Acoustic neuroma: clinical-functional finding, results and surgical complication [Il neurinoma dell'acustico: reperti clinico-funzionali, risultati e complicanze chirurgiche.]

The present work provides clinical-functional findings, results and surgical complications observed in a consecutive series of 100 subjects with acoustic neuroma (AN). Analysis of the data has made it possible to draw some important conclusions. Compromised hearing is found in 90% of the ears affected by AN. Indeed the percentage of normal hearing in such cases does not exceed 5%. There is, however, no clear correlation between degree of hearing and tumor size. The symptoms of AN do not always present unilateral or asymmetrical hearing loss, unilateral tinnitus and/or dizziness. At times AN presents atypical symptoms and can even be asymptomatic. Sudden onset of unilateral hearing loss, acute vertigo, persistent monolateral tinnitus and even isolated symptoms of the V or VI cranial nerve should lead one to suspect AN. Only by applying the diagnosis of suspected AN in a large number of cases is it possible to lower the time gap between the onset of symptoms and the definitive diagnosis of AN, increasing the number of cases diagnosed while the AN is still small. Auditory brainstem responses (ABR) are still the means of choice for screening and following up subjects where AN is suspected. Reduced ABR sensitivity reported in the literature for intracanal ANs must induce further testing with magnetic resonance imaging with gadolinium in all subjects where an AN is suspected, even when the ABR is normal. Recording of transient evoked otoacoustic emissions in the presence and in the absence of contralateral white noise has proved to be a simple, inexpensive, non-invasive test for the diagnosis of suspected retrocochlear pathologies. A deficit in vestibular function is most frequently encountered when the AN is already quite large and an alteration in the smooth pursuit test is only found when the AN involves the brainstem. These data have led us to conclude that vestibular reflex studies do not play any role in early diagnosis of AN. Surgical exeresis is the treatment of choice in those cases where "watch and scan" (only hearing ear in the absence of neurological complications; AN < 0.5 cm in the ponto-cerebellar angle, particularly in elderly patients) is not indicated. The enlarged translabyrinthine approach is indicated in all cases of AN, no matter what the tumor size and extent of pre-operative hearing. Promptly and correctly treating intra and postoperative complications, most frequently encountered in patients with AN > 2 cm, reduces the mortality and morbidity to a minimum. Modern otological microsurgery and monitoring techniques make it possible to preserve the VIIth facial nerve in more than 90% of the ears, consequently preserving or nearly preserving normal VIIth nerve function 1 year after surgery in at least three out of four patients. No matter what approach is used, hearing can be preserved measurably in approximately 50% of the ears undergoing surgery and to a socially useful or nearly useful level in a significantly lower proportion of patients. In this regard the most satisfactory results are obtained when preoperative hearing is normal and the AN is < 2 cm.