Use of balloon occlusion and substances to protect ischemic brain during resection of posterior fossa AVM. Case report

The successful resection of a large posterior fossa arteriovenous malformation (AVM) is reported. A balloon catheter was used for temporary intraoperative occlusion of the basilar artery and feeding vessels of the AVM. Prior to occlusion of these arteries, newly tested substances to protect the ischemic brain were administered to prolong occlusion time. Resection of the AVM was completed without complication, and the patient returned to normal life. This is a useful intraoperative procedure for the resection of AVM's considered inoperable by conventional approaches.     

Thalamic arteriovenous malformation with an unusual draining system--case report

A 52-year-old man suddenly experienced headache and vomiting. Computed tomography demonstrated a small area of hemorrhage in the right cerebellar hemisphere. Angiography revealed a thalamic arteriovenous malformation (AVM) fed by the bilateral medial posterior choroidal arteries and left marginal tentorial artery, and drained into the confluence via the cerebellar veins without flow into the supratentorial venous system. The draining veins included two varices, one of which, in the right cerebellar hemisphere, was thought to be the source of bleeding. The AVM nidus was removed via the right occipital transtentorial approach. A portion of a drainer adhered to the surface of the great vein of Galen but without opening into the galenic system and all drainers from this thalamic AVM flowed into the infratentorial cerebellar venous system.     

Aneurysm of the anterior inferior cerebellar artery at the internal auditory meatus: report of two cases

Aneurysm of the vertebrobasilar system is not a rare lesion but constituting 5-10% of all intracranial aneurysms. Aneurysm at the peripheral part of the anterior inferior cerebellar artery (AICA), however, is rare and only 20 cases have been reported previously. In this report, two cases of aneurysm arising at the junction between the AICA and internal auditory artery and extending into the internal auditory meatus are reported. The first patient was a 51-year-old male who was admitted because of sudden onset of dizziness, rt. tinnitus and deafness. Left vertebral angiograms demonstrated an AVM in the rt. cerebellar hemisphere and two aneurysms on the feeding arteries, one on the superior cerebellar artery and the other on the meatal loop of the rt. AICA. Removal of the AVM and neck clipping of the aneurysms, which were found unruptured, were performed through the rt. suboccipital approach. The second patient was a 42-year-old female who was admitted because of sudden onset of severe headache and vomiting followed by rt. tinnitus, deafness and double vision. CT scan showed subarachnoid clot mainly located in the rt. cerebellopontine angle. Repeated vertebral angiograms revealed an aneurysm at the meatal loop of the rt. AICA. Complete neck clipping was carried out. The clinical features of the aneurysms of this location can be divided into three subgroups according to the characters of onset: sudden onset with subarachnoid hemorrhage, insidious onset of the VII th, VIII th, nerve palsies by the mass effect of the aneurysm, intermittent episodes of the VIII th nerve disfunction due to the insufficiency of the internal auditory artery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trigeminal neuralgia associated with primitive trigeminal artery: report of two cases

Two cases of trigeminal neuralgia associated with the primitive trigeminal artery are reported. From 1981, the authors have treated 131 trigeminal neuralgia patients with microvascular decompression. Among them, we encountered two rare cases of trigeminal neuralgia associated with the primitive trigeminal artery (PTA) and its variant (PTAV). Case 1 is a 74-year-old woman who was admitted to our hospital due to pain of maxilla and mandible. We diagnosed her pain as trigeminal neuralgia. Preoperative angiogram showed the primitive trigeminal artery arising from the cavernous portion of the right internal carotid artery (ICA). She underwent a microvascular decompression operation. We found that her right trigeminal nerve was compressed by the right superior cerebellar artery (SCA) and the right anterior inferior cerebellar artery (AICA). We transferred the offending arteries, and her pain disappeared. Case 2 is a 48-year-old man who was admitted to our hospital due to severe mandibular pain. We diagnosed his pain as trigeminal neuralgia, and he underwent a microvascular decompression operation. His left trigeminal nerve was found compressed by the left SCA and the AICA, and the AICA was arising from the direction of Meckel's cave. His severe pain disappeared completely after operation. Postoperative angiogram of his left ICA showed an aberrant artery arising from the cavernous portion of the ICA, to the region of the left AICA. This aberrant artery is a variant of PTA (PTAV). PTA and PTAV, the so called persistent congenital arteries, are said to accompany aneurysms and other vascular lesions, and affect hemodynamic stress.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nidus embolization of cerebral arteriovenous malformation fed mainly by a pericallosal artery prior to surgical excision. Case report

