A combined subtemporal and transventricular/transchoroidal fissure approach to medial temporal lesions

OBJECTIVE: To minimize therapeutic morbidity such as cognitive function disturbance and vascular injury to perforating arteries, preoperative functional mapping of the basal temporal lobe functions was performed and the medial temporal lesions were resected via a combined subtemporal and transventricular/transchoroidal fissure approach. METHODS: Twenty-one patients with medial temporal lesions including tumors, arteriovenous malformations, and medial temporal lobe epilepsy underwent operation. The neurovascular structures in the ambient cistern were first dissected free from the medial temporal lobe with a conventional subtemporal approach. Then, the temporal horn was opened through the basal surface of the temporal lobe. Finally, the ambient cistern was accessed from the temporal horn through the choroidal fissure. In five patients whose lesions were revealed to be located on the dominant side by preoperative intracarotid amytal administration test (Wada test), functional mapping of the basal temporal lobe language cortex was monitored for 1 week by use of a subdural electrocorticogram grid before the extirpation surgery. The entrance point from the temporal base to the temporal horn was determined by the result of the functional mapping. RESULTS: The lesions were resected safely and completely in all cases. Language and cognitive functions were preserved even in patients with the basal language area on the dominant side. CONCLUSION: Surgeons can confirm the important neurovascular structures from the subtemporal route and from the transtemporal horn route by a combined subtemporal and transventricular/transchoroidal fissure approach. This approach is especially effective for avoiding ischemic complications by allowing direct confirmation of the anterior choroidal and thalamoperforating arteries.     

Microsurgical approaches to the perimesencephalic cisterns and related segments of the posterior cerebral artery: comparison using a novel application of image guidance

OBJECTIVE: To describe the exposure obtained through six approaches to the perimesencephalic cisterns with an emphasis on exposure of the posterior cerebral artery and its branches. METHODS: Dissections in 12 hemispheres exposed the crural, ambient, and quadrigeminal cisterns and related segments of the posterior cerebral artery. A Stealth Image Guidance workstation (Medtronic Surgical Navigation Technologies, Louisville, CO) was used to compare the approaches. RESULTS: The transsylvian approach exposed the interpeduncular and crural cisterns. The subtemporal approach exposed the interpeduncular and crural cisterns as well as the lower half of the ambient cistern. Temporal lobe retraction and the position of the vein of Labbé limited exposure of the quadrigeminal cistern. Occipital transtentorial and infratentorial supracerebellar approaches exposed the quadrigeminal and lower two-thirds of the ambient cistern. Transchoroidal approaches exposed the posterior third of the crural cistern, the upper two-thirds of the ambient cistern, and the proximal quadrigeminal cistern. Transchoroidal approaches exposed the posterior portion of the P2 segment (P2p) in 9 of 10 hemispheres and were the only approaches that exposed the lateral posterior choroidal arteries and the plexal segment of the anterior choroidal artery. Occipital transtentorial and infratentorial supracerebellar approaches provided access to the P3 segment in all cases and exposed the P2p segment in 4 of 10 hemispheres. The subtemporal approach provided access to the cisternal and crural segments of the anterior choroidal and medial posterior choroidal arteries and exposed the P2p segment in 3 of 10 hemispheres. CONCLUSION: Surgical approaches to lesions of the perimesencephalic cisterns must be tailored to the site of the pathological findings. The most challenging area to expose is the upper half of the ambient cistern, particularly the P2p segment of the posterior cerebral artery.     

