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Prospective experimental.The aim of this study was to develop a quantitative sensory test (QST) that could be used for assessing the level and the density (degree of impairment) of spinal cord injury (SCI) and for monitoring neurological changes in patients with SCI.National Spinal Injuries Centre, Stoke Mandeville Hospital, Buckinghamshire Hospitals NHS Trust, UK.Perceptual threshold to 3 Hz cutaneous electrical stimulation was measured in 30 control subjects and in 45 patients with SCI at American Spinal Injuries Association (ASIA) sensory key points for selected dermatomes between C3 and S2 bilaterally. Electrical perceptual threshold (EPT) was recorded as the lowest ascending stimulus intensity out of three tests at which the subject reported sensation. The level of SCI according to EPT results was established for right and left sides as the most caudal spinal segment at which patient's EPT was within the control range (mean +/- 2 standard deviation (SD)). The level of SCI, according to EPT, was then compared with clinical sensory level derived according to ASIA classification.In the control group, EPT depended on the dermatome tested and was lowest for T1 (1.01 +/- 0.23 mA, mean +/- SD) and highest for L5 (3.32 +/- 1.14 mA). There was strong correlation between corresponding right and left dermatomes and between repeated assessments. In the SCI group, the level of lesion according to EPT and clinical testing was the same in 43 of the 90 tests (48%). In 37 cases (41%), the EPT level was higher than the clinical level, and in 10 cases (11%), it was lower. Below the level of lesion in incomplete SCI and in the zone of partial preservation in complete SCI, the EPT values in most dermatomes were raised compared with the control group.EPT is a simple, reproducible QST that can assess both the level and the density of SCI. It seems to add sensitivity and resolution to the standard clinical testing and could be a useful adjunct in longitudinal monitoring of patients with SCI for research purposes during natural recovery and therapeutic interventions.International Spinal Research Trust (ISRT), UK, Grant CLI001.

Neurological testing tools for measuring and monitoring somatosensory function lack resolution and are often dependent on the clinician testing. In this study we have measured perceptual threshold (PT) to electrical stimulation of the skin and compared it with two-point discriminative ability (TPDA) in 12 control subjects. Tests were made on both sides of the body at American Spinal Injury Association (ASIA) key points on seven spinal dermatomes (C3 (neck), C4 (shoulder), C5 (upper arm), C6 (thumb), T8 (abdomen), L3 (knee), L5 (foot)) and in the mandibular (chin) and maxillary (cheek) fields of the trigeminal (V) nerve. Electrical stimulation (0.5 ms pulse width; 3 Hz) was applied via a self-adhesive cathode and an anode strapped to the wrist or ankle. The stimulus intensity was adjusted and PT was recorded as the lowest current at which the subject reported sensation. Sites were tested in random order. Indices for both TPDA and PT differed according to the dermatome tested but there was no correlation between TPDA and PT for any dermatome. There was good correlation between results from equivalent dermatomes on left and right sides for both PT and TPDA. Women frequently had lower mean (+/- S.E.) PTs and better TPDA than men; differences were significant (P < 0.05) for PT on the knee (women, 1.31 +/- 0.15 mA; men, 2.05 +/- 0.26 mA) and the foot (women, 2.90 +/- 0.19 mA; men, 4.13 +/- 0.28 mA) and for TPDA on the thumb (women, 3.8 +/- 0.2 mm; men, 7.8 +/- 1.3 mm) and the knee (women, 17.8 +/- 1.6 mm; men, 27.1 +/- 4.0 mm). Four subjects repeated the experiment on another day and the results correlated well with the first test for PT (r2, 0.62) and TPDA (r2, 0.48). PT differs between dermatomes in a predictable way but does not relate to TPDA. PT is easy to measure and may be a useful assessment tool with which to monitor recovery or deterioration in neuropathies, neurotrauma or after surgery.

