The Anatomical And Clinical Study Of Treating Tumors At The Trigone Of The Lateral Ventricle Using Contralateral Posterior Interhemispheric Transfalcine Transprecuneus Approach

Objective:Via anatomical study, to comprehend the anatomy of the trigone of the lateral ventricle and adjacent structures and the surgical corridors of various surgical approach, to find appropriate anatomic landmark on the medial surface of parieto-occipital lobe for interhemispheric approaches, to study the distributing pattern of bridging veins that drain into superior sagittal sinus in the parieto-occipital region, and to compare the exposure range of all the interhemispheric approaches targeted at the trigone and provide anatomical basis for designing and selecting approaches in clinical practice.Methods:By means of regional axonal and coronal sectional anatomy, regional anatomy was performed on 5 formalin-fixed and silicone-perfused Chinese cadaveric heads in order to observe the anatomy of the trigone of lateral ventricle and adjacent structures and the surgical corridors of various approaches targeted at the trigone.Craniotomies preserving the lambdoid suture were performed on 5 formalin-fixed and silicone-perfused Chinese cadaveric heads. In each specimen, the distance between the posterior fontanelle and torcular was measured, the numbers and loctions of bridging veins on either side of the midline were recoeded, the distance between the points where bridging veins joined the superior sagittal sinus and the posterior fontanelle was also measured and recorded.The brains of 5 formalin-fixed and silicone-perfused Chinese cadaveric heads were taken out of the cranium and dura, the medial surface of the parieto-occipital lobe was observed. Special attention was paid to splenium of corpus callosum, calcarine sulcus, parieto-occipital sulcus, subparietal sulcus, precuneus, isthmus of the cingulated gyrus.With the help of navigation, different types of interhemispheric approaches were demonstrated in 5 formalin-fixed and silicone-perfused Chinese cadaveric head. The navigation bar was used to represent the visual line in surgical procedure. The maximum values of the angle between the navigation bar and the median sagittal plane represent the maximum exposure to the lateral direction achieved by a surgical approach. The maximum exposure of each interhemispheric approach was calculated and compared with each other.Results:The trigone of the lateral ventricle is situated in the central core of the cerebrum. Numerous important structures are located around the trigone or in the surgical corridors leading to it. The trigone of the lateral ventricle can be approached with a lateral transcortical or medial interhemispheric approach.The mean distance between the posterior fontanelle and torcular was 45.8±3.1mm, no bridging veins were found draining into the superior sagittal sinus between the posterior fontanelle and torcular. The mean number of bridging veins joining the superior sagittal sinus before the posterior fontanelle and within the distance equal to that between the posterior fontanelle and torcular was 1.4±0.5 on the left,1.6±0.5 on the right, and 3.0±0.6 on both sides. The mean distance between the points where bridging veins joined the superior sagittal sinus and the posterior fontanelle was34.0±8.8mm on the left,30.5±10.2 mm on the right, and 32.1±9.7mm on both sides. The mean distance between the posterior fontanelle and the point where the first bridging vein before the posterior fontanelle joined the superior sagittal sinus was 29.6±6.0mm on the left,25.5±9.5mm on the right, and 21.9±7.0mm on both sides.On the medial surface of parieto-oocipital lobe, the average length of the posterior portion of calcarine sulcus was 32.9+2.7mm, the average length of the parieto-occipital sulcus was 37.2+1.8mm. The parieto-occipital sulcus intersected with calcarine sulcus and divided the calcarine sulcus into posterior and anterior portion. The number and morphology of subparietal sulcus were not constant. Therefore subparietal sulcus cannot be used as anatomic landmark of the boundary between precuneus and isthmus of the cingulated gyrus.The maximum exposure, represented by the angle between the view line and the median sagittal plane, of the homolateral transcallosal approach, the homolateral transcingualte approach, the homolateral transprecuneus approach, the contralateral transcallosal approach, the contralateral transcingualte approach, the contralateral transprecuneus approach were 13.0±3.7°,24.8±5.8°,38.5±5.9°,31.4±3.4°, 43.2±5.3°,57.0±6.6° respectively. Between the homolateral and contralateral approaches the contralateral ones provided better lateral exposure. As for the position of the cortical or callosal insision, those with a shorter distance to the border between the medial and lateral surface of the parieto-occipital lobe had a better lateral exposure. All comparison is of statistical significance. Navigation shift tended to be created with a homolateral