Acta N e u r o e h i r u r g i c a Acta Neurochir (Wien) (1996) 138:1157-1162 9 Springer-Verlag t996 Primed in Austria Aneurysm of the Internal Auditory Artery: Our Experience and Review of the Literature P. Banczerowski, L. Sipos, and J. Vajda National Institute of Neurosurgery, Budapest, Hungary Smnmary The aneurysms of the internal auditory artery (IAA) situated distal from anterior inferior cerebellar artery (AICA)-IAA junction, are extremely rare lesions. A case of distal aneurysm of IAA is presented causing subarach~3oid haemorrhage (SAH) and complete ipsilateral deafness. After the neurosurgical treatment the hearing of the patient definitely improved. The literature of distal aneurysms of AICA is reviewed focusing on the clinical features of these malformations, causing cerebello-pontine angle (CPA) symptoms with or without SAH. Keywords: Cerebral aneurysm; anterior inferior cerebellar artery; internal auditory artery; subarachnoid haemorrhage; cerebello-pontine angle symptoms. Introduction The incidence of aneuryslns of the posterior circulation has been reported between 3.3 and 29.5% (average 15%) of all cerebral aneurysms. The distribution of aneurysms in the posterior circulation in percentage is as follows: posterior cerebellar artery (PCA) 14 (7.4-34), basilar artery bifurcation (BAB) 53 (50-66), basilar artery (BA)-superior cerebellar artery (SCA) junction and SCA 8 (5-12), BA trunk 5, vertebral artery (VA), VA-BA junction, posterior inferior cerebellar artery (PICA), PICA-VA junction 20 [5, 36]. The occurrence of aneurysms of anterior inferior cerebellar artery (AICA) is less than 1% [13, 27]. Most of the distal aneurysms of AICA, excluding aneurysms of BA-AICA junction, caused subarachnoid haemorrhage [2, 4, 7, 8, 10, 12, 13-17, 19-21, 23, 25, 26-30, 32-34, 36, 38, Present study], sometimes followed by cerebellar [8], medullary [8] and lower cranial nerve signs [16, 20], with [2, 4, 7, 12, 13, 15, 17, 20, 21, 23, 25, 28, 29, 32-34, 36, Present study] or without [7, 8, 10, 14, 16, 19, 25-27, 30, 38] syndromes of cerebello-pontine angle lesions, caused 8th [2, 4, 7, 12, 15, 17, 20, 21, 23, 25, 28, 29, 32-34], 7th [2, 4, 7, 12, 13, 15, 17, 20, 21, 25, 29, 32, 34, 36], 5th [7, 21, 32] nerve dysfunction, tinnitus, nystagmus, vertigo, ataxia. In some of the cases pure CPA lesions were mimicked [3, 6, 9, 11, 18, 22, 32, 34, 39]. According to the literature, the localisation of aneurysms causing only CPA syndrome were often able to cause differential diagnostic problems. An extremely rare case of an IAA aneurysm is presented, which ruptured and caused general SAH and ipsilateral deafness. The clinical appearance is discussed, the neuroradiological pictures and neurosurgical treatment are presented. Data of aneurysms of the distal AICA in the literature are reviewed being the clinical features in focus. Case Report A 49-year-old right-handed caucasian woman suffered sudden onset of occipital headache, vertigo, nausea, and vomiting a day prior her admission the National Institute of Neurosurgery, Budapest. She was taken to a local Neurological Department, where lumbar puncture revealed blood in the cerebrospinal fluid and neurological examination revealed nuchal rigidity and deafness on the left side. There was no other focal neurological sign. Computer tomography (CT) demonstrated a moderate subaracbnoid haemorrhage along with blood sediment in the 3rd and 4th ventricles and the prepontine cistern (Fig. 1). The second day after the haemorrhage 4-vessel-digital subtraction angiography (DSA) was performed, which showed an 8 mm in diameter saccular aneurysm of the internal auditory artery (IAA), distal to the AICA-IAA junction on the left side and did not seem to penetrate into the internal