Study design: Longitudinal. Objectives: (1) To perform standard clinical neurological examinations and establish the pattern of clinical change with time following incomplete spinal cord injury (iSCI). (2) To establish the pattern of change in corticospinal electrophysiological function with time after iSCI. (3) To correlate clinical with electrophysiological findings. Setting: The National Spinal Injuries Centre, Stoke Mandeville Hospital, Aylesbury, UK and Imperial College School of Medicine, Charing Cross Hospital, London, UK. Methods: Neurological assessments and classification were performed according to American Spinal Injuries Association and International Medical Society of Paraplegia (ASIA/IMSOP) standards. Twenty-one patients (ages 18–72 years) with iSCI (level C2–C7, ASIA impairment grades C–D) and 10 healthy control subjects (ages 27–57 years) were studied. Electrophysiological tests of corticospinal function were carried out using transcranial magnetic stimulation (TMS) of the motor cortex and electromyographic (EMG) recordings from thenar muscles. Both tests were performed on a number of occasions, beginning 19–384 days and ending 124–1109 days post-injury, and the group data were pooled into time epochs of 50 or 100 days post-injury for analysis. Seven of the patients were studied on seven or more occasions and were also assessed individually. Results: Individual and pooled data indicated that neurological scores improved progressively and tended to stabilise by around 300 days post-injury. When the patients were first assessed, the mean latency for motor evoked potentials (MEPs) and inhibition of voluntary EMG were significantly different from control values. There was no significant change in latency on subsequent sessions for either the grouped or individual patient data. There was no correlation between clinical assessment and electrophysiological data. Conclusion: We conclude that the weakened inhibition seen following iSCI is established within a few days of the time of spinal cord trauma. We argue that reduced corticospinal inhibition may be a prerequisite for the recovery of useful motor function. Sponsorship: The work was supported by a project grant from The Wellcome Trust. Spinal Cord (2000) 38, 292–300.

Synchronisation of motor unit discharges is commonly seen in hand muscles of normal man but is absent following neurologically complete spinal cord injury and reduced after stroke. These findings support the notion that some corticospinal inputs to motoneurones are shared and contribute to the observed synchrony of discharge. In this study we have examined motor unit discharge in hand muscles below the level of an incomplete spinal cord injury in an attempt to relate strength of synchrony to the integrity of the corticospinal tract. Eight patients with incomplete spinal cord injury (neurological level C3-C7) and eight control subjects took part in the study. The patients had sustained injury 14-191 weeks prior to the recordings and had since regained good motor function in their hands. Two concentric needle electrodes were inserted into the first dorsal interosseus muscle which subjects were instructed to contract weakly so that potentials from individual motor units could be reliably identified on both recordings. Synchrony was detected by constructing cross-correlograms between the discharges of pairs of individual motor units. The amount of synchronous firing was determined from the magnitude of any peak in the cross-correlogram, as the probability above chance (XP) of one motor unit firing with respect to the other and vice versa. The degree of synchrony was lower (P < 0.05) in the patient group (mean XP 0.06) than in the control group (mean XP 0.09). The incidence of significant synchrony was lower in the patient group (41.8 %) than in the control group (92.9 %). The mean (+/- S.E.M.) frequency of motor unit discharge was slightly lower (P < 0.05) in patients (9.7 +/- 0.4 impulses s-1) than controls (10.8 +/- 0.5 impulses s-1). The mean width of synchrony peaks was narrower (P < 0.05) in patients (11.4 +/- 1.1 ms) than controls (13.2 +/- 0.6 ms). We conclude that the weaker synchrony of motor unit discharge in incomplete spinal cord injury may reflect permanent damage to some corticospinal axons.

