Aneurysm of the Distal Anterior Inferior Cerebellar Artery at the Medial Branch: A Case Report and Review of the Literature Hidekatsu Mizushima, M.D., Nobusuke Kobayashi, M.D., Sawabe Yoshiharu, M.D., Hanakawa Kazuo, M.D., Kenji Dohi, M.D.,* Ken Sasaki, M.D.,* and Kiyoshi Matsumoto, M.D.* Departments of Neurosurgery, Shioda Hospital, Chiba, Japan; *Showa University School of Medicine, Tokyo, Japan Mizushima H, Kobayashi N, Yoshiharu S, Kazuo H, Dohi K, Sasaki K, Matsumoto K. Aneurysm of the Distal Anterior Inferior Cerebellar Artery at the Medial Branch: A Case Report and Review of the Literature. Surg Neurol 1999;52:137– 42. BACKGROUND Distal aneurysms of the anterior inferior cerebellar artery (AICA) are rare. Most have been located at the cerebellopontine angle. Only three cases, including ours, located in the medial branch of the AICA have been reported in the literature. METHODS A 55-year-old female presented with epilepsy that she experienced for the first time. Computed tomography and magnetic resonance imaging revealed no abnormality. Digital subtraction angiography (DSA) disclosed a rare aneurysm at the medial branch of the distal anterior inferior cerebellar artery. In the blood workup on her admission, a mild inflammatory sign was found, and bacterial aneurysm was suggested as the presumptive differential diagnosis. Repeated DSA was performed 3 months after admission, but the aneurysm did not disappear. She then underwent a suboccipital craniotomy in the prone position. neurysms of the vertebrobasilar system represent 5 to 10% of all intracranial aneurysms. The incidence of aneurysm of the distal anterior inferior cerebellar artery (AICA) is reported to be 0.1– 0.5% and is therefore considered a rare aneurysm of the posterior fossa. Fifty-eight patients who underwent surgical treatment of aneurysms of AICA have been reported, but most of the aneurysms described were located at the cerebellopontine angle, and were associated with the internal auditory artery. Only three cases, including ours, that were not located in the territory of the internal auditory artery, but in the medial branch of the AICA, have been reported in the literature.We will report a case of aneurysm that arose from the medial branch of the AICA and was associated with epilepsy, and clarify the clinical features and pitfalls in these cases and review the previous reports. A RESULTS The aneurysm was clipped and partially resected for the pathological examination. Histologic examination revealed a true aneurysm. She was discharged without neurological deficit. CONCLUSIONS In this report, we summarize the previous cases and discuss the location and clinical manifestations of aneurysms of the AICA through a review of the literature. © 1999 by Elsevier Science Inc. KEY WORDS Anterior inferior cerebellar artery , peripheral aneurysm. Address reprint requests to: Dr. H. Mizushima, Showa University School of Medicine, Department of Neurosurgery, 1–5-8 Hatanodai, Shinagawa-ku, Tokyo, 142 Japan. Received April 21, 1998; accepted June 1, 1998. © 1999 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 CASE REPORT A 55-year-old woman suffered a sudden onset of tonic convulsion for 10 –15 minutes on July 30, 1996 and was admitted to our hospital. On admission, vital signs included blood pressure of 124/66, a regular pulse of 80, and a temperature of 37.7°C. Her consciousness level was 13 points (E3V4M6) on the Glasgow Coma Scale. No neurological deficits were found, but her blood workup revealed an increase in c-reactive protein (CRP: 6.5 mg/dL). She had no history of epilepsy. Computed tomography (CT) (Figure 1) and magnetic resonance imaging (MRI) demonstrated the absence of subarachnoid hemorrhage (SAH), tumor, and cerebral infarction. 