I. Pyykkö

Computerized Posturography, a Development of the Measuring System

A computerized posturography system is composed of a custom made strain gauge force platform and it utilizes commercially available amplifiers. The body sway response signals are digitized for the calculation of the following parameters by a computer: average velocity of body sway, mean value for fore-aft and lateral body sway, and maximal amplitude of body sway. Calf muscles were exposed to vibration to disturb the postural control. The program contains appropriate filters to remove transient and quantification noise.

Vibration syndrome among Finnish forest workers between 1972 and 1990

SummaryA longitudinal study on vibration syndrome among professional forest workers was carried out in Finland from 1972 to 1990. In the course of the follow-up the weighted vibration acceleration of chain saws decreased from about 14 to 2 m/s2. The prevalence of vibration-induced white finger (VWF) decreased gradually from 40% to 5%. Numbness occurred mainly at night, and its prevalence decreased from 78% to 28%. During part of the follow-up period (1975–1990) the complaints of hand muscle weakness decreased from 19% to 9%. Disorders of the musculoskeletal system were considered to cause more disability than VWF. The decreased vibration acceleration and the lighter weight of chain saws were considered the main reasons for the decrease in the prevalence of vibration-induced symptoms.

Postural Stability, Neck Proprioception and Tension Neck

We examined whether tension neck (TN) may due to inadequate proprioceptive and vestibular activation of the cervico-collic reflex (CCR). CCR and vestibulospinal responses (VSRs) were recorded from 106 forest workers by stimulating the neck, lumbar or calf proprioceptors by vibration. The VSRs were recorded with posturography. TN occurred in 27 out of 106 subjects. The subjects with TN (48.5 years) were older than those without TN (43.1). The mean body sway during quiet stance was the same in both groups during the neck stimulation. In subjects with tension neck stimulation of neck or lumbar proprioceptors caused excessive, unpredictable body excursion in the lateral and anteroposterior direction that continued after stimulation. Results from stimulation of lower limb proprioceptors did not significantly differ between the 2 groups. In logistic regression analysis a model to predict TN consisting of perstimulatory postural stability (odds ratio 1.4) and poststimulatory postural stability (odds ratio 1.8) turned out to be statistically significant. The anatomical findings of CCR in the medulla oblongata suggest that neck muscle afferents control the posture and muscle activity of the neck. The erroneus facilitation of proprioception in TN subjects indicate that TN may be raised by inadequate facilitation of CCR.

Vibration stimulus induced EEG bursts in isoflurane anaesthesia

The EEG and heart rate reactions to vibration stimulus were studied in 14 patients during moderately deep surgical isoflurane anaesthesia, at a level when EEG showed a burst suppression pattern. Vibration applied to the palm of the hand induced bursts in EEG in 12 patients, usually with a latency of about 0.5 sec from the onset, or from the end of the 3 sec stimulus. Increases in heart rate were seen at bursts related to both vibration onset and offset, as well as at spontaneous bursts. With spontaneous bursts, an initial positive wave was frequently seen. In 6 patients the vibration induced bursts were different in shape from the spontaneous bursts; no initial positive wave was seen before the negative DC shift in Cz-Fz recording. We conclude that EEG bursts can be evoked by a non-noxious stimulus such as vibration in patients during isoflurane anaesthesia.

Changes in Vestibulo-ocular Reflex of Elderly People

Dizziness is a common symptom in elderly people. Head autorotation test (HART) has earlier shown no significant vestibulo-ocular reflex (VOR) disturbances in healthy elderly subjects. We used our recently developed HART to determine VOR in 14 elderly volunteers without otoneurological diseases and sedative medications. Gain and phase were determined in 5 frequency bands from 0.5 to 5 Hz. The gain of the elderly was significantly increased to 1.11-1.27 in the frequency range of 3-5 Hz compared with the controls. The phase lead of 7-8 degrees in the frequency bands of 2 and 4 Hz differed significantly from normative values of the controls. The percentage of the elderly to reach high-frequency head movements was diminished to 50% in the frequency band of 3 Hz and to 36% in the frequency band of 4 Hz (controls 100% and 95%, respectively). The individual HART results were abnormal in 86% of the elderly. The high-frequency VOR of the elderly was inaccurate in magnitude and timing. More than half of aged subjects were not able to generate voluntary fast head movements. These findings may explain the high prevalence of dizziness and falls in elderly subjects.