Lateral ventricular volumes were monitored and quantified using accurately registered magnetic resonance images (MRIs) in six healthy individuals 30 min before and up to 4 h after ingestion of a glucose drink. The volume of the lateral ventricles increased by an average (+/- S.E.M.) of 2.4 +/- 0.4% as blood glucose levels rose from 4.8 +/- 0.2 mmol l-1 to 8.4 +/- 0.4 mmol l-1. This was followed by a peak decrease of 5.99 +/- 3.3% below initial fasting volumes as blood glucose levels fell to 5.0 +/- 0.3 mmol l-1. We suggest that the secondary volume decrease demonstrates a homeostatic process of brain volume regulation for which the mechanism remains uncertain.

Study design: Preliminary longitudinal clinical trial. Objectives: To test the efficacy of repetitive transcranial magnetic stimulation (rTMS) in modulating corticospinal inhibition and improving recovery in stable incomplete spinal cord injury (iSCI). Setting: National Spinal Injuries Centre, Stoke Mandeville Hospital, Bucks, UK and Division of Neuroscience, Imperial College Faculty of Medicine, Charing Cross Hospital, London, UK. Methods: Four stable iSCI patients were treated with rTMS over the occipital cortex (sham treatment) and then over the motor cortex (real treatment). Patients were assessed using electrophysiological, clinical and functional measures before treatment, during sham treatment, during the therapeutic treatment and during a 3-week follow-up period. Results: Cortical inhibition was reduced during the treatment week. Perceptual threshold to electrical stimulation of the skin, ASIA clinical measures of motor and sensory function and time to complete a peg-board improved and remained improved into the follow-up period. Conclusion: In this preliminary trial, rTMS has been shown to alter cortical inhibition in iSCI and improve the clinical and functional outcome. Sponsorship: This work was supported by the International Spinal Research Trust.

A rhythmic modulation of motor unit discharge at 17-24 Hz has been observed in the tibialis anterior muscle of subjects who display a high degree of short-term synchrony. Motor unit discharges were recorded both from extensor digitorum communis in the arm and tibialis anterior in the leg during voluntary isometric contractions. Time domain analysis of motor unit discharges in both muscles revealed a prominent central peak in the cross-correlograms that was interpreted as short-term synchrony. In tibialis anterior, but not in extensor digitorum communis, the primary, central peak was accompanied by secondary peaks. These were symmetrically or unilaterally present at an average time lag of 52 ms (range 37-68 ms) with respect to the primary peak. In both muscles other peaks occurred at time lags equivalent to the mean interspike interval of motor unit discharge (range 80-150 ms). In all subjects frequency domain analysis of the discharges of pairs of motor units revealed prominent peaks of coherence in the range 17-24 Hz. The actual frequency matched closely the reciprocal of the time lag interval between primary and secondary peaks of the cross-correlogram of the same motor units. Coherence was less evident for motor unit discharges in extensor digitorum communis and no prominent peaks occurred in the range 17-24 Hz. We propose that the secondary peaks and the rhythmicity may involve recurrent inhibition activated by the synchronous discharge of motor units. The presence of this pattern of discharge in tibilias anterior but not extensor digitorum communis would fit with recent animal and human work suggesting that recurrent inhibition is poorly represented in certain distal muscles of the forelimb.

