J Neurosurg 66:352-356, 1987 Surgical treatment of arteriovenous malformations of the striatothalamocapsular region YU-QUAN SHI, M.D., AND XIAN-CHENG CHEN, M.D. Department of Neurosurgery, Hua Shan Hospital, Shanghai, People's Republic of China Sixteen patients with arteriovenous malformations (AVM's) located in the striatothalamocapsular region were treated microsurgically at the Hau Shan Hospital, Shanghai. These AVM's had a tendency to bleed intracerebrally and typically presented with hemiplegia, hemianesthesia, and hemianopsia. AngiographicaUy the lesions were primarily located in the triangle of Reil. Postoperative outcome was not as good as that of AVM's in other locations, but the operation may have prevented the risk of further hemorrhage. This report details the operative technique used and the clinical course in this group of patients. KEY WORDS arteriovenous malformation 9 intracerebal hemorrhage subarachnoid hemorrhage surgical excision 9 A MONG 108 cases of intracranial arteriovenous malformations (AVM's) treated by microsurgery, 16 cases (14.8%) were located in the striatothalamocapsular (STC) region. These A V M ' s were found in the deep portion o f the cerebral hemisphere, lateral to the body o f the lateral ventricle, and medial to the island of Reil. The most frequent clinical manifestation was hemorrhage into the cerebrum resulting in three typical neurological deficits: hemiplegia, hernianesthesia, and hemianopsia. Because o f the close approximation to the ventricle, intraventricular and subarachnoid hemorrhage c o m m o n l y occurred. On the lateral projection of arteriograms these lesions are located in the triangle o f Reil (Fig. 1 left) and may extend to adjacent areas. On the anteroposterior view the lesions are seen lateral to the A2 and A3 segments of the anterior cerebral artery (ACA), medial to the M2 and M3 segments o f the middle cerebral artery (MCA), and above the M~ portion of the MCA (Fig. 1 right). The arterial supply arises from the lenticulostriate artery, the anterior choroidal artery, cortical branches of the MCA and the ACA, the artery of Heubner, and the posterior choroidal artery. The venous drainage is to the deep cerebral veins such as the thalamostriatal, internal cerebral, and basal veins. The treatment of these A V M ' s has been controversial. Most authors have suggested that they should not be approached surgically, ~-5 and others have recommended treatment by embolization. All o f the patients in the present series were treated with a direct operative approach to the AVM. 352 Summary of Cases Patient Population and Presentation There were eight males and eight females in this series of patients with A V M ' s in the STC region; their ages ranged from 15 to 38 years with a mean of 26 years. The lesion was located on the left in seven cases. Clinical signs and s y m p t o m s are summarized in Table 1. Subarachnoid hemorrhage (SAH) occurred in all cases and was the initial s y m p t o m in 14 cases; it occurred twice in four cases, three times in three cases, and four times in one case. In one case the initial symptom was subjective numbness and weakness on the right side; these episodes recurred for 7 years until the patient presented with SAH, right hemiparesis, and dysphasia. These s y m p t o m s were presumably due to repeated small parenchymal hemorrhages. One patient had focal seizures as the first symptom. Clinical findings of hemiplegia, hemianesthesia, and hemianopsia appear to be the most typical features of this lesion. Diagnosis and Treatment Computerized t o m o g r a p h y scans were carried out in eight cases. On plain scans, four showed intracerebral hemorrhages and four had abnormal attenuation. After contrast enhancement, irregular areas of increased attenuation were seen in all eight patients. Carotid arteriography was performed in all 16 cases, unilaterally in 10 and bilaterally in six. Vertebral arteriography was carried out in one patient. The angiographic circulation of these malformations is summarized in Table 2. J. Neurosurg. / Volume 66/March, 1987 AVM of the striatothalamocapsular region FIG. 1. Diagrams of a carotid arteriogram showing the striatothalamocapsular region which defines this group of arteriovenous malformations within a triangle on the lateral view (left) and within a circle on the anteroposterior view (right). TABLE 1 Symptoms and signs of16 A VM's of the STC region* Symptoms & Signs No. Cases Percent symptoms subarachnoid hemorrhage 16 100 headache 12 75 hemiparesis 10 62.5 impaired consciousness 10 62.5 hemianesthesia 5 31.2 