The Site of Impulse Generation in Transcranial Magnetic Stimulation of the Facial Nerve

The facial nerve can be stimulated in its intracranial course through transcranial magnetic stimulation (TMS). We studied the site of impulse generation produced by TMS by comparing the latencies of the muscle evoked potentials (MEPs) elicited with TMS and intracranial electrical stimulation (IES) of the facial nerve during neurosurgical posterior fossa procedures. In a series of 25 patients, the mean latency of the TMS elicited MEPs, recorded in the orbicularis oris muscle, was 5.0 ms (SD 0.58). Also IES of the distal part of the facial nerve in the internal acoustic meatus showed a mean latency of 5.0 ms (SD 0.68). Proximal IES in the root entry zone of the facial nerve, and intermediate IES between root entry zone and meatus, produced MEPs with significantly longer latencies compared to TMS and distal IES (p < 0.05). The findings suggest that the TMS induced facial nerve activation, leading to a MEP response, takes place within the internal acoustic meatus.

Increased incidence of retching and vomiting during periovulatory phase after middle ear surgery

PurposeTo assess the effect of the menstrual cycle on post-operative retching and vomiting (R& V) after middle ear surgery, and the efficacy of prophylaxis against R& V in female patients with transdermal scopolamine during either general or local anaesthesia and with intravenous ondansetron during general anaesthesia.MethodA post hoc analysis of the data on 85 female patients with normal menstrual cycles from three prospective studies on the prophylaxis of postoperative nausea and vomiting after middle ear surgery on 205 patients.ResultsPeriovulatory period (menstrual dates 11–24) and history of motion sickness were predictors for R& V. During 2–24hr, both the percentage of patients needing droperidol and the mean number of doses were lower in the perimenstrual group (menstrual dates 25-10) than in the periovulatory group 27 vs 51% (P < 0.05) and 0.2 vs 0.7 (P < 0.01), respectively. Prophylaxis with transdermal scopolamine was a predictor for lowered R& V (P < 0.05) and resulted in fewer doses of droperidol (0.4 ± 0.7 vs 1.4 ± 1.5, P < 0.01). This reduction was significant during the periovulatory period (from 1.4 ± 1.3 to 0.3 ± 0.5, P < 0.005). Ondansetron reduced the mean need for droperidol from 1.4 ± 1.5 to 0.6 ± 0.8, (P < 0.05).ConclusionThe incidence of R& V after middle ear surgery was lower during the perimenstrual phase. In the periovulatory phase, transdermal scopolamine was more efficient as prophylaxis against R& V than ondansetron. All female patients scheduled for middle ear surgery should be considered individually to receive prophylaxis against R& V.RésuméObjectifÉvaluer l’influence du cycle menstruel sur les efforts pour vomir et les vomissements (EV) postopératoire après une chirurgie de l’oreille moyenne; évaluer chez des patientes l’efficacité de la prophylaxie de la scopolamine transdermique sur les EV pendant l’anesthésie générale ou locale et de l’ondansetron iv pendant l’anesthésie générale.MéthodesUne analyse des données recueillies chez 85 patientes dont les cycles menstruels étaient normaux à partir de trois études prospectives portant sur la prophylaxie des nausées et vomissements postopératoires après une chirurgie de l’oreille moyenne impliquant 205 patients.RésultatsLa période périovulatoire (du 11e au 24e jours du cycle) et une histoire du mal des transports ont été des facteurs pronostiques des EV. Pendant 2–24 h, le pourcentage de patientes nécessitant du dropéridol et le nombre moyen des doses requises étaient tous deux moins élevés dans le groupe périmenstruel (jours des menstruations 25–10) que dans la période périovulatoire 27 vs 51% (P < 0,05) et 0,2 vs 0,7 (P < 0,01) respectivement. La prophylaxie à la scopolamine transdermique était un facteur pronostique en ce qui concerne la diminution de la fréquence des EV (P < 0,05) et fait baisser le nombre des doses de dropéridol (0,4 ± 0,7 vs 1,4 ± 1,5, P < 0,01). Cette réduction était significative pendant la période périovulatoire (de 1,4 ± 1,3 à 0,3 ± 0,5 P < 0,005). L’ondansetron a diminué le besoin moyen de dropéridol de 4 ± 1,5 à 0,6 ± 0,8 (P < 0,05).ConclusionL’incidence des EV après une chirurgie de l’oreille moyenne était plus basse pendant la période périmentruelle. Dans la phase périovulatoire, la scopolamine transdermique était plus efficace pour prévenir les EV que l’ondansetron. Toutes les patientes programmées pour une chirurgie de l’oreille moyenne devraient être considérées individuellement pour recevoir un traitement préventif contre les EV.