Microsurgical anatomy of the choroidal fissure

The microsurgical anatomy of the choroidal fissure was examined in 25 cadaveric heads. The choroidal fissure, the site of attachment of the choroid plexus in the lateral ventricle, is located between the fornix and thalamus in the medial part of the lateral ventricle. The choroidal fissure is divided into three parts: (a) a body portion situated in the body of the lateral ventricle between the body of the fornix and the thalamus, (b) an atrial part located in the atrium of the lateral ventricle between the crus of the fornix and the pulvinar, and (c) a temporal part situated in the temporal horn between the fimbria of the fornix and the lower surface of the thalamus. The three parts of the fissure are the thinnest sites in the wall of the lateral ventricle bordering the basal cisterns and the roof of the third ventricle. Opening through the body portion of the choroidal fissure from the lateral ventricle exposes the velum interpositum and third ventricle. Opening through the temporal portion of the choroidal fissure from the temporal horn exposes the structures in the ambient and crural cisterns. Opening through the atrial portion of the fissure from the atrium exposes the quadrigeminal cistern, the pineal region, and the posterior portion of the ambient cistern. The neural, arterial, and venous relationships of each part of the fissure are reviewed. The operative approaches directed through each part of the fissure are also reviewed.     

The transsylvian trans-limen insular approach to the crural,ambient and interpeduncular cisterns

Summary Background. The authors introduce the transsylvian trans-limen insular approach to the crural, ambient and interpeduncular cisterns.Method. The transsylvian trans-limen insular approach was performed in 7 patients; 3 for aneurysm, 2 for isolated temporal horn hydrocephalus, one for tumour and one for an arteriovenous malformation. This approach is summarized in 4 procedures; the exposure of the inferior limiting sulcus of the insular cortex, the exposure of the inferior horn of the lateral ventricle, the dissection of the inferior part of the choroidal fissure and the splitting of the inferior border of the limen insula.Findings. Four among 7 patients underwent surgery for the lesions in the crural or ambient cistern. The other 3 patients underwent surgery for the lesion in the interpeduncular cistern. Two patients of the latter group postoperatively had temporal lobe infarction.Conclusions. The transsylvian trans-limen insular approach may be indicated for lesions in the crural and the anterior ambient cisterns, and the lesions which need wider exposure of the interpeduncular cistern. For the former lesions, this approach can afford good results. For the latter lesions, careful brain retraction and some other techniques to avoid temporal lobe infarction are necessary. Further neuropsychological assessment should be also necessary to prove the validity of this approach.     

Clipping of an aneurysm of the posterior cerebral artery via the transcortical transchoroidal-fissure approach: a case report

A 65-year-old woman suddenly developed severe headache with nausea. Computed tomographic scans revealed a diffuse subarachnoid hemorrhage with thick hematoma of the left ambient cistern. Cerebral angiogram did not show any aneurysm. On the 7th day after admission, 3D-CT angiogram showed an aneurysm of the left posterior cerebral artery. On the 14th day, axial and coronal magnetic resonance images showed the aneurysm, surrounding structures and the choroidal fissure. On the 26th day after admission, successful neck clipping was performed through the temporal horn via the inferior temporal gyrus. The postoperative course was uneventful except for transient aphasia. This approach may be preferable in such cases, because it protects the brain from the detrimental effects of strong temporal retraction and provides a wider working space. In our case, thin slice MRI and MRA showing the aneurysm in the ambient cistern and the choroidal fissure were useful for deciding the appropriate approach.     

Case of clipping of a ruptured aneurysm of the posterior cerebral artery (P2) via the transchoroidal-fissure approach

A 59-year-old female was found to be drawn in a swimming pool and transferred to our hospital. The patient was comatose on admission (Hunt & Kosnk: Grade IV). Computed tomography (CT) showed diffuse subarachnoid hemorrhage (SAH) with thick hematoma in the left ambient cistern. Conventional cerebral angiography and 3D-digital subtraction angiography revealed aneurysms (ANs) of the left posterior cerebral artery (P2), and bifurcation of the left internal carotid and posterior communicating arteries (IC-PC). Successful neck clipping was performed the same day through the temporal horn via the insula for ruptured P2 AN, and the non-ruptured IC-PC AN was also obliterated using a pterional approach. Postoperative course was uneventful except for initial disturbance of consciousness and aphasia. The patient was discharged with no neurological deficit 1 month after surgery. This approach may be preferable in cases involving high positioned PCA AN in the ambient cistern, particularly in the acute phase of severe SAH, as the brain is protected from the detrimental effects of strong temporal retraction and a wider working space is provided.     

