Quantitative 3D evaluation of step ascent and descent in individuals with Down syndrome--analysis of a daily challenging task.

BACKGROUND: Step ascent and descent can perturb stability increasing the incidence of falls, especially in older individuals with functional limitations and intellectual disabilities, such as those with Down syndrome (DS). The aim of this study was to investigate the biomechanics and motor coordination of step ascent and descent in adults with DS and compare them with a group of healthy individuals, considering movement kinematics and kinetics. METHOD: Fourteen adults with DS and 12 similarly aged adults without DS who were free of known motor problems were quantitatively assessed during ascending and descending a step using an optoelectronic system (BTS SMART-D), force platforms and video recording. Kinematic and kinetic parameters were identified and calculated for each study participant and comparisons were made between the DS and a control group (CG). RESULTS: Despite similar age ranges, subjects in the DS group performed the step ascent and descent movements slower, with longer duration and with a more accentuated range of motion of the trunk and of the ankle joint than those in the CG. Additionally, the double stance phase on the step was substantially longer in the DS group when represented as a percentage of the entire stepping sequence (ascent, double stance on the step and descent). In terms of kinetics, ground force platform data revealed that the DS subjects showed higher instability in the medio-lateral direction during double support phase than similarly aged CG subjects and cannot be attributed to age-associated changes in stability. CONCLUSIONS: These findings help to elucidate the complex biomechanical strategy of people with DS during a step ascent and descent movement task and may have a major role in the multidimensional evaluation and tailored management for them.

Longer brainstem auditory evoked response latencies of individuals with fragile X syndrome related to sedation.

Brainstem auditory evoked response latencies were studies in 75 males (13 with fragile X syndrome, 18 with mental retardation due to other causes, and 44 with no disability). Latency values were obtained for each ear for the positive deflections of waves I (P1), III (P3), and V (P5). Some individuals with mental retardation required sedation. Contrary to previous report, latencies obtained for individuals with fragile X did not differ from those obtained for persons without mental retardation. Persons receiving sedation, whether or not their retardation was due to fragile X, had longer latencies for wave P5 than persons who did not receive sedation. This effect of sedation may also explain the previously reported increased latencies for persons with fragile X.

Aberrant lateralization of brainstem auditory evoked responses by individuals with Down syndrome.

Brainstem auditory evoked response latencies were studied in 80 males (13 with Down syndrome, 23 with developmental disability due to other causes, and 44 with no disability). Latencies for waves P3 and P5 were shorter for the Down syndrome than for the other groups, though at P5, as compared to latencies for the nondisabled group, the difference was not significant. The pattern of left versus right ear responses in the Down syndrome group differed from those of the other groups. This finding was related to research noting decreased lateralization of and decreased ability at receptive and expressive language among people with Down syndrome. Some individuals required sedation. A lateralized effect of sedation was noted.

Comparison of the developmental changes of the brainstem auditory evoked response (BAER) in taurine-supplemented and taurine-deficient kittens.

A similar development of the brainstem auditory evoked response is present in taurine-supplemented and taurine-deficient kittens between the second postnatal week and the third month of life. Between birth and the second postnatal week kittens from mothers fed the 1% taurine diet showed earlier maturation of the brainstem auditory evoked response as indicated by lower threshold, shorter P1 latency and shorter central conduction time when compared to the kittens from mothers fed the 0.05% taurine diet. These results suggest an important role of taurine in the anatomical and functional development of the auditory system.

Brainstem auditory-evoked responses with and without sedation in autism and Down's syndrome.

Brainstem auditory-evoked responses (BAER) were obtained from 46 control, 16 Down's syndrome, and 48 autistic male subjects. Six Down's syndrome and 37 autistic subjects were tested with sedation. Sedated and unsedated Down's syndrome subjects displayed shorter absolute and interpeak latencies for early components of the BAER whereas the sedated autistic group showed longer latencies for the middle and late components. The prolongation of latencies in the sedated autistic group was unrelated to age or intellectual level. Although individuals requiring sedation may have a higher probability of neurological impairment, an effect of sedation on the BAER cannot be ruled out.

State-dependent variations in brainstem auditory evoked responses in human subjects.

BAERs from 16 subjects during 3 sessions varied in the latency or amplitude of some components depending upon level of arousal as indicated by EEG patterns. There was a general tendency for activation to produce the fastest responses with the largest amplitudes and for drowsiness to produce the slowest responses with the smallest amplitudes. The latency of P2 was significantly prolonged during drowsiness, relative to those during relaxation or activation. For right-ear stimulation, P5 latency was longest during drowsiness, and shortest during activation while for left-ear stimulation the shortest latency occurred during relaxation. The amplitudes of Wave II and Wave VII were significantly smaller during drowsiness than during activation. Although the differences were below the level of clinical significance, the data indicate a modification in the characteristics of brainstem transmission as a function of concurrent activity in other brain areas.