INTRODUCTION This report summarizes preliminary findings of three quantitative sensory tests (QSTs) that were evaluated as part of the International Spinal Research Trust (ISRT) Clinical Initiative study. ISRT commissioned this work in preparation for future clinical trials of new spinal cord injury (SCI) interventions. The wider Clinical Initiative study assesses numerous clinical and neurophysiological tests of motor, sensory, and autonomic function that could be used for monitoring the efficacy of new therapeutic interventions. The ISRT Clinical Initiative has a few specific requirements. Firstly, to minimize functional loss to the patient in case of any neurological deterioration, ISRT anticipates that the first clinical trials of spinal cord repair sponsored by them will be conducted in patients with thoracic lesions. Therefore, the newly developed tests must be applicable in the thoracic region, for which SCI diagnosis currently relies mainly on clinical sensory testing. Secondly, the first interventions are expected to produce only minor improvements and possibly over a few spinal segments only; therefore, the newly developed tests must be able to detect these small changes. The tests presented here were developed with these requirements in mind, although they can be used in patients with any level and type of injury. An overall progress review of the ISRT Clinical Initiative study was presented in the ISRT lecture at the International Spinal Cord Society's Annual Scientific Meeting in Beijing, China (October 2003) and was published in 2004 by Ellaway et al. [1]. The present article includes three of the sensory tests discussed in Ellaway et al. [1] and provides additional data acquired since that publication. However, at the time this article was prepared, the ISRT Clinical Initiative study was still ongoing and final results were unavailable. Hence, all the results reported here should be treated as preliminary. Once complete, final results will be submitted for publication as separate articles in peer-reviewed journals. The three tests discussed in this article are QSTs that assess the perceptual thresholds (PTs) (lowest stimulus intensity that a subject can perceive) for three types of stimulation: electrical, vibration, and thermal. All three stimulation types had been used previously for assessing sensory function, mainly in peripheral neuropathies [2-6], radiculopathies [7-8], and brachial plexus lesions [9]. Some QSTs have been used in patients with incomplete SCI [10-12]. For this study, the techniques were adapted to suit patients with SCI of any level, including thoracic, and of any impairment grade. Between them, the three QSTs were expected to include both of the sensory modalities tested in clinical examination (i.e., pinprick and light touch); thermal thresholds would predominantly test spinothalamic function, vibration threshold would test posterior column function, and electrical threshold would test both sensory functions. METHODS AND PRELIMINARY RESULTS The ISRT Clinical Initiative study was approved by the Aylesbury Vale Local Research Ethics Committee. Control subjects and patients with SCI were given a written information sheet and a verbal explanation of all the procedures. Written consent was obtained from all subjects. For each of the three tests (electrical, vibration, and thermal PTs), normative values and reproducibility of the technique were established in control subjects before performing the test in the patients with SCI. Wherever possible, stimuli were applied over American Spinal Injury Association (ASIA) sensory key points or, at least, within ASIA dermatomes (Figure 1). All patients also had a clinical neurological examination and classification performed according to ASIA standards [13-14] so that the QST results could be correlated with clinical sensory examination results. Consistent with ASIA standards, clinical sensory level was determined separately for the right and left sides of the body and defined as the most caudal spinal segment with normal sensory function for both sensory modalities (i. …

Objective: The clinical and functional assessment of back muscles in human spinal cord injury (SCI) has received little attention. The aim of this study was to develop a method to assess the level of a thoracic spinal cord lesion based on the reflex activation of back muscles. Methods: In 11 control subjects and in 12 subjects with clinically complete thoracic SCI (T2–T12), either a spinous process or an erector spinae muscle was prodded to elicit short latency reflexes recorded electromyographically at the spinal level of stimulation. An electromagnetic servo, attached to a blunt probe, applied stimuli at a frequency of 1 Hz and amplitude of 3 mm. Two trials of 50 mechanical prods were conducted at each site. Results: Reflexes were evoked in control subjects in 82% of trials when the spinous process was prodded, and in 80% of trials when the muscle was prodded. In contrast, reflexes in SCI subjects could be elicited in 90–100% of trials two segments either above or below the lesion. Reflex responses in control subjects had a mean (SEM) latency of 5.72 (0.53) ms when the spinous process was prodded, and 5.42 (0.42) ms when the muscle was prodded. In the SCI subjects, responses had slightly (but insignificantly) longer latencies both above and below the lesion to either stimulus. The amplitude of reflex responses, expressed as a percentage of the background EMG, was on average 2–3 times larger at the three vertebral levels spanning the lesion in SCI subjects than at sites above or below the lesion or at any level in control subjects. Conclusion: We propose that the size of these mechanically evoked reflexes may be useful in determining the level of thoracic SCI. Furthermore, the reflexes might provide a valuable tool with which to monitor recovery after an intervention to repair or improve function of a damaged spinal cord.

