Negative influence of preoperative tinnitus on hearing preservation in vestibular schwannoma surgery.

BACKGROUND: Goals of vestibular schwannoma (VS) microsurgery are maximal resection, facial nerve (FN) preservation and in selected cases, hearing preservation (HP). Postoperative HP rates are related to clinical and radiographic factors: size of tumor, preoperative hearing, hypertension, diabetes, and presence or absence of preoperative tinnitus. In this retrospective review we evaluated the influence of preoperative tinnitus on HP after VS surgery in patients with preoperative socially useful hearing (SUH). METHODS: Twenty-five patients with SUH underwent VS micro neurosurgery by retrosigmoid (RS) approach. Selection criteria were pure tone audiogram ≤50dB loss and speech discrimination score >50% (50/50 criterion, AAO-HNS class A-B). In relation to maximum diameter, we identified two size-groups: 1) group A ≤2cm (13 cases); 2) group B >2cm (12 cases). HP attempt was assisted by intraoperative ABR evoked by LS CE-Chirp® (Interacustics, Middelfart, Denmark) acoustic stimuli. RESULTS: Mean age was 44.3 years (20-64); average maximum diameter 2,0cm (0,8-4). Preoperative tinnitus was present in 10 patients (40%): all of them had a Class B-hearing. Total and nearly-total (>95%) resection was possible in all. Mortality and major morbidity were zero. In all, facial nerve (FN) was anatomically and functionally preserved; in 10 an incomplete FN deficit was followed by complete recovery within 2-8 weeks. At a follow-up ranging from 8 to 17 months (average 12.7 months), socially useful hearing (SUH) preservation rate was 52%, with significant differences in relation to size: 61.5% group A and 41.7% group B (P=0.014). Postoperative AAO-HNS C (serviceable) hearing was observed in 36%, deafness in 12%. At last follow-up, among the 10 patients with preoperative tinnitus 6 worsened from Class-B to Class-C, 3 remained in Class-B, and one was deaf. As regards SUH preservation, 3 of 10 patients with preoperative tinnitus and 10 of 15 without it remained in Class-A-B (P=0.006). CONCLUSIONS: Microsurgery represents the first therapeutic option for small growing VS with SUH. Our data confirm that key-hole RS removal of VS with intraoperative LS-CE-Chirp ABR monitoring allows good rate of SUH preservation, especially maximum diameter does not exceed 2cm. Preoperative tinnitus seems to indicate a lower hearing reserve and predicts a lower likelihood of HP.

Hearing preservation after removal of small vestibular schwannomas by retrosigmoid approach: comparison of two different ABR neuromonitoring techniques.

BACKGROUND AND OBJECTIVE: Goals of small vestibular schwannoma (VS) microneurosurgery are as follows: radical resection, facial nerve (FN) preservation, and hearing preservation (HP). Microsurgical advances make HP possible in many patients with preoperative socially useful hearing (SUH). We evaluated postoperative HP in VS with maximum diameter < 2 cm monitored with two different auditory brainstem response (ABR) techniques. MATERIALS AND METHODS: Twenty-eight consecutive non-randomized patients with SUH suffering from small VS underwent keyhole microneurosurgery by retrosigmoid (RS) approach. Selection criteria are as follows: speech discrimination > 50%, pure tone audiogram < 50 dB loss (50/50 criterion; AAO-HNS classes A-B), maximum diameter < 2 cm. HP was attempted with intraoperative ABR, evoked by classical Click (16 cases, group 1) and LS-CE-Chirp® stimulus (12, group 2). RESULTS: Mean age was 47.5 years (16-75); average maximum diameter was 1.35 cm (0.5-1.9 mm). Total and nearly total resection (> 95%) was obtained in all, as confirmed by 24-48-h postoperative enhanced MRI. Mortality and major morbidity were 0. In all cases, FN was preserved; in 3, incomplete deficit recovered within few weeks. Socially useful HP (pre- and postoperatively) was 64.3% (18 of 28): 56.25% group 1 and 75% group 2 (p = NS). Postoperative ipsilateral deafness was observed in 5 cases of group 1 (p < 0.0001). Preoperative tinnitus had negative impact on HP (p < 0.05). CONCLUSIONS: Microsurgery can cure small growing VS with SUH. Our limited experience confirms that keyhole RS removal assisted by intraoperative ABR monitoring leads to valuable rates of SUH. LS-CE-Chirp-evoked ABRs allow a safe, effective, and clear neurophysiological feedback and are faster and, thus, more useful than the Click-ABR.

Vestibular schwannoma and hearing preservation: Usefulness of level specific CE-Chirp ABR monitoring. A retrospective study on 25 cases with preoperative socially useful hearing.