auditory meatus. The IAA originated from the AICA. The left AICA and the aneurysm was not filled from the ipsilateral vertebral artery and the right external occipital artery originated from the right vertebral artery (Fig. 2 a, b). Pre-operative audiometry revealed a total 1158 P. Banczerowski et al.: Aneurysm of the AICA Fig. 1. CT scan shows moderate bleeding in the 4th ventricle and the prepontine cistern hearing loss on the left and normal hearing on the right side. The patient lying in park-bench position a lateral suboccipital craniotomy was performed on the left side on the eleventh day after the rupture. The cerebellar hemisphere was retracted medially and the postero-lateral surface of the petrous temporal bone and ponto-cerebellar angle were exposed where signs of chronic subarachnoid haemorrhage were seen. Following the dissection of the arachnoid layer the aneurysmal sac and 7th, 8th nerve complex became visible. The proximal segment of the IAA was identified overlying the aneurysm (Fig. 3 a). The distal segment of the IAA was situated between the 7th, 8th nerve complex and the aneurysmal sac. The neck of the aneurysm was found wide and too turgid to be clipped directly because an occlusion of the parent artery was feared. Both proximal and distal portions of IAA were temporarily clipped, the aneurysm was opened and was found to be partially thrombosed. After removing the thrombus the aneurysm was clipped using a 5 mm straight Yasargil clip (Fig. 3 b). The postoperative course was uneventful. An intra-operative opening of the aneurysmal sac proved the secure clipping and made control angiography unneccessary. We performed, however, control audiometry which demonstrated the return of useful hearing in the left ear (Fig. 4). The patient was discharged in good condition on the 8th day following operation. Discussion Fig. 2 a, b. Anteroposterior (a) and lateral (b) views of the right vertebral subtraction angiography show a saccular aneurysm of IAA. The right external occipital artery originates from the right vertebral artery 38, 39] of A I C A a n e u r y s m s have so far b e e n reported since the first p u b l i c a t i o n by Schwartz et al. [32] in T h e a n e u r y s m s of the peripheral p o r t i o n of A I C A are very rare, but a n e u r y s m s of I A A distal from A I C A - I A A j u n c t i o n are e v e n m o r e infrequent. Two t h o u s a n d six h u n d r e d patients with i n t r a c r a n i a l a n e u - 1948. A m o n g them 27 female (71%), 11 m a l e (29%) and 3 patients with u n k n o w n sex were reported with a female p r e d o m i n a n c e . The m e a n age of female patients r y s m s (about 3800 a n e u r y s m s were clipped) were operated on at the N a t i o n a l Institute of Neurosurgery, B u d a p e s t since 1977 and there were no a n e u r y s m s of I A A except this case. T h e I A A in m o s t of the cases originates from A I C A , s o m e t i m e s from the SCA, BA, and P I C A [37]. F o r t y cases [ 2 4 , 6 - 2 3 , 2 5 - 3 0 , 3 2 - 3 6 , was 45.5, (range 2 0 - 7 2 ) m a l e patients 45.1 (range 2 1 - 6 0 ) years. We g r o u p e d the reported cases into five categories according to the clinical onset of distal a n e u r y s m s of A I C A (Table 1). I n most of the cases the initial s y m p toms were signs of the s u b a r a c h n o i d h a e m o r r h a g e , P. Banczerowski et al.: Aneurysm of the AICA 1159 -10 ,I ' Ii 10 2O 30 40 50 60 70 I ----O--- REAC ...... 80 REBC -- -- -- i 250 500 r a i N - - 90 ! 