Michihiro Kohno

OBJECTIVE: Surgery for tumors around the jugular foramen has significant risks of dysphagia and vocal cord palsy due to possible damage to the lower cranial nerve functions. For its treatment, long-term tumor control by maximum resection while avoiding permanent neurological damage is required. To accomplish this challenging goal, the authors developed an intraoperative continuous vagus nerve monitoring system and herein report their experience with this novel neuromonitoring method. METHODS: Fifty consecutive patients with tumors around the jugular foramen (34 jugular foramen schwannomas, 11 meningiomas, 3 hypoglossal schwannomas, and 2 others) who underwent microsurgical resection under continuous vagus nerve monitoring within an 11-year period were retrospectively investigated. Evoked vagus nerve electromyograms were continuously monitored by direct 1-Hz stimulation to the nerve throughout the microsurgical procedure. RESULTS: The average resection rate was 96.2%, and no additional surgery was required in any of the patients during the follow-up period (average 65.0 months). Extubation immediately after surgery and oral feeding within 10 days postoperatively were each achieved in 49 patients (98.0%). In 7 patients (14.0%), dysphagia and/or hoarseness were mildly worsened postoperatively at the latest follow-up, but tracheostomy or gastrostomy was not required in any of them. Amplitude preservation ratios on intraoperative vagus nerve electromyograms were significantly smaller in patients with postoperative worsening of dysphagia and/or hoarseness (cutoff value 63%, sensitivity 86%, specificity 79%). CONCLUSIONS: Intraoperative continuous vagus nerve monitoring enables real-time and quantitative assessment of vagus nerve function and is important for avoiding permanent vagus nerve palsy, while helping to achieve sufficient resection of tumors around the jugular foramen.

Background Although many reports state that only the lateral suboccipital retrosigmoid approach (LSO) should be used for removal of cerebellopontine angle (CPA) epidermoid cysts, it is preferable to use various surgical approaches as appropriate for each patient, for radical resection with an optimal operative field under direct visualization, and for the preservation of cranial nerve (CN) functions. In the present study, we hence focused on the importance of surgical approach selection for removal of CPA epidermoid cysts and analyzed the results of CPA epidermoid cysts after surgery in our series. Methods Fifty-four patients who underwent surgery for CPA epidermoid cysts were retrospectively analyzed, regarding their surgical approaches, removal rates, preservation rates of CN function 1 year after surgery, and recurrence. Surgical approaches were selected for patients according to the size and extension of the tumor. Results Surgical approaches consisted of LSO (20 cases), anterior transpetrosal approach (ATP; 3 cases), combined transpetrosal approach (27 cases), and ATP + LSO (4 cases). Mean tumor content removal and capsule removal rates were 97.4% and 78.3%, respectively. Preservation rates of facial nerve function and useful hearing were 94.4% and 90.7%, respectively. The mean postoperative follow-up time was 62.8 months, and there were two cases of recurrence requiring reoperation about 10 years after surgery. Conclusions For CPA epidermoid cyst surgeries, selection of the appropriate surgical approach for each patient and radical resection with an optimal operative field under direct visualization enable tumor removal without the need for reoperation for a long time, with preservation of CN functions.

Background In patients with a vestibular schwannoma, some studies have reported that useful hearing preserved initially after surgery deteriorates gradually in the long term. Studies with more patients are needed to clarify the maintenance rate of postoperative hearing function and to identify prognostic of hearing function. Method Ninety-one patients (mean age, 39.5 years; mean tumor size, 18.9 mm) with preserved useful hearing immediately after surgery were retrospectively analyzed. The useful hearing was defined as the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) classes A and B. Hearing tests, including auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE), were evaluated preoperatively, immediately after surgery, and at outpatient follow-up. Results At the final follow-up (mean, 63.0 months), the useful hearing was maintained in 79 patients (87%), and the hearing class remained unchanged during the follow-up period in 40 patients (44%). Significant predictors of useful hearing maintenance were AAO-HNS class A immediately after surgery, improvement of ABR, and the absence of postoperative DPOAE deterioration. Postoperative DPOAE deterioration correlated with hearing class deterioration. Conclusions Despite hearing being preserved in vestibular schwannoma patients immediately after surgery, Thirteen percent lost their useful hearing during the long follow-up period, and hearing class worsened in 55% of the patients. This study, which analyzed one of the largest series of vestibular schwannoma patients, demonstrated that retrocochlear condition is a key factor for useful hearing maintenance. In patients with vestibular schwannoma who have preserved hearing function, regular postoperative monitoring of hearing function is as important as regular MRI.

