Long-term prognosis of preserved hearing function after surgery in patients with cerebellopontine angle tumors other than vestibular schwannoma

Abstract

Background: In our previous study on vestibular schwannomas (VSs), we found that preserved useful hearing function in patients immediately after surgery gradually deteriorated in long-term period, and was lost in 13% of patients 5 years after surgery. In this retrospective study, we aimed to investigate the long-term hearing prognosis of patients with cerebellopontine angle (CPA) tumors other than VSs, and clarify whether the phenomenon of hearing deterioration after surgery occurs only in patients with VSs.

Method: Patient backgrounds and otologic data were investigated in 70 patients (meningioma: 37; trigeminal schwannoma: 9; facial nerve schwannoma: 4; jugular foramen schwannoma: 9; and epidermoid cysts: 11) with preserved useful hearing function after surgery (American Academy of Otolaryngology-Head and Neck Surgery classification Class A or B).

Results: Of the 70 patients (average age: 44 years; tumor diameter: 35 mm; resection rate: 96%; follow-up period: 62 months; 61 patients in Class A and 9 patients in Class B immediately after surgery), 60 patients (86%) had unchanged, 5 patients (7%) had improved, and 5 patients (7%) had worsened hearing class during the follow-up period. Only 1 patient (facial nerve schwannoma) experienced a change from Class B to C, and was out of useful-hearing range at the final follow-up (the useful hearing preservation rate: 99%). Distortion product otoacoustic emissions (DPOAEs) reflecting inner ear function were detected in 61 patients (87%) at the final follow-up, and only 4 patients (6%) demonstrated a worsening of DPOAEs during the postoperative follow-up period.

Conclusions: Useful hearing function after surgery was preserved at a high rate during a long-term postoperative period in patients with typical CPA tumors other than VSs. Compared with patients with VSs, in whom hearing loss owing to inner ear dysfunction is not rare in the long-term after surgery, patients with CPA tumors demonstrated a apparently lower incidence of inner ear dysfunction and a more favorable long-term hearing prognosis. In patients with CPA tumors, not only hearing improvement by the surgery but also its long-term preservation can be expected. In this study, we confirmed that the phenomenon of postoperative hearing deterioration occurs only in patients with VSs among all CPA tumors.

Keywords: CP angle; Hearing prognosis; Jugular foramen; Meningioma; Postoperative hearing function; Transpetrosal approach.

Fig. 1

Patients selections and preoperative/postoperative hearing tests. Target patients (CPA meningioma, trigeminal schwannoma, facial nerve schwannoma, jugular foramen schwannoma, and epidermoid cyst) were extracted in the order shown in the chart. CPA: cerebellopontine angle; CN: cranial nerve; EPD: epidermoid cyst; FNS: facial nerve schwannoma; JFN: jugular foremen schwannoma; MGM: meningioma; NF2: neurofibromatosis type2; TS: trigeminal schwannoma; VS: vestibular schwannoma

Fig. 2

Distribution and proportion of hearing class at postoperative/final follow-up. In the target patients, 61 (87.1%) and 9 (12.9%) were in postoperative AAO-HNS classification Class A and Class B, respectively. Of the patients whose postoperative hearing class was Class A, four patients exhibited a decline to Class B at the final follow-up. Of the patients that were Class B after surgery, six patients did not exhibit any change in hearing class at the final follow-up (improved to Class A: 5 patients; worsened to Class C: I patient). AAO-HNS: American Academy of Otolaryngology-Head and Neck Surgery; F/U: follow-up; postOP: postoperative

Fig. 3

Detections of DPOAEs at three point (preoperative, postoperative, and follow-up point) and changes of DPOAEs during postoperative follow-up period. At the final follow-up point, DPOAEs were detected in 61 patients (87.1%) and undetected in 9 patients (12.9%). Of nine patients where DPOAEs were undetected, DPOAEs in five patients were undetected since preoperative point, and DPOAEs in four patients were detected immediately after surgery, but the detections either worsened or disappeared during the follow-up period. DPOAEs: distortion product otoacoustic emissions