111 cases. Acta Neurochir 138:1287-94, 1996 

9. Kodama N, Sato M, Sasaki T. Treatment of ruptured cerebral aneurysm in moyamoya disease. Surg Neurol 46:62-6, 1996 

10. Kodama N, Suzuki J. Moyamoya disease associated with aneurysm. J Neurosurg 48:565-9, 1978 

11. Konishi Y, Kadowaki C, Hara M, Takeuchi K. Aneurysms associated with moyamoya disease. Neurosurgery 16:484-91, 1985 

12. Kowada M, Momma F, Kikuchi K. Intracranial aneurysm associated with cerebrovascular moyamoya disease: report of a case and review of 13 cases. Br J Radiol 52:236-7, 1979 

13. Kwon TH, Moon SH, Lim DJ, Park YK, Chung HS, Lee HK, et al. Intracranial aneurysm associated with moyamoya disease. J Korean Neurosurg Soc 28:1661-5, 1999 

14. Locksley HB. Natural history of subarachnoid hemorrhage, intracranial aneurysms and arteriovenous malformations: based on 6368 cases in the cooperative study. J Neurosurg 25:219-39, 1966 

15. Maki Y, Nakata Y. Autopsy of hemangiomatous malformation of the internal carotid artery at the base of brain. No To Shinkei 17:764-6, 1965 

16. Massoud TF, Guglielmi G, Vinuela F, Duckwiler GR. Saccular aneurysms in moyamoya disease: endovascular treatment using electrically detachable coils. Surg Neurol 41:462-7, 1994 

17. McCormick WF, Nofzinger JD. Saccular intracranial aneurysms: an autopsy study. J Neurosurg 22:155-9, 1965 

18. Muizelaar JP. Early operation of ruptured basilar artery aneurysm associated with bilateral carotid occlusion (moyamoya disease). Clin Neurol Neurosurg 90:349-55, 1988 

19. Nagamine Y, Takahashi S, Sonobe M. Multiple intracranial aneurysms associated with moyamoya disease: case report. J Neurosurg 54:673-6, 1981 

20. Ueki K, Meyer FB, Mellinger JF. Moyamoya disease: the disorder and surgical treatment. Mayo Clin Proc 69:749-57, 1994 

21. Waga S, Tochio H. Intracranial aneurysm associated with moyamoya disease in childhood. Surg Neurol 23:237-43, 1985 

22. Yabumoto M, Funahashi K, Fujii T, Hayashi S, Komai N. Moyamoya disease associated with intracranial aneurysms. Surg Neurol 20. 20-4, 1983 

23. Yamagishi N, Hashizume K, Matsuzawa N, Marunaka S, Kitaguchi K, Furuya H, et al. Anesthetic management of revascularization for moyamoya disease. Masui 40:1132-7, 1991