The influence of cervical collar immobilization on optic nerve sheath diameter

Abstract

Background: Prior research has revealed that cervical collars elevate intracranial pressure (ICP) in patients with traumatic brain injury. Two recent small studies evaluated the change in optic sheath nerve diameter (ONSD) measured by ultrasound as a proxy for ICP following cervical collar placement in healthy volunteers. Objective: We sought to validate the finding that ONSD measured by ultrasound increases after cervical collar placement within an independent data set. Methods: This was a prospective, crossover study involving volunteers. Participants were randomized to either have the ONSD measured first without a cervical collar or initially with a cervical collar. Two sonographers performed independent ONSD diameter measurements. Continuous data were analyzed by matched-paired t -tests. Alpha was set at 0.05. The primary outcome parameter was the overall mean difference between ONSD measurements with the cervical collar on and off. Multiple linear regression was performed to examine the relationship between variables and the primary outcome parameter. Results: There were 30 participants enrolled in the study. Overall mean ONSD for participants without the collar was 0.365 ± 0.071 cm and with the collar was 0.392 ± 0.081 cm. The mean change in ONSD for participants with and without the collar was 0.026 ± 0.064 cm (95% confidence interval of difference: 0.015–0.038; P < 0.001). Multiple regression analysis did not identify any variables associated with the variation in ONSD observed for collar versus noncollar. Conclusions: We confirmed that ONSD does vary by a measurable amount with placement of a rigid cervical collar on healthy volunteers when assessed by ultrasound.

Effect of a cervical collar on optic nerve sheath diameter in trauma patients

“…The mean ONSD in the axial plane for the right and left optic nerves was 5.04 ± 0.46 mm and 5.11 ± 0.46 mm respectively on CT images without cervical collar patients. These findings suggest that patients without cervical collars and without orbital or cranial pathology have similar mean ONSD measurements to those made in healthy patients on CT. Yard et al [10] evaluated whether the cervical collar change the ONSDs, and it was observed that the cervical collar increased the ONSD. Colak et al [16] evaluated the relationship between the ONSD and cervical collar use in trauma patients.…”

“…In various studies, the optic nerve sheath diameter (ONSD) has been shown to be a useful marker for indirectly measuring the ICP. [8][9][10] ONSD can be measured with computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound (US). [11,12] In the literature, there are many studies in which ONSD measurements of trauma patients with cervical collars were obtained using the US.…”

Current status of point of care ultrasonography for the perioperative care of trauma patients

“…When performing serial exams, be careful to use the same positioning and environment, or account for changes in positioning or other activities that increase ICP such as coughing, cervical collar, and derangements such as kinked endotracheal tube [78].…”

Diagnostic utility of point of care ultrasound in identifying cervical spine injury in emergency settings

“…10,11 Recent evidence suggests the application of a rigid cervical collar for a short period results in a change of optic nerve sheath diameter in healthy volunteers. 12 So the ideal C-spine clearance protocols must balance the risk of missed injury against the potential for increased morbidity from prolonged spinal immobilisation.…”