Acute Cervical Spinal Cord Injury Alters Swallow Motor Patterns

Abstract

Cervical spinal cord injuries (cSCIs) can cause swallow disorder (dysphagia), potentially resulting in aspiration and pneumonia. Dysphagia is characterized by disruption of the swallow motor pattern, which involves sequential activation of muscles that propels the bolus into the esophagus while avoiding the airway. Normal swallow includes diaphragm activity that generates negative pressure, drawing the bolus into the esophagus. Centers in the brainstem control the swallow patterns. Thus, despite reports of dysphagia in some patients with cSCI, little consideration has been given to the potential contributions of spinal circuitry to swallow. We aim to characterize swallow dysfunction in cats with cSCI. Using EMG to record breathing patterns, water‐induced swallow in pentobarbital‐anesthetized spontaneously breathing cats is captured before and after acute high cervical hemisections (at C2 or C3). EMGs are recorded from the mylohyoid, thyrohyoid, thyroarytenoid, thyropharyngeus, cricopharyngeus (upper esophageal sphincter), and diaphragm muscles, and trans‐diaphragmatic pressure is measured by monitoring esophageal and stomach pressures. After hemisection, swallow is dramatically altered, as indicated by a dysfunctional swallow motor pattern. Coordinated, sequential muscle activation necessary for proper movement of a bolus through the pharynx is lost, esophageal pressure is positive rather than negative due to reduced activation of the diaphragm, and upper airway EMG activity increases. These alterations in behavior‐specific muscle recruitment patterns are profoundly dysphagic, indicating that disruption of spinal circuits in the high cervical spinal region can produce major dysfunction in swallow motor patterns. This work may inform screening and treatment protocols of the cSCI patient population, in which dysphagia is likely to be underdiagnosed.Support or Funding InformationNIH grants HL 111215, NS 110169 and OT20D001983, the Craig H. Neilsen Foundation Pilot Research Grant 546714, Kentucky Spinal Cord and Head Injury Research Trust, the Commonwealth of Kentucky Challenge for Excellence, VA RR&D B9249S and the Rebecca F. Hammond Endowment.