Biomedical subjects

M Magnusson

Publications and source records attributed to M Magnusson.

231 records · Page 13Linked to original sources

PubMedDate not supplied

Velocity and asymmetry of optokinetic nystagmus in the evaluation of vestibular lesions.

Optokinetic nystagmus (OKN) at a constant stimulus velocity of 90 degrees/s was studied in 50 healthy subjects and three different groups of patients: 10 with vestibular neuritis (VN), 17 with unilateral infratentorial lesion (UI) and 13 patients with bilateral infratentorial lesion (BI). Among healthy subjects, OKN decreased with age in those over 42 and 44 years for maximum and mean velocity, respectively. The maximum velocity of OKN discriminated between the healthy subjects and the groups of patients rather better than did mean velocity of OKN. Asymmetry of either mean or maximum velocity contributed only marginally to correct group assignment. By subjecting test data on velocity and asymmetry variables to linear discriminant function analysis, 80% of subjects could be correctly classified as healthy/not healthy, and 64% assigned to the correct group according to diagnosis. Analysis of OKN data satisfactorily discriminated BI and UI patients from VN patients and healthy subjects, and is thus useful in assessing infratentorial vestibular lesions.

Adolescent↗

PubMedDate not supplied

The relationship between caloric response, oculomotor dysfunction and size of cerebello-pontine angle tumours.

Seventy-nine consecutive patients, 70 patients with acoustic neurinomas (ACN) and 9 patients with cerebello-pontine angle tumours of other etiology (o-CPA) were analysed with respect to tumour size and the result of the caloric and oculomotor tests. The size of the tumour was judged by the largest diameter calculated from the computerized tomography. A highly significant linear relationship between tumour size and caloric side difference was found for the group of ACN patients who had normal oculomotor function. A unilateral loss of caloric response on the tumour side was found in 75% of the ACN patients with tumours larger than 20 mm, but not in any of the ACN patients with tumours smaller than 10 mm. Oculomotor dysfunction (OMD), defined as disturbed pursuit eye movements and/or gaze nystagmus was frequently found in the patients with ACN larger than 20 mm (77%), and was present in all but one of the o-CPA patients. However, the caloric response on the tumour side was significantly more impaired in the group of ACN patients with OMD than in the o-CPA group. A combined view of the oculomotor and caloric test results offers a possibility to obtain a rough estimate of tumour size as well as to distinguish ACNs from other types of tumours in the cerebello-pontine angle.

Adult↗

PubMedDate not supplied

Significance of pressor input from the human feet in lateral postural control. The effect of hypothermia on galvanically induced body-sway.

The significance to human postural control of pressor information from the feet was investigated during vestibular disturbance in seven normal subjects who were exposed to bipolar biaural galvanic stimulation of the vestibular nerves before and after their feet were anaesthetized with hypothermia. The increase in body sway in the lateral plane induced by the galvanic stimulus was enhanced when the feet were anaesthetized, and adaptation of postural control to the galvanic stimulus was delayed. It is concluded that pressor information from the feet contributes significantly to postural control in humans and is important in compensating for vestibular disturbance.

Adaptation, Physiological↗

PubMedDate not supplied

Galvanically induced body sway in the anterior-posterior plane.

Anterior-posterior body sway was evoked with monopolar bi-aural galvanic stimulus of the vestibular nerves in normal subjects and recorded with a force platform, two experiments being conducted. In an experiment of paired design, 9 normal subjects showed an increase in anterior-posterior sway as compared with lateral sway when exposed to the stimulus. In a second experiment another group of 10 normal subjects were exposed to a galvanic stimulus between a neck electrode and two electrodes placed on the arms, but there was no change in the relationship between anterior-posterior and lateral body sway. It is concluded that monopolar galvanic stimulus of the vestibular nerves can induce anterior-posterior body sway, a phenomenon which can be utilised to investigate the vestibulo-spinal contribution in postural control in the anterior-posterior plane.