Anterior thalamoperforating artery aneurysm associated with internal carotid artery occlusion: case report.

OBJECTIVE AND IMPORTANCE: We describe a rare case of a ruptured distal anterior thalamoperforating artery aneurysm associated with right internal carotid artery occlusion. CLINICAL PRESENTATION: A 59-year-old woman experienced sudden occipital headache, vomiting, and subsequent coma as a result of massive intraventricular hemorrhage. An initial angiogram revealed only an occlusion of the right internal carotid artery just distal to the posterior communicating artery. Repeat angiography 1 month later, however, revealed a saccular aneurysm at a distal anterior thalamoperforating artery in addition to the occlusion of the internal carotid artery. INTERVENTION: We approached this aneurysm through the right temporal horn after opening the ambient cistern. The aneurysm, which was located in the brain parenchyma just medial to the temporal horn, was successfully resected. CONCLUSION: This rare aneurysm probably developed as a result of hemodynamic stress on the anterior thalamoperforating artery after occlusion of the internal carotid artery and/or secondary to chronic hypertension.     

How I do it – selective amygdalohippocampectomy via subtemporal approach

Background

Surgery is superior over medicamentous treatment of pharmacoresistant mesial temporal lobe epilepsy caused by hippocampal sclerosis. The armamentarium of surgical procedures comprises standard temporal lobectomy and more selective procedures. Selective amygdalohippocampectomy can be performed via transcortical, transsylvian or subtemporal approach.

Method

Describe the selective amygdalohippocampectomy through the subtemporal approach

Conclusion

After the detailed preoperative epilepsy evaluation, surgery can be offered to pharmacoresistant epilepsy patient with hippocampal sclerosis. Selective amygdalohippocampectomy can be safely performed through the subtemporal approach. The good knowledge of the mesial temporal lobe anatomy is necessary when performing this procedure.

Key points

? Perform the subtemporal craniotomy with additional bone removal up to temporal petrous part to minimize retraction of the brain. ? Release the CSF from the subarachnoid sulcal space in order to relax the temporal lobe. Dissect the arachnoid around basal temporal veins and protect them with hemostatic material in order to avoid vein rupture. ? After gyrus fusiformis corticotomy, always follow the white matter in order to enter the temporal horn. ? Place the self-retraining retractor gently to secure an unobstructed view of the intraventricular mesial temporal lobe structures. ? Visualize the choroid plexus and the inferior choroidal point. They represent the two most important landmarks. ? While performing the anterior disconnection the goal is to reach the arachnoid of the interpeduncular and crural cistern medially and the tentorial edge laterally. ? Follow the tentorial edge and the arachnoid of the temporal base to securely perform the lateral disconnection. ? Perform the posterior disconnection at the level of the mesencephalon superior colliculi. ? During the medial disconnection the dissection of the arachnoid of the hippocampal sulcus must be done as close to the hippocampus as possible in order to avoid damage to the brain stem perforators or the loop of the anterior choroidal artery. ? Knowledge of mesial temporal lobe anatomy is crucial.     

Operative neurosurgery: personal view and historical backgrounds (4). Selective amygdalohippocampectomy SAHE

