Recovery from a spinal cord injury: significance of compensation, neural plasticity, and repair

Clinical algorithm for improved prediction of ambulation and patient stratification after incomplete spinal cord injury

The extent of ambulatory recovery after motor incomplete spinal cord injury (miSCI) differs considerably amongst affected persons. This makes individual outcome prediction difficult and leads to increased within-group variation in clinical trials. The aims of this study on subjects with miSCI were: (1) to rank the strongest single predictors and predictor combinations of later walking capacity; (2) to develop a reliable algorithm for clinical prediction; and (3) to identify subgroups with only limited recovery of walking function. Correlation and logistic regression analyses were performed on a dataset of 90 subjects with tetra- or paraparesis, recruited in a prospective European multicenter study. Eleven measures obtained in the subacute injury period, including clinical examination, tibial somatosensory evoked potentials (tSSEP), and demographic factors, were related to ambulatory outcome (WISCI II, 6minWT) 6 months after injury. The lower extremity motor score (LEMS) alone and in combination was identified as most predictive for later walking capacity in miSCI. Ambulatory outcome of subjects with tetraparesis was correctly predicted for 92% (WISCI II) or 100% (6minWT) of the cases when LEMS was combined with either tSSEP or the ASIA Impairment Scale, respectively. For individuals with paraparesis, prediction was less distinct, mainly due to low prediction rates for individuals with poor walking outcome. A clinical algorithm was generated that allowed for the identification of a subgroup composed of individuals with tetraparesis and poor ambulatory recovery. These data provide evidence that a combination of predictors enables a reliable prediction of walking function and early patient stratification for clinical trials in miSCI.

Dermatomal Somatosensory Evoked Potentials and Electrical Perception Thresholds During Recovery From Cervical Spinal Cord Injury

Background. Dermatomal somatosensory evoked potentials (dSSEPs) not only provide a neurophysiological readout comparable with conventional SSEPs but also provide an opportunity to track changes in sensory function corresponding to individual dermatomes (ie, a single spinal segment) above, at, and below the level of spinal cord injury (SCI). Objectives. This study aimed to determine the reliability and responsiveness of dSSEPs and electrical perception thresholds (EPTs) to monitor changes in sensory function after cervical SCI. Methods. Initial and follow-up dSSEPs and EPTs were recorded from cervical dermatomes (C4-C8) of patients with traumatic tetraplegia (C3-C8; ASIA Impairment Scale A-D) during recovery after SCI (n = 18). Results. Follow-up examination of 74 initial dSSEPs unaffected by SCI (n = 18) revealed no significant change in latency (Δ = 0.0 ± 1.4 ms; P = .9) or EPT sensitivity (Δ = 0.1 ± 0.8 mA; P = .3). In 41 dSSEPs initially delayed after SCI (n = 14), latencies significantly decreased on follow-up examination (Δ = -3.1 ± 2.9 ms; P < .01) without a corresponding increase in sensitivity of the EPT (Δ = 0.2 ± 3.4 mA; P = .7). dSSEPs that were not measurable initially were subsequently recorded in 11 dermatomes (n = 5) on follow-up examination. This conversion of abolished-to-recordable dSSEPs was often preceded by the perception of an initial EPT and associated with a concomitant recovery of EPT at follow-up. Conclusion. dSSEPs and EPT can be reliably recorded to monitor changes in sensory function for each individual spinal segment after cervical SCI. dSSEPs may be potentially useful to monitor the safety of a therapeutic drug or cell transplant in early-phase (I/II) clinical trials as well as document the potential efficacy of interventions where the standard neurological assessment might not detect subtle therapeutic effects.

Olfactory mucosal autografts and rehabilitation for chronic traumatic spinal cord injury

BACKGROUND/OBJECTIVE

Basic science advances in spinal cord injury (SCI) are leading to novel clinical approaches. The authors report a prospective, uncontrolled pilot study of the safety and outcomes of implanting olfactory mucosal autografts (OMA) in 20 patients with chronic, sensorimotor complete or motor complete SCI.

METHODS

Seven paraplegic and 13 tetraplegic subjects (17 men and 3 women; 19-37 years old) who sustained a traumatic SCI 18 to 189 months previously (mean = 49 months) were enrolled. Preoperative rehabilitation that emphasized lower extremity stepping using either overground walking training or a robotic weight-supported treadmill training was provided for 25 to 39 hours per week for a median of 4 months at 3 sites. No change in ASIA Impairment Scale (AIS) motor scores for the lower extremities or AIS grades of completeness was found. OMAs were transplanted into 1.3- to 4-cm lesions at C4-T12 neurological levels after partial scar removal. Therapy was continued postoperatively. Preoperative and postoperative assessments included AIS scores and classification, electromyography (EMG) of attempted voluntary contractions, somatosensory evoked potentials (SSEP), urodynamic studies with sphincter EMG, spinal cord magnetic resonance imaging (MRI), and otolaryngology and psychology evaluations. The Functional Independence Measure (FIM) and Walking Index for Spinal Cord Injury (WISCI) were obtained in 13 patients.

RESULTS

All patients survived and recovered olfaction. One patient was rehospitalized for aseptic meningitis. Minor adverse events occurred in 4 others. The mean duration of follow-up was 27.7 months (range = 12-45 months). By MRI, the lesion site was filled in all patients with no neoplastic overgrowth or syringomyelia. AIS grades improved in 11 of 20 patients, 6 (A --> C), 3 (B --> C), and 2 (A --> B), and declined in 1 (B --> A). Improvements included new voluntary EMG responses (15 patients) and SSEPs (4 patients). Scores improved in the FIM and WISCI (13/13 tested), and urodynamic responses improved in 5 patients.