Adult↗

PubMedDate not supplied

Significance of pressor input from the human feet in anterior-posterior postural control. The effect of hypothermia on vibration-induced body-sway.

The importance to postural control of the mechanoreceptors of the soles was investigated in thirteen healthy subjects. Body-sway velocity was evaluated before and after exposing the subject's feet to hypothermia, and when calf muscles were exposed to vibration at frequencies between 20 and 100 Hz. Subjects were tested both with eyes open and closed. Body-sway velocity was found to increase significantly during hypothermia of the feet. The difference in body-sway between hypothermal and normothermal conditions was less prominent when the subject's eyes were open though the difference was significant in both cases. The present results indicate the importance of the mechanoreceptors of the soles to postural control and elucidate their interaction with compensatory visual input in maintaining postural control. These findings also suggest, that factors affecting pressor input should be taken into consideration when assessing patients with complaints of dysequilibrium.

Adult↗

PubMedDate not supplied

Galvanically induced asymmetric optokinetic after-nystagmus.

The effect of an asymmetric vestibular input on the symmetry of horizontal optokinetic after-nystagmus (OKAN) was studied in twenty healthy subjects. Optokinetic nystagmus (OKN) was elicited by a whole-field optokinetic drug, rotating at 90 degrees/s, and eye-movements were recorded by a DC electro-oculographic technique (EOG). The ratio of OKAN following right and left-beating OKN respectively was computed. An asymmetric vestibular input was generated by a continuous bi-polar, bi-aural galvanic stimulus (1 mA) to the vestibular nerves during the optokinetic stimulation and the recording of the OKAN. During galvanic stimulation the relation between left and right-beating OKAN was asymmetric, compared with the OKAN found after optokinetic stimulation only. The galvanic stimulus caused a preponderance for OKAN with the fast phase beating toward the cathode. Thus, the small vestibular asymmetry induced by the galvanic stimulus, which was not strong enough to produce nystagmus by itself, caused an asymmetric OKAN. These findings suggest that examination of OKAN may be of value to detect small vestibular asymmetries in peripheral vestibular disorders in man.

Adult↗

PubMedDate not supplied

Electrocochleographic signal analysis: condensation and rarefaction click stimulation contributes to diagnosis in Menière's disorder.

Thirty patients with Menière's disorder, 11 patients with cochlear hearing loss of other aetiologies and 10 normally-hearing subjects, were investigated using transtympanic electrocochleography (TT ECochG). Alternating polarity clicks, condensation and rarefaction clicks and long tone-bursts of 1 kHz were used for stimulation. The latencies of the AP responses to click stimulation were evaluated. It was found that the latency differences between the condensation and rarefaction click-evoked responses were significantly larger in patients with Menière's disorder as compared to normal subjects and to patients with other cochlear hearing losses. It was found that the sensitivity of TT ECochG, obtained by using measurements of SP-AP ratios and the SP amplitude at 1 kHz burst stimulation, increased from 83 per cent to 87 per cent by addition of the con-rar shift measurement. The specificity of TT ECochG obtained by this combination of variables was 100 per cent in our material. The results of the study indicate that the latency shift found in responses evoked by clicks of opposite polarities in TT ECochG, can be a useful parameter in the detection of suspected endolymphatic hydrops.

Acoustic Stimulation↗

PubMedDate not supplied

Asthma clinical pathway: an interdisciplinary approach to implementation in the inpatient setting.

Asthma is a leading cause of admission to the pediatric inpatient setting. Despite advances in the treatment of this chronic condition, morbidity and mortality continue to increase. It is also a source of significant variation in clinical practice and redundancy of care elements across various disciplines involved in the management of patients with asthma. A clinical pathway was developed and implemented by a multidisciplinary team at The Children's Hospital of Philadelphia. The unique approach used to strategize implementation combined the expertise of registered nurses, respiratory therapists, medical staff, and case managers and was a significant factor in the pathway's ultimate success. The result was a more standardized and efficient approach to care. Outcome measurements revealed decreased length of stay with no increase in the re-admission rate and cost savings.