Selective amygdalohippocampectomy SAHE has been pioneered by Yasargil et al in the mid 1970 within the scope of surgical treatment for intractable mesial temporal lobe epilepsy MTLE. In this article, the author has emphasized microsurgical points to be kept in mind in carrying out the procedure from the experience of just more than 200 surgeries performed by himself during the last 14 years. Historical backgrounds of development of this technique, necessary topographic anatomy, perioperative management and our results were also presented. (1) Simple temporal lobectomy (S-lobectomy)--> Epilepsy temporal lobectomy (E-lobectomy)--> SAHE has been the way of development, in which the amygdala and hippocampus are resected together at Elobectomy while not at S-lobectomy. At SAHE, the whole temporal lobe remains intact in order to preserve cognitive function as much as possible, although part of the temporal stem is cut as transsylvian access rout to the temporal horn and the hippocamopus. For a novice of this surgery, it is recommended to begin with S-lobectomy then proceed to SAHE after having trained himself by cadaver dissection. (2) Among several approaches for hippocampectomy, the transsylvian SAHE is considered to remain as a standard access to the amygdala and hippocampus also on the dominant hemisphere. Furthermore this approach can be used for other fields of neurosurgery: tentorial edge meningiomas, P2-P3 junction aneurysms and lesions of the insula and basal ganglia. (3) As for the method of SAHE, after having entered through the temporal stem into the temporal horn, the hippocampus is dissected between the medial margin of the collateral eminence and the tela chorioidea -fimbria hippocampi. By this way, most of the amygdala and anterior 2/3 of the hippocampus can be extirpated. En bloc resection enables precise histological examination and further molecular biological research considered to be indispensable for understanding the pathophysiology and treatment of intractable MTLE. (4) Following structures should be preserved at the time of SAHE. Laterocaudal group in the vicinity of the tentorial margin: Oculomotor nerve, posterior cerebral artery PCA with posterior communicating artery Pcom, medial posterior choroidal artery, A. temporalis posterior, trochlear nerve. Mediocranial group in the vicinity of the brain stem: Crus cerebri, AchoA, Tractus opticus, A. parietooccipitalis, Corpus geniculatum laterale. (5) In order to avoid surgical complications to be kept in mind. 1: AchoA should be preserved at any cost. 2: hemorrhagic diathesis due to longstanding medication of antiepileptics especially valproate should be corrected with fresh frozen plasma FFP, thrombocyte-preparation and/or Minirin. (6) Good results (Engel I+II) to stop or alleviate intractable seizures remarkably could be obtained in more than 80% of patients in our previous report and also in this series of consecutive 190 cases. Strict indication based on presurgical epileptological examinations including special electroencephalography EEG leading like Foramen ovale electrode, selective Wada test and interdisciplinary discussion are mandatory. These careful procedures bring good outcome by preventing complications especially postoperative deterioration of cognitive function.     

Microsurgical anatomy of the interpeduncular cistern and related arachnoid membranes

OBJECT: The goal of this study was to investigate the microsurgical anatomy of the interpeduncular cistern and related arachnoid membranes. METHODS: The interpeduncular cistern and related arachnoid membranes were studied in eight Han Chinese adult human cadaveric brains with the aid of an operating microscope. The interpeduncular cistern is one area in the cranial cavity in which the arachnoid membranes and trabeculae are extremely luxuriant and complicated. The Liliequist membrane, the medial pontomesencephalic membrane, and the lateral pontomesencephalic membranes form the walls of the interpeduncular cisterns. The basilar artery (BA) bifurcation membrane, posterior perforated membrane, and arachnoid trabeculae fill the cistern. These arachnoid membranes and trabeculae adhere to the hypothalamus, brainstem, and oculomotor nerves, and bind the bifurcation of the BA, posterior cerebral arteries, superior cerebellar arteries, posterior communicating arteries, and their perforating branches. CONCLUSIONS: Arachnoid membranes and trabeculae complicate the exposure and dissection of lesions within the interpeduncular cistern. All arachnoid membranes and trabeculae should be dissected and incised sharply during surgical procedures. The BA bifurcation membrane and the posterior perforated membrane must be incised after opening the Liliequist membrane for sufficient exposure of deep structures within the interpeduncular cistern.     

The posterior subtemporal keyhole approach combined with the transchoroidal approach to the ambient cistern: microsurgical anatomy and image-guided quantitative analysis

Purpose  

The aim of this study is to describe microsurgical anatomy and to quantitatively analyze exposure using the posterior subtemporal keyhole (PSK) approach combined with the transchoroidal keyhole (TCK) approach to the ambient cistern.     

