The Thalamic Arteriovenous Malformations Have Better Prognosis than Basal Ganglia Malformations Regarding Obliteration: Prognostic Factors Analysis.

BACKGROUND: Arteriovenous malformations (AVMs) are rare vascular congenital lesions that affect mainly patients during their productive years of life. In order to obtain a better quality of life for patients with this disease, a multidisciplinary approach is recommended. Radiosurgery is one of the treatment modalities available for AVMs, but many factors may influence the effectiveness of this strategy. Classically, it has been said that deep-seated lesions have a particular behavior compared with AVMs in other regions, but a differentiation between thalamic lesions and those located in the basal ganglia has not been made. METHODS: Institutional records for central core AVMs treated with radiosurgery between January 2004 and January 2014 were retrospectively analyzed. Brainstem lesions were excluded from the analysis. RESULTS: Forty-nine patients with deep-seated AVMs were included. Forty-three (87.8%) were located in the thalamus and 6 (12.2%) in the area of basal ganglia. The nidus mean volume was 4.1 cm3 (SD: 4.1), the maximum diameter mean was of 19.5 mm (SD: 8.0). The prescription dose was 18.2 Gy (SD: 2.1), and the follow-up time was 75.8 months (SD: 32.5). There was a greater obliteration rate in thalamic AVMs compared with those located in the basal ganglia: 81.4% versus 33.3% (P = 0.026), respectively. There was no association between categorical variables and obliteration rate. CONCLUSIONS: Stereotactic radiosurgery is a good option for patients with thalamic and basal ganglia AVMs, but a multidisciplinary approach to decision-making is mandatory in order to achieve the best results.

Thalamic arteriovenous malformation fed by the artery of Percheron originating from the contralateral posterior cerebral artery in a child.

PURPOSE: Artery of Percheron (AOP) is a rare variant of thalamoperforating artery with a single common trunk feeding both thalami and with or without contribution to the rostral midbrain. We report the first case of thalamic arteriovenous malformation (AVM) fed by AOP with hemorrhagic onset. METHODS: A 12-month-old girl suddenly weakened and developed coma. Left thalamic hemorrhage was detected with the third and both lateral ventricles' hematoma. Thalamic AVM was discovered to be fed by an AOP originating from the contralateral posterior cerebral artery. RESULTS: Endovascular embolization of AVM was impossible due to a risk of bilateral thalamic infarction and anatomical inaccessibility. Thalamic AVM was removed by high superior parietal approach without new neurological symptoms. CONCLUSION: The first case of thalamic AVM fed by AOP originating from the contralateral posterior cerebral artery is reported. Surgical removal of AVM would be at the heart of treatment in order to avoid bilateral thalamic infarction.

Deep arteriovenous malformations in the Basal Ganglia, thalamus, and insula: microsurgical management, techniques, and results.

BACKGROUND: Arteriovenous malformations (AVMs) in the basal ganglia, thalamus, and insula are considered inoperable given their depth, eloquence, and limited surgical exposure. Although many neurosurgeons opt for radiosurgery or observation, others have challenged the belief that deep AVMs are inoperable. Further discussion of patient selection, technique, and multimodality management is needed. OBJECTIVE: To describe and discuss the technical considerations of microsurgical resection for deep-seated AVMs. METHODS: Patients with deep AVMs who underwent surgery during a 14-year period were reviewed through the use of a prospective AVM registry. RESULTS: Microsurgery was performed in 48 patients with AVMs in the basal ganglia (n=10), thalamus (n=13), or insula (n=25). The most common Spetzler-Martin grade was III- (68%). Surgical approaches included transsylvian (67%), transcallosal (19%), and transcortical (15%). Complete resection was achieved in 34 patients (71%), and patients with incomplete resection were treated with radiosurgery. Forty-five patients (94%) were improved or unchanged (mean follow-up, 1.6 years). CONCLUSION: This experience advances the notion that select deep AVMs may be operable lesions. Patients were highly selected for small size, hemorrhagic presentation, young age, and compactness-factors embodied in the Spetzler-Martin and Supplementary grading systems. Overall, 10 different approaches were used, exploiting direct, transcortical corridors created by hemorrhage or maximizing anatomic corridors through subarachnoid spaces and ventricles that minimize brain transgression. The same cautious attitude exercised in selecting patients for surgery was also exercised in deciding extent of resection, opting for incomplete resection and radiosurgery more than with other AVMs to prioritize neurological outcomes.

