Transtentorial approach for acoustic neuroma resection

Acoustic neuroma is a common benign tumor in the brain. The incidence rate is about 8% to 12% of intracranial tumors, and 75% to 95% of the total number of tumors in the cerebellopontine angle. The tumor originates from the nerve sheath of the vestibular branch of the eighth cranial nerve and is located at the inner ear hole. Tumors usually grow in the cerebral horn of the cerebellum, and the tumor is divided into four stages according to the direction, size and clinical manifestation of the tumor. Phase 1: The tumor is small, involving only the vestibular and cochlear nerves, dizziness, dizziness, tinnitus and hearing loss. Phase 2: The tumor is about 2 cm in diameter, causing symptoms of facial nerve and trigeminal nerve damage. Phase 3: The diameter of the tumor is more than 3cm, involving the 9, 10, 11 cranial nerves, dysphagia, cough, hoarseness, and can affect the cerebellum, causing ataxia. No. 4: The tumor has oppressed the brain stem, or displaced the brain stem, causing hydrocephalus, increased intracranial pressure and brain stem symptoms. Early limited to most small acoustic neuromas in the internal auditory canal, affecting only the vestibular and cochlear nerves. CT, MRI scan combined with skull X-ray film, brainstem auditory evoked potential, etc., can be diagnosed early. The improvement of surgical methods and the application of microsurgical techniques can often achieve complete tumor resection, while preserving facial nerves. Early surgery may still restore the hearing part. However, it is sometimes difficult for a tumor to reach full cut. Familiar with the local anatomy of the cerebellopontine angle and the selection of appropriate surgical methods, as well as intraoperative facial nerve monitoring, is necessary to improve the success rate of surgery and facial nerve retention. Treating diseases: acoustic neuroma Indication Transcranial approach for auditory neuroma resection is applicable to: 1. The acoustic neuroma is huge in volume and has grown into the middle cranial fossa to the midline and through the cerebellar hiatus. 2. The auditory neuroma was operated by one side of the suboccipital mastoid, and failed to reach the full cut. The remaining brain nodules on the upper part of the cerebral horn and the cerebellar lobes of the cerebellum were used to compress the brain stem. Contraindications Late acoustic neuroma has severe brain stem damage and is exhausted in the body. Preoperative preparation If the intracranial pressure is significantly increased, continuous drainage of the ventricle should be done before surgery. Surgical procedure Do the dome pillow After the scalp incision is self-twisting, it bypasses the top nodule, turns to the occiput along the sagittal line, and then reaches the mastoid along the upper line. The flap is turned over the pillow, and 5 to 6 holes are drilled by the incision to form a bone flap, which is turned to the temporal side. 2. Exposure of the tumor The posterior part of the temporal lobe and the occipital lobe are lifted along the rock bone, and the brain tissue is retracted with a serpentine fixed retractor, and enters the cerebellar meridian region along the cerebellum. The cerebellum sometimes contains enlarged veins leading to the superior sinus and straight sinus, and there is a bridge vein and occipital lobes. The latter should be cleaved after electrocoagulation. The upper pole of the acoustic neuroma can be found in the cleft hole area of the cerebellum. The tumor was nodular, and the cranial line of the cerebellum was pulled by silk thread, and the cerebellum was cut 1 cm behind the rock bone. Open the cerebellum, the front pole of the acoustic neuroma and the main body of the tumor. The midbrain and pons are pushed back and forth by the tumor, and the relationship between the tumor and the trigeminal nerve root, abductor nerve, posterior cerebral artery and superior cerebellar artery is determined. 3. Resection of the tumor Open the arachnoid membrane of the ring pool, enter the ring pool and the bridge pool, separate the front pole of the tumor and its supply artery branch, and cut it one by one when entering the tumor. The inner side of the tumor is freed to separate from the trigeminal nerve root and brain stem. The envelope and blood vessels are electrocoagulated on top of the tumor, and then the tumor is incised, and most of the tumor tissue is excised from the envelope. If the tumor has a soft texture, it is easy to scrape or aspirate, and the bipolar coagulation or cotton pad is used to stop bleeding. If the tumor is tough, it needs to be cut with a sharp knife. After the tumor volume shrinks and the capsule partially collapses, the lower end of the tumor is continued. The electrocoagulation is cut off into the blood supply artery branch of the tumor, so that most of the tumor is free, and finally the tumor is released to the inner ear hole. In the free process, the tumor is gently pulled backwards and the surface nerve is located to detect the facial nerve located at the leading edge of the tumor. Generally, the nerve is compressed in an arc shape, and the facial nerve is carefully separated from the front of the tumor and protected. The detached tumor was excised in sections. The residual tumor tissue in the inner ear hole can be removed by removing the posterior wall of the inner ear hole. 4. Wash the wound, the cerebellar incision is not sutured, and the drainage tube is placed in the bridge pool for closed drainage. The dura mater of the occipital apex was sutured and suspended to stop bleeding, and the incision was sutured layer by layer. complication 1. Meningitis: postoperative local compression and dressing is not enough, forming a pseudocyst, secondary infection. 2. Facial nerve injury: This complication has been significantly reduced under the application of microsurgical techniques. 3. Brain stem injury: The surgery directly damages or damages the supply artery. 4. The 9th and 10th cranial nerve injuries. 5. The 5th and 7th cranial nerve injuries cause corneal ulcers.