Experiences with Total Removal of Tumors of the Acoustic Nerve

Evolving Role of Non-Total Resection in Management of Acoustic Neuroma in the Gamma Knife Era

OBJECTIVE

To examine patients with residual tumor after vestibular schwannoma (VS) resection with focus on need for further therapy, including stereotactic radiosurgery (SRS) and revision surgery.

STUDY DESIGN AND SETTING

Retrospective review at two tertiary otology referral centers.

PATIENTS AND INTERVENTION

Patients undergoing primary surgery for VS from 2007 to 2017.

MAIN OUTCOME MEASURE

Degree of resection and need for further treatment.

RESULTS

Of 289 patients undergoing surgery, 38 (13.1%) underwent subtotal resections (<95% of tumor resected) and 77 (26.6%) underwent near-total resections (≥95% but <100%). Patients with any residual tumor had larger tumors preoperatively (mean estimated volume 6.3 cm versus 2.1 cm, p < 0.0005) but were otherwise clinically and demographically similar to the population as a whole. Further treatment (surgery or SRS) was needed in 4.6, 14.3, and 50.0% of patients after gross total, near-total, and subtotal resections, respectively (p < 0.0005). Patients undergoing additional therapy had larger residual tumors (median post- to preoperative estimated volume ratio 0.09 versus 0.01, p < 0.0005). Patients undergoing subtotal and near-total resections had poorer facial function at ultimate follow up than those undergoing gross total resections (p = 0.001), likely due to larger tumors and more difficult resections. Literature review revealed higher rates of gross total resection as well as facial palsy in the pre-SRS era.

CONCLUSION

Residual tumor following VS resection is more common today than in the pre-SRS era. Availability of SRS may encourage leaving residual tumor intraoperatively to preserve neural structures. Current surgical strategies decrease surgical morbidity but necessitate further treatment in over 10% of cases.

Efficacy of irradiation for incompletely excised acoustic neurilemomas

The records of 124 patients treated for acoustic neurilemoma at the University of California, San Francisco, from 1945 through 1983 were reviewed. Patients were classified by the extent of surgical resection: total, nearly total (90% to 99% resection), subtotal (less than 90% resection), or biopsy. Thirty-one patients received irradiation as part of their primary treatment. Total resection of tumor, without irradiation, was associated with a 3% chance of local recurrence. One of 15 patients who had nearly total resection of their tumor and did not receive postoperative irradiation suffered a recurrence, compared with neither of the two patients who received postoperative irradiation (greater than 45 Gy) following nearly total resection. Postoperative irradiation (greater than 45 Gy) decreased the recurrence rate after subtotal resection from 46% (six of 13 cases without irradiation) to 6% (one of 17 cases: p = 0.01). All three patients treated by biopsy alone received postoperative irradiation (greater than 45 Gy), and none had a recurrence. Six patients were treated with preoperative irradiation because of excessive tumor vascularity; four are without evidence of disease 12 to 23 years later. Only three of seven patients treated with irradiation for tumor recurrence after surgical resection survived. It is concluded that postoperative irradiation significantly decreased the chance for local tumor progression following subtotal resection of acoustic neurilemoma, and that postoperative irradiation may be effective therapy following treatment by biopsy. Patients with total or nearly total resection appeared not to benefit from postoperative irradiation.

Preservation of hearing in patients undergoing excision of acoustic neuromas and other cerebellopontine angle tumors

Microsurgical techniques have made it possible to identify and preserve the cochlear nerve from its origin at the brain stem and along its course through the internal auditory canal in patients undergoing removal of small or medium-sized acoustic neuromas or other cerebellopontine angle (CPA) tumors. In a consecutive series of 100 patients with such tumors operated on between 1975 and 1981, an attempt was made to preserve the cochlear nerve in 23. The decision to attempt to preserve hearing was based on tumor size and the degree of associated hearing loss. In cases of unilateral acoustic neuroma, the criteria for attempted preservation of hearing were tumor size (2.5 cm or less), speech reception threshold (50 dB or less), and speech discrimination score (60% or greater). In patients with bilateral acoustic neuromas or tumors of other types, the size and hearing criteria were significantly broadened. All patients were operated on through a suboccipital approach. Hearing was preserved postoperatively in six (31.6%) of the 19 patients with unilateral acoustic neuromas, although the cochlear nerve was preserved in 16. Of the six patients with postoperative hearing, three retained excellent hearing, and the other three had only sound awareness and poor discrimination. Hearing was preserved in three cases with other CPA tumors, including an epidermoid cyst and small petrous meningiomas in the internal auditory canal. Of the two cases with bilateral tumors, hearing was preserved in one. Of the 23 patients in whom hearing preservation was attempted, nine (39.1%) had some postoperative hearing, which in six was equal to or better than the preoperative level. Thus, it is worthwhile to attempt hearing preservation in selected patients with CPA tumors.

Technique of hearing preservation in small acoustic neuromas

The ideal operation for acoustic neurinoma would not only provide total excision without injury to the brain stem and with preservation of facial nerve function, but would also allow retention of useful hearing in those patients who come to operation with intact hearing function. Documented preservation of useful hearing in the rather extensive literature concerning acoustic neurinomas is rare. An operative technique has been developed utilizing a retromastoid approach, brain stem auditory-evoked potentials and direct auditory monitoring, facial nerve electromyography, and microsurgical techniques that have enabled us to preserve useful hearing in three and some hearing in two of six consecutive patients who had preoperative hearing. Rules regarding preservation and criteria regarding documentation of hearing preservation are outlined.

Preservation of facial and acoustic nerves in the total removal of large and small acoustic tumors. Report of two cases

Two cases are presented in which an acoustic tumor was totally removed without the aid of an operating microscope. In one of them, a large lesion was excised, with restoration of the patient's hearing postoperatively. The anatomical problems are analyzed, and the relevant literature is reviewed briefly.

The two-stage excision of huge acoustic neurinomas

Total removal of huge acoustic neurinomas was carried out in 23 patients by means of a two-stage suboccipital transmeatal approach with microsurgical technique. There was no operative mortality. Good results were obtained in 18 (78%) of the patients who have returned to normal activities or full-time employment. Five patients (22%) have residual preoperative neurological deficits causing a reduced level of activity. All of these, except one, are able to care for themselves. None of the patients has had any further significant neurological deficit caused by the operative procedures. Anatomical integrity of the facial nerve was maintained in 17 patients (74%). Surgical technique, operative morbidity, and results are thoroughly discussed. The potential advantages of this technique are stressed.

Total removal of acoustic neurinomas

The authors analyze the results of total removal of acoustic neurinomas in 120 patients operated on between January, 1967, and January, 1976. The facial nerve was preserved after surgery in 65 patients (54.2%). The use of microsurgical techniques in the last 3 years of study permitted preservation of the seventh nerve in 26 of 35 operated patients (74.3%). Of 103 patients examined postoperatively, 96 retained their full or partial capacity for work (93.2%). Ten patients (8.3%) died after surgery. In the last 3 years, 35 patients were operated on without a single death.

Experiences with radically operated acoustic tumours

A series of one hundred acoustic tumours submitted to radical operation is reviewed. The authors emphasize the possibilities of early correct diagnosis without contrast studies, draw attention to variations in nature and site of the tumour, and evaluate preservation of the facial nerve.