Acoustic tumour detection with early auditory evoked potentials and neuroradiological methods.

A total of 43 patients with surgically identified acoustic neuromas were tested. Results of early auditory evoked potentials (EAEP) and of neuroradiological methods were analysed. Abnormal EAEPs were observed in all patients. In 73% of the cases the EAEP indicated the retrocochlear site of the lesion; in 27%, however, the results did not localize the exact site of the lesion owing to a lack of waves I, II and III due to a pronounced hearing loss. Neuroradiological procedures provided an indication of the site and extent of the tumour. The number of true positives was 21 of 29 cases with polytomography of the petrous bone, 23 of 28 with computed tomography and in all cases when pontine angle cisternography and computed tomography combined with gas cisternography were performed. The EAEPs provide a screening-test for acoustic tumour detection at an early stage. Wave abnormalities indicative of a lesion at the acoustic nerve should lead to a neuroradiological investigation and are particularly valuable in cases with small intracanalicular tumours.