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Sample sizes and statistical methods in interventional studies on individuals with spinal cord injury: A systematic review.

ABSTRACT: 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.

SUBMITTER: Zimmermann G

PROVIDER: S-EPMC6771853 | biostudies-other | 2019 Aug

REPOSITORIES: biostudies-other

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Sample sizes and statistical methods in interventional studies on individuals with spinal cord injury: A systematic review.

Zimmermann Georg G Bolter Lisa-Maria LM Sluka Ronny R Höller Yvonne Y Bathke Arne C AC Thomschewski Aljoscha A Leis Stefan S Lattanzi Simona S Brigo Francesco F Trinka Eugen E

Journal of evidence-based medicine 20190623 3

<h4>Aim</h4>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.<h4>Methods</h4>We system ...[more]

PMID: 31231977

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Project description:With emerging applications of spinal cord electrical stimulation in restoring autonomic and motor function after spinal cord injury, understanding the neuroanatomical substrates of the human spinal cord after spinal cord injury using neuroimaging techniques can play a critical role in optimizing the outcomes of these stimulation-based interventions. In this study, we have introduced a neuroimaging acquisition and analysis protocol of the spinal cord in order to identify: (i) spinal cord levels at the lumbosacral enlargement using nerve root tracing; (ii) variability in the neuroanatomical characteristics of the spinal cord among individuals; (iii) location of the epidural stimulation paddle electrode and contacts with respect to the spinal cord levels at lumbosacral enlargement; and (iv) the links between the anatomical levels of stimulation and the corresponding neurophysiological motor responses. Twelve individuals with chronic, motor complete spinal cord injury implanted with a spinal cord epidural stimulator were included in the study (age: 34 ± 10.9 years, sex: 10 males, 2 females, time since injury: 8.2 ± 9.9 years, American Spinal Injury Association Impairment Scale: 6 A, 6 B). High-resolution MRI scans of the spinal cord were recorded pre-implant. An analysis of neuroanatomical substrates indicates that the length of the spinal column and spinal cord, location of the conus tip and the relationship between the spinal cord levels and vertebral levels, particularly at the lumbosacral enlargement, are variable across individuals. There is no statistically significant correlation between the length of the spinal column and the length of the spinal cord. The percentage of volumetric coverage of the lumbosacral spinal cord by the epidural stimulation paddle electrode ranges from 33.4 to 90.4% across participants. The location of the spinal cord levels with respect to the electrode contacts varies across individuals and impacts the recruitment patterns of neurophysiological responses. Finally, MRI-based spinal cord modelling can be used as a guide for the prediction and preplanning of optimum epidural stimulation paddle placement prior to the implant surgery to ensure maximizing functional outcomes. These findings highlight the crucial role that the neuroanatomical characteristics of the spinal cord specific to each individual play in achieving maximum functional benefits with spinal cord electrical stimulation.

Project description:BackgroundTranscutaneous spinal cord stimulation (tSCS) is a non-invasive modality in which electrodes can stimulate spinal circuitries and facilitate a motor response. This review aimed to evaluate the methodology of studies using tSCS to generate motor activity in persons with spinal cord injury (SCI) and to appraise the quality of included trials.MethodsA systematic search for studies published until May 2021 was made of the following databases: EMBASE, Medline (Ovid) and Web of Science. Two reviewers independently screened the studies, extracted the data, and evaluated the quality of included trials. The electrical characteristics of stimulation were summarised to allow for comparison across studies. In addition, the surface electromyography (EMG) recording methods were evaluated.ResultsA total of 3753 articles were initially screened, of which 25 met the criteria for inclusion. Studies were divided into those using tSCS for neurophysiological investigations of reflex responses (n = 9) and therapeutic investigations of motor recovery (n = 16). The overall quality of evidence was deemed to be poor-to-fair (10.5 ± 4.9) based on the Downs and Black Quality Checklist criteria. The electrical characteristics were collated to establish the dosage range across stimulation trials. The methods employed by included studies relating to stimulation parameters and outcome measurement varied extensively, although some trends are beginning to appear in relation to electrode configuration and EMG outcomes.ConclusionThis review outlines the parameters currently employed for tSCS of the cervicothoracic and thoracolumbar regions to produce motor responses. However, to establish standardised procedures for neurophysiological assessments and therapeutic investigations of tSCS, further high-quality investigations are required, ideally utilizing consistent electrophysiological recording methods, and reporting common characteristics of the electrical stimulation administered.

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Sample sizes and statistical methods in interventional studies on individuals with spinal cord injury: A systematic review.

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Sample sizes and statistical methods in interventional studies on individuals with spinal cord injury: A systematic review.

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