Nidus embolization of large arteriovenous malformation (AVM) by silastic spheres is not rarely performed prior to surgical excision of AVM. This technique is highly indicated for the large AVM supplied by the middle and the posterior cerebral arteries since silastic spheres injected into either the internal carotid or the vertebral arteries usually enter the middle or the posterior cerebral arteries due to less sharp angle from the main arteries. The authors report a case whose AVM, fed mainly by the anterior cerebral artery, was successfully embolized with silastic spheres using balloon catheter technique. On December 1, 1983, a 27-year-old man was admitted to our department with chief complaint of headache and clonic convulsion of the left upper and lower limbs. Convulsion began in 1973 and severe headache suddenly appeared two months prior to admission. He was neurologically asymptomatic on admission. Right internal carotid angiogram taken on admission showed a presence of large arteriovenous malformation in the medial portion of the right fronto-parietal lobe and corpus callosum fed mainly by the right pericallosal artery. Nidus embolization with silastic spheres was planned to make surgical removal easier. To prevent stray of silastic spheres into the right middle cerebral artery, balloon, introduced into the M1, was inflated for a few minutes, during which time, injection of 40 silastic spheres of 1.5 and 2.0 mm in diameter was performed via the right internal carotid artery. The nidus was significantly reduced and total removal of the nidus was successfully done 28 days following the embolization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ruptured Pseudoaneurysm after Gamma Knife Surgery for Vestibular Schwannoma

Ruptured aneurysms of anterior inferior cerebellar artery (AICA) after radiotherapy for vestibular schwannoma (VS) are rare, and no definite treatment has been established for distal AICA pseudoaneurysms. We describe a 61-year-old man who underwent Gamma Knife surgery (GKS) for left VS. Follow-up magnetic resonance imaging (MRI) revealed partial regression of the tumor. Twelve years after GKS, he suffered from subarachnoid hemorrhage. Initial angiogram showed no vascular lesions; second left vertebral angiogram, 10 days after admission, demonstrated a pseudoaneurysm in the lateral pontine segment of the left AICA. The proximal portion of the AICA was occluded by a coil. Postoperative MRI revealed an infarction on the left side of the pons and brachium pontis. Although the patient suffered from mild postoperative cerebellar ataxia and facial and abducens nerve palsy, he was discharged 1 month postoperatively requiring no assistance with activities of daily living. Twelve months later, he recovered satisfactorily with a modified Rankin Scale grade of 1, and no recanalization of the aneurysm was found on MR angiography. Endovascular parent artery occlusion for ruptured aneurysms at distal AICA carries the risk of brain stem infarction, but should be considered when no other option is available such as after radiotherapy for VS.     

A case of ruptured aneurysm associated with spinal arteriovenous malformation presenting with hematomyelia: case report

BACKGROUND

Spinal cord arteriovenous malformation (AVM) associated with spinal aneurysm is not particularly rare, but cases presenting with hematomyelia are relatively rare compared to those with subarachnoid hemorrhage (SAH). We report a rare case of successfully treated spinal AVM associated with ruptured aneurysm presenting with hematomyelia.

CASE DESCRIPTION

A 52-year-old male was admitted to our hospital with sudden onset of tetraplegia, respiratory disturbance, and superficial sensory disturbance. Computed tomography revealed hematomyelia at the level of C3–4. Gadolinium-enhanced magnetic resonance imaging showed small, enhanced lesions. Angiography revealed an intradural perimedullary arteriovenous malformation associated with two aneurysms on the feeding arteries. Administration of high-dose methylprednisolone gradually ameliorated his symptoms. Direct surgical obliteration was performed on the 30th day after the onset. The bilateral C3 cervical radicular arteries and the nidus were coagulated. Angiography performed after surgery showed neither the aneurysms nor the nidus. He was discharged with only mild weakness in the left upper extremity and mild left hypesthesia 3 months after surgery, and was fully independent.

CONCLUSION

We report a case of hematomyelia caused by ruptured aneurysm associated with spinal arteriovenous malformation that was successfully treated with surgical obliteration.     

A glioma with an arteriovenous malformation: an association or a different entity?

