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KISEP KOR J CEREBROVASCULAR DISEASE September 2000 Vo. 2, No 2, page 200-4

Arteriovenous Malformation at Cerebellopontine Angle Associated with a Fenestration of the Vertebral Artery Jung Yong Ahn, MD and Seong Oh Kwon, MD Department of Neurosurgery, College of Medicine, Pochon CHA University, Sungnam, Korea ABSTRACT

A fenestration of the vertebral artery is considered to be an unusual vascular variation that is defined as a bypass artery along the extracranial or at intracranial segment of the artery. A fenestration of the vertebral artery associated with an arteriovenous malformation at the cerebellopontine angle is extremely rare. We report a case of the ruptured arteriovenous malformation with a fenestration of verte-bral artery. The embryologic genesis and clinical significance of a fenestration of the vertebral artery are discussed. ((((Kor J Cerebrovascular Disease 2:200-4, 2000))))

KEY WORDS：Arteriovenous malformation·Fenestration·Vertebral artery.

Introduction

An abnormal configuration of the cerebral arteries that has a bypass artery extending into an extracranial or intra-cranial segment is in general referred to as a duplication or fenestration.2)5) This condition has been diagnosed more fre-quently with the advent of cerebral angiographic investigation. This anomaly is frequently associated with other congenital intracranial and extracranial vascular abnormalities includ-ing saccular or dissecting aneurysms.1)6)7)10)12)15) However, a fenestration in association with an arteriovenous malforma-tion (AVM) is much less common.10)13)14) In this report, we describe a rare case of an AVM supplied by the right anter-ior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) in conjunction with a fenestration of the left vertebral artery.

Case Report

An 18-year-old girl had a sudden onset of severe head-ache and recurrent vomiting while studying at night. Neur-

ological examination on admission disclosed that she was drowsy, with a positive cerebellar sign on right side. A co-mputed tomographic scan (CT scan) revealed cerebellar hemorrhage, particularly dense at the right cerebellopontine angle (CP angle) and cerebellar hemisphere, but did not reveal obstructive hydrocephalus (Fig. 1A). Magnetic res-onance imaging revealed an acute hemorrhage on the right cerebellum with edematous changes (Fig. 2A). An AVM nidus in the hematoma was suspected near the right CP angle. The coronal T2-weighted image revealed two dilated vessels feeding the nidus (Fig. 2B). A subsequent fourv-essel angiograms showed an arteriovenous malformation (AVM) fed from the right anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) (Fig. 3A and B). It drained medially into the right inferior vermian vein and laterally into the inferior hemispheric vein, then subsequently into the transverse sinus. The AVM was approximately 2×2×3 cm in size. The right PICA was originated in an unusual manner from the basilar trunk. Coincidentally the left vertebral artery (VA) was anomal-ously fenestrated. Both branches of the fenestration arose from the level of C1, extended to the intracranial segment, and reached the confluence of the vertebral arteries. The right PICA was originated from the larger limb of the fe-nestration. Surgery was planned for the day following adm-ission but clinical changes forced a reevaluation. A second CT scan of the brain disclosed the hemorrhage to be slightly enlarged and obstructive hydrocephalus (Fig. 1B). She ur-

논문접수일：2000년 6월 7일 심사완료일：2000년 7월 8일

교신저자：교신저자：교신저자：교신저자：Jung Yong Ahn,Jung Yong Ahn,Jung Yong Ahn,Jung Yong Ahn, Department of Neurosurgery, Pundang

CHA Hospital, Pochon CHA University, 351, Yatap-dong, Pundang-

gu, Sungnam 463-070, Korea

TEL：(031) 780-5262·FAX：(031) 780-5269

E-mail：jyahn@cha.ac.kr

Jung Yong Ahn·Seong Oh Kwon

Kor J Cerebrovascular Disease 2:200-4, 2000 201

Fig. 1. A：Initial computed tomographic scan showing a cerebellar hemorrhage, particularly dense in the right cerebellopo-ntine angle and cerebellar hemisphere. B：Preoperative computed tomographic scan demonstrating an obstructive hydro-cephalus.

Fig. 2. A：Magnetic resonance imaging, axial T2-weighted imaging, revealing acute hemorrhage with dilated vessel at the cerebellopontine angle, suggesting an arteriovenous malformation. B：Magnetic resonance imaging, coronal T2-weighted imaging, disclosing two dilated vessels, suggesting two arterial feeders.

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Arteriovenous Malformation with Fenestration of the Vertebral Artery

202 Kor J Cerebrovascular Disease 1:200-4, 2000

Fig. 4. Postoperative left angiogram, anteriorposterior and lateral view, taken 14 days after resection of the arteriovenousmalformation, showing complete removal of the nidus.

Fig. 3. A：Preoperative right vertebral angiogram, anteriorposterior view, showing an arteriovenous malformation fed fromthe right anterior inferior cerebellar artery and posterior inferior cerebellar artery. B：Preoperative left vertebral angiogram, anteriorposterior view, demonstraing a fenestration arising from the level of C1 and reaching the confluence of the vertebralarteries.

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Jung Yong Ahn·Seong Oh Kwon

Kor J Cerebrovascular Disease 2:200-4, 2000 203

gently was treated with extraventricular drainage (EVD) for obstructive hydrocephalus the day after her admission.

