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Factors related to postural stability and the course of recovery after vestibular schwannoma surgery were analyzed in a retrospective study of 177 patients and in a prospective study of 44 patients. Before surgery, 7 of the 44 patients in the prospective group complained of postural instability. The body sway velocity was measured. In the retrospective study, the sway velocity was abnormal under nonvisual control in 63% of the patients and under visual control in 34%. The sway velocity correlated with tumor size, smooth pursuit deficit, and postoperative work history. We compared patients with abnormal postural control to those with normal postural control, and found that the former relied to a greater extent on visual information and the latter on proprioceptive information. In the prospective study, the sway velocity increased after the operation, and 1 year after surgery it had not returned to preoperative values. In the logistic regression analysis, a translabyrinthine approach, rehabilitation, the patient's age, and preserved function of the facial nerve predicted a good outcome of postural stability. The retrosigmoid approach and depression were the most significant risk factors for postoperative gait difficulties. Vestibular rehabilitation increased the reliance on proprioception for maintenance of postural control and improved postural stability.

The goal of our study was to examine the usefulness of preserved hearing after unilateral vestibular schwannoma removal. The patients were assessed by clinical evaluation, preoperative and postoperative audiometric evaluation, operative findings, and postoperative functional results. Hearing was preserved in 47 of 119 patients. The postoperative hearing was better than 30 dB in 10 patients. During the follow-up, the hearing decreased 5 dB on average, and almost all of the decrement occurred during the first 6 months. Subjectively, the preserved hearing assisted in understanding of speech in 62% of the patients. Tinnitus did not interfere with understanding of speech. The age of the patients was the most significant factor associated with preserved hearing. Sixty-six percent of the patients with hearing preservation rated their preserved hearing as valuable. Neither tinnitus nor speech distortion reduced the appreciation for hearing preservation. We conclude that efforts to preserve hearing are worthwhile.

Our aim was to elucidate the aetiology of persistent postoperative headache, a common sequel for several years after vestibular schwannoma surgery through the retrosigmoid approach. Twenty-seven patients with reported major postoperative headache were tested for vestibular responses and cervico-collic reflexes. The role of local anaesthesia injected into the neck muscle insertions or around the occipital nerves was evaluated. Sixteen patients operated on for vestibular schwannoma, but without headache, and 12 healthy volunteers served as control groups. Vestibular responses and cervico-collic reflexes deteriorated equally in the patients regardless of whether or not they had a postoperative headache. Local anaesthesia did not alter the results. The posturography results were increased among both patient groups. Sumatriptan alleviated pain in nine patients and abolished it completely in one out of these nine patients. Vestibular imbalance or abnormal activation of neck muscles do not explain postoperative headache. Occipital nerve entrapment or neuralgia explains the headache in a few patients. The relatively pronounced sumatriptan effect may, however, suggest a trigeminal nerve mediated cause for postoperative headache.

Purpose: To characterize the clinical picture with vestibular schwannoma, we retrieved 122 patients with vestibular schwannoma from the vestibular unit of the Helsinki University Central Hospital., Procedures: The patients filled out a questionnaire concerning their symptoms, earlier diseases, accidents, and the use of tobacco and alcohol. This information was then completed with results of audiometric, neurotologic and imaging studies. The data were prospectively stored to the database of neurotologic expert system called ONE., Results: The average tumor size was 21 mm. Most of the patients had hearing loss (94%) and tinnitus (83%) but only half of them (49%) had vertigo attacks. The most common initial symptom was hearing loss combined with tinnitus (34%, n=44). Vertigo only was the initial symptom for 12 patients. The mean duration of a vertigo attack was from 5 min to 4 h and the intensity of the attack was regularly mild (37%) or moderate (32%). The vertigo of the vestibular schwannoma patients differed from vertigo in other diseases by the absence (63%) or low intensity (18%) of nausea. Spontaneous nystagmus was present in 56 patients (46%), and caloric asymmetry (>25%) was observed in 66% (n=69). Caloric asymmetry increased with tumor size. The prevalence of headache was 18% (n=21). Sudden slips seldom (7%) occurred., Conclusion: Hearing loss and tinnitus are the main symptoms of vestibular schwannoma. Only half of patients have vertigo. Screening to detect vestibular schwannoma is more yielding in sudden deafness patients rather than in patients with Meniere's disease.

