Diaphragm muscle denervation following mid‐cervical contusion injury (871.6)

Abstract

Respiratory failure is one of the most important complications of cervical spinal cord injury. The level of injury critically determines the severity of the complications. We hypothesized that higher cervical contusion injuries will compromise the motor neuron pool and the descending bulbospinal projections, causing greater functional compromise than contusions at lower levels. Unilateral contusion was performed on adult rats at either the C3 or C5 levels vs. laminectomy. No deficit was seen in ventilatory and non‐ventilatory behaviors as assessed by whole body plethysmography or chronic diaphragm electromyography up to 2 weeks. Contusion injuries at either level resulted in similarly sized cavity formation. Phrenic motor neuron loss differed, with C3 contusion causing a 50% loss of phrenic motor neurons, and C5 contusion only 20% loss compared to the contralateral side. The percent of NMJs that were denervated followed a segmental pattern. Following C3 contusion, ventral regions of the diaphragm displayed denervation of ~30% of NMJs compared to 1‐3% in the C5 contusion and laminectomy groups. In contrast, following C5 contusion, denervation was evident only in dorsal regions (~10%). These results show minimal ventilatory impairment following contusion injuries to the mid‐cervical spinal cord that result in phrenic motor neuron loss and evidence of diaphragm muscle denervation.Grant Funding Source: Supported by NIH grant R01 HL096750 and the Mayo Clinic