dysphasia 5 31.2 seizure attacks 3 18.8 weakness of limbs 3 18.8 paresthesia 2 12.5 signs hemiplegia 14 87.5 pyramidal signs 13 81.2 increased tendon reflex 12 75.0 hemianesthesia 10 62.5 dysphasia 5 31.2 hemianopsia 4 25.0 meningismus 3 18.7 ataxia 2 12.5 anisocoria 1 6.2 paralysis of conjugate 1 6.2 upward gaze muscular atrophy of 1 6.2 lower limb no neurologicalsign 2 12.5 * AVM = arteriovenous malformation; STC = striatothalamocapsular. All 16 patients were treated by direct operation: 14 by excision (13 of which were complete) a n d two by ligation of the feeding arteries. I n o n e case treated by ligation there was c o m p l e t e r e s o l u t i o n of arteriovenous s h u n t i n g on postoperative angiography, a n d in the other a reduction was n o t e d i n the size o f the AVM. J. Neurosurg. / Volume 6 6 / M a r c h , 1987 FIG. 2. Incisions and approaches for arteriovenous malformations of the striatothalamocapsular region: incision for a pterional approach (1), and incision for a midtemporal approach (2). The dotted lines indicate bone flaps. Operative Procedure T h e operative p r o c e d u r e was designed to reduce d a m age to the s u r r o u n d i n g structures b y m i n i m i z i n g operative t r a u m a a n d a v o i d i n g i n c i s i o n s c a u s i n g neurological d a m a g e . In m o s t cases a m i d t e m p o r a l osteoplastic flap was created (Fig. 2). I n s o m e cases, particularly in 353 Y. Q. Shi and X. C. Chen FIG. 3. Drawings showing the operative approach. Left: View of the split sylvian fissure and dissection along the middle cerebral artery with the medial branches divided. Right: Incision into the lateral ventricle through the base of the sylvian fissure exposing the vascular malformation in the striatothalamocapsular region. TABLE 2 Circulation of l 6 STC region A VM's* Feeding & Draining Vessels No. of Cases arterial supply anterior choroidal artery 10 lenticulostriate artery 7 MI branches 3 artery of Heubner 2 PCA & PCoA branches 1 venous drainage deep cerebral to internal 13 cerebral vein basal vein 2 lenticulostriate vein l * STC = striatothalamocapsular; AVM = arteriovenous malformation; M~ = first segment of the middle cerebral artery; PCA = posterior cerebral artery; PCoA = posterior communicating artery. lesions located anteriorly, the pterional approach described by Ya~argil and Fox was preferred. 6 The goal was to adequately expose the sylvian fissure. In the pterional approach, the anterior part o f the sylvian fissure is usually visible upon reflection o f the dural flap. With the use of a midtemporal flap, the sylvian fissure may be identified by locating the superficial sylvian veins which run anteriorly and inferiorly and delineate the upper margin of the temporal lobe (Fig. 3 left). The arachnoid overlying the sylvian veins is incised and the fissure is gently split with a pair of brain spatulas until the surface of the insula is reached. 354 During the course o f the dissection several cortical branches of the M C A are encountered. By following these branches one reaches the main trunk of the MCA. Branches of the MCA that look dilated and run medially in the direction o f the lesion should be coagulated or clipped but not those that traverse outwardly to the temporal lobe. This dissection should be carried as far medially as possible until the striatal arteries are exposed and coagulated or clipped. If the dissection is carried further the carotid bifurcation may be reached and the anterior choroidal and posterior communicating arteries may be seen. In general, dissecting this far or ligating these vessels at this stage is not advisable. Attention should then be directed posteriorly to the inferior portion of the fissure which is the closest approach to the lateral ventricle. A transverse or oblique incision is then made in the bottom of the fissure and deepened until the lateral wall of the ventricle has been opened. A self-retaining retractor will keep the ventricle exposed. The A V M is usually embedded in the lateral wall of the lateral ventricle with dilated draining veins leading medially (Fig. 3 right). If the anterior choroidal artery is involved it may be dissected at this point, coagulated, and divided. The margin of the A V M should be well delineated and dissection carried out close to the margin. All arteries of whatever size may be thoroughly coagulated and divided. Arteries larger than 0.5 m m in diameter may be considered for clip ligation. Once the A V M mass is nearly free, our custom has been to dissect out the draining veins and then doubly