Supracerebellar-supratrochlear and infratentorial-infratrochlear approaches: gravity-dependent variations of the lateral approach over the cerebellum.

OBJECTIVE: Lateral supracerebellar-infratentorial approaches are established for lesions in ambient cistern and posterolateral midbrain, but published surgical experiences do not describe results with this approach in the sitting position. Gravity retraction of the cerebellum opens this surgical corridor and dramatically alters exposure, creating 2 variations of the lateral supracerebellar-infratentorial approach: the supracerebellar-supratrochlear approach and the infratentorial-infratrochlear approach. METHODS: We reviewed our experience treating cavernous malformations and arteriovenous malformations (AVMs) of the posteroinferior thalamus and posterolateral midbrain by use of supracerebellar-supratrochlear and infratentorial-infratrochlear approaches. Microsurgical technique, clinical data, radiographic features, and neurological outcomes were evaluated. RESULTS: During an 11-year surgical experience with 341 cavernous malformation patients and 402 AVM patients, 8 patients were identified, 6 with cavernous malformations and 2 with AVMs. Infratentorial-infratrochlear approaches were used in 4 patients (50%), including 3 with inferolateral midbrain cavernous malformations. Supracerebellar-supratrochlear approaches were used in 4 patients (50%), including 2 with posterior thalamic lesions surfacing on pulvinar. Resections were radiographically complete in all cases. There were no new, permanent neurological deficits, nor were there any medical or surgical complications. There has been no evidence of rebleeding or recurrence. CONCLUSIONS: Gravity retraction of the cerebellum transforms the lateral supracerebellar-infratentorial approach, enhancing exposure and approach trajectories that can be achieved with patients in prone or lateral positions. The increased upward viewing angle of the supracerebellar-supratrochlear approach accesses the posteroinferior thalamus. The increased downward-viewing angle of the infratentorial-infratrochlear approach accesses cerebellomesencephalic fissure and posterolateral midbrain. These approaches open wide corridors for safe surgical resection of symptomatic cavernous malformations and AVMs.

High-grade dural arteriovenous fistula simulating a bilateral thalamic neoplasm.

Dural arteriovenous fistulae (dAVF) provide a diagnostic challenge and must be part of a broad differential in pursuit of a difficult diagnosis or unusual presentation. This case report demonstrates an initially misguided diagnosis of bilateral thalamic neoplasm and demonstrates the importance of continued pursuit until the correct diagnosis is obtained. Moreover, to our knowledge, this is the first reported case of a dAVF simulating a bilateral thalamic neoplasm. We present a patient with a provisional diagnosis of bilateral thalamic neoplasm based on clinical history and an advanced imaging workup including MR spectroscopy. Subsequent biopsy suggested venous congestion, hypoxia, and edema without neoplasia. Routine post-operative CT the following day revealed suggestion of dAVF due to the presence of residual contrast from prior unrelated abdominal CT. Cerebral angiography eventually revealed a Cognard grade IIb dAVF. Trans-arterial Onyx embolization resulted in a dramatic clinical and radiographic improvement. This case highlights an unusual presentation and challenging diagnosis of a dAVF and the importance of pursuing the correct diagnosis.

Gamma knife radiosurgery for arteriovenous malformations of basal ganglia, thalamus and brainstem--a retrospective study comparing the results with that for AVMs at other intracranial locations.