0090-3019/99/$–see front matter PII S0090 –3019(99)00042–7 138 Surg Neurol 1999;52:137–42 1 Initial CT scan at admission shows the absence of subarachnoid hemorrhage and intraventricular hematoma. Electro-encephalogram (EEG) showed mildly abnormal findings: the basal wave was 12–13 Hz, wave was dominant, and a 6-Hz slow wave was found in the parieto-occipital area. We treated her conservatively with anti-convulsant drugs. Fourteen days after admission, left vertebral angiography disclosed a peripheral aneurysm of the right AICA at the medial branch. The right AICA originated from the left vertebral artery, indicating that the aneurysm was not supplied by the right vertebral artery (Figure 2). Unfortunately, we did not perform a lumbar puncture. Based on the inflammatory sign on admission and the location and shape on DSA, we suggested a bacterial aneurysm as the presumptive diagnosis and prescribed antibiotics. However, the echocardiogram revealed the absence of endocarditis. Twenty-two days after admission, we repeated the DSA, but the aneurysmal size did not change. The patient was discharged from our hospital on Octo- 2 Mizushima et al ber 30 and we followed her as an outpatient for about 2 months. On November 6, the third DSA was performed, but the aneurysm did not disappear and the size and shape were unchanged. Clipping was performed on December 10. The lesion was approached using a medial suboccipital craniectomy. On opening of the dura, the cerebellar cortex was intact and SAH could not be seen. We dissected the space between the right tonsil and the vermis. The peripheral AICA was found to pass through this space and gave off a lateral branch to form the meatal loop and a medial branch. Distal to this medial branch, an aneurysm without a hematoma was exposed. We applied a No. 1 Sugita clip (Mizuho Ikakogyo Co., Ltd., Tokyo, Japan) successfully and an additional aneurysmectomy was performed to check for the existence of a bacterial aneurysm. Postoperatively, the patient developed pneumonia, but there was no hearing loss or facial Peripheral aneurysm of the right AICA originated from the left vertebral artery (arrowheads). The aneurysm was supplied by the left vertebral artery, not by the right vertebral artery. Distal AICA Aneurysm 3 Surg Neurol 139 1999;52:137–42 Postoperative angiography demonstrated no filling of the aneurysm and good flow through the left vertebral artery. palsy. Postoperative vertebral angiography revealed complete neck clipping of the aneurysm and satisfactory AICA patency (Figure 3). Histologic examination with hematoxin-eosin (HE) staining demonstrated neither arteritis nor bacterial or fungal colonies. Elastica van Gieson stain revealed disappearance of the elastic lamina and degenerated smooth muscle fibers of the tunica media. One month after the operation, the patient was discharged without neurological deficit. As for medial branch aneurysms of the distal AICA, 2 cases have been reported in the literature. [29,37] One case presented with SAH with fourth ventricle hemorrhage, and the other case with cerebello-pontine signs including the 6th, 7th and 8th cranial nerves. Fortunately, we found the distal AICA aneurysm during an examination for the patient’s epilepsy. Fine [8] studied the causes of epileptic seizures in patients whose ages were over 50 years and concluded that about 40 – 45% of their causes were cerebrovascular disease. Sbeih et al DISCUSSION Aneurysms