100 125 1000 2000 4000 8000 e/s Fig. 4. Postoperative pure tone audiogram. R E A C right ear air conduction, REBC right ear bone conduction, L E A C left ear air conduction (masking), LEBC left ear bone conduction (masking) Fig. 3 a, b. Intra-operative photographs show the aneurysm of IAA (a) before and (b) after clipping. An aneurysm, Aa internal auditory artery, N 8th nerve followed by cerebello-pontine angle symptoms and signs immediately or within a few days. In sixteen cases (39%) symptoms of both SAH and CPA lesions have been reported. Thirteen cases (31.7%) presented with SAH, this was in some cases followed by cerebellar, medullary or lower cranial nerve signs, without signs of CPA lesion. Eight patients (19.5%) had CPA symptoms, which in most of the cases presented differential diagnostic problems. In some cases acoustic neurinoma was suspected pre-operatively, since CT scan demonstrated a contrast enhancing mass [6, 22, 34] at the internal acoustic meatus and/or an erosion of its bony wall [6, 9, 34, 39]. Eight patients had hearing disturbance, 6 (75%) vertigo, 5 (62.5%) tinnitus, another 5 facial palsy, and 3 (37.5%) showed trigeminal nerve involvement. Three (7.3%) cases appeared with initial signs of CPA followed by SAH. In these cases the aneurysms were explored after the SAH. Two of them started with signs of facial palsy followed by hypacusis and dizziness, the rest with signs of hearing loss and combined with tinnitus as welt as dizziness. One patient (2.4%) could not be fitted into either group. In twenty-nine (70.7%)cases the presenting sign of the aneurysm was SAH and in those cases there was no doubt about the diagnosis. In 55% of the patients with SAH, where CPA signs developed after the haemorrhage these gave some help in identifying the site of the vascular malformation. In twenty-seven cases (65.8%) CPA symptoms developed with or without SAH (16 cases of SAH + CPA, 8 cases of CPA, 3 cases of CPA + SAH). In three cases (7.3%) the SAH called attention to the aneurysms of AICA after the initial CPA signs. Most of distal AICA aneurysms originated from the arterial loop near the internal acoustic meatus, frequently caused CPA signs [7, 27]. The cause of 8th and 7th nerve palsies can be ischaemic [7, 24], direct nerve compression [7] or the presence of haemosiderin after SAH within the inner ear [1]. If the aneurysm of the IAA compresses the 7th and/or 8th nerve the sac should be removed in order to achieve a good recovery of the nerve. If pre-operative hearing disturbances appeared haemo-rheological therapy might be useful. According to the literature in 37.5% of the cases hearing loss or disturbances improved significantly following the operation, which was the case with our patient. According to Kiya et al. [17] the 1160 P. Banczerowski et al.: Aneurysm of the AICA Table 1. S u m m a r y o f Publicated Cases of A n e u r y s m s of Distal Anterior Inferior Cerebellar Artery No. Author (ref. no.) Age/sex Initial signs and symptoms Features 1 Schwartz, 1948 [32] 27/F SAH + CPA 2 Krayenbfihl and Yasargil, 1957 [18] Castaigne et al. 1967 [4] 69/U Haedaehe, vomiting, hearing loss, ataxia, nystagmus, dizziness, 5th and 7th nerve palsies Hearing loss, tinnitus, facial palsy, trigeminal neuralgia 3 9 Weibel et al. 1967 [36] Hitselbelger and Gardner 1968 [11] Glasscock 1969 [9] Hori etal. 1971 [12] Malter and Robertson 1971 [20] Porter and Eyster 1973 [29] 10 11 12 13 14 15 16 17 18 Benedetti et al. 1975 [2] Johnson and Kline 1978 [13] Mori et al. 1978 [22] Higuchi et al. 1978 [10] Takara et al. 1980 [33] Zlotnik et al. 1982 [39] Pelliccioli 1982 [28] Cantore et aI. 1982 [3] Nishimoto et al. 1983 [25] 4 5 6 7 8 62/F 61/F U 49/M 35/F 41/F 20/F 49/F 54/M 48/M 53/M 56/F 44f? U 35/M 48f? 63/F 40/M 28/F 59/F 40/F 47/F 20 Gfics et al. 1983 [8] 21 22 23 24 25 Nakagawa et al. 1984 [23] Matsubara and Sakakura 1985 [21] Dalley et al. 1986 [6] Ueki el al. 1986 [35] Uede et aI. 1986 [34] 26 27 28 Kamano et al. 1986 [15] Nowak et