Case report A 58-year-old male was admitted with headache to our neurosurgery clinic. His neurological examination revealed slight left hemiparesis. The radiological evaluation with contrast administred magnetic resonance imaging (MRI) scan demonstrated a right temporo-parietal ring enhancing mass lesion surrounded by edema which was resembling a typical glioma (Fig. 1). The patient was operated on via a temporo-parietal craniotomy and an arteriovenous malformation surrounded by abnormal glial tissue was observed during the exposure. A nidus supplied by several branches arising from the middle cerebral artery (MCA) was obvious. The venous drainage of the malformation was to the superficial venous system. The observed arterial feeders and the draining vein were coagulated and the nidus was macroscopically totally excised. The frozen examination from surrounding glial tissue revealed a high grade glioma. The tumor was also macroscopically totally excised. Postoperatively, the cerebral angiogram demonstrated a right temporal arteriovenous malformation with a centrally excised nidus. The remaning major feeders involved the angular gyrus and the posterior temporal arteries. The venous drainage was to the straight and sigmoid sinuses (Fig. 2). The final histopathological examination of the specimen revealed an arteriovenous malformation surrounded by a high grade glioma (Fig. 3). The patient refused a second operation for total removal of the AVM. Postoperatively, he is doing well with improvement of his left hemiparesis.     

Coil embolization with a hyperform occlusion balloon for an acutely ruptured wide-necked basilar tip aneurysm: case report

A 54-year-old woman was admitted to our hospital because of severe headache. CT scan demonstrated subarachnoid hemorrhage (SAH), and cerebral angiography revealed a wide-necked basilar tip aneurysm with a bleb and a small basilar artery-left superior cerebellar artery aneurysm. She was treated with coil embolization using a neck remodeling technique one day after SAH. Guiding catheters were introduced into the bilateral vertebral artery via the transfemoral route. A Hyperform occlusion balloon catheter was introduced into the left posterior cerebral artery (PCA) through the left vertebral artery, and was placed at the neck of the basilar tip aneurysm for neck remodeling. Then, the microcatheter for coil deployment was placed in the dome of the aneurysm through the right vertebral artery. The coil was deployed in the aneurysm while the balloon was inflated across the neck. The inflated Hyperform occlusion balloon was partially herniated into the dome of the aneurysm. The distal part of the balloon was positioned in the left PCA segment, and its proximal part was positioned in the basilar artery. The balloon conformed easily to the aneurysmal neck and its surrounding vessel structure. When the balloon was deflated, the coil did not protrude into the parent artery, and was stable in the aneurysm. Angiography immediately after the procedure showed complete occlusion of the aneurysm with patency of both PCAs. The Hyperform occlusion balloon is very compliant and supple, so it easily changes from its cylindrical shape when inflated to expand into the origin of the arterial branches emerging from the aneurysm neck. We think this balloon is a useful device for treating wide-necked aneurysms located at arterial bifurcation.     

Adult pial arteriovenous fistula and superior sagittal sinus stenosis: angiographic evidence for high-flow venopathy at an atypical location. Case report

The authors present the case of a 69-year-old man who suffered from bilateral cortical venous hypertension due to a brain pial arteriovenous malformation (AVM) with a high-flow fistula. The AVM became complicated by the development of a high-grade stenosis of the posterior superior sagittal sinus (SSS). A comparison of cerebral angiograms obtained at different times revealed that the severe SSS stenosis had developed within a 5-year period and was located distal to the nidus of the left parietal AVM nidus, away from the entrance of the dominant superior superficial cortical draining vein into the SSS. The high-flow fistula was occluded with detachable coils and the AVM nidus was further embolized with acrylic. The SSS stenosis was mechanically dilated by means of balloon angioplasty and stent placement. This case provides angiographic evidence to support the hypothesis that a pial arteriovenous fistula in an adult can cause high-flow occlusive venopathy in a major sinus within a relatively short time and that this acquired high-flow occlusive venopathy can develop at an atypical location distant from the nidus of the AVM.     