Patients can often recover good motor function in muscles below an incomplete spinal cord injury. Within a few days of injury natural processes lead to down-regulation of inhibitory pathways within the motor cortex than can be demonstrated electrophysiologically. We believe that this natural change might encourage motor recovery by allowing an increased excitability of surviving descending corticospinal neurones. Repetitive transcranial magnetic stimulation (rTMS) can produce similar changes in corticospinal inhibition in normal uninjured individuals, albeit rather short-lasting. In this preliminary study we have delivered a sham rTMS over one week followed by another week of real treatment to four stable incomplete spinal cord injury patients who already showed reduced inhibition compared with controls. Intracortical inhibition was further reduced during the week of treatment but recovered basal levels within the three-week follow-up period. Longer-term improvements were seen in the clinical scores for both motor and sensory function, perceptual threshold to electrical stimulation of the skin and the time taken to complete a standard peg-board test. Although the measurable electrophysiological effects of rTMS are short-lived it would appear that functional recovery persists for at least three weeks after the treatment. Spinal cord injury patients might be more susceptible to the plastic cortical changes evoked by rTMS than non-injured individuals. This preliminary study provides promising data on which to base a larger investigation with the aim of substantiating the use of rTMS as a tool for routine use in rehabilitation.

Clinical practice and scientific research may soon lead to treatments designed to repair spinal cord injury. Repair is likely to be partial in the first trials, extending only one or two segments below the original injury. Furthermore, treatments that are becoming available are likely to be applied to the thoracic spinal cord to minimise loss of function resulting from damage to surviving connections. These provisos have prompted research into the improvement of clinical and physiological tests designed (1) to determine the level and density of a spinal cord injury, (2) to provide reliable monitoring of recovery over one or two spinal cord segments, and (3) to provide indices of function provided by thoracic spinal root innervation, presently largely ignored in assessment of spinal cord injury. This article reviews progress of the Clinical Initiative, sponsored by the International Spinal Research Trust, to advance the clinical and physiological tests of sensory, motor and autonomic function needed to achieve these aims.

This study examined post-exercise changes in corticospinal excitability in five 'elite' rowers and six nonrowers. Transcranial magnetic stimulation (TMS) was delivered to the motor cortex and bilateral electromyographic (EMG) recordings were made from erector spinae (ES) muscles at L3/L4 spinal level and from the first dorsal interosseous (FDI) muscle of the dominant hand. Each subject completed two exercise protocols on a rowing ergometer: a light exercise protocol at a sub-maximal output for 10 min and an intense exercise protocol at maximum output for 1 min. A trial of ten magnetic stimuli was delivered before each of the protocols and, on finishing exercise, further trials of ten stimuli were delivered every 2 min for a 16 min period. Amplitudes of motor-evoked potentials (MEPs) in each of the three test muscles were measured before exercise and during the recovery period after exercise. The non-rowers showed a brief facilitation of MEPs in ES 2 min after light and intense exercise that was only present in the elite rowers after intense exercise. In the period 4-16 min after light exercise, the mean (+/- S.E.M.) MEP amplitude (relative to pre-exercise levels) was less depressed in the elite rowers (79.4 +/- 2.1%) than in the non-rowers (60.9 +/- 2.5%) in the left ES but not significantly so in the right ES. MEP amplitudes in FDI were significantly larger in the elite rowers, averaging 119.0 +/- 3.1% pre-exercise levels, compared with 101.2 +/- 5.8% in the non-rowers. Pre-exercise MEP latencies were no different in the two groups. After light exercise MEP latencies became longer in the elite rowers (left ES, 16.1 +/- 0.5 ms; right ES, 16.1 +/- 0.4 ms; dominant FDI, 23.4 +/- 0.2 ms) than in the non-rowers (left ES, 15.0 +/- 0.3 ms; right ES, 15.2 +/- 0.3 ms; dominant FDI, 21.5 +/- 0.2 ms). There were no differences in MEP depression or latency between elite rowers and non-rowers after intense exercise. We conclude that the smaller degree of MEP depression in the elite rowers after light exercise reflects less central fatigue within corticospinal control pathways than that seen in the non-rowers. The longer latency of MEPs seen in the elite rowers may reflect recruitment of more slower-conducting fatigue-resistant motor units compared with the non-rowers. These differences may be because the energy requirements for the non-rowers during light exercise are closer to their maximum capacity, leading to more fatigue. This notion is supported by the lack of any difference between groups following intense exercise when both groups were working at their own maximum.

