Rectal Tonometer for Detection of Spinal Cord Injury

Abstract Approximately 18,000 new spinal cord injuries (SCIs) occur each year in the U.S., according to data from the National Spinal Cord Injury Statistical Center. The prevalence of people living with SCIs is estimated to be around 294,000 individuals. The most common causes of SCIs are vehicle accidents (38%), falls (32%), violence and gunshot wounds (14%), sports-related injuries (8%), and other causes (4%). SCIs are diagnosed using structural information from MRI images and functional information from bedside neurological exams, including digital rectal examination (DRE). The DRE is a quick bedside neurological assessment used to evaluate the integrity of the sacral nerve roots (S2–S4) and spinal cord function. While MRI is invaluable for visualizing structural damage, it cannot replace the functional insights provided by a DRE in the acute assessment of SCI. Multiple studies have assessed the accuracy of the DRE for evaluating abnormal anal tone. Clinicians correctly recognize anal sphincter pressure changes only 64% of the time. This paper presents the development of a hand-held sensor (tonometer) designed to measure rectal pressure. The device utilizes a hollow elastomeric probe that assesses contractile pressure through changes in the pressure of enclosed air. Preliminary results from the calibrated devices on two test subjects indicate sufficient sensitivity and good repeatability of the measurements. Average resting tone and squeeze tone were found to be around 40 mm Hg and 100 mm Hg, respectively. These values are consistent with the pressure levels determined by anorectal manometry.