Presymptomatic DNA and MRI diagnosis of neurofibromatosis 2 with mild clinical course in an extended pedigree

Neurofibromatosis 2 (NF2), a dominantly inherited disorder, typically manifests as bilateral vestibular schwannomas and predisposes to other nervous system tumors. In this study, we present a large pedigree with a benign course of NF2 (mild Gardner type) characterized by slowly growing vestibular schwannomas but few other manifestations. The family was thoroughly investigated with neurologic, ophthalmologic, and neuro-otologic methods including gadolinium-enhanced MRI of the head and spine and DNA linkage analysis. In the clinical analysis of 22 family members, MRI was superior to neuro-otologic methods in the detection of asymptomatic tumors. Based on the DNA linkage analyses we identified the NF2 mutation carriers with a high degree of certainty. These DNA markers (CRYB2, NEFH, D22S268, and D22S280) can also be used for presymptomatic diagnosis in other NF2 families. Early detection of NF2 gene mutation carriers has become possible using linkage analysis in familial NF2. MRI screening of carriers will reveal presymptomatic vestibular schwannomas (and other CNS tumors), making early intervention possible, but an efficient treatment strategy to prevent deafness has not yet been established.

Abrupt unilateral deafness modifies function of human auditory pathways

We studied nine patients with unilateral abrupt deafness caused by acoustic neuroma surgery. Cortical responses to tones delivered to the intact ear were recorded postoperatively with a 122-channel whole-scalp neuromagnetometer. In three patients, followed for 12 months with 2-4 measurements, evoked responses originating in the auditory cortices were weak and delayed one month after the operation in both hemispheres. During the follow-up, the amplitudes reached the control level. No response abnormalities were found in patients who were studied 1.5-4.5 years after the operation. Our findings suggest that abrupt unilateral deafness causes immediate changes in the function of auditory pathways of adult humans and that reorganization takes place within 1 year.

A comparison of static and dynamic calibration techniques for the vestibulo-ocular reflex signal

We investigated two calibration techniques commonly used with eye movement signals pertaining to the vestibulo-ocular reflex. Eye movement signals were recorded electro-oculographically as usual and calibrated using both static and dynamic calibration techniques. The calibration values of normals and patients were computed and compared to each other. Also gain parameters of vestibulo-ocular reflex which depend on the calibration were computed. We found that both techniques are chiefly equally valid, and there are no considerable differences in results computed with either one.

An essay on power of expert systems versus human expertise

In connection with several recent studies of medical informatics, the usefulness and use of expert systems have been both criticized and defended. We have examined the issue of the inference power of expert systems compared to that of human experts. At an abstract level we have shown that there is no doubt that expert systems could successfully complement human experts within strictly limited and well-defined specialties, and actually be of reasonable aid in diagnosis, provided that the expert systems have been correctly and effectively elaborated. Also practical experiments were conducted with our recently implemented expert system.

Database for vertigo

An interactive database has been developed to assist the diagnostic procedure for vertigo and to store the data. The database offers a possibility to split and reunite the collected information when needed. It contains detailed information about a patient's history, symptoms, and findings in otoneurologic, audiologic, and imaging tests. The symptoms are classified into sets of questions on vertigo (including postural instability), hearing loss and tinnitus, and provoking factors. Confounding disorders are screened. The otoneurologic tests involve saccades, smooth pursuit, posturography, and a caloric test. In addition, findings from specific antibody tests, clinical neurotologic tests, magnetic resonance imaging, brain stem audiometry, and electrocochleography are included. The input information can be applied to workups for vertigo in an expert system called ONE. The database assists its user in that the input of information is easy. If not only can be used for diagnostic purposes but is also beneficial for research, and in combination with the expert system, it provides a tutorial guide for medical students.

Cochlear vascular pathology and hydrops in otosclerosis

Three ears with otosclerosis were found incidentally in a series of human temporal bones examined to evaluate cochlear sensorineural degeneration. Otosclerosis was identified with microdissection, surface preparation technique and transmission electron microscopy. Vascular abnormalities were present in all ears, and otosclerosis involved the cochlear endosteum extensively, mainly in the scala tympani of the basal turn. In the scala tympani of the lower half of the basal turn, shunts had formed so that venules deviated abruptly from their normal radiating course towards the spiral vein, left the scala and entered into otosclerotic foci. There was a marked loss of radiating venules in areas where otosclerosis affected the endosteum of the scala. In the pair of bones capillaries in the stria vascularis were extremely dilated, the widest being 80 microns in diameter. The third single bone from a patient with Meniere's disease had severe cochleo-saccular hydrops. Ten serially sectioned temporal bones with known otosclerosis were reviewed. Two of the bones, one of which had cochleo-saccular hydrops, displayed vascular shunts in the scala tympani and enormously dilated strial capillaries with a maximum diameter of 139 microns.