of the posterior fossa have been reported to account for 8 to 12% of all intracranial aneurysms [7,33,52]. Among these aneurysms of the posterior fossa, those of the distal AICA are very rare, with a reported incidence of 0.1– 0.5% [23]. However, with the development of CT and MRI, an increasing number of reports have appeared; 56 cases have been reported in the literature (Table 1). In these reports, the aneurysms occurred predominantly in women (39:16, unknown: 1) and the patient ages ranged from 20 to 72 years, with a median of 47 years. The locations of these aneurysms are summarized in Fig. 4. Most (94%) were located in the lateral branch, especially in the vicinity of the internal auditory canal. Only three cases, including ours, were located in the medial branch of the AICA. The most common onset was subarachnoid hemorrhage (SAH) (81%), followed by cerebello-pontine signs (16%), such as a disturbance in hearing, facial palsy, and headache with vomiting; in these cases the aneurysms were unruptured. Dalley et al [6] suggested dividing them into two categories: those that had an acute onset accompanied by an SAH and involvement of the 7th and 8th cranial nerves, and those with a more insidious onset accompanied by the syndrome of symptoms of a cerebellopontine mass. Lateral branch: ① Internal auditory meatus nearby, 45 cases (80%); ② Distal from meatal loop, 6 cases (11%); ③ Proximal from meatal loop, 1 case; ④ First bifurcation, 1 case; ⑤ Medial branch, 3 cases (5%) (including ours). Unknown, 1 case. Total ⫽ 57 cases. 4 140 Surg Neurol 1999;52:137–42 1 Mizushima et al Summary of Published Cases of Aneurysms of the Distal Anterior Inferior Cerebellar Artery AUTHOR REFERENCE NO. YEAR AGE/SEX 1 Schwartz H G 2 Krayenbuhl H and Yasargil M G 3 Castaigne P et al 4 Weibel J et al 5 Hitselberger W E and Gardner G Jr. 6 Glasscock S P and Davison C 7 Hori T et al 8 Malter I J and Robertson G 9 Porter R J and Eyster E F 10 Benedetti A et al 11 Mori K et al 12 Higuchi H et al 13 Johnson J H Jr. and Kline D G 14 Takara E et al 15 Zlotnik E I et al 16 Cantore G P et al 45 27 5 52 16 12 18 30 40 3 35 15 21 48 55 4 1948 1957 1967 1967 1968 1969 1971 1972 1973 1975 1978 1978 1978 1980 1982 1982 27/F 69/? 62/F 61/F ? 49/M 35/F 41/F 20/F 49/F 48/M 53/M 54/M 56/F 44/F 35/M 17 Nishimoto A et al 18 Nishimoto A et al 37 37 1983 1983 48/F 40/M 19 Gacs G et al 20 Gacs G et al 21 Nakagawa K et al 22 Matsubara T and Sakakura M 23 Dalley R W et al 24 Ueki K et al 25 Ueda T et al 26 Ueda T et al 27 Fukuya T et al 28 Fukuya T et al 29 Kaech D et al 30 Inoue Y et al 31 Ookura Y et al 32 Kiya K et al 33 Kamii H et al 34 Gleeson MJ et al 35 Takase T et al 36 Kumon Y et al 37 Oana K et al 11 11 36 31 6 51 50 50 9 9 22 20 39 26 24 13 49 28 38 1983 1983 1984 1985 1986 1986 1986 1986 1987 1987 1987 1987 1987 1989 1989 1989 1990 1990 1991 59/F 28/F 40/F 47/F 21/F 54/F 51/M 42/F 60/M 72/F 44/M 43/F 61/F 64/F 20/F 57/F 46/M 38/F 44/F 38 Sugawara T et al 39 Zager E L 40 Fuse T et al 47 54 10 1991 1991 1992 46/F 25/F 53/F [44] also reported that convulsions were observed in 1–7% of patients with SAH. Sahs et al [43] stated that convulsions accounted for 4% of the warning symptoms of SAH. However, it was difficult in our case to connect the epilepsy with SAH because of the absence of SAH findings in the operative view and the location of the aneurysm in the posterior fossa. It was also difficult to connect the epilepsy with cerebrovascular disease because of the negative findings on the MRI study. The recent development of MR angiography and MODE OF ONSET LOCATION OF AN Insidious Unknown