Surgical management of arteriovenous malformations in the posterior fossa

The authors reported 3 cases of dural arterio-venous malformation (AVM) in the posterior fossa and discussed mainly on surgical treatment. Case 1: 53-year-old man was admitted to our clinic with complaints of amnesia, visual impairment, dysarthria and gait disturbance. Neurological examination on admission disclosed slight disturbance of consciousness, bilateral papilledema, horizontal nystagmus, dysarthria and ataxic gait. Contrast CT showed a presence of vermiform irregular high density with enlarged ventricle, indicating phlebectasia in the brainstem and the cerebellum. Angiograms revealed a presence of dural AVM at the straight sinus fed by branches of external carotid artery and vertebrobasilar circulation with appearance of phlebectasia due to increase in straight sinus pressure on later phase. Dural sinus isolation for the affected sinus was performed under large occipital craniotomy which was initially reported by Hugosson and Bergstr?m. Case 2: 55-year-old man was admitted to our hospital with complaint of gait disturbance. Neurological examination at the time of admission disclosed signs of raised intracranial pressure and caudal cranial nerves disturbance. Bruit synchronized with radial pulse was audible over the left occipital region. Angiograms showed a presence of dural AVM at the left transverse and sigmoid sinus with many feeding arteries and abnormal venous returns. Isolation of the involved sinuses was performed as same as in case 1. Case 3: 39-year-old woman was admitted to our clinic with complaints of protrusion of eyes and uncomfortable machinery noise over the right retromastoid region.(ABSTRACT TRUNCATED AT 250 WORDS)     

The impact of arteriovenous malformation radiosurgery on the brain: From morphology and perfusion to neurocognition

The therapeutic aims of brain arteriovenous malformation (AVM) radiosurgery are multiple. Protecting patients from rebleeding is the prime goal. Among the others, hemodynamics, perfusion and neurocognition recovery are interesting and important. Anatomically AVM contains an abnormal cluster of vascular networks (nidus) between arteries and veins. Hemodynamically the nidus contains a low resistance and causes high-flow transnidal shunts between both sides of the nidus. The shunts cause hypotension in the neighboring arteries and diversion of blood from the adjacent brain tissues. The diversion disturbs brain hemodynamics. Radiosurgery, by eliminating the nidus, reconstitutes normal brain hemodynamics. From the early stage after radiosurgery, the abnormal transnidal flows gradually decrease, and the adjacent hemodynamics recovers toward normal. For nonhemorrhagic AVM, improvement of seizure control and stable or improved neurological status are observed clinically. The radiosurgical effects are also reflected in the recovery of metabolism in the adjacent brain and neurocognitive function paralleling the hemodynamic normalization. Morphological cure of AVM and the associated recovery of brain hemodynamics, metabolism and neurocognitive function form the therapeutic rationale of AVM radiosurgery.     

A case of hemorrhagic non traumatic arteriovenous fistula of the scalp]

Arteriovenous malformation of the scalp in an uncommon disease and treatment for this lesion is difficult and controversial. A twenty-three-year-old male, who reported no history of head trauma, presented with spontaneous hemorrhage from the left temporal scalp. Neurologically he was normal except the tinnitus. Left external carotid angiography demonstrated arteriovenous malformation fed by the superior temporal and posterior auricular arteries. A dilated tortuous occipital artery was also recognized. The lesions were able to be surgically resected, alleviating intraoperative massive hemorrhage by proximal temporary occlusion of the external carotid artery at the left neck. Small feeding arteries from the meningeal artery which were not recognized on preoperative angiography were found at surgery. The arteriovenous fistula was successfully resected without any cosmetic problem.     

Persistent primitive hypoglossal artery associated with arteriovenous malformation--case report.

A case of persistent primitive hypoglossal artery (PPHA) associated with arteriovenous malformation (AVM) is reported. A 46-year-old male suddenly developed severe headache followed by transient unconsciousness and was admitted to our hospital 2 hours later. A computed tomographic scan showed subarachnoid hemorrhage. Angiograms revealed an AVM in the left cerebellar hemisphere and an ipsilateral PPHA. The AVM was completely removed and he was discharged 1 month after surgery without neurological deficit. Only three cases of PPHA associated with intracranial AVM have been reported in the literature. One patient died of rebleeding from the AVM before surgery, and another was conservatively treated because the AVM was too large for resection. The remaining one was surgically treated only by ligation of the feeding arteries. Ours is the first case treated by total removal of the AVM. Since these four cases, including ours, account for 3.0% of 134 cases of PPHA reported, PPHA associated with AVM is considered rare.     

