Management of vestibular schwannoma: A pilot case series with postoperative ABR monitoring.

OBJECTIVE

Auditory brainstem response (ABR) monitoring is regularly used in surgery of vestibular schwannoma to achieve hearing preservation. Despite ABR preservation at the end of surgery, there are cases with postoperative deafness. To date it is unclear whether these are false positive ABR data or cases of secondary hearing loss. In this pilot study, we focused on the early postoperative phase and possible ABR changes in this period.

PATIENT AND METHOD: In a prospective study from March 2008 to April 2009, eleven patients (5 female and 6 male) with vestibular schwannoma and preoperative residual hearing were investigated by repeated postoperative ABR investigation at seven dates during the first week. ABR results, hearing function and tumor extension were categorized according to Hannover classification system. The postoperative developments of the first week after surgery are described.

RESULTS

Hearing preservation was achieved in 55% (6 of 11) of the patients. In the early postoperative phase, three patients with an ABR loss at the end of surgery showed some kind of recovery. In one case, a permanent recovery could be reproduced and developed step by step during the early postoperative phase. Three patients showed a postoperative deterioration resulting in a complete ABR loss. In one of these cases, it was probably a technical problem, but in the two other cases it was a real impairment. In 8 of 11 ABR, quality changed considerably during the early postoperative phase.

CONCLUSION

This pilot study identifies considerable change of ABR formation occurring in a considerable proportion of patients early after vestibular schwannoma resection. Obviously, in some patients, the endoperative state of the ABR is not the final state. Some patients show a postoperative improvement and some a deterioration towards a complete loss of all ABR components. Whether secondary hearing loss could be presented by early detection, will be a matter of further studies.