ligate them with fine silk ligatures followed by J. Neurosurg. / Volume 6 6 / M a r c h , 1987 AVM of the striatothalamocapsular region FIG. 4. Case 1. a: Preoperative carotid arteriogram, lateral view. b: Preoperative carotid arteriogram, anteroposterior view. c: Postoperative carotid arteriogram, lateral view. d: Excised surgical specimen (measure in centimeters). coagulation and division. In this way, the AVM may be excised as a single mass. The veins should be ligated in close approximation to the A V M mass in order to minimize risk to the internal cerebral vein, lenticulostriate veins, and great vein o f Galen. Outcome The only postoperative death was early in the series, for an operative mortality rate o f 6%. Four patients (25%) had increased deficits after surgery. In one this completely resolved and in another the left arm remained paralyzed. The other two patients died more than 2 years after the operation, one from a febrile illness and the other from recurrent SAH presumably from an aneurysm although no autopsy was obtained. Thus, 12 (75%) of the patients had an excellent longterm outcome. Illustrative Cases Case 1 This 23-year-old w o m a n had been hospitalized twice for recurrent SAH, 4 years and 1 year previously. At the present admission she was found to have a left hemiparesis with the a r m weaker than the leg. Bilateral cerebral angiography showed a large A V M in the STC region of the right hemisphere which was supplied by branches of the MCA and ACA with drainage through the deep cerebral veins to the straight sinus (Fig. 4). Complete excision of the A V M was carried out as described above. Postoperatively the hemiparesis was transiently worse. By 6 months she had returned to her preoperative status and was doing well. A letter from her family reported that she died 28 months after surgery of a presumably unrelated febrile illness. J. Neurosurg. / Volume 6 6 / M a r c h , 1987 Case 2 This 26-year-old w o m a n was admitted for evaluation of repeated episodes of right-sided n u m b n e s s followed by weakness of 7 years' duration. The most recent event occurred 10 months prior to admission and resulted in hemiparesis and difficulty with speech. A left carotid arteriogram revealed a small A V M in the STC region (Fig. 5). The arterial supply was from the anterior choroidal and lenticulostriate arteries, and venous drainage was to the deep cerebral veins. Complete excision o f the A V M was carried out. In the immediate postoperative period the patient had no increase in her deficit and over the following year she gradually improved to the point where her only deficit was paralysis of the fight hand. Comment Arteriovenous malformations o f the STC region are particularly hazardous because of their location and the apparent likelihood of hemorrhage with resulting neurological deficit. Although surgery for this lesion m a y 355 Y. Q. Shi and X. C. Chen FIG. 5. Case 2. a: Preoperative carotid arteriogram, lateral view. b: Preoperative carotid arteriogram, anteroposterior view. c: Postoperative carotid arteriogram, lateral view. d: Excised surgical specimen (measure in centimeters). carry a higher risk than that for A V M ' s in other locations, it appears justified in order to reduce the risk o f recurrent hemorrhage. The operative procedure described here provides direct access to the A V M with m i n i m a l brain trauma, initial access to the arterial supply, a n d visualization o f the v e n o u s drainage from the A V M to the deep venous structures. References 1. Fujita K, Matsumoto S" Anterior choroidal artery arteriovenous malformation. Its clinical manifestations and surgical treatment. Surg Neurol 22:347-352, 1984 2. Heros RC: Arteriovenous malformations of the medial temporal lobe. Surgical approach and neuroradiological characterization. J Neurosurg 56:44-52, 1982 3. Kelly P J, Alker GJ Jr, Zoll JG: A microstereotactic approach to deep-seated arteriovenous malformations. Surg Neurol 17:260-262, 1982 4. U HS, Rosenberg J: Complete recovery from hemiplegia following excision of a giant basal ganglia arteriovenous malformation. Surg Neurol 15:328-330, 1981 5. Viale GL, Turtas A, Pau A: Surgical removal of striate arteriovenous malformations. Surg Neurol 14:321-324, 1980 356 6. Ya~argil MG, Fox JL: The microsurgical approach to intracranial aneurysms. Surg Neurol 3:7-14, 1975 Manuscript received March 28, 1986. Address reprint requests to: Yu-quan Shi, M.D., Department of Neurosurgery, Hua Shan Hospital, Shanghai 200040, People's Republic of China. J. Neurosurg. / Volume 6 6 / M a r c h , 1987