The vestibulo-ocular reflex stabilizes gaze during head movements by producing compensatory eye movements. Retinal image velocity (RIV) is defined as the difference between the eye and head velocities. The RIV of 20 vestibular schwannoma (VS) patients and 17 healthy controls was measured with a head autorotation test. The head autorotation test had a sensitivity of 80% and a specificity of 88%. The mean RIV (degree/second) +/- 95% confidence intervals of the VS patients in the 5 frequency bands of 1 to 5 Hz was respectively 4.8 (4.2 to 5.5), 11.5 (8.6 to 14.4), 21.7 (15.5 to 27.9), 25.2 (17.1 to 33.4), and 26.1 (13.1 to 39.1). The RIV of the VS patients was asymmetrically larger on the operated side (P<0.05) in the frequency band of 1 Hz. The mean RIV was significantly (P<0.05) larger in the VS patients than in the controls in the frequency bands of 1 to 4 Hz. The vestibulo-ocular reflex is inaccurate after VS surgery; but the inaccuracy may not lead to the occurrence of any symptoms.

Postoperative headache was studied among 251 patients who underwent operation for vestibular schwannoma. A questionnaire based on the McGill Pain Questionnaire and the Finnish Pain Questionnaire was sent to the patients. Twenty-one expressions describing postoperative headache were extracted with a factor analysis. The pain intensity was expressed on a visual analog scale, and the risk factors for postoperative headache were evaluated. Immediately after the operation, 154 subjects reported headache. Eighty-nine of the patients had had headache before operation, whereas 65 patients experienced headache only after operation. An average of 8.9 years after surgery, 93 patients still reported headache. Headache was a major problem for 27 subjects; 18 of the 27 had suffered from headache before operation. A retrosigmoidal approach, postoperative gait problems, preoperative headache, and small tumor size predicted postoperative problems with headache. When headache is present before operation, it tends to continue after operation, and if headache continues for 1 year, it usually persists without being reduced.

The aim of the study was to evaluate aetiological factors for postoperative headache after vestibular schwannoma (VS) surgery with respect to asymmetric activation of vestibular reflexes. After surgery, 27 VS patients with persistent postoperative headache, 16 VS patients without headache and 9 healthy controls were examined. The vestibular, cervicocollic and cervicospinal reflexes were evaluated to study whether asymmetric activation of vestibular reflexes could cause headache. The effect of neck muscle and occipital nerve anaesthesia and the effect of sumatriptan on headache were also evaluated. The vestibular function of VS patients with headache did not differ from that of VS patients without headache, but was abnormal when compared to that of normal controls. The cervicospinal and cervicocollic reflexes did not differ in the patient groups. Injection of lidocaine around the operation scar gave pain relief to two patients, and one of them had occipital nerve entrapment. Infiltration of lidocaine deep in the neck muscles in the vicinity of the C2 root did not alleviate headache, but caused vertigo. Nine patients with musculogenic headache got pain relief from supportive neck collars, and two patients with cervicobrachial syndrome got pain relief from manual neck traction. The study shows that asymmetric activation of cervicocollic reflexes does not seem to be the reason for headache. Headache seems to be linked to neuropathic pain, allegedly caused by trigeminal irritation of the inner ear and the posterior fossa, which has recently been linked to vascular pain.

The purpose of the study was to evaluate the usefulness of hearing preservation in vestibular schwannoma (VS) surgery. Hearing preservation was attempted in 123 of 383 patients operated on during the years 1979 to 1993 at Helsinki University Hospital. Hearing was preserved in 47 cases. Pure-tone averages (PTA) better than 30 dB were found in 12 cases postoperatively. Seventy percent of the patients rated their hearing preservation as valuable or very valuable. Only 8% did not find hearing preservation useful. Postoperatively, tinnitus was present in 62% of the patients, and it was a moderate problem in only 23% of the patients. In only one subject was the tinnitus a handicap that reduced the quality of life. Based on these experiences, we encourage surgeons to continue efforts to preserve hearing in VS surgery.

The aim of this study was to evaluate the effect of operation on tinnitus in vestibular schwannoma (VS) patients. Altogether, 251 VS patients who underwent surgery during the years 1979 to 1993 at Helsinki University Central Hospital were included in the study. Information on preoperative tinnitus was collected from previously acquired data and postoperative tinnitus was evaluated. Preoperatively, 62.6% of the patients had experienced tinnitus. Of those with preoperative tinnitus, 47.4% also had it postoperatively, but of those 93 patients without preoperative tinnitus, 39.8% had tinnitus postoperatively. Tinnitus is one of the primary symptoms of VS, together with hearing impairment and disequilibrium. The risk of postoperative tinnitus is almost 40%, and with preoperative tinnitus, the risk is 7.6% higher. In the majority tinnitus was not related to the surgery. Only a few patients had severe problems with tinnitus; difficulty understanding speech was the major complaint.