The pathogenesis of chronic fatigue syndrome (CFS) remains unknown. Thresholds and latencies of motor evoked potentials (MEPs) in response to transcranial magnetic stimulation (TMS) are normal but intracortical inhibition has not been investigated. Eleven patients with CFS were compared with 11 control subjects. Each patient completed a questionnaire using visual analogue indices of pain, fatigue, anxiety and depression. Subjects released a button to initiate simple (SRTs) and choice reaction time (CRTs) tasks; for each task, movement times were measured between release of the initiation button and depression of a second button 15 cm away. Subjects held a 10 % maximum voluntary contraction in the thenar muscles of their dominant hand while TMS was applied to the motor cortex; the duration and extent of inhibition of surface electromyographic (EMG) activity were assessed at stimulus strengths above and below the threshold for MEPs. Patients had significantly (P0.05) higher mean indices of fatigue than of pain, anxiety or depression. Mean (+/- S.E.M.) SRTs (but not CRTs) were longer in patients (309 +/- 45 ms) than in controls (218 +/- 9 ms). Movement times were longer in patients for both SRTs and CRTs. TMS thresholds, expressed as a percentage of the maximum stimulator output, were not significantly (P0.05) different in both groups for both MEPs (patients, 34 +/- 3%; controls, 36 +/- 3%) and inhibition of voluntary contraction (patients, 29 +/- 2%; controls, 34 +/- 4%). The duration and extent of inhibition did not differ significantly between groups at any stimulus strength. The pattern of change in duration and extent of inhibition with increasing stimulus intensity was no different in the two groups. The duration and extent of corticospinal inhibition in patients with CFS did not differ from controls, adding further evidence to the notion that the feeling of fatigue and the slowness of movement seen in CFS is not manifest in corticospinal output pathways.

OBJECTIVES—Motor evoked potentials (MEPs) and inhibition of voluntary contraction to transcranial magnetic stimulation (TMS) of the motor cortex have longer latencies than normal in patients with incomplete spinal cord injury (iSCI) when assessed using surface EMG. This study now examines the modulation of single motor unit discharges to TMS with the aim of improving resolution of the excitatory and inhibitory responses seen previously in surface EMG recordings. METHODS—A group of five patients with iSCI (motor level C4-C7) was compared with a group of five healthy control subjects. Single motor unit discharges were recorded with concentric needle electrodes from the first dorsal interosseus muscle during weak voluntary contraction (2%-5% maximum). TMS was applied with a 9 cm circular stimulating coil centred over the vertex. Modulation of single motor unit discharges was assessed using peristimulus time histograms (PSTHs). RESULTS—Mean (SEM) threshold (expressed as percentage of maximum stimulator output (%MSO)) for the excitatory peak (excitation) or inhibitory trough (inhibition) in the PSTHs was higher (p