Trigeminal Neuralgia Caused by Nerve Compression by Dilated Superior Cerebellar Artery Associated with Cerebellar Arteriovenous Malformation: Case Report

Intracranial arteriovenous malformation (AVM) is a rare cause of trigeminal neuralgia (TGN). In this presented case, successful resolution of AVM-related TGN following embolization and gamma knife radiosurgery (GKRS) was obtained. A patient suffered from TGN on the left side, which was thought to be caused by root entry zone compression by dilated superior cerebellar artery (SCA) associated with cerebellar AVM. The cerebellar vermis AVM was embolized in endovascular surgery. The AVM was reduced in size and TGN was partially relieved. The patient subsequently underwent GKRS for the residual nidus. TGN was completely resolved within one year and a half. GKRS following embolization of the nidus improved the flow-related dilation of the SCA and completely relieved TGN.     

Retrospective analysis of a 10-year experience of stereotactic radio surgery for arteriovenous malformations in children and adolescents

OBJECT: To obtain information essential to the decision to perform radiosurgery for arteriovenous malformations (AVMs) in children and adolescents, the authors retrospectively analyzed their experience with gamma knife surgery for AVMs in 100 patients ranging in age from 4 to 19 years. METHODS: Follow-up periods ranged from 6 to 124 months (median 71 months), and the actuarial obliteration rates demonstrated by angiography were 84.1, 89.4, and 94.7% at 3, 4, and 5 years, respectively. Factors associated with better obliteration rates in univariate analysis included the following: a patient age of 12 years or younger; a mean nidus diameter of 2 cm or less; a nidus volume of 3.8 cm3 or less; a maximum diameter of the nidus less than 3 cm; and a Spetzler-Martin grade of III or less. Radiation-induced neuropathy was seen in four patients, and the risk factors were considered to be a nidus in the brainstem and a maximum radiation dose greater than 40 Gy. Hemorrhage developed during the latency interval in four patients, and one patient with a cerebellar AVM died of the hemorrhage. The annual bleeding rate was 1.5%. Feeding arteries located in the posterior cranial fossa and an AVM nidus located in the cerebellum were significantly associated with the risk of hemorrhage. After angiographically verified obliteration of the nidus, 51 patients continued to be observed from 1 to 110 months (median 67 months); hemorrhage developed in one patient 38 months after nidus obliteration. CONCLUSIONS: Radiosurgery is an acceptable treatment for small AVMs in children and adolescents in whom a higher obliteration rate can be achieved with lower risks of interval hemorrhage compared with the reported results in the general population. Careful follow-up observation seems to be required, however, even after angiographically verified obliteration.     

Tentorial dural arteriovenous malformation--a case report (author's transl)]

A case of tentorial dural AVM was reported. A 52 years old man came to the Jichi Medical School hospital on July 29, 1974, with the chief complaints of intermittent left exophthalmos, diplopia and left blepharoptosis, which had been noted since March of 1974. He had episodes of severe headache attack since 3 years prior to the hospital visit. Angiography done at the out-patient department demonstrated the dural AVM with the nidus in the left tentorium. The nidus was fed by the left posterior middle meningeal artery, the dural branch of the left occipital artery, the left posterior cerebral artery, the left superior cerebellar artery and the dural branches of vertebral artery. It was drained to the vein of Labbé and the two cortical veins of the occipital lobe. He was appointing admission under the diagnosis of dural AVM, but he had an apopleptic attack three days before the appointed date, so was admitted in emergency. Neurological examination on admission: The patient was in drowsy state, papilledema on the both sides and right hemiparesis including the face were noted. The bruit was not audible. Left CAG revealed intracerebral hematoma in the left tempotal lobe, so that the removal of the intracerebral hematoma and the middle meningeal artery ligation were carried out after his general condition improved, on October 18, 1974. On October 30, 1974, the second operation was performed in an attempt of the radical excision of the AVM nidud. But, unfortunately, the patient fell into the shock state so that the operation had to be stopped at the stage of the ligation of the feeders running in the dura of the posterior fossa. The third operation was done on February 19, 1975. The AVM nidus was removed with the left transverse sinus and a part of tentorium. He was discharged on March 3, 1975, with only the right homonymous hemianopsia. Nine months after his discharge, there was no sign of recurrence of AVM. Pathological findings: The left transverse sinus was almost occupied with AVM tissue. The endothelium of arteries were hypertrophied and the internal elastic bnadles were partly defected. Veins showed also hspertrophy of the endothelium and the thrombus formation. The dural AVM of the posterior fossa is not a rare malady, especially in the recent years, probably due to the technical advances in the roentgenology, such as magnification techniques as well as selective arterial catheterization. The most common signs and symptoms of this disease picked up from the reports of 112 cases in the literature are: bruit 47%, headache 44%, papilledema 26% and SAH 24%. The extra cranial ligation of feeders were reportedly carried out on 39 cases, but only 9 cases (23%) were effective. Therefore, the radical excision of the nidus would be the most desirable method for the complete treatment of the dural AVM.     