Database for Vertigo

An interactive database has been developed to assist the diagnostic procedure for vertigo and to store the data. The database offers a possibility to split and reunite the collected information when needed. It contains detailed information about a patient's history, symptoms, and findings in otoneurologic, audiologic, and imaging tests. The symptoms are classified info sets of questions on vertigo (including postural instability), hearing loss and tinnitus, and provoking factors. Confounding disorders are screened. The otoneurologic tests involve saccades, smooth pursuit, posturography, and a caloric test. In addition, findings from specific antibody tests, clinical neurotologic tests, magnetic resonance imaging, brain stem audiometry, and electrocochleography are included. The input information can be applied to workups for vertigo in an expert system called ONE. The database assists its user in that the input of information is easy. It not only can be used for diagnostic purposes but is also beneficial for research, and in combination with the expert system, it provides a tutorial guide for medical Students.

Prognosis of falls among elderly nursing home residents

The survival rate of 207 nursing home residents who fell during a two-month study period was followed for 12 months and compared with that of 94 residents of the same nursing home who did not fall during the same period. One year after the fall, 74 fallers and 13 controls had died. In the group of fallers, the main factors associated with mortality were male gender, dementia, Parkinsonism, the use of antidepressants, diuretics and vasodilators. Among the controls, the main factors associated with mortality were Parkinsonism, diabetes and the use of diuretics. Thirty-eight fallers (33 women and 5 men) and one (female) control suffered a fracture; 32 of them required hospital attention, and 15 (47%) died during the same hospital stay. These results indicate that falls are an ominous sign, particularly if the subject has dementia, depression or Parkinsonism, or uses diuretics. The male subjects in this study had a lower injury rate than females, but their mortality rate was higher. In terms of prevention, the major concern should be the effective treatment of depression and Parkinsonism. Withdrawal of diuretics, when possible, may have an effect on mortality. Physical training and other stimulating activities should be beneficial, but subjects with severe dementia seem to be beyond this kind of prevention.

Reasoning in expert system ONE for vertigo work-up

An otoneurological expert system (ONE) was developed to help collect data and diagnose the work-up of vertigo of both central and peripheral diseases causing vertigo. Patient history and otoneurological and other examination results are used in the reasoning process. The history is interactively collected and is complemented with clinical examination results. The case history data can be either mandatory or supportive. Mandatory questions are used to confirm a diagnosis, and conflicting answers are used to reject an unlikely disease. Supportive questions support or suppress a diagnosis, but their presence is not obligatory. The reasoning procedure of ONE scores every question independently for different diagnoses, depending on how well they agree with the symptom entity of a disease. Diagnostic criteria are set for each disease, in Meniere's disease, for example, the full triad is required. Graphic displays illustrate the linear and nonlinear correlation between the symptoms and diseases. For instance, both second-long Tumarkin-type attacks and attacks lasting hours give a high score while intermediately long attacks score much lower in Meniere's disease. To be able to take even rare diseases into consideration we try to diminish the possibility of a wrong decision rather than maximize the likelihood of reaching only one right decision.

Predictable and pseudo random saccades in patients with acoustic neuroma

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.

Middle ear imaging in neurotological work-up

Middle ear imaging constitutes a homogeneous test battery for evaluation of neurotological disease. The imaging comprises infra-sound fistula test, ABR, tympanoscopy, ECoG, and trans-promontiorial cochlear blood flow measurement. We used a fistula test with infra-sound loading on posturography. In tympanoscopy we used 5 degrees and 25 degrees endoscopes with a diameter of 1.9 mm and length of 125 mm. In blood flow measurement we used laser-Doppler system with a stainless steel tip placed on the basal turn against stira vascularis. The flux was analyzed with a computer with custom-made software. In ECoG, a silver ball electrode was placed on the round window. In 64 cases evaluated we were not able to verify a spontaneous PLF by tympanoscopy. Symptoms typical for spontaneous PLF with positive fistula test turned out to be caused by endolymphatic hydrops. Sudden deafness usually did not show reduced cochlear blood flow, but often an endolymphatic hydrops. Fistula test was positive in about 25% of cases with endolymphatic hydrops. Tympanoscopy caused very few complication. The procedure takes about one hour and is done ambulatorily.