Microanatomy of the subependymal arteries of the lateral ventricle

BACKGROUND: Scarce information about the anatomy of the subependymal arteries (SEAs) is present in the scientific literature. METHODS: Twenty cerebral hemispheres with injected arteries were microdissected, and the magnetic resonance imaging scans of 100 patients with lacunar infarcts were examined. RESULTS: The SEAs were found to range in diameter from 40 to 490 microm (mean, 149 microm) and in number between 3 and 12 (average, 5.2). Of these, numbers from 1 to 3 originated from the anterior choroidal artery (AChA), between 1 and 10 from the lateral posterior choroidal artery (LPChA), 1 from the medial posterior choroidal artery (MPChA), and 1 from the internal carotid artery. The SEAs most often arose from the choroidal branches (90%) and less frequently from the thalamic (30%), caudate (35%), or thalamocaudate twigs (20%). The SEAs of the AChA supplied the walls of the temporal horn (100%), the occipital horn (85%), and the atrium (35%). Those of the LPChA perfused the walls of the occipital horn (15%), the atrium (65%), the body of the ventricle (100%), and partially the frontal horn. The SEAs of the MPChA partially nourished the body and the frontal horn (10%). The SEAs may also occasionally supply the caudate nucleus (20%) and the stria terminalis. The anastomoses involving the SEAs were absent. In spite of this, ischemia in the territory of a single SEA was noticed in only 1% of our patients. CONCLUSIONS: The SEAs are tiny vessels that supply the walls of the lateral ventricle, as well as the caudate nucleus and the stria terminalis occasionally. The obtained anatomic data can have important neurosurgical implications in intraventricular operations.     

White matter fiber dissection of the optic radiations of the temporal lobe and implications for surgical approaches to the temporal horn

OBJECT: The aim of this anatomical study was to define more fully the three-dimensional (3D) relationships between the optic radiations and the temporal horn and superficial anatomy of the temporal lobe by using the Klingler white matter fiber dissection technique. These findings were correlated with established surgical trajectories to the temporal horn. Such surgical trajectories have implications for amygdalohippocampectomy and other procedures that involve entering the temporal horn for the resection of tumors or vascular lesions. METHODS: Ten human cadaveric hemispheres were prepared with several cycles of freezing and thawing by using a modification of the method described by Klingler. Wooden spatulas were used to strip away the deeper layers of white matter progressively in a lateromedial direction, and various association, projection, and commissural fibers were demonstrated. As the dissection progressed, photographs of each progressive layer were obtained. Special attention was given to the optic radiation and to the sagittal stratum of which the optic radiation is a part. The trajectories of fibers in the optic radiation were specifically studied in relation to the lateral, medial, superior, and inferior walls of the temporal horn as well as to the superficial anatomy of the temporal lobe. In three of the hemispheres coronal sections were made so that the relationship between the optic radiation and the temporal horn could be studied more fully. In all 10 hemispheres that were dissected the following observations were made. 1) The optic radiation covered the entire lateral aspect of the temporal horn as it extends to the occipital horn. 2) The anterior tip of the temporal horn was covered by the anterior optic radiation along its lateral half. 3) The entire medial wall of the temporal horn was free from optic radiation fibers, except at the level at which these fibers arise from the lateral geniculate body to ascend over the roof of the temporal horn. 4) The superior wall of the temporal horn was covered by optic radiation fibers. 5) The entire inferior wall of the temporal horn was free from optic radiation fibers anterior to the level of the lateral geniculate body. CONCLUSIONS: Fiber dissections of the temporal lobe and horn demonstrated the complex 3D relationships between the optic radiations and the temporal horn and superficial anatomy of the temporal lobe. Based on the results of this study, the authors define two anatomical surgical trajectories to the temporal horn that would avoid the optic radiations. The first of these involves a transsylvian anterior medial approach and the second a pure inferior trajectory through a fusiform gyrus. Lateral approaches to the temporal horn through the superior and middle gyri, based on the authors' findings, would traverse the optic radiations.     