Three cases of scalp arteriovenous malformations

Three cases of scalp arteriovenous malformation (AVM) are presented and the pertinent literature is reviewed. Case 1 was a 50-year-old male who was admitted to hospital with a pulsatile mass involving the right parietal region. Selective angiography revealed a scalp AVM fed by bilateral superficial temporal and right occipital arteries. The AVM was embolized with Gelfoam pieces through catheterization and there was no evidence of recurrence of the lesion after follow-up period of three years. Case 2 was a 25-year-old male who was noticed to have a birth mark in the left occipito-parietal region and was hospitalized with a pulsatile gradually expanding mass after an episode of minor trauma in the same region. Selective angiography revealed a cirsoid type scalp AVM fed by bilateral superficial temporal and occipital arteries, and the authors performed a total resection of the mass because of selective Gelfoam embolization was not successful. Case 3 was a 49-year-old male who was hospitalized with the chief complaints of left tinnitus and pulsatile left supra-auricular mass. There was no history of trauma. Selective angiography revealed a scalp AVM fed by the left superficial temporal and occipital arteries and the authors performed a selective Gelfoam embolization and this was successful, but three months later, the AVM recurred and mainly fed by instead this was the left posterior auricular artery. Preoperative selective Gelfoam embolization followed by a total resection of the AMV with minimal blood loss.(ABSTRACT TRUNCATED AT 250 WORDS)     

Surgery of high-flow arteriovenous malformation: with special reference to normal perfusion pressure breakthrough phenomenon

Hemodynamic changes are of importance while removing large and high-flow arteriovenous malformations (AVM), because a phenomenon called "normal perfusion pressure breakthrough" may occur. In this report, we evaluated hemodynamic changes in 14 cases of high-flow AVM with cerebral angiogram and intraoperative monitoring of cortical-surface blood flow. The criteria we used for high-flow AVM are; nidus larger than 4 cm, a few large feeders, high-flow shunt in the nidus, and reduced circulation or dilated arteries in the adjacent brain tissue. For last 2 years, we experienced 14 cases of high-flow AVM which fulfilled the criteria, and 9 of these were operated on for total removal of AVM. Of those, 2 cases evolved postoperative local edema and hemorrhage and was thought to be due to "normal perfusion pressure breakthrough." Intraoperative monitoring of cortical-surface blood flow was useful to predict occurrence of "perfusion breakthrough", because blood flow in the adjacent brain tissue increased markedly with feeder clipping. Intraoperative barbiturate protection and postoperative controlled hypotension were thought to be useful for prevention of "normal perfusion pressure breakthrough", though the details of mechanisms are unknown.     

Dural arteriovenous malformation of the anterior fossa with subarachnoid hemorrhage

Idiopathic dural arteriovenous malformation which occurs in the posterior fossa uses predominantly transverse and sigmoid sinuses. Cavernous sinus comes next and others are rather rare. However, we have recently experienced such a rare case which was operated on and cured completely. The malformation was fed through the anterior ethmoid artery and drained to the cortical vein. The case was a 36-year-old male and admitted in our clinic for having headache and nausea as the chief complaints. He was diagnosed subarachnoid hemorrhage due to the following findings: CT scans showed a high density zone localized in the sylvian vallecula. Cerebrospinal fluid obtained by a lumbar puncture was found to be bloody. No neurological abnormality other than neck stiffness and positive Kernig's sign was observed. Under study of right carotid arteriography, dural AVM was evident. The anterior ethmoidal artery which branched out from the ophthalmic artery fed the AVM. The cortical vein which ran on the surface of the frontal base was its drainer via a small nidus. There was no abnormality seen on a left carotid arteriogram. Surgery was proceeded with the right frontal craniectomy in extra- and intradural approach. At first, anterior ethmoidal artery was cut at the cribriform plate extradurally. After dura was incised, both the nidus and drainer were coagulated intradurally. The nidus was located at inner surface of the dura. The arachnoid hemorrhage was thought to be caused by rupture of this drainer.(ABSTRACT TRUNCATED AT 250 WORDS)