Recurrent Acute Insidious Recurrent Acute Acute Acute Insidious Recurrent Acute Acute Acute Insidious Recurrent Lt-CPA Rt-CPA Lt-IAC Rt-CPA Rt-IAA Rt. Unknown Lt-IAM Rt-distal lateral branch Rt-IAM Rt-CPA Rt-IAM Lt-IAM Rt-IAM Lt-IAA Lt-IAA Lt-distal lateral branch (giant AN) Acute Rt-IAM Acute Lt-medial branch (embedded in the pons) Acute Lt-CPA (unknown) Acute Rt-CPA (unknown) Acute Lt-IAM Acute Lt-CPA Acute Lt-IAC Other acute ? Distal lateral branch Acute Rt-IAC Acute Rt-IAM Acute Lt-IAM Acute Lt-IAM Acute Lt-IAA (with DAVM) Acute Rt-IAM Acute Lt-IAA Acute Rt-IAM Acute Lt-vicinity of jugular foramen Recurrent Lt-IAM Acute Lt-IAM Acute Rt-IAA Other acute Lt-distal lateral branch (hemispheric branch) Acute Lt-IAA Acute Rt-distal lateral branch Acute Rt-IAM three dimensional CT (3D-CT) techniques have allowed their use in various fields of brain disease. We used MRA and 3D-CT in this patient to demonstrate the cause of the epilepsy, but were not able to detect the distal AICA aneurysm. This might be attributed to the fact that the aneurysm was located in the posterior fossa and the size of the aneurysm was under 3 mm [1]. However, MRA or 3D-CT should be used to exclude the possibility of aneurysms when examining patients with epilepsy. Distal AICA Aneurysm 1 Surg Neurol 141 1999;52:137–42 Continued AUTHOR REFERENCE NO. YEAR AGE/SEX MODE OF ONSET LOCATION OF AN 41 Fuse T et al 42 Rinehart R et al 43 Hada H et al 44 Mochida H et al 45 Pritz M B 46 Pritz M B 47 Pritz M B 48 Matsumoto S et al 49 Kamiya K et al 50 Kamiya K et al 51 Honda Y et al 52 Yokoyama S et al 53 Kyoshima K et al 54 Spallone A et al 55 Ildan F et al 56 Banczerowski P et al 10 42 14 34 41 41 41 32 25 25 17 53 29 46 19 2 1992 1992 1993 1993 1993 1993 1993 1993 1994 1994 1994 1995 1995 1995 1996 1996 48/F 25/M 62/F 72/F 33/M 21/M 41/M 49/F 60/M 71/M 62/F 38/F 61/F 46/F 43/F 49/F Acute Insidious Acute Acute Insidious Acute Acute Acute Acute Acute Acute Acute Acute Acute Insidious Acute Lt-IAA Lt-IAM Lt-IAA Lt-IAA Lt-CPA (giant AN.) Lt-first bifurcation Lt-distal lateral (with AVM) Rt-IAA Rt-IAM Rt-IAM Lt-IAA Rt-IAA Rt-medial branch Rt-IAM Rt-CPA Rt-IAA CPA: cerebellopontine angle, IAC: internal auditory canal, IAA: internal auditory artery, IAM: internal auditory meatus, AICA: anterior inferior cerebellar artery. REFERENCES 1. Aoki S, Sasaki Y, Machida T, Ohkubo T, Minami M, Sasaki Y. Cerebral aneurysms. Detection and delineation using 3D-CT angiography. AJNR 1992;13:1115–20. 2. Banczerowski P, Sipos L, Vajda J. Aneurysm of the internal auditory artery. Our experience and review of the literature. Acta Neurochir 1996;138:1157– 62. 3. Benedetti A, Curri D, Carbonin C. Aneurysm of the internal auditory artery revealed by a partial cerebellopontine angle syndrome. Neurochirurgia 1975;18: 126 –30. 4. Cantore GP, Ciappetta P, Vagnozzi R, Bazzao L. Giant aneurysm of the anterior inferior cerebellar artery simulating a cerebellopontine angle tumor. Surg Neurol 1982;18:76 – 8. 5. Castaigne P, Pertuiset B, Cambier J, Brunet P. Aneurisme de l’artere auditive interne revele par une paralysie faciale recidivante; Cure radicale. Press Med 1967;22: 2493– 6. 6. Dalley RW, Robertson WD, Nugent RA, Durity FA. Computed tomography of anterior inferior cerebellar artery aneurysm mimicking an acoustic neuroma. J Comput Assist Tomogr 1986;10: 881–94. 7. Duvoisin RC, Yahr MD. Posterior fossa aneurysms. Neurology 1965;15: 231– 41. 8. Fine W. Epileptic syndromes in the elderly. Geront Clin 1966; 8: 121–33. 9. Fukuya T, Kishikawa T, Ikeda J, Kudo S, Kuwano H, Matsumoto S, Fujii K. Aneurysms of the peripheral portion of the anterior inferior cerebellar artery. Report of two cases. Neuroradiology 1987; 29: 493– 6. 