Postural control in restless legs syndrome with medication intervention using pramipexole.

Central dopamine regulation is involved in postural control and in the pathophysiology of restless legs syndrome (RLS) and Parkinson's disease (PD). Postural control abnormalities have been detected in PD, but there are no earlier studies with regard to RLS and postural control. Computerized force platform posturography was applied to measure the shift and the velocity (CPFV) of center point of forces (CPF) with eyes open (EO) and eyes closed (EC) in controls (n = 12) and prior and after a single day intervention with pramipexole in RLS subjects (n = 12). CPFV (EO) was significantly lower in the RLS group (p < 0.05) than in controls. After pramipexole intake, the difference disappeared and the subjective symptom severity diminished. Pramipexole did not significantly influence CPFV (EC) or CPF shift direction. Subjects with RLS used extensively visual mechanisms to control vestibule-spinal reflexes to improve or compensate the postural stability. Further research is needed to clarify altered feedback in the central nervous system and involvement of dopamine and vision in the postural control in RLS.

Head tilt is pronounced after an ipsilateral head roll in patients with vestibular schwannoma.

The study aimed to measure utricular function by directly quantifying head tilt in vestibular schwannoma (VS) patients using regular video-oculography (VOG) equipment with integrated head-position sensor, and to correlate the results with patients' symptoms and signs. We recorded head tilting after exclusion of visual cues (static head tilt), and after returning to the centre following lateral head rolls towards each side [subjective head vertical (SHV)]. Head tilt in 43 patients was measured preoperatively and approximately 4 months postoperatively, and compared to that of 20 healthy subjects. Symptoms were assessed with a structured questionnaire. Static head tilt in patients was significantly greater than in controls (1.0° ± 0.9°) preoperatively (1.6° ± 1.5°, p = 0.04) and postoperatively (1.7° ± 1.5°, p = 0.01). Mean SHV in patients was significantly greater than in controls (1.2° ± 1.0°) preoperatively (2.0° ± 1.9°, p = 0.03) and postoperatively (2.5° ± 1.8°, p = 0.001), increasing non-significantly after surgery (p = 0.3). Side-specific SHV after ipsilateral head rolls was significantly greater than after contralateral head rolls preoperatively (2.8° ± 3.3° vs. -0.5° ± 3.0°, p = 0.001) and postoperatively (3.3° ± 3.0° vs. 0.6° ± 3.2°, p < 0.001). The intensity of dizziness increased postoperatively (p = 0.04), but its effect on quality of life remained unchanged. In conclusion, commercial VOG equipment including a head-position sensor allows direct evaluation of head tilt in VS patients. The slight head tilt towards the ipsilateral side becomes most evident after returning from an ipsilateral head roll.

Suppression of spontaneous nystagmus during different visual fixation conditions.

Analysis of spontaneous nystagmus is important in the evaluation of dizzy patients. The aim was to measure how different visual conditions affect the properties of nystagmus using three-dimensional video-oculography (VOG). We compared prevalence, frequency and slow phase velocity (SPV) of the spontaneous nystagmus with gaze fixation allowed, with Frenzel's glasses, and in total darkness. Twenty-five patients (35 measurements) with the peripheral vestibular pathologies were included. The prevalence of nystagmus with the gaze fixation was 40%, and it increased significantly to 66% with Frenzel's glasses and regular room lights on (p < 0.01). The prevalence increased significantly to 83% when the regular room lights were switched off (p = 0.014), and further to 100% in total darkness (p = 0.025). The mean SPV of nystagmus with visual fixation allowed was 1.0°/s. It increased to 2.4°/s with Frenzel's glasses and room lights on, and additionally to 3.1°/s, when the regular room lights were switched off. The mean SPV in total darkness was 6.9°/s. The difference was highly significant between all test conditions (p < 0.01). The frequency of nystagmus was 0.7 beats/s with gaze fixation, 0.8 beats/s in both the test conditions with Frenzel's glasses on, and 1.2 beats/s in total darkness. The frequency in total darkness was significantly higher (p < 0.05) than with Frenzel's glasses, and more so than with visual fixation (p = 0.003). The VOG in total darkness is superior in detecting nystagmus, since Frenzel's glasses allow visual suppression to happen, and this effect is reinforced with gaze fixation allowed. Strict control of visual surroundings is essential in interpreting peripheral nystagmus.

Subjective head vertical test reveals subtle head tilt in unilateral peripheral vestibular loss.

