Microsurgical Operative Treatment To Tentorial Meningiomas (58 Cases Report)

Objective: (1).To conclude the clinical and anatomic characters of tentorial meningiomas. (2).To seek classification method for the tentorial meningiomas and how to choose surgical approaches. (3).To summarize operative skills in order to enhance the total resections rates, lower the mortality and disability rates.Methods: Review the 58 cases of tentorial meningiomas from July,2003 to June 2008 in our department and analyze their epidemiology, clinical symptoms, neuroimaging features, surgical approaches and curative effects. All the 58 cases were operated on using microsurgical techniques under general anesthesia. According to Aziz classification, we choose propotional operative routes, and control the extent of resection with syncretio and erosion. There are 28 cases with the infratentorial-supracerebellar approach, 5 cases with retrosigmoid approach, 14 cases with occipital transtentorial approach, 9 cases with infratentorial- supracerebellar and occipital transtentorial approaches, 2 cases with fronto- temporal approach, 6 cases with cornu coccipitale ventriculi lateralis prickings.Results: We have 55 cases with Simpson I or II grade resection, 3 cases with Simpson III grade resection. 29 cases have the venous sinus invasions. 22 cases have the transverse sinus invasions. 2 of the 58 cases died and 3 cases appeared new neurological deficits. We have 42 cases followed up for 6 to 60 months, and all the patients are able to work or self-care without recurring.Discussions: Tentorial meningioma is rare and only accounts for 2%-9% of meningiomas. Most patients are among 40-60 years old with an average course of 10-35 months. 65%-85% are women. Most cases of tentorial meningiomas have no clinical symptoms or locational signs, but only appear symptoms when the diameter is above 30mm. Different symptoms depend on location of the tumor adherence, direction of growth, size of tumor body, and also will see to whether it leads to obstructive hydrocephalus, or affects the periphery structures, such as cranial nerves, cerebellum, brain stem, or occipital lobe. Symptoms are frequently to be seen as: 1. Intracranial hypertension 2. Cranial nerves damage 3. Cerebellum symptoms 4. Symptoms of brain stem compression 5. Symptoms of occipital lobe compression.According to the radiological anatomy, Aziz sorted the tentorial meningiomas into 3 groups: (1) anteromedial group comprising the anterior incisural, middle incisural, and falcotentorial meningiomas, (2) lateral group comprising the posterolateral and posteromedial meningiomas, and (3) torcular group meningiomas. And each group was further sorted to supratentorial, infratentorial and straddle types. Anterior Incisural Meningiomas are operated with the frontotemporal approach. Supratentorial type of Middle Incisural Meningiomas is operated with subtemporal craniotomy with zygomatic osteotomy, and the middle infratentorial tumors are approached with a lateral suboccipital craniotomy. Supratentorial type of the Falcotentorial Meningiomas is approached with occipital transtentorial way, and infratentorial type is treated with suboccipital approach. Supratentorial type of the Posterolateral Tentorial Meningiomas is accessed via the posterior subtemporal approach or the occipital transtentorial approach, and infratentorial type is approached via retrosigmoid approach. Posteromedial meningiomas are approached using an occipital transtentorial approach for tumors in the supratentorial space and using a suboccipital supracerebellar infratentorial approach for tumors with infratentorial extension. Torcular meningiomas are approached via a combined supracerebellar- infratentorial and occipital-transtentorial approach. Lesions that span the infratentorial and supratentorial space to a significant degree are approached by combining the approach to the supratentorial aspect of the tumor with the infratentorial approach.Safe surgical resection should be the principal goal in treating tentorial meningiomas. Safe resection is defined as either gross total resection with preservation of neurovascular structures or subtotal resection in which residual tumor remains attached to neurovascular structures for subsequent radiation therapy or observation. Good preoperative preparation is especially important, including studying the imaging files such as CT/MRI, learning the attachment of tumor, direction of growth, adjoin structures, feeding arteries, invaded venous sinus. CA, MRA and DSA could show the feeding arteries and venous returning, so we can block up the blood feeding of tumor to reduce bleeding early in the operation. Further, we could learn how the deep veins and venous sinus are invaded, and then deal with them well in the operation. We can make the operation easier with preoperative embolizationvia via arteriography.Mastering good microsurgical techniques and relevant microdissection knowledge is basic to do a surgical resection for tentorial meningiomas. Radiotherapy can be used after surgical resection of tentorial meningiomas that are far from the brain stem.Tentorial meningiomas often invade or originate from the venous sinus. It is generally agreed to fully resect the venous sinus that is completely obstructive. Patients may suffer from serious complications because of thrombosis of venous sinus, though it is dealt with neoplasty when the venous sinus is invaded. It is widely agreed to preserve the venous sinus that is invaded but still open.Conclusion: 1. Using microsurgical technique, understand relevant microdissection, choose right approach and good preoperative preparation will enhance the cure rate, reduce operative mortality and complications, decrease regrowth. 2. The method to sort tentorial meningiomas by radiological anatomy is brief, practical, and easy to learn. 3. We should control the resection extent well. Safe surgical resection is the chief objective. It is right to try to resect tumors completely, but it will be also appropriate to do subtotal resection when it is hard to clear the tumor. The remained tumors still attach to nerves and vessels, so radiotherapy or observation is needed after surgical resection.