al. 1986 [26] Fukuya et al. 1987 [7] 21/F 54/F 51/M 42/F 58/F 63/F 60/M 29 30 31 Kaech et al. 1987 [14] Kiya et al. 1989 [17] Kamii et al. 1989 [16] 72/F 44/M 64/F 20/F 32 33 34 35 Kumon et al. 1990 [19] Oana etal. 1991 [27] Zager et al. 1991 [38] Pritz 1993 [30] 36 Present study, 1994 38/F 44/F 25/F 21/M 41/M 49/F CPA Facial palsy, headache, vomiting, tinnitus, decrease of hearing, nystagmus, staggering while walking Headache, confusion, facial palsy, convulsion, dysphasia, diplopia Hearing loss CPA + SAH Hearing loss, dizziness, inappropriate lacrimation Headache, vomiting, facial palsy, deafness tinnitus, nystagmus Semicomatose, vomiting, nuchal rigidity, papilloedema, 6th-12th nerve palsies General malaise, headache, diplopia, hearing loss, vertigo, facial palsy, right sided-hemiparesis Facial palsy, hypacusis, nausea, headache dizziness, lateropulsion Headache, nausea, vomiting, tinnitus, facial palsy, nuchal rigidity Hearing loss, vertigo, tinnitus, vomiting Headache, nausea, vomiting, tinnitus Headache, nausea, vomiting, hearing loss, disturbance of consciousness Hearing loss, headache, tinnitus, nystagmus, vertigo, trigeminal palsy Hearing loss, dizziness, tinnitus, headache Vertigo, facial paresis, trigeminal neuralgia, hearing loss Headache, nausea, vomiting, vertigo, tinnitus, nystagmus, decreased hearing, nuchal rigidity Headache, nausea, vomiting, vertigo, facial weakness, hypacusis Orbital pain, vertigo, tinnitus, diplopia, facial weakness, adiadochokinesis SAH, diplopia, cerebellar et medullary sy. Symptoms of SAH, cerebellar signs Headache, vomiting, vertigo, hearing loss, tinnitus, nystagmus Headache, vomiting, vertigo, 5th-8th nerve palsies, cerebellar signs CPA SAH + CPA SAH + CPA Hearing loss, tinnitus, vertigo, facial palsy Syndrome of Horner Tinnitus, vertigo, deafness Headache, nausea, vomiting, hearing loss, facial palsy, diplopia, tinnitus Headache, vertigo, facial palsy, nuchal rigidity, deafness Headache, nausea Headache, vertigo, nausea, lost consciousness, nuchal rigidity, nystagmus, bilateral deafness Headache peripheral facial palsy, hearing loss, trigeminal palsy Symptoms of SAH, drowsy, disorientated Headache, vomiting, tinnitus, diplopia, facial palsy, hearing disturbance Disphagia, difficulty of swallowing, headache, vomiting, convulsion, disturbance of consciousness Headache, vomiting Headache, vomiting Headache, nausea, photophobia, trigeminal palsy, meningismus, diplopia Headache, nausea, vomiting, meningismus, photophobia, nuchal rigidity Headache, nausea, vomiting, meningismus photophobia Headache, vertigo, nausea, vomiting, nuchal rigidity, deafness S A H subarachnoid haemorrhage, C P A cerebello-pontine angle symptoms, N unclassable, U unknown sex. SAH + CPA CPA SAH + CPA CPA + SAH SAH + CPA CPA SAH SAH + CPA CPA CPA + SAH CPA SAH + CPA SAH + CPA SAH SAH SAH SAH + CPA SAH + CPA CPA N CPA SAH + CPA SAH + CPA SAH SAH SAH + CPA SAH SAH + CPA SAH SAH SAH SAH SAH SAH SAH + CPA P. Banczerowski et al.: Aneurysm of the AICA paresis o f the 7th n e r v e i m p r o v e d in 69% o f the cases, w h i c h s h o w e d that the f u n c t i o n o f this n e r v e is m o r e l i k e l y to i m p r o v e . A l t h o u g h m o r e than 90% o f cases o f C P A s y m p t o m s are c a u s e d b y n e o p l a s m s such as v e s t i b u l a r s c h w a n n o m a s , m e n i n g i o m a s etc., but distal a n e u r y s m s o f A I C A can cause s i m i l a r s y m p t o m s , i n c l u d i n g e n l a r g e m e n t o f the internal a c o u s t i c m e a tus. I f the C P A signs a p p e a r t o g e t h e r with s y m p t o m s o f S A H , the p o s s i b i l i t y o f an a n e u r y s m o f the distal A I C A is fairly high. A l l p a t i e n t s in a s a t i s f a c t o r y