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Vestibular schwannoma surgery: Intraoperative cochlear nerve action potential monitoring
P204
Otolaryngology Head and Neck Surgery
Scientific Posters
139
Vestibular Schwannoma Surgery: Absent ABR Does Not Contraindicate Attempted Hearing Preservation JOSEPH B. ROBERSON, Jr., MD, and JAMES R. McAULEY, MD, Palo Alto, Calif.
Seven patients with unilateral vestibular schwannoma (average size 16.5 ram, range 10 to 30 mm) and absent auditory brain stem response (ABR) potentials have undergone resection via a middle fossa or combined approach with attempted hearing preservation. Six patients have had successful heating preservation (average follow-up 17 months, range 11 to 26 months). One patient lost hearing (class C to D), one patient's hearing deteriorated but remained serviceable (class A to B), one patient's hearing remained unchanged (class B), and four patients had improvement of hearing (class B to A, B to A, D to A, D to B). All patients had successful intraoperative cochlear nerve action potential monitoring despite the absence of surface recorded ABR waveforms. Three of six patients with hearing preservation had improvement or relief from tinnitus. Preoperative patient demographics, pure tone averages, speech testing (PBmax and SSI), ENG, otoacoustic emissions with and without contralateral suppression, and auditory brain stem response tracings; intraoperative cochlear nerve action potential monitoring data; postoperative pure tone averages, speech testing, auditory brain stem response, complications, tinnitus, and facial nerve outcome are reported. Absence of surface recorded ABR waveforms does not contraindicate successful hearing preservation surgery for vestibular schwannomas. 140
Vestibular Schwannoma Surgery: Intraoperative Cochlear Nerve Action Potential Monitoring JOSEPH B. ROBERSON, Jr., MID, and JAMES R. McAULEY, MD, Palo Alto, Calif.
Sixteen patients with unilateral vestibular schwannoma have undergone resection using two different intraoperative monitoring strategies in a prospective study. Eight patients had intraoperative cochlear nerve action potential (CNAP) monitoring utilized. In the other eight patients, intraoperative surface recorded auditory brain stem response (ABR) monitoring was utilized. Preoperative patient age, tumor size, hearing level, and follow-up is not statistically different between the two groups. Six of eight patients with CNAP monitoring had hearing preservation (75%), while two of eight patients with ABR monitoring had hearing preservation (25%). Four of six patients who had CNAP testing utilized with preserved hearing had significantheating improvement. The presence of a CNAP waveform at the conclusion of tumor dissection strongly correlated with preserved hearing (six of six patients), while absence of CNAP strongly correlated with hearing loss (two of two patients). Patient
August 1997
demographics as well as preoperative pure tone averages (PTA), speech testing (PBmax), AAO-HNS hearing category, otoacoustic emissions with and without contralateral suppression, and auditory brain stem response data; intraoperative monitoring data; and postoperative PTA, PBmax, AAOHNS heating category, facial nerve outcome, complications, and tinnitus are presented for all patients. Cochlear nerve action potential nerve monitoring is a useful technique to improve hearing preservation rates during vestibular schwannoma surgery. 141
The Surgical Management of Hemifacial Spasm Secondary to Basilar Arterial Compression JOHN M. LASAK, MD, THOMAS O. WILLCOX, MD, WILLIAM A. BUCHHEIT, MD, and VIJAY M. RAO, MD, Philadelphia, Pa.
Today there is general consensus that hemifacial spasm (HFS) can be the result of vascular compression of the facial nerve within the cerebellopontine angle (CPA). The posterior inferior cerebellar artery is the offending vessel approximately 68% of the time. In a series of over 700 patients with a vascular cause of their HFS, the basilar artery was responsible in only 0.3% of cases. This report defines the radiologic evaluation, treatment options, and surgical management of HFS in a patient with a vascular compression syndrome due to a large tortuous basilar artery. Methods: We describe the management of a 69-year-old woman with a history of right hemifacial spasm for 7 years. The HFS had been effectively treated with botulinum toxin injections for 6 years; however, the efficacy had diminished over the last year despite alteration of her injection regimen. Magnetic resonance angiography (MRA) revealed a large ectatic, tortuous basilar artery abutting the seventh and eighth nerve complex in the right CPA. The patient elected operative treatment and a retrosigmoid craniectomy and seventh and eighth nerve complex decompression was performed. Continuous facial nerve and brain stem monitoring was implemented. At surgery an ectatic basilar artery was found to be deviating into the CPA compressing the facial nerve. A piece of Teflon~ felt was interposed between the nerve and vessel and the procedure was completed without complication. Results: Complete resolution of the HFS with normal seventh nerve and unchanged eighth nerve functionpostoperatively. Conclusions: The management of all patients with hemifacial spasm should include MRA to rule out the possibility of a neurovascular compression syndrome. If the MRA shows a vascular loop compressing the seventh nerve in the CPA, a surgical decompression procedure should be offered to the patient. Nonsurgical candidates and those who do not wish operative intervention can be offered botulinum toxin injections; however, repeated injections over long periods of time may become ineffective, as in our patient.