Algorithms↗

PubMedDate not supplied

Longitudinal assessment of oxygen cost and velocity in children with myelomeningocele: comparison of the hip-knee-ankle-foot orthosis and the reciprocating gait orthosis.

Oxygen consumption and cost and velocity were evaluated over time in 23 children with myelomeningocele to determine whether differences exist when children walk with hip-knee-ankle-foot orthoses (HKAFOs) versus reciprocating gait orthoses (RGOs). Children using HKAFOs had similar oxygen cost as children using RGOs while achieving a faster velocity. Children walking with HKAFOs into adolescence had a faster velocity and lower oxygen cost than children who discontinued use of their HKAFOs. No significant differences in velocity or oxygen cost were found between children who continued to walk with RGOs and those who discontinued use of their RGOs. Upright ambulation may progress from ambulation with an RGO, when the child's upper extremity strength to mass ratio is low, to an HKAFO when upper extremity strength improves and velocity or keeping up with peers is of concern. Wheelchair mobility should be offered when speed and an energy-efficient method of community mobility are desired.

Adolescent↗

PubMedDate not supplied

Reduction of gain and time constant of vestibulo-ocular reflex in man induced by diazepam and thiopental.

The effect of intravenous administration of two sedatives, diazepam (0.3 mg/kg) and thiopental (6.0 mg/kg), on the vestibulo-ocular reflex (VOR) in man was investigated on 9 volunteers. The VOR was evoked with a velocity step rotation test and gain and time constant of prerotatory and postrotatory nystagmus were measured. Both drugs reduced VOR gain. Diazepam-induced reduction lasted 8 h and thiopental-induced reduction 1 h. A reduction of the VOR time constant was found lasting about 1 h for both drugs, but with a tendency for the thiopental effect to last longer. These findings, not previously described in man, differ from what has been found in macaques and rabbits injected with diazepam. The reduction of gain and time constant were not correlated with the blood concentration of either drug. The present results suggest that in man the VOR gain and time constant are both reduced by different types of sedatives although with different time courses. On the basis of previously shown effect of alertness on the VOR, it is hypothesized that diazepam and thiopental, besides having a specific effect on central nervous system structures important to the VOR, also induce reduction of the VOR through a general sedation of the CNS.

Adult↗

PubMedDate not supplied

Asymmetric optokinetic afterresponse in patients with vestibular neuritis.

The symmetry of primary and secondary optokinetic afternystagmus (OKAN I and OKAN II, respectively) was studied in 14 patients with vestibular neuritis, as well as in 50 normals. The patients were examined at onset of symptoms and at follow-up 3 and 12 months later. At onset, OKAN was found mainly to reflect the spontaneous nystagmus. Although the spontaneous nystagmus disappeared in all patients within 3 months, both OKAN I and OKAN II was asymmetric at the 3- and 12-month check-ups. OKAN beating toward the lesioned ear was weaker than the OKAN beating toward the healthy ear. Thus, the asymmetric vestibular function was reflected not only in the OKAN I, but also by an asymmetry in OKAN II. Between the 3- and 12-month check-ups, asymmetry in OKAN declined, even among those patients who showed no improvement in caloric response during that time. The decreasing asymmetry in OKAN with time after lesion was, however, related to the disappearance of a positional nystagmus. Hence, the results may be interpreted as suggesting OKAN not only to be affected by vestibular side-difference, but also to be modified by the process responsible for vestibular compensation following a peripheral vestibular lesion.

Adolescent↗

PubMedDate not supplied

Asymmetric optokinetic afterresponse in patients with small acoustic neurinomas.