BACKGROUND AND OBJECTIVES: Decision-making regarding the therapy of vestibular schwannoma (VS) changed over the last decades, during which curative microsurgery has been promoted. Goals of VS microsurgery are: extensive resection, facial nerve (FN) preservation and, in selected cases, hearing preservation (HP). The aim of this study is to evaluate postoperative HP with reference to tumor size in patients operated on with Level Specific (LS)-CE-Chirp® ABR monitoring. PATIENTS AND METHODS: Twentyfive consecutive patients with socially useful hearing (SUH) underwent VS microneurosurgery by retrosigmoid (RS) approach. Selection criteria were: pure tone audiogram <50dB loss and speech discrimination score >50% (50/50 criterion; AAO-HNS class A-B). In relation to maximum diameter, we identified 2 size-groups: A) ≤2cm (13 cases); B) >2cm (12 cases). HP attempt was assisted by intraoperative ABR evoked by LS CE-Chirp® acoustic stimuli. RESULTS: Mean age was 44,3 years (20-64); average maximum diameter 2,04cm (8 40mm). Total and nearly-total (>95%) resection was possible in all. Mortality and major morbidity were zero. In all, FN was anatomically and functionally preserved; in 10 an incomplete FN deficit (House-Brackmann II and III) was followed by complete recovery (House-Brackmann I). SUH preservation rate was 52%, with significant differences in relation to size: 61,5% group A and 41,7% group B (p = 0,014). Postoperative AAO-HNS C (serviceable) hearing was observed in 36%, deafness in 12%. CONCLUSION: Microsurgery represents a valid therapeutic option for small growing VS with SUH. Our data confirm that RS removal of VS with intraoperative ABR monitoring allows good rate of SUH preservation, especially if maximum diameter does not exceed 2cm. LS-CE-Chirp ABR represent a safe and effective method for monitoring cochlear nerve, with fast and clear intraoperative neurophysiological feedback.

Position and Course of Facial Nerve and Postoperative Facial Nerve Results in Vestibular Schwannoma Microsurgery.

OBJECTIVE: To investigate the variation in the position and course of the facial nerve (FN) in patients undergoing vestibular schwannoma (VS) microsurgery by the keyhole retrosigmoid approach and the relationship between FN position and postoperative facial results. METHODS: The series consists of 100 patients who underwent VS microsurgery during a 5-year period in whom the position and course of the FN could be confirmed by direct stimulation. The course of the FN was classified into 4 patterns according to its position: anterior (ventral) surface of the tumor (A), anterior-superior (AS), anterior-inferior (AI), and dorsal (D). RESULTS: The distribution of patterns was as follows: AS in 48 cases, A in 31, AI in 21, and D in zero. For tumors <1.5 cm, the AS pattern was most common (68.4%). For tumors ≥1.5 cm, the proportion of A and AI positions increased (31.4% and 25.5%). Significant differences were observed between position and course patterns of the FN and postoperative nerve results. Patients with AS and AI patterns had better House-Brackmann FN function compared with patients with the A pattern (P < 0.05). Moreover, in tumors >3.0 cm, the FN tended to adhere strongly to the tumor capsule, and postoperative facial deficits were more frequent (P < 0.05). CONCLUSIONS: The AS pattern was most common for smaller VSs. The A position and course and adhesion of the FN to the tumor capsule were the 2 factors most strongly associated with worse postoperative FN result.

Cavernous hemangioma of the internal auditory canal encasing the VII and VIII cranial nerve complex: case report and review of the literature.

Cavernous angiomas originating in the internal auditory canal are very rare. In the available literature, only 65 cases of cavernomas in this location have been previously reported. We describe the case of a 22-year-old woman surgically treated for a cavernous hemangioma in the left internal auditory canal, mimicking on preoperative magnetic resonance imaging MRI an acoustic neuroma. Neurological symptoms were hypoacusia and dizziness. The cavernous angioma encased the seventh and, partially, the eighth cranial nerve complex. A "nearly total" removal was performed, leaving a thin residual of malformation adherent to the facial nerve. Postoperative period was uneventful; hearing was unchanged, but the patient had a moderate inferior left facial palsy (House-Brackmann grade II) slightly improved during the following weeks. On the basis of the observation of this uncommon case, we propose a revision of the literature and discuss clinical features, differential diagnosis, and treatment.

CE-Chirp® ABR in cerebellopontine angle surgery neuromonitoring: technical assessment in four cases.

Continuous monitoring of wave V of auditory brainstem response (ABR), also called brainstem auditory evoked potential (BAEP), is the most common method used in intraoperative neuromonitoring (IONM) functionality of cochlear nerve during surgery in cerebellopontine angle (CPA). CE-Chirp® ABR represents a recent development of classical ABR. CE-Chirp® is a new acoustic stimulus used in newborn hearing testing, designed to provide enhanced neural synchronicity and faster detection of larger amplitude wave V. In four cases, CE-Chirp® ABR was performed during cerebellopontine angle (CPA) surgery. CE-Chirp® ABR represented a safe and effective method in neuromonitoring functionality of vestibulocochlear nerve. A faster neuromonitoring feedback to surgical equipe was possible with CE-Chirp ABR®.