Vestibular PREHAB and gentamicin before schwannoma surgery may improve long-term postural function.

BACKGROUND: Unilateral vestibular deafferentation (uVD), as performed in vestibular schwannoma surgery, results in a chronic vestibular deficit, though most of the insufficiency can be compensated by other sensory input. By vestibular training (prehabituation) performed before surgery, motor adaptation processes can be instigated before the actual lesion. The adaptation processes of the altered sensory input could be affected if the vestibular ablation and surgery were separated in time, by pretreating patients who have remaining vestibular function with gentamicin. OBJECTIVE: To determine whether presurgical deafferentation would affect postsurgery postural control also in a long-term perspective (6 months). METHOD: 41 patients subjected to trans-labyrinthine schwannoma surgery were divided into four groups depending on the vestibular activity before surgery (with no clinical significant remaining function n = 17; with remaining function n = 8), whether signs of central lesions were present (n = 10), and if patients with remaining vestibular activity were treated with gentamicin with the aim to produce uVD before surgery (n = 6). The vibratory posturography recordings before surgery and at the follow-up 6 months after surgery were compared. RESULTS: The subjects pretreated with gentamicin had significantly less postural sway at the follow-up, both compared with the preoperative recordings and compared with the other groups. CONCLUSION: The results indicate that by both careful sensory training and separating the surgical trauma and the effects of uVD in time, adaptive processes can develop more efficiently to resolve sensory conflicts, resulting in a reduction of symptoms not only directly after surgery but also perhaps up to 6 months afterwards.

Improved postural control through repetition and consolidation.

Research regarding the optimal frequency of training in postural control rehabilitation has been sparse. Posturography with vibratory proprioceptive stimulation was performed with eyes open and closed on 36 healthy subjects divided into 3 groups. Each group was tested 5 times, though with different time-intervals; 20 minutes, 3 hours and 24 hours respectively. Two different adaptive processes seems to be involved in the formation of a new movement pattern when exposed to a postural disturbance, one fast adaptation active during each test occasion and a second adaptation active between the consecutive tests. As the same adaptation pattern was found regardless the repetition time interval, the results imply either that the consolidation process of the new motor memory is time-independent or that the stimulus was sufficiently strong to induce fast consolidation thus leaving the time-interval unimportant. The findings suggest that it is primarily the number of repetitions in the exercises that governs the outcome of training, whereas the time interval between the exercises is of less importance.

Analysis of short- and long-term effects of adaptation in human postural control.

The short-term (i.e., days) and long-term (i.e., months) effects of adaptation to posturography examinations were investigated in 12 normal subjects who were repeatedly examined for five consecutive days and again after 90 days. The examinations were conducted both with eyes open and closed, and the perturbations were evoked by a pseudorandomly applied vibration stimulation to the calf muscles. The evoked anteroposterior responses were analyzed with a method considering adaptation in the slow changes in posture and in the stimulus-response relationship. Repetition of examinations on a daily basis revealed a gradual improvement of postural-control performance. The body sway induced by the stimulation was significantly reduced and the dynamical properties changed. Most of the improvements remained after 90 days, but some parameters such as the complexity of the control system used were increased to the initial level. The results confirm previous observations that postural control contains several partially independent adaptive processes, observed in terms of alteration of posture and as a progressive reduction of body sway induced by stimulation. The method used for the adaptation analysis in this study could be applied to analyze biological systems with multiple individual adaptive processes with different time courses or characteristics, or where the adaptation processes are related to multiple internal or external factors.

Adaptation of postural control to perturbations--a process that initiates long-term motor memory.

The objective was to investigate postural control adaptation during daily repeated posturography with vibratory calf stimulation. The posturography was performed with eyes open and closed daily for 5 days and after 90 days on 12 healthy subjects. The postural control adaptation could be described as two separate processes, a rapid adaptation during the test progress and a long-term habituation between consecutive test days. The adaptive improvements gained during the 5 days consecutive testing, largely remained 90 days later but seemed restricted to the same test situation. The findings suggest that balance rehabilitation should include a variety of repeated exercises, which are sufficiently long to induce habituation.

A comparison of genome-scans performed in multicase families with systemic lupus erythematosus from different population groups.

Systemic lupus erythematosus is a disease of unknown etiology. Multiple genetic factors are believed to be involved in its pathogenesis. In addition, and due to genetic heterogeneity, these factors and/or their combinations may be different in different ethnic groups, while some might be shared between populations. We have performed genome scans in multicase families from three different population groups, two from Northern Europe, with a high degree of homogeneity, and the third from a recently admixed population of Mexican Mestizos. Although our family material is relatively small, the results presented here show that using family sets from well defined populations are sufficient to detect susceptibility loci for SLE. Our results also reveal the chromosomal regions most likely to contain susceptibility genes for SLE.

Synergetic effect between interleukin-1 receptor antagonist allele (IL1RN*2) and MHC class II (DR17,DQ2) in determining susceptibility to systemic lupus erythematosus.

We investigated whether IL1RN alleles separately or in combination with MHC class II variants, contribute to susceptibility to SLE and to analysed if IL1RN alleles are markers of disease severity. We investigated 81 patients from a defined area in southern Sweden diagnosed between 1981-1992 and 10 consecutive Caucasian families with multiple cases of SLE. As control group 189 healthy blood donors was used. PCR amplification of defined gene sequences was used in determining the IL1RN polymorphism as well as the MHC class II variants. The IL-1RA levels were measured by an immunoassay. We found an increased frequency of IL1RN*2 in both the epidemiological cohort and in the multicase families (P < 0.01). Alone IL1RN*2 and MHC class II (DR17,DQ2) separately increased the SLE risk moderately. The occurrence of IL1RN*2 and MHC class II variants DR17 and DQ2 together increased the risk to develop SLE by a sevenfold. The IL-1RA gene polymorphism did not correlate with disease severity or with renal involvement. We found an association between IL1RN*1 and arthritis (P < 0.001). Serum level of IL-1RA did not correspond to any specific IL1RN allele. An increased frequency of IL1RN*2 suggests the presence of a gene, implemented in SLE-susceptibility, in the IL1RN region of chromosome 2. IL1RN*2 and specific variants of MHC class II act in synergy to increase disease susceptibility. IL1RN*1 may be a marker of risk for development of arthritis.