Directional asymmetry of primary and secondary optokinetic afternystagmus (OKAN I and OKAN II, respectively) was studied in 20 patients with small acoustic neurinomas (< or = 20 mm), and results were compared to those for 24 normal controls. The optokinetic afterresponse was induced by 60 s of horizontal whole-field optokinetic stimulation in both directions. Among patients, the optokinetic afterresponse was asymmetric, OKAN I and OKAN II beating toward the lesioned ear being significantly weaker than the OKAN I and OKAN II beating toward the healthy ear. Hence, in these patients with gradual deterioration of vestibular function, the vestibular side-difference was reflected both in OKAN I and OKAN II. Although asymmetry in OKAN I was frequently observed among controls, it was significantly more pronounced among the patients. Moreover, patients could be distinguished by the occurrence of OKAN II, as it did not occur at all among controls exposed to the same stimulation.

Adult↗

PubMedDate not supplied

Auditory function after spinal anesthesia.

OBJECTIVE: To determine the effect of spinal anesthesia using 26-gauge needles on hearing. METHODS: Eighteen male patients undergoing transurethral resection of the prostate (TURP) or other transurethral procedures under spinal or epidural anesthesia were studied prospectively to reveal possible auditory side effects of dural puncture or absorption of irrigation fluid to the blood stream. Measurement of auditory function by pure tone, Bekesy and speech audiometry, and measurement of serum concentrations of sodium, potassium, urea, and glucose were performed preoperatively and postoperatively. Clinical examination of cranial nerve functions was performed postoperatively. RESULTS: No mean change in hearing ability was seen in any group. One patient had severe, transient, low-frequency hearing loss with simultaneous severe postdural puncture headache. A statistically significant postoperative fall in serum osmolarity was noted in the epidural TURP group. CONCLUSION: Transient, severe hearing loss may still occur after spinal anesthesia using a 26-gauge needle. Minor hearing loss does not seem to be a problem with this needle size.

Aged↗

PubMedDate not supplied

Dizziness of suspected cervical origin distinguished by posturographic assessment of human postural dynamics.

Useful clinical tests are lacking for the controversial entity "cervical vertigo". In earlier studies patients assumed to suffer from cervical vertigo or dizziness manifested disturbed postural control as compared to healthy subjects, but were hard to distinguish from patients with other balance disorders. Using posturography in which stance was perturbed by a vibratory stimulus applied towards the calf muscles, we studied 16 consecutive patients with recent onset of neck pain and concomitant complaints of vertigo or dizziness, but normal findings at otoneurological examination and electronystagmography; 18 patients with recent vestibular neuritis; and 17 healthy subjects. We performed system identification of a model of the control of upright human stance, using the vibratory stimulus as input and the recorded body sway as output. According to values for the three normalized parameters of the transfer function of the model (i.e., swiftness, stiffness, and damping), cervical vertigo patients were distinguished both from healthy subjects (P < 0.001), and from vestibular neuritis patients (P < 0.001). It was also possible to distinguish the vestibular neuritis group from the group of healthy subjects (P < 0.01). The results show disturbed postural control in patients with cervical vertigo to differ from that in patients with recent vestibular neuritis, and indicate posturographic assessment of human posture dynamics to be a possible future tool for use in diagnosing cervical vertigo.

Adult↗

PubMedDate not supplied

Effects of different treatments on postural performance in patients with cervical root compression. A randomized prospective study assessing the importance of the neck in postural control.

Patients with cervical root compression were used as a "model" to investigate the possible importance of neck disorders and cervical sensory information in postural control. We assessed postural performance with posturography before and after treatment in 71 consecutive patients with MRI-verified cervical root compression without medullary compression. The patients were randomized to surgery (n = 22), physiotherapy (n = 24) or treatment with cervical collars (n = 25). There were no differences in postural performance or pain intensity between the groups before treatment. After treatment, the surgery group manifested significant improved postural performance and reduced neck pain scores, as compared to the two conservative treatment groups, and their postural performance had improved to the same level manifested by healthy controls. The conservative treatment groups manifested no consistent significant changes in postural performance or pain scores. Decreased muscular tension due to reduction of cervical pain after surgery and normalization of cervical proprioception are suggested as possible explanations of the improved postural control.

Female↗