Introduction

Gastrointestinal symptoms, most often constipation and fecal incontinence, can arise due to lesions or diseases of the central nervous system. These symptoms affect up to 80% of patients with spinal cord injury (SCI), multiple sclerosis (MS), and spina bifida (SB).¹

Injury above the conus medullaris (upper motor neuron) results in hyperreflexic bowel and a tight anal sphincter, which causes constipation and fecal retention.  Stool evacuation is induced by reflex activity in the rectum.  Injury at the conus medullaris and cauda equina (lower motor neuron) results in areflexic bowel and loss of peristaltic control, resulting in prolonged stool transit particularly in the rectosigmoid region.  Furthermore, loss of control over the external anal sphincter can result in fecal incontinence. Completeness of the injury also impacts bowel function.  Patients with incomplete SCI may retain sensation of rectal fullness and the ability to evacuate bowels.²

Emotional and behavioral disturbances may alter autonomic control of bowel function and influence toilet habits. Interruption of afferent sensory or efferent motor pathways can affect regulation of bowel function. Finally, systemic factors and medications used for MS can affect visceral and pelvic floor function.³

Individuals with spina bifida (SB) often have a neurological deficit below the level of the lesion, usually at the conus medullaris or cauda equina. This results in areflexic bowel and prolonged stool transit in the rectosigmoid region.  Anal resting and squeeze pressures are reduced and sensitive, causing fecal incontinence.^4,5