CONCLUSION

OMA is feasible, relatively safe, and possibly beneficial in people with chronic SCI when combined with postoperative rehabilitation. Future controlled trials may need to include a lengthy and intensive rehabilitation arm as a control.

Electrophysiological outcomes after spinal cord injury

Electrophysiological measures can provide information that complements clinical assessments such as the American Spinal Injury Association sensory and motor scores in the evaluation of outcomes after spinal cord injury (SCI). The authors review and summarize the literature regarding tests that are most relevant to the study of SCI recovery--in particular, motor evoked potentials and somatosensory evoked potentials (SSEPs). In addition, they discuss the role of other tests, including F-wave nerve conductance tests and electromyography, sympathetic skin response, and the Hoffman reflex (H-reflex) test as well as the promise of dermatomal SSEPs and the electrical perceptual threshold test, newer quantitative tests of sensory function. It has been shown that motor evoked potential amplitudes improve with SCI recovery but latencies do not. Somatosensory evoked potentials are predictive of ambulatory capacity and hand function. Hoffman reflexes are present during spinal shock despite the loss of tendon reflexes, but their amplitudes increase with time after injury. Further, H-reflex modulation is reflective of changes in spinal excitability. While these tests have produced data that is congruent with clinical evaluations, they have yet to surpass clinical evaluations in predicting outcomes. Continuing research using these methodologies should yield a better understanding of the mechanisms behind SCI recovery and thus provide potentially greater predictive and evaluative power.

Recent advances in rehabilitation of stroke survivors

This report discusses the newest approaches to rehabilitation of post-stroke patients. Recent studies have clinical implications for the treatment of stroke at all stages, and chronic aphasia.

Spinal cord injury-induced attenuation of GABAergic inhibition in spinal dorsal horn circuits is associated with down-regulation of the chloride transporter KCC2 in rat

Most spinal cord injury (SCI) patients suffer from chronic pain. Effective therapy for this pain is lacking, and the underlying mechanisms are poorly understood. The spinal superficial dorsal horn (SDH) contains neuronal circuits capable of modulating primary afferent information involved in pain processing. KCC2 is an isoform of the K(+)-Cl(-) cotransporter that contributes to the regulation of transmembrane anion gradient which plays a key role in shaping GABA(A) receptor-mediated signalling in the CNS. We tested the hypothesis that SCI causes down-regulation of KCC2 distal to the injury and contributes to the neuronal hyperresponsiveness and pain-related behaviours. SCI was a hemisection at T(13) level of adult Sprague-Dawley rats. Spinal sagittal slices with attached dorsal roots (DR) were prepared from L(4) to L(6) level. The reversal potentials of GABA responses (E(GABA)) and DR-evoked IPSPs and EPSPs of L(4-6) SDH neurones in sham-operated and SCI rats were compared using gramicidin-perforated patch-clamp recordings. Here we report that thoracic SCI-induced down-regulation of KCC2 in the lumbar SDH parallels the development of allodynia. The subsequent changes of E(GABA) in SDH neurones attenuate the GABA(A) receptor-mediated inhibitory synaptic transmission. These changes cause certain normally subthreshold primary A and C fibre inputs to evoke action potential output in SDH neurones. We conclude that SCI induces KCC2 down-regulation and subsequent changes of E(GABA) in the SDH below the injury site. The resulting disinhibition unmasks normally ineffective SDH neuronal circuits and may contribute to the below-level central pain-related behaviours after incomplete SCI.

Central and peripheral timing variability in children with heavy prenatal alcohol exposure

BACKGROUND

The study examined whether prenatal alcohol exposure is associated with increased motor timing variability when the timing response is partitioned into central clock variability, which indexes information processing at the central nervous system (CNS) level and motor delay variability, which reflects timing processes at the level of the peripheral nervous system.

METHODS

Eighteen children with histories of prenatal alcohol exposure and 22 control children were assigned to young (7 to 11 years) or older (12 to 17 years) groups. Children tapped a single response key with the index finger in synchrony with a series of externally generated tones (the paced phase). At the conclusion of these tones, children continued tapping (the continuation phase) while attempting to maintain the same rate of tapping imposed by the paced phase. Two blocks of tapping were completed with inter-tone-intervals set at either 400 or 900 milliseconds. Inter-response interval, central clock variability, and motor delay variability produced during the continuation phase were the dependent variables.

RESULTS

Mean inter-response interval for the 4 groups did not differ for either time interval. Central clock variability produced by the young alcohol-exposed group was significantly greater than the two older groups for the 400 millisecond interval and all other groups for the 900 millisecond interval. Motor delay variability produced by the young alcohol-exposed group was significantly greater than the other three groups for both time intervals. Central and motor delay variability in children with and without alcohol exposure was directly related to the duration of the interval to be reproduced.

CONCLUSIONS

Central and peripheral timing variability was significantly greater for the young alcohol-exposed children. This atypical timing may be related to the teratogenic effects of alcohol, although the negative effects are limited to younger alcohol-exposed children since there were no differences in central and peripheral timing variability between the older alcohol-exposed children and controls.