A crash course in spinal cord injury

Reorganization and preservation of motor control of the brain in spinal cord injury: a systematic review

Reorganization of brain function in people with CNS damage has been identified as one of the fundamental mechanisms involved in the recovery of sensorimotor function. Spinal cord injury (SCI) brain mapping studies during motor tasks aim for assessing the reorganization and preservation of brain networks involved in motor control. Revealing the activation of cortical and subcortical brain areas in people with SCI can indicate principal patterns of brain reorganization when the neurotrauma is distal to the brain. This review assessed brain activation after SCI in terms of intensity, volume, and somatotopic localization, as well as preservation of activation during attempted and/or imagined movements. Twenty-five studies meeting the inclusion criteria could be identified in Medline (1980 to January 2008). Relevant characteristics of studies (level of lesion, time after injury, motor task) and mapping techniques varied widely. Changes in brain activation were found in both cortical and subcortical areas of individuals with SCI. In addition, several studies described a shift in the region of brain activation. These patterns appeared to be dynamic and influenced by the level, completeness, and time after injury, as well as extent of clinical recovery. In addition, several aspects of reorganization of brain function following SCI resembled those reported in stroke. This review demonstrates that brain networks involved in different demands of motor control remain responsive even in chronic paralysis. These findings imply that therapeutic strategies aimed at restoring spinal cord function, even in people with chronic SCI, can build on preserved competent brain control.

Transplantation of porous tubes following spinal cord transection improves hindlimb function in the rat

STUDY DESIGN

Experimental.

OBJECTIVE

To determine the effects of a porous tube transplant in spinal cord transected rats.

SETTING

Acadia University, Wolfville, Nova Scotia, Canada.

METHODS

Female rats were randomly assigned to three experimental groups: control (Con, n=8), spinal cord transected (Tx, n=5) and spinal cord transected with transplant (TxTp, n=7). The rats in the TxTp and Tx groups received a complete spinal cord transection at the T10 level and the TxTp group immediately received a porous tube transplant.

RESULTS

Locomotor activity rated on the Basso, Beattie, Bresnahan scale improved significantly in the TxTp animals over the 4 weeks such that final scores were 21, 1.4 and 7.1 for the Con, Tx and TxTp groups, respectively. As expected, the muscle to body mass ratios of the hindlimb skeletal muscles of the Tx group were decreased (soleus 35%, plantaris 29% and gastrocnemius 29%) and this was also observed in the TxTp group (soleus 33%, plantaris 23% and gastrocnemius 30%). Cytochrome c oxidase (CYTOX) activity in the plantaris was decreased by Tx but maintained in the TxTp group (Con=82.2, Tx=44.8 and TxTp=72.8 U/min/g).

CONCLUSION

Four weeks after the spinal cord transection, plantaris CYTOX activity and locomotor function improved with porous tube implantation.

SPONSORSHIP

Natural Sciences and Engineering Research Council.

Tail muscles become slow but fatigable in chronic sacral spinal rats with spasticity

Paralyzed skeletal muscle sometimes becomes faster and more fatigable after spinal cord injury (SCI) because of reduced activity. However, in some cases, pronounced muscle activity in the form of spasticity (hyperreflexia and hypertonus) occurs after long-term SCI. We hypothesized that this spastic activity may be associated with a reversal back to a slower, less fatigable muscle. In adult rats, a sacral (S2) spinal cord transection was performed, affecting only tail musculature and resulting in chronic tail spasticity beginning 2 wk later and lasting indefinitely. At 8 mo after injury, we examined the contractile properties of the segmental tail muscle in anesthetized spastic rats and in age-matched normal rats. The segmental tail muscle has only a few motor units (<12), which were easily detected with graded nerve stimulation, revealing two clear motor unit twitch durations. The dominant faster unit twitches peaked at 15 ms and ended within 50 ms, whereas the slower unit twitches only peaked at 30-50 ms. With chronic injury, this slow twitch component increased, resulting in a large overall increase (>150%) in the fraction of the peak muscle twitch force remaining at 50 ms. With injury, the peak muscle twitch (evoked with supramaximal stimulation) also increased in its time to peak (+48.9%) and half-rise time (+150.0%), and decreased in its maximum rise (-35.0%) and decay rates (-40.1%). Likewise, after a tetanic stimulation, the tetanus half-fall time increased by 53.8%. Therefore the slow portion of the muscle was enhanced in spastic muscles. Consistent with slowing, posttetanic potentiation was 9.2% lower and the stimulation frequency required to produce half-maximal tetanus decreased 39.0% in chronic spinals. Interestingly, in spastic muscles compared with normal, whole muscle twitch force was 81.1% higher, whereas tetanic force production was 38.1% lower. Hence the twitch-to-tetanus ratio increased 104.0%. Inconsistent with overall slowing, whole spastic muscles were 61.5% more fatigable than normal muscles. Thus contrary to the classical slow-to-fast conversion that is seen after SCI without spasticity, SCI with spasticity is associated with a mixed effect, including a preservation/enhancement of slow properties, but a loss of fatigue resistance.

Is early enteral feeding safe in patients who have suffered spinal cord injury?

OBJECTIVE

To examine whether enteral feeding is a safe technique to use in the acute stage of spinal cord injury.

METHODS

We searched the departmental computerised patient database and clinical records for all patients with spinal cord injuries admitted to the Auckland Hospital Intensive Care Unit (ICU), known as the Department of Critical Care Medicine (DCCM), between January 1988 and December 2000. Patients were included in the study if they had suffered complete spinal cord transection resulting in either paraplegia or quadriplegia. Data was collected for the following variables: length of time to commence enteral feeding, type of enteral feeding, duration of enteral feeding and reasons for interrupting the feed.

RESULTS

Thirty-three patients were found and were included in the study. Twenty-seven (82%) of the patients commenced enteral feeding in the DCCM, 25 by nasogastric (NG) and 2 by nasojejunal (NJ) tube. Feeding was commenced a median of 2 days after admission and the median length of enteral feeding was 7.7 days. The main feeding complications that resulted in interrupting the feed were high gastric aspirates. One patient commenced on enteral feeding developed medical complications that prevented continuation. Two patients on NG feeding converted to NJ feeding.

CONCLUSION

No major complications associated with enteral feeding were seen in this study. This would indicate that enteral feeding can be safely administered in the acute stage of spinal cord injury provided complications are monitored for daily.

Acute Treatment of Spinal Cord Injury

At the authors' institution, a multidisciplinary team of trauma physicians, neurosurgeons, and anesthesiologists evaluates patients with suspected spinal cord injury. Our initial goal after resuscitation and evaluation is to assure adequate tissue oxygenation through blood pressure support and oxygen supplementation. This supplementation helps ensure maximal oxygen delivery to the injured spinal cord. It is important that a detailed and standardized neurologic examination is performed and repeated often to detect neurologic decline. Immediately after a potential spinal cord injury is identified, methylprednisolone is administered (ideally during transport from the accident scene). Plain x-rays of the spine are the first films obtained. Once a fracture is identified, a computerized CT scan through the identified region is done. If the injury involves the cervical spine, and reduction is needed to correct a deformity, closed reduction with placement of a halo-fixation device is performed in the emergency room. We believe that reduction to normal spinal alignment should be accomplished within a few hours of the injury. Once initial immobilization efforts are complete, the patient gets an magnetic resonance image (MRI) of the affected region. Most spinal cord injury patients at our institution do not undergo emergency surgery. Urgent surgery is only performed in those with continued neurologic decline, and MRI findings of acute compression from lesions such as a ruptured disc or epidural hematoma.