The AVM was approached via a right retromatoid su-boccipital craniotomy with the patient in the park-bench position. Two reddish dilated veins were found on the ce-rebellar cortex, medial and lateral side respectively. These were felt to be draining veins. After removal of bloody ce-rebrospinal fluid (CSF) from the cisterna magna and proper evacuation of cerebellar hemorrhage, two dilated arteries were found between the ninth cranial nerve and the largest bundle of the tenth cranial nerve. The cerebellar AVM nidus was supplied by the main branch of AICA and PICA itself. Ligation of two feeding arteries at the AVM margin with two small straight clips (Sugita clip, No. 81) was success-fully accomplished. This was then followed by meticulous microsurgical dissection of the uncertain AVM periphery, sparing the two venous drainages. The AVM nidus was intermingled with the intracerebellar hemorrhage. After ex-posure of the entire nidus, the feeding arteries were ca-uterized. Then the draining veins were separated from the nidus. After complete resection of the AVM nidus, we attempted to visualize the opposite vertebral artery, but a large limb of the fenestration was partially observed. The postoperative course was uneventful. Intracranial pressure was monitored continuously. There was no drainage of CSF. The EVD tube was removed 5 days after her operation. Complete removal of AVM nidus was confirmed with an-giogram taken 14 days after the operation (Fig. 4). At the time of discharge, there was a mild neurological deficit manifest by the right cerebellar dysfunction and the right hearing difficulty. One year later, the patient returns to ne-arly full activity and a normal life.

Discussion

Fenestration or partial duplication of the vertebral artery seldom demonstrated at time of autopsy. The angiographic demonstration of these anomalies is even rarer. More than 72 cases have been reported in the world literature.1)6-10)12-15) Most of them have been reported in Japan.

Fenestration of the vertebral artery is considered to be a developmental anomaly occurring in the embryological pr-ocesses. According to Padget’s description,11) the vertebral artery forms in the embryo between the thirtysecond and fortieth days of the fetal age. Anastomoses developing be-tween successive cervical segmental arteries lead to the fo-

rmation of a primitive vertebral artery on each side in the neck. Primitive lateral basilovertebral anastomoses appear transiently, while the basilar artery is formed by a pair of longitudinal neural arteries. When a portion of the primitive accessory basilovertebral artery remains, this later forms an intracranial fenestration of the vertebral artery.3)7) Extracra-nial duplications or fenestrations are most likely caused by persistence of cervical segmental arteries.

Some authors have stated that a fenestration of the vert-ebral artery itself was an incidental, asymptomatic finding and has no clinical significance.8)12) Other reports find that this anomaly is frequently associated with other congenital intracranial and extracranial vascular abnormalities inclu-ding saccular or dissecting aneurysms.1)6)7)10)12)15) Although the occurrence of aneurysms in the fenestration is a subject of controversy, there is evidence to suggest that existence of defects in the tunica media of the vessel at each end of the fenestration and local hemodynamic forces at the prox-imal site may precipitate aneurysm formation.2) A fenestra-tion of the vertebral artery associated with an arteriovenous malformation (AVM) is much less common.10)13)14) The association of intracranial arterial fenestration and AVMs is not well understood. Yoshimoto, et al.,14) proposed that he-modynamic stress resulting from fenestration of the feeding system of AVM might be an important factor in the enlarg-ement of the small cerebellar AVM. Even if the commonest presentation of cerebellar AVM in children is intracranial hemorrhage,4) hemodynamic stress resulting from a fenes-tration of the left vertebral artery may play a major role in the AVM rupture as in this patient. An AVM associated with fenestration of the cranial arteries may more likely to bleed than AVM without this anomaly.

There are not enough case reports available to draw firm conclusions about the possible association of vertebral artery fenestration and AVM. Further studies of this possible ass-ociation are needed.

Conclusions

We experienced a case of the ruptured arteriovenous ma-lformation at cerebellopontine angle with a fenestration of the vertebral artery. The hemodynamic stress resulting from fenestration of the feeding system of AVM might be an important factor in the enlargement of the small cerebellar AVM.

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204 Kor J Cerebrovascular Disease 1:200-4, 2000

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10) Mizukami M, Tomica T, Mine T, Mihara H. Bypass anomaly of the vertebral artery associated with cerebral aneurysm and art-eriovenous malformation. J Neurosurg 37:204-9, 1972

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12) Sanders WP, Sorek PA, Mehta BA. Fenestration of intracranial arteries with special attention to assoicated aneurysms and other anomalies. AJNR 14:675-80, 1993

13) Teal JS, Rumbaugh CL, Bergeron RT, Segall HD. Angiographic demonstration of fenestrations of the intradural intracranial ar-teries. Radiology 106:123-6, 1973

14) Yoshimoto H, Maeda H, Aoyama H, Kanazawa J, Kitaoka T, Uozumi T. Enlargement of cerebellar arteriovenous malformation associated with fenestration of the vertebral arterycase report. Neurol Med Chir (Tokyo) 32:585-8, 1992

15) Zhang QJ, Kobayashi S, Gibo H, Hongo K. Vertebrobasilar junct-ion fenestration associated with dissecting aneurysm of intracr-anial vertebral artery. Stroke 25:1273-5, 1994

= 국 문 초 록 =

추골 동맥의 개창은 두개강 내 또는 외의 추골 동맥의 우회 동맥으로 정의되는 드문 혈관 변이이다. 추골 동맥의 개창과 동반된 소

뇌 교각의 동정맥 기형은 매우 드물다. 본 교실에서는 추골 동맥의 개창과 동반된 소뇌 교각의 동정맥 기형 1례를 경험하였다. 추골 동

맥에 위치한 개창의 발생학적 기원과 임상적인 중요성을 논하고자 한다. 중심 단어：동정맥 기형·개창·추골 동맥.