We retrieved information on 128 patients with vestibular schwannoma (VS) and 243 patients with Ménière's disease (MD) from the database of the otoneurologic expert system (ONE). The patients filled in a questionnaire concerning their symptoms, earlier diseases, accidents and tobacco and alcohol use. This information was then integrated with results of audiometric, otoneurologic and imaging studies. Forty-nine (38%) of the VS patients had the full triad of vertigo, hearing loss and tinnitus. The vertigo mimicked that in MD in 18 (14%) patients. The mean age of these patients was 48 years. There were 7 men and 11 women. The tumour was small (< 2 cm) in eight patients and medium-sized (2-4 cm) in seven patients. The mean attack duration in these 18 patients ranged from 5 min to 4 h. The attacks most commonly (69%) occurred only once or twice a year. Their intensity was moderate. Half of the patients had spontaneous nystagmus. Caloric asymmetry > 25% was detected in 61% of the patients. Tinnitus in these patients was mostly (49%) mild. Intense tinnitus was present only in 12% of patients. Headache was present in 25% of these patients.

The aim of the study was to evaluate the course of vestibular schwannoma (VS) when surgery was not attempted. The tumor may be slowly growing and surgery a risk for a patient. Twenty-eight patients out of 390 VS patients during years 1981-1995 were primarily recommended a non-surgical treatment. Another 3 patients refused the operation. Altogether 23 women and 8 men were evaluated. Their age varied from 30.6 to 74.6 years (median 56.7 years). Tumor size varied from 5 to 30 mm (median 15.0 mm) at the beginning of the follow-up. Patients symptoms, condition and other illnesses were recorded. Seven patients had neurofibromatosis 2 (3 of them had one hearing ear), 2 had severe mental problems, 5 patients had their only hearing ear and 11 patients were not recommended an operation because of their age and other illnesses. Patients were controlled with MRI at intervals from 1 to 3 years. The follow-up time varied from 1 to 20 years (median 2.0 years). The average tumor growth rate among unilateral VS patients was 0.035 cm/year and among bilateral tumors the average tumor growth rate was 0.015 cm/year. Two patients were later operated on, one 2 years after diagnosis because of the tumor growth and the other one 4 years after diagnosis-she had refused an operation earlier. Two patients could not be reached. Another patient had tumor growth but because of his illnesses he got a radiation beam instead of an operation. The majority of the patients could live fairly normal lives and required no treatment. Surgery is not the only alternative to VS patients. Wait-and-see policy is also a good alternative to those who have high operation risk or who refuse an operation.

In the head autorotation test (HART) gain is commonly used to determine the vestibulo-ocular reflex (VOR). The purpose of this work was to evaluate the relevance of phase (the phase difference between the eye and corresponding head movement) in describing the VOR. The phase was determined in 5 frequency bands in both degrees and milliseconds (ms) in 4 groups: 30 healthy adults, 15 elderly subjects, 37 vestibular schwannoma (VS) patients, and 35 Meniere's disease (MD) patients. In healthy adults and in MD patients the phase was close to nil in the frequency bands of 3 and 4 Hz. In elderly subjects phase lead was between 5.0 and 15.5 ms in each frequency band. Patients with VS showed a phase lag of -4.2 to -7.6 ms. The mean phase of the elderly in the frequency band of 3 Hz differed statistically significantly from that of MD and VS patients, and in the frequency band of 4 Hz from that of healthy adults and VS patients. In summary, the elderly had phase lead and VS patients showed increased phase lag in the frequency bands higher than 2 Hz. The phase is useful parameter together with gain in evaluating VOR and it seems to change in aged subjects and in patients with permanent vestibular lesion.

We have been able to culture acoustic neuroma (AN) tissues by taking small tumor pieces during surgery from the cisternal or, preferably, metal part of the tumor where macroscopic tissue degeneration is not prominent. The AN pieces were transported in culture tubes to our cell laboratory where they were sliced and transferred to culture medium. The AN tissue demands a crude culture suspension containing laminin. We have been successful in culturing 15 successive ANs. The cells have different morphological features with characteristics of type Anthony A and B. Four main cell types were recognized: ameboid microglia-like cells, spindle-shaped cells, racket-shaped cells, and kite-shaped cells. However, no immortal cell line could be established. Some of the cultures were viable for up to 4 months.

We investigated the effect of visual control on postural stability on a moving platform in 36 patients with Menière's disease (MD) in 25 patients with operated acoustic neurinoma (AN) and in 19 healthy controls. The force platform was placed on rails and oscillated linearly at frequencies from 0.2 to 5 Hz at a constant velocity of 30 mm/s. In all subjects, the support surface oscillation produced postural instability that differed significantly from the base line stability. The body sway velocity increased almost linearly with the increase of stimulation frequency. The MD patients swayed more than the AN patients at base line measurements in non-visual conditions but not during platform movement. In visual conditions the AN patients stabilized their posture significantly better than the MD patients, who showed deteriorating visual control of posture during platform movement. The controls differed from the patients in all test conditions except 5 Hz stimulation, which causes the body segment to fall into resonance. The Romberg quotients (RQ) in MD patients was significantly poorer during platform movement than in controls, except at 5 Hz stimulation. The AN patients had higher RQ values than controls, and mainly used vision to compensate their vestibular deficit. Thus, patients with MD fail to control their posture efficiently with vision during movement which may explain the visually induced dizziness in MD patients.

