Objective: Endolymphatic sac tumours (ELSTs) of the inner ear occur in 16% of patients with the hereditary tumor syndrome von Hippel-Lindau disease (vHL). ELSTs of all sizes can cause irreversible hearing loss which can, however, be prevented through early diagnosis and treatment. We aim to emphasize the challenges of prophylactic ELST screening and to explore the role of audiometry in pre-symptomatic ELST screening. Design: For a period of 17 years our patient was screened for ELSTs with inner-ear MRI (magnetic resonance imaging), audiometry, and clinical interviews. Study sample: A male vHL patient who became deaf in one ear due to a radiologically undetectable ELST. Results: Despite annual MRIs, the ELST was not visible until four months after onset of deafness when it appeared as a 1.4 × 1.4 mm tumor mass. Although his hearing was objectively within normal limits for the first 14 years, a distinct pattern of low-frequency hearing loss could retrospectively be seen at all audiometries. Conclusions: Audiometry is a candidate screening tool for detection of non-symptomatic pre-MRI-visible ELSTs, and we have initiated an international collaborative study to further determine its application. At present, we suggest an ELST screening protocol of yearly audiological assessment and inner ear MRI.