BACKGROUND: The sigmoid sinus is the biggest obstacle when approaching the posterior fossa and temporal bone. Adequate sinus exposure is required to obtain a sufficient operative field, but sinus injury is a potentially life-threatening complication. OBJECTIVE: To present our experience of sigmoid sinus injury and its management during surgeries in the cerebellopontine angle and intrapetrous region, with operative videos. METHODS: A total of 450 consecutive surgeries (385 retrosigmoid and 65 transmastoid approaches) over a 4-yr period were retrospectively investigated, focusing on sigmoid sinus injury, its repair technique, and long-term patency of the sinus. RESULTS: Pinhole-sized bleedings were controlled sufficiently by bipolar coagulation or fibrin glue-soaked hemostatic fabric. For lacerations of smaller than 3 mm, the sinus wall was reconstructed by suturing. For larger or unsuturable holes, patching a Gore-Tex membrane on a fibrin glue sheet (without any suturing) was used for the reconstruction. Hemostatic agents were not used for large lacerations to avoid any potential risks of delayed sinus occlusion. Major sinus injury requiring suturing or Gore-Tex patching occurred in 13 cases (2.9%). The bleeding was immediately controlled without sinus clamping, and surgery was not discontinued owing to the injury in any of them. The patients had no postoperative symptoms associated with sinus injury. In all the reconstructed sinuses, patency was confirmed on magnetic resonance imaging at the final follow-up. CONCLUSION: Sigmoid sinus injury can be well managed with long-term patency by utilizing different repair techniques. Initial safe and adequate exposure around the injury site was essential for all of these repair procedures.

Surgical removal of glomus jugulare tumors is challenging owing to the complex anatomy of the temporal bone and craniocervical region, aggressive tumor invasion into the nearby structures, and their hypervascularity. However, recent advances in skull base techniques, intraoperative neuromonitoring, and radiological interventions have enabled their relatively safe resection, while giving priority to functional preservation. This video demonstrates a case of a glomus jugulare tumor treated by the extradural transjugular transsigmoid approach with high-cervical exposure and tympamoplasty, after preoperative embolization. A 47-year-old woman presented with progressive hearing disturbance, pulsatile tinnitus, and hemifacial spasm. Neuroimaging displayed a hypervascular tumor occupying the temporal bone, extending to the cervical region through the jugular foramen, and to the external auditory canal. Preoperative feeder occlusion was successfully performed without any additional symptoms, while carefully evaluating the provocative test. Near-total resection of the tumor was achieved through the transjugular transsigmoid approach with high-cervical exposure under detailed neuromonitoring, including continuous facial nerve monitoring and auditory brainstem response. In this patient, in whom the tumor did not invade intradurally and the sigmoid sinus was already occluded preoperatively, the sinus was managed only by coagulation, to avoid unnecessary dural opening and the risk of cerebrospinal fluid leakage. Anterior facial nerve rerouting was not required since the tumor removal was accomplished through the corridor above and below the fallopian bridge. The patient had no new neurological deficits, and her pulsatile tinnitus and hemifacial spasm disappeared after the surgery. Her hearing disturbance improved postoperatively.The link to the video can be found at: https://youtu.be/gqf3dxHlv_0.

Background Advances in various diagnostic and/or treatment modalities, including radiological imaging, neuromonitoring, and microsurgical techniques, have resulted in treatments of vestibular schwannomas being aimed at preserving facial and hearing functions while achieving optimal tumor control. Method We describe our surgical technique for hearing preservation in vestibular schwannoma surgery. Conclusion The retrosigmoid transmeatal approach under continuous neuromonitoring (auditory brainstem response, cochlear nerve action potentials, and continuous facial nerve monitoring) enables gross-total resection of vestibular schwannomas, while preserving hearing and facial functions. Radiological assessment and microsurgical techniques, such as meticulous tumor dissection, are also essential for functional preservation with sufficient tumor removal.

The surgical management of trigeminal schwannomas often requires complicated skull base approaches based on detailed anatomical understanding because of the involvement of multiple compartments of the trigeminal nerve from its root to the peripheral branches. When there is vital anatomical anomaly around the tumor, this can make the surgical management and anatomical understanding more difficult. ^1,2 This video demonstrates the microsurgical removal of a dumbbell-shaped trigeminal schwannoma via the anterior transpetrosal transtentorial approach in a patient with a persistent primitive trigeminal artery, the most common persistent embryonic carotid-vertebrobasilar anastomosis. A 32-yr-old woman presented with progressive facial sensory impairment, dizziness, and slight diplopia because of right abducens palsy. Neuroimaging revealed a right Meckel's cave tumor extending to both the middle and posterior cranial fossae and displacing the abducens nerve inferomedially. The persistent primitive trigeminal artery, which is an anomalous communication between the cavernous carotid and basilar arteries, was identified ventral to the tumor. While preserving most of the noninvaded trigeminal nerve, gross-total resection was achieved under direct visualization of the abducens nerve and persistent primitive trigeminal artery, piercing the dura of the posterior cavernous sinus and coursing medially along the clivus. The patient's facial sensory impairment and diplopia almost disappeared without new neurological deficits or tumor recurrence during the follow-up period of 1 yr. Three-dimensional reconstructed images demonstrated the anatomical relationship of the tumor, the persistent primitive trigeminal artery, and the extent of osseous drilling of the petrosectomy. Informed consent was obtained from the patient.