Utricular dysfunction has been indirectly measured with subjective visual horizontal or vertical testing. Video-oculography equipment with integrated head position sensor allows direct evaluation of head tilt. The aim was to assess head tilt after peripheral vestibular lesion by recording tilting of the head after excluding visual cues (static test condition), and after three lateral head tilts to both sides [subjective head vertical (SHV)]. Thirty patients with unilateral, peripheral vestibular loss were measured in the acute state, and 3 months later. Twenty healthy, age- and sex-matched subjects served as controls. Mean static tilt of 2.6 ± 1.1° in patients with acute vestibular loss differed significantly from that of 1.0 ± 0.4° in healthy subjects (p = 0.004), and from that of 1.1 ± 0.5° during the follow-up visit (p = 0.008). The mean SHV of 3.4 ± 0.7° in patients with acute vestibular loss was significantly more than that of 1.2 ± 0.5° in controls (p < 0.001). The SHV towards the lesion was 4.9 ± 1.0° while returning from the lesion side and 2.0 ± 1.0° while returning from the healthy side. The SHV was definitely abnormal in 60%, moderately abnormal in 20% and normal in 20% of the patients in acute state. Abnormal SHV persisted in only 20% of the patients indicating that recovery of the peripheral utricular function is occurring within months. In summary, head tilts slightly towards acute peripheral lesion, and this tilting is reinforced, when the head is actively moved on the lesion side.

Effect of visual information on postural control in patients with schizophrenia.

Lateralized motor and attentional abnormalities contribute to schizophrenia, but little is known about possible abnormalities in neural machinery involved in postural control. We examined postural stability of 22 patients with schizophrenia taking medication and 14 healthy control participants using computerized force platform posturography. The shift in the center point of pressure in the condition of eyes open versus eyes closed characterizes the effect of visual information on body posture. Closing the eyes had less of an effect on the center point of velocity (velocity sm/s) in the patients with schizophrenia than in the control group (median change, 36% vs. 70%, p = 0.0006). Change in the body position during eye closure tended to be directed rightwards in the control group but leftwards in the group with schizophrenia (p = 0.025). The results show that visual component had less dominance in the balance control of these patients with schizophrenia. The lateralized effect of visual information on posture was also impaired.

Video-oculography findings and vestibular symptoms on the day of stapes surgery.

Vestibular symptoms are common after stapes surgery and may prevent outpatient treatment. The cause of vestibular symptoms is unclear, and in previous studies objective measurements have been obtained few days after the surgery. The aim of the study was to evaluate the existence and nature of any early, and possibly temporary vestibular irritation that occurs immediately after surgery. Twenty-one patients who had an opening of the oval window were prospectively included. Postoperative symptoms were collected and eye position curves were recorded with video-oculography (VOG) an average of 4 h after surgery. Early vestibular symptoms were found in 11 (52%) patients. Four patients had rotatory vertigo, three had floating sensation, one experienced a tilting sensation, and two had unspecific dizziness. Two patients vomited after surgery. When VOG was performed all but one were free of symptoms. After surgery, spontaneous nystagmus was found in three (14%) asymptomatic patients when gaze fixation was prevented. The prevalence of 33% (7 of 21 patients) of latent, spontaneous, horizontal-torsional nystagmus seen only during lateral gaze towards the direction of fast phase was significantly higher (P = 0.0001) than in healthy controls. The occurrence of nystagmus did not correlate with vestibular symptoms (P = 0.30). Slight, direction-fixed, latent, spontaneous horizontal-torsional nystagmus in some patients is consistent with a minor disturbance of semicircular canals, although it was not related to the sensation of dizziness. Recordings during stapes surgery may be needed to ascertain the origin of vestibular symptoms. Regarding vestibular symptoms and signs, patients may be safely discharged a few hours after stapes surgery.

On signal analysis of three-dimensional nystagmus.

Nystagmus needs to be stimulated for healthy subjects, but in patients it can also be spontaneous. By recording spontaneous nystagmus it is possible to reveal underlying disorders of the semicircular canals of the inner ear. We developed a signal analysis technique for this purpose and tested it with 28 otoneurological patients who had disorders in their semicircular canals. Our test results support the postulate how nystagmus should appear under these conditions and agree with results presented in the otoneurological literature.

Motorized head impulse rotator in patients with vestibular schwannoma.