Distal anterior choroidal artery aneurysms

BACKGROUND: Distal AChoA aneurysms are quite rare. Only 12 operated cases have been reported in the English medical literature. Treatment of these aneurysms is also difficult because of their deep location, small size, and angioarchitecture. METHODS: The authors report 2 additional patients with aneurysms, arising from the distal AChoA and located within the temporal horn of the lateral ventricle. In the first patient, the aneurysm could also be visualized with CTA, which is the first demonstration in the literature. RESULTS: The aneurysms were explored and resected via a transtemporal/ventricular approach in both patients. One patient was discharged as neurologically intact and the other died because of severe vasospasm. CONCLUSIONS: The conclusions drawn from our experience and a comprehensive review of the literature include the following: (1) A distal AChoA aneurysm should be considered in patients with isolated medial temporal intracerebral hematoma with intraventricular extension. (2) These aneurysms are frequently very small (<5 mm). Therefore, they cannot be detected on initial angiograms in some cases. (3) These small aneurysms cannot be usually clipped without sacrificing the parent artery. (4) Sacrificing distal AChoA (beyond the plexal point) does not usually cause any neurological deficit, but, whenever possible, this artery should be preserved.     

Arteries and veins of the lateral ventricle

Tumors of the frontal horn of the lateral ventricle (LV) are only supplied by the posteromedial choroidal artery. Tumors of the body of the LV are supplied by the same artery. Tumors of the atrium of the LV with anterior extension are supplied by both posteromedial choroidal and posterolateral arteries. Tumors of the atrium with inferior extension are supplied by both anterior choroidal artery and posterolateral choroidal arteries. Tumors of the inferior horn are only supplied by anterior choroidal artery. The tumoral venous drainage is organized with three main groups of veins: a medial group, a lateral group and a choroidal group.     

向鞍上、鞍旁扩展的经蝶窦手术入路相关结构的显微解剖研究

目的为扩大经蝶窦手术提供蝶窦外侧壁和海绵窦内侧面观、蝶骨平台骨窗腹面观以及蝶窦后方斜坡周围的显微解剖参数。方法20具干颅骨漂白标本(40侧)用于观察入路相关的骨性解剖结构;15具成人头颅灌注标本(30侧)模拟扩大经蝶窦入路,研究垂体周边解剖结构的位置关系,测量相应的距离或手术相关角度。同时,利用血管铸型技术,对鞍周静脉窦及动脉分支进行形态学观察。结果后组筛窦形成蝶旁、蝶上筛房,对扩大经蝶窦入路术中视野显露有直接影响。视神经管颅口内侧缘间距为(15.7±3.2)mm,鞍结节处颈内动脉间距为(13.9±3.8)mm,鞍结节后缘与筛板后缘之间的距离平均为(23.3±3.2)mm,视神经管与矢状面夹角为36.3°±1.6°。提示扩大经蝶窦手术入路相关的骨窗为“”型。结论扩大经蝶窦入路向鞍旁、鞍前、蝶骨平台扩展适合沿中线生长的的中、小型病灶。向鞍旁海绵窦扩展时,垂体与海绵窦段颈内动脉关系密切,增加施行扩大经蝶手术的风险。术中最易损伤的是颈内动脉和外展神经。     

Saccular aneurysm of the distal anterior choroidal artery--case report.

The authors report a case of a distal anterior choroidal artery aneurysm in a 75-year-old female who presented with nausea, vomiting, and severe headache. Computed tomographic (CT) scans revealed a hematoma in the right lateral ventricle and a subarachnoid hemorrhage in the right parasellar-Sylvian cistern. Cerebral angiography showed a saccular aneurysm at the right distal anterior choroidal artery. The authors intended to operate at the chronic stage, and carried out conservative management. After 1 month her condition suddenly worsened and she died, although a CT scan showed no remarkable changes. At autopsy, a pulmonary artery thrombosis was considered the cause of death. The aneurysm was identified in the temporal horn of the right lateral ventricle, and was a true aneurysm.     

Choroid plexus arteriovenous malformations.