OBJECTIVE: The objective of this retrospective study was to study the outcome in patients with basal ganglia, thalamus and brainstem (central/deep) arteriovenous malformations (AVMs) treated with gamma knife radiosurgery (GKS) and to compare the results with that for AVMs at other intracranial locations. METHODS AND RESULTS: The results of 53 patients with central AVMs and 255 patients with AVMs at other locations treated with GKS at our center between April 1997 and March 2005 with minimum follow-up of 1 year were analyzed. CENTRAL AVMS: Forty of these 53 AVMs were Spetzler-Martin grade III, 11 were grade IV, and 2 were grade V. The mean AVM volume was 4.3 cm(3) (range 0.1-36.6 cm(3)). The mean marginal dose given was 23.3 Gy (range 16-25 Gy). The mean follow-up was 28 months (range 12-96 months). Check angiograms were advised at 2 years after GKS and yearly thereafter in the presence of residual AVM till 4 years. Presence of a residual AVM on an angiogram at 4 years after radiosurgery was considered as radiosurgical failure. Complete obliteration of the AVM was documented in 14 (74%) of the 19 patients with complete angiographic follow-up. Significantly lower obliteration rates (37% vs. 100%) were seen in larger AVMs (>3 cm(3)) and AVMs of higher (IV and V) Spetzler-Martin grades (28% vs. 100%). The 3- and 4-year actuarial rates of nidus obliteration were 68% and 74%, respectively. Eight patients (15%) developed radiation edema with a statistically significantly higher incidence in patients with AVM volume >3 cm(3) and in patients with Spetzler-Martin grade IV and V AVMs. Five patients (9.4%) had hemorrhage in the period of latency. COMPARISON OF RESULTS WITH AVMS AT OTHER LOCATIONS: Patients with central AVMs presented at a younger age (mean age 22.7 years vs. 29 years), with a very high proportion (81% vs. 63%) presenting with hemorrhage. Significantly higher incidence of radiation edema (15% vs. 5%) and lower obliteration rates (74% vs. 93%) were seen in patients with central AVMs. CONCLUSIONS: GKS is an effective modality of treatment for central AVMs, though relatively lower obliteration rates and higher complication rates are seen compared to AVMs at other locations.

Physiological and pathological observations on rat middle cerebral arteries and human AVM tissue cultures following single high-dose gamma irradiation.

In vitro isometric myograph and histopathological studies were performed on rat middle cerebral arteries (MCAs) to explore changes in contractile capacity following experimental Gamma Knife radiosurgery. Right MCAs were treated with 25 Gy and 50 Gy at the 50% isodose line, while contralateral vessels received 15 Gy and 20 Gy at the 20% isodose region. Survival period varied from 3 to 18 months. Reduction in contractile capacity of irradiated normal rat MCAs was detected but their lumina remained patent. In another study, we investigated human AVM tissue cultures in order to detect genetic and phenotypic modifications contributing to vessel occlusion after irradiation. In culture, the proliferation index decreased considerably following 15-, 20-, 25- or 50-Gy irradiation at the 5th posttreatment day and remained depressed during the observation period of 14 days. P53, p21Waf-1 and mdm-2 mRNA contents were elevated significantly after irradiation, indicating enhanced apoptosis. Immunohistochemistry revealed vigorous vimentin positivity in the nonirradiated control AVM cultures, which gradually decreased by the time in the irradiated specimens. Smooth muscle alpha-actin positivity was prominent in the irradiated cultivated samples, suggesting transformation of resting fibroblasts onto activated myofibroblastic elements with contractile capacity. This transformation process was confirmed by the appearance of TGF-Beta in the irradiated AVM cell lines also. These data support the hypothesis that one of the contributing factors to AVM shrinkage and obliteration after radiosurgery might be fibrocyte-myofibroblastic cell transformation in the vessel wall.

Acute and chronic swine rete arteriovenous malformation models: hemodynamics and vascular remodeling.