We studied predictive and pseudo random saccades in patients with cerebellopontine angle tumor. Target for the saccades was a laser beam which was reflected on the wall in front of the subject, and the stimulus was controlled by a computer. The fixed target was spaced at a distance of +/- 30 to each side of the subject. The random saccades jumped 20 degrees/40 degrees/60 degrees in an unpredictable manner. The saccade analysis program was based on pattern recognition. In the random saccade test none of the mean values of saccadic reaction time (SRT), saccadic accuracy (SA) and saccadic peak velocity (SPV) to the right or left differed significantly between the two groups. In the predictable saccade test there was statistically significant differences for certain variables: in right SRT (p < 0.01) and in left SRT (p < 0.01); in right SA (0.001 < p < 0.01) and in left SA (p < 0.001). The mean peak velocity (right SPV and left SPV) did not differ significantly between the two groups. When the stimulus is predictable, the saccades in a healthy subject are more timely spaced and accurate than in a patient. When the stimulus is unpredictable, "the memory of the past" has no importance and cannot help in saccade programming, and variability in the healthy subjects increases.

We examined the pseudo random smooth pursuit test in patients with cerebellopontine angle (CPA) tumors. Four different frequency combinations of sinusoids 0.15-0.35 Hz, 0.25-0.425 Hz, 0.3-0.7 Hz and 0.45-0.7 Hz were tested. Gain was calculated by comparing the smooth pursuit amplitude with stimulus after the supporting saccades had been removed. Phase was calculated by comparing maximum excursion of the eyes and stimulus. Gain was in the patients lower than in the controls in different frequency combinations, and the difference was statistically significant/highly significant in different frequency combinations. In the phase shift the differences were highly significant in the two higher frequency combinations and significant in the second frequency combination (0.25-0.425 Hz), while in the first frequency combination (0.15-0.35 Hz) the difference was not significant. The gain method was a somewhat better analyzing method than the phase shift method.

In acoustic neurinoma surgery, the surgeon is required to find a cleavage plane between the facial nerve and the tumor, and with the aid of the operating microscope this is usually achieved by fine dissection. A histological specimen of the nerve-tumor interface is available only if the facial nerve was hopelessly adherent to the tumor (usually a large or giant neoplasm) and the surgeon decided to sever the nerve to obtain a complete removal. The authors have examined immunohistochemically the nerve-tumor interface of 20 such facial nerves (six cases of neurofibromatosis 2 (NF2) and 14 of non-NF2) in a series of 351 acoustic neurinomas. The largest extrameatal dimension of the 20 tumors ranged from 20 to 51 mm (median 39 mm). In all of these 20 instances the nerve-tumor contact area was at least partially devoid of a clear-cut histological cleavage plane. Where the facial nerve trunk was attached to the surface of the tumor, nerve fibers of the contact areas either abutted directly against tumor cells or nerve fibers were seen to penetrate into the tumor tissue. Frank embedding of nerve fibers was more frequent in NF2.

The facial nerve is sometimes severed during the removal of acoustic neurinomas, either intentionally to ensure complete removal, or unintentionally because of difficulties in identification. In such cases we have, if possible, sutured the nerve stumps microsurgically, either end to end or by use of an intervening nerve graft. We analyzed the outcome of 25 instances of facial nerve suturing in a series of 219 patients operated on for acoustic neurinoma from 1979 to 1987. The first signs of recovery appeared at an average of 12 months, and there was continued improvement for several years. Recovery was graded from 1 to 6. The anastomosis was successful in 24 of the 25 sutured nerves, in that at least some facial movement and tone were restored (Grade 5 or higher). In 11 of the 25 cases, facial appearance at rest and with movement was moderately good (Grade 2 or 3). A Grade 1 result, with no perceivable facial dysfunction, was never achieved. Typically, oral muscles showed the most improvement and frontal muscles the least. Facial appearance was better at rest than with movement, which was always complicated by some degree of synkinesis. Closure of the eye was so good in 13 of the 25 cases that neither tarsorrhaphy nor an eyelid spring was necessary. When the facial nerve is severed, intraoperative suture is recommended, because it provides a chance for moderately good restoration of facial appearance.