10. Fuse T, Shindo N, Nagashima H, Kamio M, Nakamura N. Ruptured aneurysms of the anterior inferior cerebellar artery. Report of two cases. Neurol Surg Express 1992; 2: 243– 6. 11. Gacs G, Vinuela F, Fox AJ, Drake CG. Peripheral aneurysms of the cerebellar arteries. Review of 16 cases. J Neurosurg 1983; 58: 63– 8. 12. Glasscock Sp, Davison C. Middle fossa approach to the temporal bone. Arch Otolaryngol 1969; 90: 15–27. 13. Gleeson MJ, Cox TCS, Strong AJ. Aneurysm of the anterior inferior cerebellar artery mimicking an intracanalicular acoustic neuroma. J Laryngol Otol 1989; 103: 107–10. 14. Hada H, Inagawa T. A case of ruptured distal anterior inferior cerebellar artery aneurysm. Jpn J Stroke 1993;15: 323–7. 15. Higuchi H, Yajima K, Nakagawa S. A case of aneurysm of the left internal acoustic meatus. Neurol Surg 1978; 6: 401– 4. 16. Hitselberger WE, Gardner G Jr. Other tumors of the cerebello-pontine angle. Arch Otolaryngol 1968;88: 712– 4. 17. Honda Y, Tanaka R, Kameyama S. Ruptured distal anterior inferior cerebellar artery aneurysm. Case report. Neurol Med Chir 1994; 34: 763–7. 18. Hori T, Hirakawa K, Ishijima B, Manaka S, Fukushima T, Shimizu N, Sato T. Aneurysm in the internal auditory meatus. Case report. J Neurosurg 1971; 35: 605–9. 19. Ildan F, Gocer AI, Bagdatoglu H, Uzuneyupoglu Z, Tuna M, Cetinaip E. Isolated trigeminal neuralgia secondary to distal anterior inferior cerebellar artery aneurysm. Neurosurg Rev 1996; 19: 43– 6. 20. Inoue Y, Morinaga K, Matsumoto Y, Ohmiya N, Mikami J, Matsuoka T, Takeda S, Ohkawara S. A case of ruptured internal auditory meatus aneurysm. Surg Cerebral Stroke 1987; 15: 280 – 4. 21. Johnson JH Jr, Kline DG. Anterior inferior cerebellar artery aneurysms. Case report. J Neurosurg 1978; 48: 455– 60. 22. Kaech D, Tribolet de N, Lasjaunias P. Anterior inferior cerebellar artery aneurysm, carotid bifurcation aneurysm, and dural arteriovenous malformation of the tentorium in the same patient. Neurosurgery 1987; 21: 575– 82. 23. Kamano S, Kirino T, Mizuno S, et al. Intrameatal aneurysm. Neurochirurugia 1986; 29: 28 –30. 24. Kamii H, Ogawa A, Sakurai Y, Kayama T. Anterior inferior cerebellar artery aneurysm with a sudden 142 Surg Neurol 1999;52:137–42 onset of caudal cranial nerve symptoms. Neurol Surg 1989; 17: 387–91. 25. Kamiya K, Nagai H, Koide K, Yamashita N, Shimazu N. Peripheral anterior inferior cerebellar artery aneurysms. Surg Neurol 1994; 42: 46 –51. 26. Kiya K, Uozumi T, Emoto K, Matsuoka T. Anterior inferior cerebellar artery aneurysms at the internal auditory meatus. Case report. Neurol Med Chir 1989; 29: 592–5. 27. Krayenbuhl H, Yasargil MG. Die vaskularen Erkrankungen im Gebiet der Arteria vertebralis und Arteria basialis. Stuttgart: Georg Thieme, 1957,1–170. 28. Kumon Y, Sasaki S, Chaki T. Aneurysm of the distal anterior inferior cerebellar artery. Case report. Jpn J Stroke 1990; 12: 68 –73. 29. Kyoshima K, Matsuda M, Handa J. Cerebral aneurysm of the distal anterior inferior cerebellar artery. Case report. Arch Jpn Chir 1995; 64: 139 – 45. 30. Malter IJ, Robertson G,. Angiographic demonstration of anterior inferior cerebellar artery artery aneurysm by use of the base view. Radiology 1972; 103: 125– 6. 31. Matsubara T, Sakakura M,. A case of distal anterior inferior cerebellar artery aneurysm presenting as a cerebellopontine angle tumor [in Japanese]. MieIgaku 29: 323, 1985 (abstr). 32. Matsumoto S, Tsuiki H, Yoshida S, Shingu T, Sato S, Motozaki T, Ban S Yamamoto T. Aneurysm of the distal anterior inferior cerebellar artery. Case report. Kobe City-Hospital Kiyou 1993; 32: 83– 6. 