approach compared with using a contralateral approach.Conclusion:The trigone of lateral ventricle is situated deeply within the cerebrum. A number of important structures are either in close relationship with the trigone or in the surgical corridor leading to the trigone. The trigone of the lateral ventricle can be approached by numerous surgical approaches. Parieto-occiptal sulcus can serve as a reliable anatomic landmark during surgeries targeted at the trigone of the lateral ventricle. The subparietal sulcus, however, is not able nor required to serve as the anatomic landmark of the boundary between the precuneus and isthmus of the cingulated gyrus. The bridging veins in the parieto-occipital region tend to join the superior sagittal sinus before the posterior fontanelle, therefore it is safer to perform craniotomy behind the lambdoidal suture rather than behind the lambdoidal suture. Among interhemispheric approaches targeted at the trigone of the lateral ventricle, while contralateral approaches provide better exposure in the lateral direction; those with a shorter distance to the border between the medial and lateral surface of the parieto-occipital lobe provide a better lateral exposure; contralateral approach is advantageous concerning reducing retraction on normal brain tissue and maintain the accuracy of intra-operative navigation, and homolateral approach, with no need for falcine incision, has a lower rate of venous sinus damage.Part Ⅱ Clinical Study of Treating Tumors at the Trigone of the Lateral Ventricle using Contralateral Posterior Interhemispheric Transfalcine Transprecuneus ApproachObejective:To collect and summarize the clinical data of cases of tumors at the trigone of the lateral ventricle using contralateral posterior interhemispheric transfalcine transprecuneus approach and exploit the effectiveness and safety of this new approach.Methods:The clinical data of ten cases of cases of tumors at the trigone of the lateral ventricle using contralateral posterior interhemispheric transfalcine transprecuneus approach at the Neurosurgical Department of Zhongshan Hospital Fudan University (9 case) and Neurosurgical Department of Yinzhou Hospital Affiliated of Ningbo University (1 case) from April 2011 to April 2013 were collected. The surgical outcome, complication rate and technical key points were analyzed.Results:In this series of 10 cases, surgeries for 9 achieved total resection and that for 1 achieved subtotal resection, resulting in a total resection rate of 90%. There was no mortality.9 of the procedures were performed under microscope and assisted with endoscope,1 was performed only under endoscopic view. The histopathological outcomes included 7 meningeomas (5 WHO grade Ⅰ and 2 WHO grade Ⅲ),1 cavernous hemangioma,1 Choroid plexus papillary carcinoma and 1 metastatic mucinous adenocarcinoma.2 of the meningeomas were recurrent cases, which progressed from WHO grade I to WHO grade Ⅲ compared with the pathological results of previous surgeries. Follow-up periods ranged from 3 to 26 months, with an average of 14.1 months. Postoperatively, the 2 cases of anaplastic meningeomas and metastatic mucinous adenocarcinoma underwent radiotherapy. The mRS score of all cases improved after surgery, except 2 that stayed unchanged. During follow-up, no recurrence was found in cases of benign tumors, including 5 WHO grade Ⅰ meningeomas and 1 cavernous hemangioma. One of the two anaplastic meningeomas was found to have CSF dissemination 12 months postoperatively, and no recurrence was detected in the remaining case till last follow-up. Enhancing nodules were found in the temporal horn of the lateral ventricle homolateral to the tumor at 9 months postoperatively in the case of metastatic mucinous adenocarcinoma, complicated with enlarged temporal horn, and the patient received whole brain radiation therapy again. No recurrence was found in the case of Choroid plexus papillary carcinoma at 6 months follow-up.Conclusion:Contralateral posterior interhemispheric transfalcine transprecuneus approach is a safe and effective procedure to treat tumors at the trigone of the lateral ventricle, including malignant lesions like recurrent anaplastic meningeomas and metastatic mucinous adenocarcinoma. Recurrent trigonal meningeomas tend to progress to a more malignant form, and special attention should be placed on finding recurrent tumors and disseminated lesions during follow-up. The assistance provided by endoscope in microscopic surgeries can help to resect residual tumor and to clean blood clot. Pure endoscopic contralateral posterior interhemispheric transfalcine transprecuneus surgery is also a practicable and effective procedure to treat trigonal tumors. Attention should be paid to protect optic radiation, venous sinus, bridging veins from intra-operative injury. Choosing suited surgical approach, using multi-modal neuronavigation that combined radiological methods like DTI and MRV, can increase total resection rate and reduce surgical complications.