Effect of intratympanically administered gentamicin on hearing and tinnitus in Menière's disease

We have examined the effect of intratympanic gentamicin on hearing and tinnitus in 69 patients with intractable Menière's disease. Tinnitus was scored from 1 to 4 depending on its severity. The mean pure tone audiometry level before treatment was 57.5 dB and 1 year after treatment 63.5 dB Five subjects became deaf in the treated ear, and in 13 subjects hearing loss was > 10 dB and in 21 subjects 0 10 dB. In 25 subjects significant improvement (> 10 dB) was gained, and in 5 patients. Tinnitus was significantly reduced after treatment with gentamicin. A total of 66 patients had tinnitus before treatment and tinnitus relief was rated as good. Four percent of the subjects had no tinnitus, 30% had slight tinnitus. 27% moderate tinnitus. 18% severe and 8% handicapping tinnitus.

Postural control in Menière's disease and acoustic neurinoma when studied on a linearly oscillating platform

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.

Computer assisted data collection in vestibular disorders

We have developed an interactive database for vertigo than can be used to assist in the diagnostic procedure and to store the data in a form of a database. The database offers the possibility to split and reunite the collected information in a desired way. The database contains detailed information about patient history, symptoms and findings in neurotological, audiological and imaging tests. The symptoms are classified into three sets of questions: vertigo (including postural instability), hearing loss and tinnitus, and provoking factors. Confounding disorders are screened. The neurotological tests involve saccades, smooth pursuit, posturography and caloric test. In addition, findings in specified antibody testing, clinical neurotological tests. MRI, brain stem audiometry and electrocochleography are included. The input information can be applied in an expert system ONE for vertigo work-up. The database is user-friendly. Besides diagnostic purposes the database is excellent for research purposes, and combined with the expert system it works as a tutorial guide for medical students.

Using magnetic coil signals with EOG signals in computer analysis of vestibulo-ocular reflex

Since EOG signals are rather noisy, but magnetic coil signals almost noiseless, the latter type is a good reference to the former which is much easier to record. Concurrently recording magnetic coil and EOG signals we could verify some details as saccades which are often difficult to detect in noisy signals. It is important to recognise such phenomena in eye movement signals, because these affect the gain parameter computed between the vestibulo-ocular reflex signal and the head movement signal.

Vestibular evoked responses in man: methodological aspects

We have developed a stimulation method where the subject is sitting and the head is rotated with shock bursts elicited by a shaker with a repetition rate of 2 Hz. The head movement is monitored with an accelerometer mounted on the cheek by a head band. The maximum amplitude of the head movement is 3 degrees. The electrodes were places on vertex with a negative electrode on the mastoid. During stimulation, 90 dB white noise was applied to the ears to mask the noise generated by the stimulus. We recorded following responses: i) VER from ipsilateral ear, ii) VER from contralateral ear, iii) eye movement with EOG, and iv) movement of the head. Amplification and averaging of the signal were made with an evoked response recorder (Nihon Kohden, Neuropac four). From 200 to 2,000 averaged responses were collected and stored for further analysis on a floppy disc. During second stage filtering the data were fed into a microcomputer where appropriate programs were used to eliminate the EMG and movement artifacts.

Pseudo random smooth pursuit test in patients with acoustic neuroma

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.

Recovery of the sutured facial nerve after removal of acoustic neuroma in patients with neurofibromatosis-2

The authors compared the long-term recovery of sutured facial nerves after the removal of 8 neurofibromatosis-2 (NF2)-associated and 22 non-NF2 acoustic neuromas. The patients were from a series of 270 patients operated on for an acoustic neuroma between 1979 and 1989. The assessment was done with a modified House and Brackmann scale from video recordings. At least some facial movement or tone was achieved (Grade 5 or better) in all but three patients, but in none was the recovery excellent. The facial function, judged by the overall appearance in movement, recovered less in patients with NF2 (P = 0.048); a moderately good recovery (Grade 3 or better) was seen in one patient of eight with NF2, as compared with 13 of 22 with non-NF2. In conclusion, if the tumor cannot be peeled off easily from the facial nerve in patients with NF2, leaving a fragment of tumor behind is preferable to cutting and suturing the facial nerve.