CONCLUSION: Motorized head impulse rotator is an effective technique to assess peripheral vestibular function. Approximately a quarter of patients with vestibular schwannoma (VS) had preserved preoperative responses. Vestibular disability could not be predicted based on vestibulo-ocular reflex (VOR) performance during motion stimuli, or in the caloric test. OBJECTIVES: To explore motorized head impulse rotator for evaluation of angular horizontal VOR in patients with VS, and to compare these responses to those of the caloric test and the symptoms. PATIENTS AND METHODS: We prospectively recorded head and eye position during unpredictable motorized head impulses in 38 patients with VS. We calculated gain and asymmetry of VOR (mean +/- 95% CI), and the results were compared to those of the caloric test and a questionnaire regarding dizziness, hearing and quality of life. RESULTS: The VOR during motorized impulses was abnormal in 71% of patients. Asymmetry in gain correlated significantly (p < 0.001) with unilateral weakness in the caloric test. Preoperative gain was significantly lowered to 0.83 +/- 0.08 on the ipsilateral side compared to 0.98 +/- 0.06 on the contralateral side. Postoperative gain on the operated side of 0.53 +/- 0.05 was significantly different from preoperative gain (p < 0.001). Findings in vestibular tests did not correlate with subjective sensation of dizziness.

Simultaneous bilateral stapes surgery.

CONCLUSIONS: The patients recovered from the surgery as after unilateral surgery. The success rate for hearing improvement was good both subjectively and objectively, and this was also displayed in the quality of life. According to our study, simultaneous bilateral stapes surgery can be performed safely in selected patients with bilateral conductive hearing loss. OBJECTIVES: Otosclerosis is bilateral in the majority of patients. In this study we evaluated the outcome of simultaneous bilateral stapes surgery. SUBJECTS AND METHODS: Eighteen patients suffering from bilateral otosclerosis or osteogenesis imperfecta were prospectively included. After operation, hearing and vestibular function were followed by audiometry and visual feedback posturography (VFP). Patients estimated their hearing gain, the intensity of vestibular symptoms and quality of life score with a questionnaire during the follow-up period of 1 year. RESULTS: The mean improvement in pure-tone average (PTA) air conduction (PTA-AC) was 18 dB (range 1-41 dB). The mean air-bone gap (AB-GAP) diminished from 22 dB (range 10-41 dB) to 7 dB on both sides (range 0-18 dB). The mean preoperative score of 2.3 for hearing improved significantly to 4.1 (p<0.001). Vestibular symptoms were mild and temporary. The VFP was not permanently impaired in any of the patients. The quality of life score improved significantly from 3.4 to 1.3 postoperatively (p<0.001).

Motorized head impulse rotator for horizontal vestibulo-ocular reflex: Normal responses.

OBJECTIVE: To characterize the horizontal angular vestibulo-ocular reflex using a new motorized head impulse rotator and electro-oculography technique. DESIGN: Prospective case-control study. PARTICIPANTS: We included 22 healthy volunteers with unpredictable, horizontal motorized head impulses with a mean velocity of 170 degrees/s and a mean acceleration of 1550 degrees/s2. We recorded head and eye position and calculated gain, asymmetry, and latency of the vestibulo-ocular reflex. All subjects underwent testing twice while viewing a far (140 cm) target to evaluate the repeatability of the measurement. In addition, 8 of these subjects underwent testing while viewing a near (15 cm) target. We reported findings as mean +/- SD. RESULTS: The mean gain during the 30-millisecond interval before peak head velocity and during the interval when head velocity ranged from 100 degrees /s to 120 degrees/s was 1.08 +/- 0.10. The mean asymmetry in gain between sides was 3.7% +/- 2.8%, and the mean latency of the vestibulo-ocular reflex was 3.4 +/- 6.3 milliseconds. There was a statistically significant correlation between consecutive gain measurements for each subject (r = 0.59; P=.004). The mean gain for the near target was 1.26 +/- 0.10 and was significantly higher than that for the far target (P = .002). CONCLUSIONS: The vestibulo-ocular reflex measurements using our novel system are comparable to those achieved using other techniques. These results suggest that a motorized head impulse rotator with electro-oculography allows reliable and fast measurement of the vestibulo-ocular reflex. In addition, the method is safe, repeatable, and thus could be a useful tool in the clinical assessment of the vestibulo-ocular reflex.

Simultaneous bilateral stapes surgery--a pilot study.

