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Aim: Prevalence and incidence of spinal cord injury (SCI) are low. However, sample sizes have not been systematically examined yet, although this might represent useful information for study planning and power considerations. Therefore, our objective was to determine the median sample size in clinical trials on SCI individuals. Moreover, within small-sample size studies, statistical methods and awareness of potential problems regarding small samples were examined., Methods: We systematically reviewed all studies on human SCI individuals published between 2014 and 2015, where the effect of an intervention on one or more health-related outcomes was assessed by means of a hypothesis test. If at least one group had a size <20, the study was classified as a small sample size study. PubMed was searched for eligible studies; subsequently, data on sample sizes and statistical methods were extracted and summarized descriptively., Results: Out of 8897 studies 207 were included. Median total sample size was 18 (range 4-582). Small sample sizes were found in 167/207 (81%) studies, resulting limitations and implications for statistical analyses were mentioned in 109/167 (65%) studies., Conclusions: Although most recent SCI trials have been conducted with small samples, the consequences on statistical analysis methods and the validity of the results are rarely acknowledged., (© 2019 The Authors. Journal of Evidence-Based Medicine published by Chinese Cochrane Center, West China Hospital of Sichuan University and John Wiley & Sons Australia, Ltd.)

Cortical reorganization can be induced by exercise below the level of the lesion after spinal cord injury (SCI). The aim of the present study was to investigate the effect of passive and active pedaling exercise on leg motor cortical area excitability of subjects with traumatic SCI. Ten subjects with chronic cervical or thoracic SCI were enrolled in the study. We found a significant effect of pedaling on short-interval intracortical inhibition (SICI), which did not interact with the experimental condition (active vs. passive). This corresponded to a significant reduction of SICI in the subjects with SCI, together with no evidence that this pattern differed for passive vs. active pedaling. We found no significant effect of pedaling on intracortical facilitation. Our results showed that also passive cycling may be beneficial in activating motor cortical regions and possibly also facilitating motor recovery after SCI. The present study confirms and extends the findings of previous studies that have observed task-specific cortical activation during passive pedaling. Therefore passive exercise therapies when applied below the level of the lesion in subjects with SCI could promote cortical neuroplastic reorganization., (Copyright © 2016 Elsevier Inc. All rights reserved.)

We aimed in this study to investigate whether repetitive transcranial magnetic stimulation (rTMS), given as theta burst stimulation (TBS), can interfere with non-painful phantom sensations in subjects with spinal cord injury (SCI). In double-blind, sham-controlled experiments in five subjects with cervical or thoracic traumatic SCI, we evaluated the effects of a single session of inhibitory (continuous) TBS, excitatory (intermittent) TBS, or placebo TBS, on simplex and complex non-painful phantom sensations. The interventions targeted the contralateral primary motor cortex (M1), the primary sensory cortex (S1) and the posterior parietal cortex (PPC). Measurements were carried out at baseline (T0), 5 min (T1) and 30 min later (T2) after the intervention. Descriptive evaluation of results shows that non-painful phantom sensations were not affected by rTMS applied over M1. Continuous (inhibitory) TBS over S1 induced a short-lasting decrease of simple non-painful phantom sensations, while continuous TBS over PPC induced a short-lasting decrease of both simple and complex phantom sensations. Intermittent (excitatory) TBS over PPC induced a slight increase of non-painful phantom sensations. Tests for significance confirm these observations, but must be interpreted with caution because of the small sample size. In conclusion, non-painful phantom sensations may be associated to a hyperexcitability of PPC and to a lesser extent of S1, which can be normalized by inhibitory rTMS. Our preliminary findings provide further evidence that neuromodulatory techniques are able to reverse phantom sensations not only after limb amputation but also in other conditions characterized by deafferentation such as SCI., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Transcranial magnetic stimulation (TMS) is a useful non-invasive approach for studying cortical physiology. To further clarify the mechanisms of cortical reorganization after spinal cord injury (SCI), we used a non-invasive paired TMS protocol for the investigation of the corticospinal I-waves, the so-called I-wave facilitation, in eight patients with cervical SCI. We found that the pattern of I-wave facilitation significantly differs between SCI patients with normal and abnormal central motor conduction (CMCT), and healthy controls. The group with normal CMCT showed increased I-wave facilitation, while the group with abnormal CMCT showed lower I-wave facilitation compared to a control group. The facilitatory I-wave interaction occurs at the level of the motor cortex, and the mechanisms responsible for the production of I-waves are under control of GABA-related inhibition. Therefore, the findings of our small sample preliminary study provide further physiological evidence of increased motor cortical excitability in patients with preserved corticospinal projections. This is possibly due to decreased GABAergic intracortical inhibition. The excitability of networks producing short-interval intracortical facilitation could increase after SCI as a mechanism to enhance activation of residual corticospinal tract pathways and thus compensate for the impaired ability of the motor cortex to generate appropriate voluntary movements. Finally, the I-wave facilitation technique could be used in clinical neurorehabilitation as an additional method of assessing and monitoring function in SCI., (Copyright © 2015 Elsevier Inc. All rights reserved.)