Effect of hand-arm vibration on inner ear and cardiac functions in man

To evaluate distant effects of hand-arm vibration we studied Finnish forestry workers using chain saw during the years 1972 through 1990. The hearing was tested annually and individual regression curves for sensorineural hearing loss (SHL) were calculated. Robinson's model was used in prediction of SHL. The heart rate variation (HRV) indexes at rest and during deep breathing test were analyzed to measure autonomic nervous function. In Robinson's model the measured SHL (17.8 dB) respected the predicted SHL (17.2 dB). The subjects with VWF had on average, 10 dB greater hearing loss than those who did not have VWF. The regression model based increase of hearing loss during follow up correlated with ageing, not to VWF. The intercept differed significantly in those with VWF from those without VWF. We found a significant difference between HRV indexes during deep breathing test in those with the shortest and those with the longest vibration exposure. The HRV decreased with age, but multiple regression analysis showed that the total exposure time to vibration had an independent negative association with HRV indexes. Our results suggest that prolonged exposure to vibration caused by chain saw has negative effects an autonomic functions. The aggravated hearing loss in subjects with VWF may be due to vibration induced changes in the autonomic nervous system or internal factors of the blood vessels.

Vibration exposure and prevention in Finland

The number of annually compensated occupational diseases due to exposure to hand-arm vibration (HAV) has decreased during the last 15 years. The number of exposed workers has been declining in Finland, especially in forestry work, as harvesters have increasingly replaced manual chain saw operations. During the entire 1970s, forest work caused more cases of vibration-induced occupational diseases than all industrial branches together. The decrease is mainly due to the technical development of chain saws, but also to the effective health care services in Finland. Other factors such as warm transport, warm rest cabins in which to take pauses at work, warm meals, adequate protective clothing, and vocationally adjusted early medical rehabilitation have helped to cut down health hazards, especially in forest work. The number of new cases has been decreasing in Finland not only in forestry but also in other industries. In Finland a considerable amount of research has been conducted to hand-arm vibration, resulting in the increased awareness of the health risks related to certain occupations. This has helped to carry out the Primary Health Care Act (1972) followed by the Occupational Health Care Act (1979) which obligates employers to arrange occupational health care for their employees. We believe that the research activity has contributed significantly to achieving the present health in Finnish work places. The purpose of the present paper is to describe the cases of occupational exposure to HAV, and the effectiveness of different preventive measures in Finland.

Smoking habits and postural stability

PURPOSE

It has been reported that tobacco smoking temporarily affects postural stability We have examined whether smoking habits have a long-term effect on the body balance control using computer-aided posturography.

SUBJECTS AND METHODS

The postural stability of 80 male forest workers was measured with a force platform technique with eyes closed. Average body sway velocity (ASV [mm/s]) was determined and used as a stability index. Detailed interviews on tobacco smoking and otologic examinations were carried out. Smoking habits were classified into five categories: nonsmokers (53.8%), ex-smokers (17.5%) and current smokers, comprising light (3.8%), moderate (15%), and heavy (10%) smokers.

RESULTS

The smoking habits of the subjects correlated significantly with ASV, but hours of the exposure to noise and hand-arm vibration from chain saws did not. The correlation of the smoking habits remained significant even after eliminating the effect of age and exposure by partialization. Age in itself had no effect on ASV but interacted with smoking to increase ASV. The group means of ASV increased with the increase in smoking. Significant differences in ASV were found in the moderate and heavy smokers compared with the nonsmokers.

CONCLUSION

Smokers exhibited more unstable posturographic results than nonsmokers. Smoking habits were suggested to have a long-term effect on the posture control system.

Interface between the facial nerve and large acoustic neurinomas. Immunohistochemical study of the cleavage plane in NF2 and non-NF2 cases

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.

Intratympanic gentamicin in bilateral Menière's disease

Treatment of bilateral Menière's disease is a delicate task. Streptomycin has demonstrated its ability to successfully control the vertigo attacks, but in some cases it results in oscillopsia and transforms the periodic attacks to permanent instability. If the site of the active labyrinth can be determined, a more specific treatment can be tried. We have treated 14 patients with intractable bilateral Menière's disease with intratympanic gentamicin (Garamycin, 40 mg/ml) administered initially in either 1, 2, 3, or 4 injections. The patients were tested at frequent intervals and followed up for 2 years. The work capacity, severity of vertigo, and gait difficulties were scored before treatment and during each test occasion. The postural stability was evaluated on a force platform and sway velocity was analyzed. Before treatment, moderate or severe reduction of work capacity was experienced by all of the subjects, which correlated to severity of vertigo and gait problems. Two years after treatment, the vertigo attacks were eliminated in 11 subjects and controlled in three subjects. The work capacity of three subjects was still moderately or severely reduced. This reduction depended on gait disturbance and Tumarkin attacks. The average postural stability returned to pretreatment level 2 years after the treatment was begun. The outcome of the caloric responses did not correlate with the outcome of the treatment. Hearing was not significantly affected by the treatment. Intratympanic gentamicin treatment is a relatively safe and effective way to treat bilateral Meniere's disease when the symptoms can be localized to one ear.