CONCLUSIONS: The short-term postoperative results of bilateral stapes surgery were satisfactory. Hearing results between the two ears were comparable and there was no increased complication risk for the second ear. The results are encouraging, although a larger series and longer follow-up time are needed to confirm them. OBJECTIVE: The purpose of our study was to evaluate the preliminary outcome of simultaneous bilateral stapes operation. PATIENTS AND METHODS: Eight patients suffering from bilateral otosclerosis and one from osteogenesis imperfecta were prospectively included in the pilot study. Both ears were operated under general anesthesia by the same surgeon. Inclusion criteria were mean conductive hearing loss of 15 dB or more at frequencies 0.5-4.0 kHz and negative Rinne fork test (256 Hz) on both sides. Patients with mean thresholds for sensorineural hearing over 40 dB or other otoneurological diseases or medications were excluded. Pure tone audiogram was performed 3 months after the operation. RESULTS: The air-bone gap diminished from 28 (range 19-41) to 10 (range 4-23) dB in the first ear and from 24 (range 16-40) to 8 (range 3-19) dB in the second. Four patients experienced mild, temporary dizziness during rapid head movements, but that resolved fully. No patient suffered significant sensorineural hearing loss.

Using results of eye movement signal analysis in the neural network recognition of otoneurological patients.

We extracted a collection of eye movement signals employed for almost two decades in clinical otoneurological tests at a balance laboratory. During those years we designed and programmed signal analysis methods to analyse their features in detail and to compute medically important attributes. In the present study, using such attributes and their results computed we classified test cases into groups of healthy subjects and patients with multilayer perceptron neural networks. Classification succeeded in total accuracies from 60% to 90% depending on the type of eye movements, which were saccades, nystagmus, sinusoidal movements and vestibulo-ocular reflex stimulated in two different ways; these are the chief eye movement tests applied in otoneurology.

Bilateral Vestibular Hypofunction in Quantitative Head Impulse Test: Clinical Characteristics in 23 Patients.

OBJECTIVE: To explore clinical features of patients with bilateral vestibular hypofunction (BVH) verified in motorized head impulse test (MHIT). MATERIALS AND METHODS: We examined clinical records of 23 adult patients (10 males and 13 females), whose gain of the vestibulo-ocular reflex in the MHIT was bilaterally lowered. Fifteen of 62 unilateral cochlear implant (CI) recipients routinely tested both pre- and postoperatively with the MHIT had BVH. Eight of 198 vestibular outpatients selected to the MHIT due to clinical causes had BVH. Clinical characteristics and a questionnaire regarding current sensations were analyzed. RESULTS: The mean gain±SD in the MHIT was 0.26±0.17 on the right and 0.26±0.14 on the left side. The mean gain in the CI recipients did not differ from that of vestibular outpatients (p>0.05). All outpatients with BVH suffered from oscillopsia, whereas only 46% of CI recipients experienced oscillopsia (p=0.048). Instability was more prominent (p=0.004) and quality of life further decreased (p=0.012) among vestibular outpatients compared with CI patients. Most common etiology for the BVH was meningitis. Other causes were either sudden or progressive loss of labyrinthine function, bilateral Meniére's disease, and ototoxicity. CONCLUSION: BVH is rare even in a specialized clinic. Vestibular outpatients were more disabled than CI recipients with the BVH.

Postural control in male patients with hip osteoarthritis.

Earlier studies have demonstrated that postural control is worse in patients with knee osteoarthritis (OA) than in control subjects, whereas little information is available about the postural control in patients with hip OA. The aim of this study was to investigate the standing balance in different test conditions in men with hip OA and to compare the results with those of age- and sex-matched healthy controls. Twenty-seven volunteers 47-64-year-old men with hip OA and 30 randomly selected, healthy age-matched men were tested using the sensory organisation test (SOT). The center point of force velocity (CPFV (cm/s)) was also determined during one- and two-footed standing. There was no difference between the patients and controls in the SOT test, in the strategy analysis or during one-footed standing. There were no significant differences in CPFV values between the better and worse hip side. Fatiguing exercise had no effect on two-footed CPFV with eyes open, but when the eyes were closed both two and one-footed CPFV values were significantly increased (p<0.01-0.05) in both groups. No differences were found in fatiguing exercise between control and OA subjects with eyes open or closed or in one-footed trials. In OA patient's subjective pain was related to increasing CPFV (p<0.05). In conclusion, the hip OA had no effect on static balance in men.

On neural network classification of otoneurological cases on the basis of recognition results of vestibulo-ocular reflex eye movements signal.