It is well known that the standard F test is severely affected by heteroskedasticity in unbalanced analysis of covariance models. Currently available potential remedies for such a scenario are based on heteroskedasticity-consistent covariance matrix estimation (HCCME). However, the HCCME approach tends to be liberal in small samples. Therefore, in the present paper, we propose a combination of HCCME and a wild bootstrap technique, with the aim of improving the small-sample performance. We precisely state a set of assumptions for the general analysis of covariance model and discuss their practical interpretation in detail, since this issue may have been somewhat neglected in applied research so far. We prove that these assumptions are sufficient to ensure the asymptotic validity of the combined HCCME-wild bootstrap analysis of covariance. The results of our simulation study indicate that our proposed test remedies the problems of the analysis of covariance F test and its heteroskedasticity-consistent alternatives in small to moderate sample size scenarios. Our test only requires very mild conditions, thus being applicable in a broad range of real-life settings, as illustrated by the detailed discussion of a dataset from preclinical research on spinal cord injury. Our proposed method is ready-to-use and allows for valid hypothesis testing in frequently encountered settings (e.g., comparing group means while adjusting for baseline measurements in a randomized controlled clinical trial). [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) leads to severe chronic disability, but also to secondary adaptive changes upstream to the injury in the brain which are most likely induced due to the lack of afferent information. These neuroplastic changes are a potential target for innovative therapies such as neuroprostheses, e.g., by stimulation in order to evoke sensation or in order to suppress phantom limb pain. Diverging results on gray matter atrophy have been reported in patients with SCI. Detectability of atrophy seems to depend on the selection of the regions of interest, while whole-brain approaches are not sensitive enough. In this study, we discussed previous research approaches and analyzed differential atrophic changes in incomplete SCI using manual segmentation of the somatosensory cortex. Patients with incomplete SCI (ASIA C-D), with cervical (N = 5) and thoracic (N = 6) injury were included. Time since injury was ≤12 months in 7 patients, and 144, 152, 216, and 312 months in the other patients. Age at the injury was ≤26 years in 4 patients and ≥50 years in 7 patients. A sample of 12 healthy controls was included in the study. In contrast to all previous studies that used voxel-based morphometry, we performed manual segmentation of the somatosensory cortex in the postcentral gyrus from structural magnetic resonance images and normalized the calculated volumes against the sum of volumes of an automated whole-head segmentation. Volumes were smaller in patients than in controls (p = 0.011), and as a tendency, female patients had smaller volumes than male patients (p = 0.017, uncorrected). No effects of duration (subacute vs. chronic), level of lesion (cervical vs. thoracic), region (left vs. right S1), and age at onset (≤26 vs. ≥50 years) was found. Our results demonstrate volume loss of S1 in incomplete SCI and encourage further research with larger sample sizes on volumetric changes in the acute and chronic stage of SCI, in order to document the moderating effect of type and location of injury on neuroplastic changes. A better understanding of neuroplastic changes in the sensorimotor cortex after SCI and its interaction with sex is needed in order to develop efficient rehabilitative interventions and neuroprosthetic technologies. [ABSTRACT FROM AUTHOR]