c o n d i t i o n with ruptured s u p r a t e n t o r i a l a n e u r y s m s u n d e r g o a surgical r e p a i r w i t h i n 48 hours after the b l e e d i n g in our code o f practice. In cases o f H u n t - H e s s IV g r a d e w e treat the patients c o n s e r v a t i v e l y and if the p a t i e n t i m p r o v e s the o p e r a t i o n is d e l a y e d until the v a s o s p a s t i c p e r i o d is over. D u e to the i m p r o v e m e n t o f m i c r o s u r g i c a l techniques e v e n p o s t e r i o r f o s s a a n e u r y s m s should be o p e r ated on as s o o n as p o s s i b l e . A c c o r d i n g to our e x p e r i ence the r u p t u r e o f i n f r a t e n t o r i a l a n e u r y s m s that are in a w i d e s u b a r a c h n o i d space ( P I C A and p o s s i b l y I A A a n e u r y s m s ) is less f r e q u e n t l y f o l l o w e d b y v a s o spasm. T h e r e f o r e the a i m o f s u r g e r y in these c a s e s is not so m u c h to r e m o v e cisternal b l o o d in the acute stage. W e m a y o p e r a t e w h e n the p a t i e n t ' s c l i n i c a l c o n d i t i o n is stabilized. Surgical repair of peripheral IAA aneurysms seems s t r a i g h t f o r w a r d . T h e r e is still a l i v e l y d i s c u s s i o n r e g a r d i n g the p o s i t i o n in w h i c h the p a t i e n t s h o u l d be o p e r a t e d on for any C P A lesion. A l t o u g h the m a j o r i t y o f C P A s c h w a n n o m a s h a v e b e e n e x p l o r e d in the sitting p o s i t i o n at our institute, we p r e f e r r e d the p a r k b e n c h p o s i t i o n in this case b e c a u s e a g e n u i n e p r o x i m a l c o n t r o l for the a n e u r y s m was felt m o r e suitable w h e n the c e r e b e l l u m is a l m o s t f a l l i n g off the p e t r o u s b o n e in the p a r k - b e n c h position. T h e I A A a n e u r y s m in our case was a real s a c c u l a r one but there was no b r a n c h i n g at its origin, t h e r e f o r e a c l i p p a b l e n e c k h a d to be c r e a t e d in a w a y that is c o m m o n in cases with g i a n t a n e u r y s m s : t e m p o r a r y t r a p p i n g and r e l a t i v e distal c l i p p i n g . It was also i m p o r t a n t to d e c o m p r e s s the cranial n e r v e s at the m e a t u s b y gentle s e p a r a t i o n in o r d e r to g a i n f u n c t i o n a l r e c o v e r y . References 1. Arnold W, Vosteen KH (1977) Akute Ertaubung als Folge der Ruptur eines Basilarisaneurysma. HNO 25(4): 127-130 2. Benedetti A, Curri D, Carbonin (1975) Aneurysm of the internal auditory artery revealed by a partial cerebellopontine angle syndrome. Neurochirurgia 18:126-130 3. Cantore GP, Ciappetta P, Vagnozzi R, Bozzao L (11982) Giant 1161 aneurysm of the anterior interior cerebellar artery sinmlating a cerebellopontine angle tumor. 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J Neurosurgery 57 (6): 829-832 Comment The authors report a case of distal anterior inferior cerebellar artery aneurysm at the junction of the internal acoustic artery causing subarachnoid haemorrhage and hearing loss. The authors mention that peripheral AICA aneurysms are very rare and refer to the literature cited. Although I agree that peripheral AICA aneurysms are rare, they are not as rare as might be suggested. Most case reports referring to peripheral aneurysms in the posterior fossa were written in the 70s and 80s. Today, these aneurysms are a known entity and hardly reported any more. Because the case is well presented and a thorough review of the literature is included in the manuscript, it is presented to our readers. H. J. Steiger Correspondence: Peter Banczerowski, M.D., National Institute of Neurosurgery, Budapest, Amerikai fit 57, H-1145 Budapest, Hungary.