We constructed a signal analysis and recognition system to compute revealing results from vestibulo-ocular reflex eye movements and their stimulation head movements of impulsive type that were generated as passive head movements with a special device designed by us for this purpose. Further, we implemented perceptron neural networks to separate healthy subjects from patients suffering from dysfunction of vestibulo-ocular reflex in either ear. We gained high classification accuracies with this method ready for routine use.

Video-oculography findings in patients with otosclerosis.

OBJECTIVE: To evaluate the existence of vestibular irritation with video-oculography before and after stapes surgery and to examine whether there would be signs of specific end-organ irritation. STUDY DESIGN: A prospective study of preoperative and postoperative nystagmus, vertigo, and hearing thresholds. SETTING: University hospital, tertiary referral center. PATIENTS: Thirty-three patients (mean age, 47 yr) with otosclerosis. INTERVENTION: Stapedotomy/stapedectomy with laser or microdrill. MAIN OUTCOME MEASURES: Spontaneous, gaze-evoked, and head-shaking nystagmus was measured preoperatively and approximately 1 week, 1 month, and 3 months after the operation. Three dimensions of nystagmus were identified and their slow-phase velocities were calculated. RESULTS: Spontaneous horizontal nystagmus was found preoperatively in 18% (slow-phase velocities, 1.3-3.3 deg/s) and postoperatively in 11 to 19% of the patients (slow-phase velocities, 1.3-3.8 deg/s). Head-shaking nystagmus was not detected preoperatively. After the operation, 11 to 15% of the patients had head-shaking nystagmus (slow-phase velocities, 6.6-17.8 deg/s), but this prevalence did not differ statistically significantly from the preoperative level (p = 0.18). Vertical nystagmus was found equally pre- and postoperatively. Torsional nystagmus was not found. One week after the operation, nine patients (27%) had some sensation of vertigo, but it lasted over 1 month in only one patient. We found no significant correlation with vertigo and the types of nystagmus. CONCLUSION: Nystagmus with a low slow-phase velocity can occur in patients with otosclerosis. However, according to the video-oculographic findings and subjective symptoms, significant vestibular dysfunction seems to be rare and temporary after stapes surgery.

Development of virtual reality stimuli for force platform posturography.

People relying much on vision in the control of posture are known to have an elevated risk of falling. Dependence on visual control is an important parameter in the diagnosis of balance disorders. We have previously shown that virtual reality (VR) methods can be used to produce visual stimuli that affect balance, but suitable stimuli need to be found. In this study, the effect of six different VR stimuli on the balance of 22 healthy test subjects was evaluated using force platform posturography. We report in more detail and expand the results published earlier. According to the tests two of the stimuli have a significant destabilizing effect on balance. In addition a significant displacement effect on the subject's center of pressure (COP) was found. Thus it is shown that the design of VR stimuli to cause different effects on the control of balance is possible.

Influence of lossy compression on eye movement signals.

Eye movements considered in our research are physiological signals that are measured in otoneurological balance tests. They are also investigated in other areas of medicine and in psychology. When great amounts of signals are measured in clinical and research work, signal compression is of great use in storing measurements for later investigations. In this research we assessed the influence of lossy compression on medically interesting parameter values that are computed from eye movement signals. We found that high compression ratios with bit rates lower than 1.5 bits per sample on signals with an original resolution of 13 bits per sample produced results without significant changes to the medical parameters values.

Virtual reality stimuli for force platform posturography.

People relying much on vision in the control of posture are known to have an elevated risk of falling. Dependence on visual control is an important parameter in the diagnosis of balance disorders. We have previously shown that virtual reality methods can be used to produce visual stimuli that affect balance, but suitable stimuli need to be found. In this study the effect of six different virtual reality stimuli on the balance of 22 healthy test subjects was evaluated using force platform posturography. According to the tests two of the stimuli have a significant effect on balance.

Two-dimensional signal analysis reduced from three-dimensional nystagmus eye movements.

Earlier we developed signal analysis for nystagmus measured from otoneurological patients suffering from vertigo and dizziness. It was based on three rotation directions of the eye: horizontal, vertical and torsional. However, nystagmus frequently appears only in two of the former directions. In order to enable two-dimensional analysis approach on the basis of various pairs from the original three, we designed and implemented an advanced method from our earlier one. These signals can be used to investigate and model the dysfunction of semicircular canals in the inner ear. Nystagmus has to be stimulated for healthy subjects, but in patients it can also be spontaneous. The method developed was tested with the signals of 30 otoneurological patients.