OBJECTIVES (1) A biochemical investigation of the motor cortex in patients with incomplete spinal cord injury and normal control subjects using proton magnetic resonance spectroscopy (MRS). (2) To relate any altered biochemistry with the physiological changes in corticospinal function seen after spinal cord injury. METHODS a group of six patients with incomplete spinal cord injury who showed good recovery of motor function were selected. The patients were compared with five healthy control subjects. Electromyographic (EMG) responses of thenar muscles to transcranial magnetic stimulation (TMS) of the motor cortex showed that inhibition of cortical output was weaker in the patients than the controls. Proton MRS data were collected from a plane at the level of the centrum semiovale. Two 4.5 cm3 voxels in the motor cortex and a third voxel in the ipsilateral occipital cortex were examined in the patients and control subjects. RESULTS The mean level of N- acetylaspartate (NAA), expressed relative to the creatine (Cr) peak (NAA/Cr), was significantly increased in the motor cortex of the patients compared with their ipsilateral occipital cortex or either cortical area in the controls. No differences between patients and controls were seen for any of the other metabolite peaks (choline (Cho), glutamate/glutamine (Glx) or the aspartate component of NAA (AspNAA)) relative to Cr. Choline relative to Cr (Cho/Cr) was higher in the motor cortex of the control subjects than in their ipsilateral occipital cortex. This difference was not present in the patients. CONCLUSIONS Raised NAA/Cr in the motor cortex of the patients probably results from increased NAA rather than a decrease in the more stable Cr. The possible relevance of a raised NAA/Cr ratio is discussed, particularly with regard to the changed corticospinal physiology and the functional recovery seen in the patients.

OBJECTIVE To investigate changes in electromyographic (EMG) responses to transcranial magnetic stimulation (TMS) of the motor cortex after incomplete spinal cord injury in humans. METHODS A group of 10 patients with incomplete spinal cord injury (motor level C3-C8) was compared with a group of 10 healthy control subjects. Surface EMG recordings were made from the thenar muscles. TMS was applied with a 9 cm circular stimulating coil centred over the vertex. The EMG responses to up to 50 magnetic stimuli were rectified and averaged. RESULTS Thresholds for compound motor evoked potentials (cMEPs) and suppression of voluntary contraction (SVC) elicited by TMS were higher (p

Frequency of firing and regularity of discharge of human motor units, and short term synchrony between pairs of motor units, have been assessed in extensor digitorum communis (EDC) and tibialis anterior (TA) muscles in control subjects and in clinically complete paraplegic subjects. The discharge pattern of TA motor units in paraplegia ranged from extremely regular to very irregular for different motor units whereas in the control population, and in EDC of both groups, there was a narrow, but intermediate, range of regularity. There was little difference in the incidence and degree of short term synchrony (STS) in EDC between paraplegic and normal subjects. In contrast, virtually no STS of motor units was observed in the TA muscles of the paraplegic group whereas control subjects exhibited approximately the same amount of STS in their TA and EDC muscles. It is concluded that the extra burden placed on arm muscles in paraplegia does not change the amount of synchronisation between motor units. Furthermore, section of the spinal cord does not increase STS as predicted from lesions of the reticulospinal tract in cats. This may reflect the coincidental removal of supraspinal synchronising inputs of motoneurons or the reorganisation of synaptic inputs in chronic paraplegia.

This article reviews methods that have been devel- oped as part of a clinical initiative on improving outcome meas- ures for motor function assessment in subjects with spinal cord injury (SCI). Physiological motor outcome measures originally developed for limbs—transcranial magnetic stimulation (TMS) of the motor cortex to elicit motor-evoked potentials (MEPs) and mechanical stimulation to elicit spinal reflexes—have been extended to muscles of the trunk. The impetus for this develop- ment is the lack of a motor component in the American Spinal Injury Association clinical assessment for the thoracic myo- tomes. The application of TMS to the assessment of limb mus- cles is reviewed, followed by consideration of its application to the assessment of paravertebral and intercostal muscles. Spinal reflex testing of paravertebral muscles is also described. The principal markers for the thoracic SCI motor level that have emerged from this clinical initiative are (1) the threshold of MEPs in paravertebral muscles in response to TMS of the motor cortex, (2) the facilitation pattern and latency of MEPs in intercostal muscles during voluntary expiratory effort, and (3) the absence of long-latency reflex responses and the exaggeration of short-latency reflex responses in paravertebral muscles.