Among 24 arteriovenous malformations (AVMs) involving the choroid plexus, 11 were plexal type AVMs predominantly located in the choroid plexus of the lateral ventricle, and 13 were parenchymal type AVMs mainly situated in the paraventricular cerebral parenchyma. 83% of all AVMs involved both the choroid plexus and the paraventricular cerebral parenchyma. Most cases presented with intracranial hemorrhage, particularly intraventricular hemorrhage. The most serious surgical problem was a small residual nidus unrecognized at the initial operation causing postoperative hemorrhage. Five parenchymal type AVMs presented residual niduses in the choroid plexus, causing death in two cases. Two plexal type AVMs resulted in residual AVMs supplied by the cisternal segment of the anterior choroidal artery, situated in the medial temporal lobe. To prevent postoperative hemorrhage from a small residual nidus, immediate postoperative angiography while the patient is still under general anesthesia should be performed to identify any residual nidus.     

Comparison of the far lateral and extreme lateral variants of the atlanto-occipital transarticular approach to anterior extradural lesions of the craniovertebral junction

OBJECTIVE: Managing lesions situated in the anterior aspect of the craniovertebral junction (CVJ) remains a challenging neurosurgical problem. The purposes of this study were to examine the microsurgical anatomy of the anterior extradural aspect of the CVJ and the differences in the exposure obtained by the far lateral and extreme lateral atlanto-occipital transarticular approaches. The far lateral approach, as originally described, is a lateral suboccipital approach directed behind the sternocleidomastoid muscle and the vertebral artery and just medial to the occipital and atlantal condyles and the atlanto-occipital joint. The extreme lateral approach, as originally described, is a direct lateral approach deep to the anterior part of the sternocleidomastoid muscle and behind the internal jugular vein along the front of the vertebral artery. Both approaches permit drilling of the condyles at the atlanto-occipital joint but provide a different exposure because of the differences in the direction of the approach. METHODS: Fifteen adult cadaveric specimens were studied using a magnification of x3 to x40 after perfusion of the arteries and veins with colored silicone. The microsurgical anatomy of the extradural aspects of the CVJ and the two atlanto-occipital transarticular approaches were examined in stepwise dissections. RESULTS: The far lateral atlanto-occipital transarticular approach provides excellent exposure of the extradural lesions located in the ipsilateral anterior and anterolateral aspects of the extradural region of the CVJ. The extreme lateral atlanto-occipital transarticular approach provides excellent exposure, not only on the side of the exposure, but also extending across the midline to the medial aspect of the contralateral atlanto-occipital joint and the lower clivus. CONCLUSION: The far lateral and extreme lateral variants of the atlanto-occipital transarticular approach provide an alternative to the transoral approach to the anterior extradural structures at the CVJ. Compared with the transoral approach, both approaches provide a shorter operative route, avoid the contaminated nasopharynx, reduce the incidence of cerebrospinal fluid leak, and are not limited laterally by the atlanto-occipital joint.     

"Tangential" resection of medial temporal lobe arteriovenous malformations with the orbitozygomatic approach

OBJECTIVE: Arteriovenous malformations (AVMs) of the medial temporal lobe are usually resected through subtemporal-transcortical approaches that provide a trajectory that is perpendicular to the plane of the AVM. The pterional approach is sometimes used for AVMs in the uncus and amygdala, but it is not recommended for AVMs in the hippocampal region because it provides a "tangential" approach with limited access to posterior feeding arteries and draining veins. The orbitozygomatic approach enhances exposure along this tangential trajectory and was used in a consecutive series of 10 patients to determine its advantages. METHODS: During a 5.7-year period, 43 patients underwent resection of temporal lobe AVMs, 10 of which were located in the medial temporal lobe (amygdala and uncus [Region A] or hippocampus, parahippocampus, and fusiform gyrus [Region B]). AVMs were evenly distributed by region and by hemispheric dominance and included two Spetzler-Martin Grade IV lesions. An orbitozygomatic approach was used in all cases. RESULTS: Complete resection was accomplished in nine patients, and one patient underwent multimodality management with postoperative stereotactic radiosurgery. Good outcomes (Rankin outcome score 相似文献