BACKGROUND AND PURPOSE: An acute and a chronic arteriovenous malformation (AVM) model were developed by using the swine rete to study hemodynamics and vascular remodeling. The models were also used to study in vivo polymerization kinetics and the distribution of various N-butyl 2-cyanoacrylate (NBCA) and Lipiodol mixtures. METHODS: In the acute swine AVM model, retrograde flow through the left side of the rete was created by the placement of an endovascular shunt through the ipsilateral ascending pharyngeal artery. In the chronic model, flow was redirected retrograde through the left side of rete and ascending pharyngeal artery by creating an arteriovenous fistula between the ipsilateral jugular vein and the common carotid artery. After a period of at least 6 months, the entire head with the rete was connected to a perfusion loop driven by a peristaltic pump. A total of 30 swine were used for both the acute (n = 23) and chronic groups (n = 7). Hemodynamic parameters, including the flow and pressure drop across the rete, were recorded before NBCA embolization. Image processing was used on high-resolution radiographs of the explanted retia to measure the total rete length. Measurements of rete vessel calibers were based on histology. RESULTS: The pressure gradients across retia were higher in the chronic model than in the acute model, but they did not reach the level of statistical significance (23.7 +/- 12.0 mm Hg vs 15.4 +/- 1.4 mm Hg). The rete blood outflow was significantly higher in the chronic model compared with the acute one (139.9 +/- 100.3 mL/min vs 32.5 +/- 17.6; P = .03). The rete length in the chronic model was significantly higher than in the acute model (593.1 +/- 39.9 vs 401.3 +/- 65.2 pixel; P < .001). The average vessel diameter of the rete in the chronic group was 520 microm and 320 microm in the control animals. CONCLUSION: Increased pressure gradients and flow in the chronic swine rete AVM model may be related to increased size and decreased impedance. The resulting hemodynamic changes reflect a true flow-induced vascular remodeling rather than a simple change related to aging and size of the animal.

The unilateral spatial neglect phenomenon in patients with arteriovenous malformations of deep brain structures.

Clinical-neuropsychological investigations were performed in 187 patients with arteriovenous malformations (AVM) of deep brain structures; 28 had AVM of the caudate nucleus, 35 of the thalamus, 45 of the cingulate gyrus, 43 of the hippocampus, and 36 of the corpus callosum. A total of 47 patients displayed neglect phenomena of different modalities, while unfixed neglect was demonstrated in 40 cases using special tests. The vast majority of patients showed neglect of left-sided space and the left side of the body, while only three patients showed right-sided neglect. These three patients had signs of left-handedness. In the development of neglect in all patients was associated with post-hemorrhagic or post-operative damage to the white matter (the projections of sensory bundles of the parietal and occipital lobes, the periventricular white matter) or the thalamus and corpus callosum. In hemispheric lesions, neglect developed on the background of the corresponding derangements (hemihypesthesia hemianopsia) and were of the same modality. In cases of damage to the corpus callosum, neglect could develop without accompanying sensory disturbances or the phenomenon could occur on different sides (in cases of simultaneous left hemisphere damage). This supports the independent nature of the neglect phenomenon.

Cavernous malformations of the brainstem: experience with 100 patients.

OBJECT: In this study the authors review surgical experience with cavernous malformations of the brainstem (CMBs) in an attempt to define more clearly the natural history, indications, and risks of surgical management of these lesions. METHODS: The authors retrospectively reviewed the cases of 100 patients (38 males and 62 females; mean age 37 years) harboring 103 lesions at treated a single institution between 1984 and 1997. Clinical histories, radiographs, pathology records, and operative reports were evaluated. The brainstem lesions were distributed as follows: pons in 39 patients, medulla in 16, midbrain in 16, pontomesencephalic junction in 15, pontomedullary junction in 10, midbrain-hypothalamus/thalamus region in two patients, and more than two brainstem levels in five. The retrospective annual hemorrhage rate was most conservatively estimated at 5% per lesion per year. Standard skull base approaches were used to resect lesions in 86 of the 100 patients. Intraoperatively, all 86 patients were found to have a venous anomaly in association with the CMB. Follow up was available in 98% (84 of 86) of the surgical patients. Of these, 73 (87%) were the same or better after surgical intervention, eight (10%) were worse, and three (4%) died. Two surgical patients were lost to follow-up review. Incidences of permanent or severe morbidity occurred in 10 (12%) of the surgically treated patients. The average postoperative Glasgow Outcome Scale score for surgically treated patients was 4.5, with a mean follow-up period of 35 months. CONCLUSIONS: The natural history of CMBs is worse than that of cavernous malformations in other locations. These CMBs can be resected using skull base approaches, which should be considered in patients with symptomatic hemorrhage who harbor lesions that approach the pial surface. Venous anomalies are always associated with CMBs and must be preserved.