Otolaryngology Head and Neck Surgery
Scientific Posters
139
Vestibular Schwannoma Surgery: Absent ABR Does Not Contraindicate Attempted Hearing Preservation JOSEPH B. ROBERSON, Jr., MD, and JAMES R. McAULEY, MD, Palo Alto, Calif.
Seven patients with unilateral vestibular schwannoma (average size 16.5 ram, range 10 to 30 mm) and absent auditory brain stem response (ABR) potentials have undergone resection via a middle fossa or combined approach with attempted hearing preservation. Six patients have had successful heating preservation (average follow-up 17 months, range 11 to 26 months). One patient lost hearing (class C to D), one patient's hearing deteriorated but remained serviceable (class A to B), one patient's hearing remained unchanged (class B), and four patients had improvement of hearing (class B to A, B to A, D to A, D to B). All patients had successful intraoperative cochlear nerve action potential monitoring despite the absence of surface recorded ABR waveforms. Three of six patients with hearing preservation had improvement or relief from tinnitus. Preoperative patient demographics, pure tone averages, speech testing (PBmax and SSI), ENG, otoacoustic emissions with and without contralateral suppression, and auditory brain stem response tracings; intraoperative cochlear nerve action potential monitoring data; postoperative pure tone averages, speech testing, auditory brain stem response, complications, tinnitus, and facial nerve outcome are reported. Absence of surface recorded ABR waveforms does not contraindicate successful hearing preservation surgery for vestibular schwannomas. 140
Vestibular Schwannoma Surgery: Intraoperative Cochlear Nerve Action Potential Monitoring JOSEPH B. ROBERSON, Jr., MID, and JAMES R. McAULEY, MD, Palo Alto, Calif.
Sixteen patients with unilateral vestibular schwannoma have undergone resection using two different intraoperative monitoring strategies in a prospective study. Eight patients had intraoperative cochlear nerve action potential (CNAP) monitoring utilized. In the other eight patients, intraoperative surface recorded auditory brain stem response (ABR) monitoring was utilized. Preoperative patient age, tumor size, hearing level, and follow-up is not statistically different between the two groups. Six of eight patients with CNAP monitoring had hearing preservation (75%), while two of eight patients with ABR monitoring had hearing preservation (25%). Four of six patients who had CNAP testing utilized with preserved hearing had significantheating improvement. The presence of a CNAP waveform at the conclusion of tumor dissection strongly correlated with preserved hearing (six of six patients), while absence of CNAP strongly correlated with hearing loss (two of two patients). Patient
August 1997
demographics as well as preoperative pure tone averages (PTA), speech testing (PBmax), AAO-HNS hearing category, otoacoustic emissions with and without contralateral suppression, and auditory brain stem response data; intraoperative monitoring data; and postoperative PTA, PBmax, AAOHNS heating category, facial nerve outcome, complications, and tinnitus are presented for all patients. Cochlear nerve action potential nerve monitoring is a useful technique to improve hearing preservation rates during vestibular schwannoma surgery. 141
The Surgical Management of Hemifacial Spasm Secondary to Basilar Arterial Compression JOHN M. LASAK, MD, THOMAS O. WILLCOX, MD, WILLIAM A. BUCHHEIT, MD, and VIJAY M. RAO, MD, Philadelphia, Pa.
Today there is general consensus that hemifacial spasm (HFS) can be the result of vascular compression of the facial nerve within the cerebellopontine angle (CPA). The posterior inferior cerebellar artery is the offending vessel approximately 68% of the time. In a series of over 700 patients with a vascular cause of their HFS, the basilar artery was responsible in only 0.3% of cases. This report defines the radiologic evaluation, treatment options, and surgical management of HFS in a patient with a vascular compression syndrome due to a large tortuous basilar artery. Methods: We describe the management of a 69-year-old woman with a history of right hemifacial spasm for 7 years. The HFS had been effectively treated with botulinum toxin injections for 6 years; however, the efficacy had diminished over the last year despite alteration of her injection regimen. Magnetic resonance angiography (MRA) revealed a large ectatic, tortuous basilar artery abutting the seventh and eighth nerve complex in the right CPA. The patient elected operative treatment and a retrosigmoid craniectomy and seventh and eighth nerve complex decompression was performed. Continuous facial nerve and brain stem monitoring was implemented. At surgery an ectatic basilar artery was found to be deviating into the CPA compressing the facial nerve. A piece of Teflon~ felt was interposed between the nerve and vessel and the procedure was completed without complication. Results: Complete resolution of the HFS with normal seventh nerve and unchanged eighth nerve functionpostoperatively. Conclusions: The management of all patients with hemifacial spasm should include MRA to rule out the possibility of a neurovascular compression syndrome. If the MRA shows a vascular loop compressing the seventh nerve in the CPA, a surgical decompression procedure should be offered to the patient. Nonsurgical candidates and those who do not wish operative intervention can be offered botulinum toxin injections; however, repeated injections over long periods of time may become ineffective, as in our patient.