33. McDonald CA, Korb M. Intracranial aneurysms. Arch Neurol Psych 1939; 42: 298 –328. 34. Mochida H, Tomita S, Watanabe S, Ohya S, Yuzurihara M. Ruptured aneurysm of the anterior inferior cerebellar artery. Case report. Asahi Chuo-ihou 1993; 16: 341–3. 35. Mori K, Miyazaki H, Ono H,. Aneurysm of the anterior inferior cerebellar artery at the internal auditory meatus. Surg Neurol 1978; 10: 297–300. 36. Nakagawa K, Sasaki S, Kimura H, Matsuoka K. Aneurysm of the anterior inferior cerebellar artery at the internal auditory meatus. Surg Neurol 1984; 21: 231–5. 37. Nishimoto A, Fujimoto S, Tsuchimoto S, Matsumoto Y, Tabuchi K, Higashi T. Anterior inferior cerebellar aneurysm. Report of three cases. J Neurosurg 1983; 59: 697–702. 38. Oana K, Murakami T, Beppu T, Yamaura A, Kanaya H. Aneurysm of the distal anterior inferior cerebellar artery unrelated to the cerebellopontine angle. Case report. J Neurosurg 1991; 28: 899 –903. 39. Ookura Y, Mori H, Tsuchida T. Aneurysm of the distal anterior inferior cerebellar artery. Case report. Niigata J Med Sci 1987;101: 689 (abstr). 40. Portyer RJ, Eyster EF. Aneurysm in the anterior infe- Mizushima et al rior cerebellar artery at the internal acoustic meatus. Report of a case. Surg Neurol 1973; 1: 27– 8. 41. Pritz MB. Aneurysms of the anterior inferior cerebellar artery. Acta Neurochir 1993; 120: 12–9. 42. Rinehart R, Harre RG, Roski RA, Dolan KD. Aneurysm of the anterior inferior cerebellar artery producing hearing loss. Ann Otol Rhinol Laryngol 1992; 101: 705– 6. 43. Sahs AL, Perret GE, Locksley HB, Nishioka H , eds. Intracranial aneurysms and subarachnoid hemorrhage: A cooperative study. Philadelphia: Lippincott, 1969. 44. Sbeih I, Tamas LB, O’Laoire SA. Epilepsy after operation for aneurysms. Neurosurgury1986; 19: 784 – 8. 45. Schwartz HG. Arterial aneurysm of the posterior fossa. J Neurosurg 1948; 5: 312– 6. 46. Spallone A, Santis S De, Giuffre R. Peripheral aneurysms of the anterior inferior cerebellar artery. Case report and review of literature. Br J Neurosurg 1995; 9: 537– 41. 47. Sugawara T, Hirayama A, Goto H. A case of anterior inferior cerebellar artery aneurysm with a subarachnoid hemorrhage. Jpn J Cli Radiol 1991; 36: 943–5. 48. Takara E, Inoue N, Kohno H. Disappearance of the co-existing aneurysm and arteriovenous malformation after wrapping of aneurysm. Neurol Surg 1980; 8: 587–91. 49. Takase T, Kajikawa H, Hirota N, Tamura Y, Ukita T, Deguchi J. Distal anterior inferior cerebellar artery aneurysm. Report of a case and a review of the literature. Hiroshima J Med Sci 1990; 43: 1053–9. 50. Ueda T, Matsumura S, Ohtani M, Kurokawa Y, Tanabe S, Hashi K. Aneurysm of the anterior inferior cerebellar artery at the internal auditory meatus. Report of two cases. Neurol Surg 1986; 14: 1263– 8. 51. Ueki K, Morita A, Teraoka A. A case of the anterior inferior cerebellar artery aneurysm. Clin Neurol 1986; 26: 26 (abstr). 52. Weibel J, Fields WS, Campos RJ. Aneurysms of the posterior cervicocranial circulation. Clinical and angiographic considerations. J Neurosurg 1967; 26: 223– 34. 53. Yokoyama S, Kadota K, Asakura T, Kawazoe K. Aneurysm of the distal anterior inferior cerebellar artery. Case report. Neurol Med Chir 1995; 35: 587–90. 54. Zager EL. Isolated trigeminal sensory loss secondary to a distal anterior inferior cerebellar artery aneurysm. Case report. Neurosurgery 1991; 28: 288 –91. 55. Zlotnik EI, Sklyut JA, Smejanovich AF, Stasenko EN. Saccular aneurysm of the anterior inferior cerebellarinternal auditory artery. J Neurosurg 1982; 57: 829 – 32.