Arteriovenous malformation and diaschisis.

We investigated the haemodynamic dysfunction and secondary thalamic and brainstem atrophy in 24 patients with angiographically proven cerebral arteriovenous malformations (AVM) and no clinical history of cerebral haemorrhage. Cerebral blood flow (CBF) was measured by the method using either stable Xenon or single photon emission computerized tomography (SPECT). Morphological changes in the thalamus and brainstem were evaluated by magnetic resonance imaging (MRI). Two factors are considered to influence hypoperfusion in the ipsilateral cerebral and contralateral cerebellar hemisphere and secondary atrophy of the thalamus and brainstem. One is the size of the nidus and the other is the involvement of the basal ganglia. It is presumed that continuous haemodynamic stress over a long period of time may cause irreversible histological changes in areas remote from the lesion, especially in the AVM which demonstrates involvement of the basal ganglia or a large nidus.

Argon laser-induced arterial photothrombosis. Characterization and possible application to therapy of arteriovenous malformations.

The common carotid, femoral, and middle cerebral arteries in the rat have been occluded thrombotically by means of a rose bengal dye-sensitized photochemical reaction initiated in vascular endothelium by the 514.5-nm beam of an argon laser, focused for maximum excitation efficiency of the photosensitizer according to a derived criterion. The total energy required for vessel occlusion was approximately 1 joule (J) for the middle cerebral artery and 140 to 180 J for the femoral and carotid arteries. At energy fluences (energy deposited per unit area) of 3.5 kJ/sq cm for the middle cerebral artery and 35 kJ/sq cm for the larger arteries, occlusion was observed within 3 minutes. The middle cerebral artery thrombus consisted entirely of aggregated platelets; in the larger arteries the thrombi were composed of platelet aggregates and groups of red blood cells interspersed within a matrix of coagulum. Vessels irradiated similarly in the absence of rose bengal dye displayed no morphological or functional damage. Because the photochemical reaction is mediated by electronic-state transitions, the process of photothrombosis (as opposed to photocoagulation) can be initiated in vessels with high flow rates without the requirement of increased temperature. The photothrombotic technique may be useful in the treatment of arteriovenous malformations owing to its significant enhancement of the efficiency and permanency of vessel occlusion.

Interhemispheric approach for the surgical removal of thalamocaudate arteriovenous malformations.

A series of 250 surgically treated cerebral arteriovenous malformations (AVM's) is presented, in which 22 lesions were located primarily in the thalamus and caudate nucleus. A standardized interhemispheric approach through the posterior corpus callosum and into the atrium of the lateral ventricle was utilized for the surgical removal of these AVM's. Total removal was confirmed by angiography in 18 patients; removal was subtotal in four cases. There were no deaths in this group of patients. Disturbances of recent memory pre- and postoperatively were seen in half of the patients, but most of these deficits were temporary. Other complications included: postoperative homonymous hemianopsia (six cases), transient hemiparesis (three cases), hemisensory loss (two cases), Parinaud's syndrome (one case), and recurrent hemorrhage 2 years after surgery (one case). All 22 patients returned to their previous occupations and are leading independent lives. The results of this experience indicate that thalamocaudate AVM's can be effectively treated by resection.

Spontaneous thrombosis of deep cerebral veins: a complication of arteriovenous malformation.

An uncommon type of stroke in children is presented. An intracranial arteriovenous malformation in a 13-year-old boy spontaneously occluded about 22 months after surgical intervention. Precipitating factors, such as bacterial infections, could not be demonstrated in this patient, who had been attending school since the time of the craniotomy. The histological features of venous encephalomalacia in the galenic territory are contrasted with hemorrhagic encephalomalacia as seen after arterial occlusions: in the former, hemorrhages are more widespread and edema is more pronounced.