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PubMed1988

Criteria for preservation of vestibulocochlear nerve function during microsurgical removal of acoustic neurinomas.

A careful examination of the shape, location and course of the 8th cranial nerve in medium-sized and large tumours exhibits three distinct variants. In all cases where cochlear function was preserved, the type III variant (12%) in the cranial nerve tumour relationship was observed. The author's experience clearly indicates that, if a tumour is resected in toto, anatomical nerve continuity cannot be preserved in the type I and II variants (48%, respect. 40%). However, in the type I and II variants the patients invariably had preoperative hearing loss. The important criteria which must be considered in order to preserve cochlear function when extirpating acoustic neurinomas are an anatomically intact nerve, the origin of the tumour and its direction of spread, further more the shape, location and course of the 8th nerve components, the quality of preoperative cochlear nerve function, the pattern of vascularization of the statoacoustic nerve and the inner ear, and lastly, but not least a possible infiltration of the vestibular and/or cochlear nerves by the tumour itself. Objective hearing function could be preserved in 62% of small neurinomas (grade II) and 10% of large tumours (grades III and IV).

Audiometry, Pure-Tone↗
PubMedDate not supplied

Intermedius nerve involvement and testing in acoustic neuromas.

The clinical findings in 125 patients with surgically confirmed acoustic neuromas are presented, with special regard to the involvement of the intermedius nerve in the diagnosis. In assessing the function of the intermedius nerve the examination of the nasolacrimal reflex and the sensation of taste on the anterior two-thirds of the tongue are used. The methods of investigation are described in detail. The material consisted of 20 medium-sized and 105 large tumours; no intracanalicular tumor was found. Hearing loss was the initial symptom in 85% of the patients, 10% had tinitus and 4% vertigo as the first symptom. Apart from the VIII cranial nerve symptoms, a defective nasolacrimal reflex was the most significant evidence of cerebellopontine angle pathology. The test was positive in 65% of the medium-sized tumours, in the entire material, 85%. The figures are higher than the incidence of trigeminal nerve symptoms. This in contrast to the reports of most authors. The tests described are simple and quick to perform, and it is emphasized that they should be applied to all patients with unilateral hearing loss of unknown origin.

Adult↗
PubMed1987

Intra-operative electrocochleography to monitor cochlear potentials during acoustic neuroma excision.

Intra-operative electrocochleography (ECochG) was used in an attempt to monitor the action potential of the cochlear nerve during acoustic neuroma surgery in 14 patients with useful pre-operative hearing. Five patients had ECochG potentials preserved and yet only three could hear when tested audiometrically later. Of those losing the potentials intra-operatively all were subsequently deaf and the pattern of waveform loss allowed determination of the probable cause of hearing loss. Complete excision of the tumour was achieved in each case regardless of the ultimate effect on the AP as it was not felt justified to risk subsequent recurrence. In common with other studies one of the best prognostic factors for these preservation of hearing was found to be the size of the tumour.

Adult↗
PubMed2002

Prediction of facial nerve outcome using electromyographic responses in acoustic neuroma surgery.

OBJECTIVE: To determine whether early and late postoperative facial nerve function can be predicted on the basis of electromyographic responses in acoustic neuroma surgery. SETTING: Prospective blinded study. DESIGN: Tertiary referral center. PATIENTS AND METHODS: Burst and train electromyographic responses were recorded intraoperatively during the last step of vestibular schwannoma removal. The responses were classified and compared with early and late postoperative facial function in 49 patients who underwent enlarged translabyrinthine acoustic neuroma surgery. RESULTS: In the early postoperative period, 20 of 22 patients with an irritable pattern and 10 of 13 patients with an ordinary pattern had Grade III or better facial nerve function, whereas all 3 patients with a stray pattern and 9 of 11 patients with a silent pattern had Grade V or VI. In the late postoperative period, on the other hand, Grade III or better facial nerve function was achieved in 37 of 38 patients with an irritable, stray, or ordinary pattern, but the facial nerve function remained at Grade V or VI in 2 patients with the silent pattern. CONCLUSION: Patients with mechanically evoked facial electromyographic responses to the last step of tumor dissection may not experience severe facial nerve dysfunction or show a remarkable improvement. However, patients with silent electromyographic responses during this step tend to experience severe facial nerve dysfunction early in the postoperative course, and some patients may not show any functional improvement.

Adult↗
PubMed2002

Vestibular function after acoustic neuroma removal with preservation of one branch of the vestibular nerve.

BACKGROUND: Vestibular compensation after acoustic neuroma surgery is affected by many parameters. Apart from surgical approach, age of the patient, and comorbidity, the use of rehabilitative vestibular training and the degree of preoperative vestibular compensation play their respective roles. OBJECTIVE: To examine whether and how surgical preservation of one branch of the vestibular nerve affects the compensation process in patients after acoustic neuroma removal. STUDY DESIGN: Prospective study involving 29 patients with acoustic neuromas. In 15 patients operated on by the middle fossa or retrosigmoid approach, one branch of the vestibular nerve could be preserved intraoperatively, and the course of the compensation process was followed (Group 1). Fourteen other patients with acoustic neuroma, who were operated on via a translabyrinthine approach, served as a control group (Group 2). MAIN OUTCOME MEASURE: The evaluation of vestibular compensation was accomplished clinically, by electronystagmography, and by dynamic posturography. RESULTS: An accelerated vestibular compensation was found in all examinations for Group 1, and 3 months after surgery 47% of the patients in this group were back to work without substantial restrictions, compared with 29% of Group 2. At the end of 6 months, however, there was no more significant difference between the two groups. CONCLUSION: The long-term results of vestibular compensation do not seem to be influenced by partial preservation of the vestibular nerve, whereas the compensation process seems to be accelerated when the nerve is partially preserved.

Electronystagmography↗