Imaging/brief research report
Emergency Department Sonographic Measurement of Optic Nerve Sheath Diameter to Detect Findings of Increased Intracranial Pressure in Adult Head Injury Patients

Presented at the annual meeting of the Society of Academic Emergency Medicine, May 2005, New York, NY.
https://doi.org/10.1016/j.annemergmed.2006.06.040Get rights and content

Study objective

Our objective is to determine whether a bedside ultrasonographic measurement of optic nerve sheath diameter can accurately predict the computed tomographic (CT) findings of elevated intracranial pressure in adult head injury patients in the emergency department (ED).

Methods

We conducted a prospective, blinded observational study on adult ED patients with suspected intracranial injury with possible elevated intracranial pressure. Exclusion criteria were age younger than 18 years or obvious ocular trauma. Using a 7.5-MHz ultrasonographic probe on the closed eyelids, a single optic nerve sheath diameter was measured 3 mm behind the globe in each eye. A mean binocular optic nerve sheath diameter greater than 5.00 mm was considered abnormal. Cranial CT findings of shift, edema, or effacement suggestive of elevated intracranial pressure were used to evaluate optic nerve sheath diameter accuracy.

Results

Fifty-nine patients were enrolled in the study. Average age was 38 years, and median Glasgow Coma Scale score was 15 (interquartile 6 to 15). Eight patients with an optic nerve sheath diameter of 5.00 mm or more had CT findings that correlated with elevated intracranial pressure. The sensitivity for the ultrasonography in detecting elevated intracranial pressure was 100% (95% confidence interval [CI] 68% to 100%) and specificity was 63% (95% CI 50% to 76%). The sensitivity of ultrasonography for detection of any traumatic intracranial injury found by CT was 84% (95% CI 60% to 97%) and specificity was 73% (95% CI 59% to 86%).

Conclusion

Bedside ED optic nerve sheath diameter ultrasonography has potential as a sensitive screening test for elevated intracranial pressure in adult head injury.

Introduction

Elevated intracranial pressure is a challenging and potentially fatal complication of acute head trauma in patients who present to the emergency department (ED).1, 2 This group of patients may require rapid intervention to prevent a poor outcome. Clinicians need an accurate tool to distinguish those with elevated intracranial pressure from the vast majority of patients with head injury who have no elevated intracranial pressure. The physical examination is limited in its ability to accurately detect elevated intracranial pressure caused by injury, sedation, or paralysis as part of their out-of-hospital care.2 Although computed tomography (CT) scanners are the most common diagnostic tests for these patients in US hospitals, there are situations in which a rapid bedside means of evaluating intracranial pressure would be advantageous. These situations include unstable multiorgan-system trauma patients, remote settings with prolonged transport time, or mass casualty occurrences.

The optic nerve sheath diameter has been suggested as a possible indicator of elevated intracranial pressure.3, 4, 5, 6, 7 Our objective was to determine whether dilation of the optic nerve sheath, as measured in the ED with a bedside ultrasonographic measurement, could accurately predict the findings of elevated intracranial pressure as seen in cranial CT in adult patients with acute head trauma.

Section snippets

Study Design

We conducted a prospective, blinded, observational study on adult ED patients suspected of having elevated intracranial pressure as a result of acute head trauma. Patients or their representatives were provided informed consent before their inclusion in the study. This study was approved by the institutional review board of Carolinas Medical Center, Charlotte, NC.

Setting

This research was conducted at a large, urban, regional, teaching ED and Level I trauma center with an annual census of 105,000 and

Results

Fifty-nine patients were enrolled in the study, with an average age of 38 ± 17 (SD) years, with 72% male sex. Most of our patients were motor vehicle crash patients (76%), but other mechanisms of injury were represented, including falls (12%), blunt assault (9%), and penetrating assault (3%). The population had a median Glasgow Coma Scale (GCS) score of 15 (IQR 6 to 15); 16 were patients intubated at ultrasonography, either by out-of-hospital personnel or in the trauma bay. Fifty-four patients

Limitations

This study had several limitations, most notably its small size, observational methods, and convenience sampling. In addition, 5 patients had only 1 eye measured, which may have affected the derived statistical accuracy.

The study center physicians were experienced with ultrasonography in the emergency setting, and those centers with less experience may find varying results.

The criterion standard used as follow-up and comparison with the optic nerve sheath diameter ultrasonography is not a

Discussion

The evaluation of the head injury patient with elevated intracranial pressure in the setting of multiple trauma presents significant challenges. Most head injury patients have concomitant injuries that require detection and treatment.1 Findings of severe head injury can be various and nonspecific. The findings of severe head injury with elevated intracranial pressure often alter the treatment for trauma patients.10 Such decisions include transfer to the operating room versus the CT suite,

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Supervising editor: E. John Gallagher, MD

Author contributions: VST and MB conceived the study and designed the trial. VST supervised the conduct of the trial and data collection. VST, MN, TF, and TS undertook recruitment of participating centers and patients and managed the data, including quality control. HJN provided statistical advice on study design and analyzed the data. VST drafted the article, and all authors contributed substantially to its revision. VST takes responsibility for the paper as a whole.

Funding and support: The authors report this study did not receive any outside funding or support.

Publication dates: Available online September 25, 2006.

Reprints not available from the authors.

1

Dr. Neulander is currently affiliated with Northeast Medical Center, Concord, NC.

2

Dr. Foster is currently affiliated with Lutheran General Hospital, Chicago, IL.

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