Effects of Atropine and Scopolamine on Bradycardia and Emetic Symptoms in Otoplasty

Objective: To assess the effects of unilateral or bilateral otoplasty on bradycardia and postoperative nausea and vomiting (PONV) and the efficiency of transdermal scopolamine in the prophylaxis of PONV. Study Design: Post hoc assessment of the data from a double‐blind, randomized study. Methods: Fifty otoplasty patients were studied; half of them received randomly and in double‐blind fashion a transdermal therapeutic system (patch) of scopolamine (TTS‐scopolamine) as prophylaxis against PONV before general anesthesia. The placebo group received atropine 10 μg·kg−1 intravenously during induction. Results: The scopolamine‐treated patients suffered more from moderate peroperative bradycardia (8/25; P < .05) than the atropine‐treated patients (1/25). Two patients wearing a half of the TTS‐scopolamine patch needed intravenous atropine. After unilateral otoplasty, none of the TTS‐scopolamine‐treated patients and 50% of the atropine‐treated patients suffered from PONV. After bilateral operation, the respective incidences were 39% and 81% (P < .01). After unilateral otoplasty no patient needed droperidol, but after bilateral otoplasty, 12 of 19 of the atropine‐treated and 4 of 18 (P < .05) of the scopolamine‐treated patients needed droperidol. The mean numbers of doses of droperidol were 0.8 ± 0.9 and 0.3 ± 0.6 (P < .05), respectively. Two additional patients, wearing half of the TTS‐scopolamine patch, suffered from mild central anticholinergic syndrome. Conclusion: TTS‐scopolamine offers effective prophylaxis against PONV (auriculoemetic reflex), but does not protect from bradycardia (auriculocardiac reflex) in otoplasty. Cutting of the TTS‐scopolamine patch may lead to undesirable side effects.

Vestibulo-ocular and Vestibulo-spinal Reflexes in Evaluation of Vestibular Lesions

In order to evaluate to what extent different diseases causing vertigo can be detected by studying vestibulo-spinal and vestibulo-ocular reflexes, 146 patients were examined. The diagnosis classes were: periodical attacks, position induced attacks, vestibular neuronitis, brain concussion, cerebrovascular disorders and acoustic neurinoma. Dynamic posturography was performed on all the patients, standard bithermal caloric test on 129 and voluntary saccades on 127 patients. The proportion of pathological test results in posturography exceeded that in the caloric test in all but one diagnosis class. In vestibular neuronitis the amount of abnormal test results was low in posturography, probably due to vestibular compensation. Posturography tested with eyes open and with 80 Hz vibration revealed disturbances in equilibrium the most sensitively.

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 Menières 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.