When is an acoustic neuroma not an acoustic neuroma? Pitfalls for radiosurgeons

A Review of Posterior Fossa Lesions

Posterior fossa lesions can occur in patients of all ages. Patients present with subtle findings of hearing loss, tinnitus, headache, cranial neuropathies, imbalance, vertigo, nausea, and vomiting depending on the location and type of lesion. The presentation can be particularly insidious as the most common symptom is slowly progressive hearing loss. Posterior fossa lesions should be included in the differential diagnosis for patients with this presentation and appropriate audiologic testing and imaging should be performed. Management involves collaboration between multiple subspecialties and has evolved significantly over the years leading to increased patient involvement and improved outcomes.

The Preoperative Diagnostic Value of MRI and Otoneural Tests in Acoustic Neuroma

Objectives

To determine the preoperative diagnostic accuracy of MRI and otoneural tests (ONT) for acoustic neuroma (AN) in a cohort of unselected patients with pontocerebellar angle tumors. To find a convenient way to screening out the potential asymptomatic AN patient earlier.

Design

This diagnostic accuracy study was performed in a central hospital and included a consecutive sample of unilateral incipient pontocerebellar angle tumor patients referred for MRI and ONT before surgery. Different AN features of MRI and ONT were collected and concluded into preoperative diagnostic variables or variable combinations. Those of MRI and ONT are analyzed and compared with biopsy results by multivariable receiver operating characteristic (ROC) analysis. The early-stage group, the course of which is 1 year or less, was separately computed and compared.

Results

Eighty-three subjects were collected from June 2013 to June 2019; 62 were confirmed AN postoperatively by biopsy, whereas others are not AN. The area under the curve (AUC) of MRI was 0.611, whereas the AUC of ONT was 0.708. In the early-stage group, the AUC of MRI was 0.539, and the AUC of ONT was 0.744.

Conclusions

ONT was able to identify more subjects affected by unilateral incipient AN than MRI preoperatively. Given that ONT is a functional test for internal auditory canal nerves, it is an optimal screening test for AN patients because it provides more information than MRI for the further clinical plan. It is particularly noteworthy for identifying asymptomatic AN patients and for early stage. Therefore, it may help more patients from unnessesary surgery. Furthermore, an MRI follow-up is suggested if the patient was found alert in ONT.