Can ocular ultrasound predict intracranial hypertension? A pilot diagnostic accuracy evaluation in a UK emergency department.
OBJECTIVE
To determine if ultrasound guided measurement of the optic nerve sheath diameter accurately predicted elevated intracranial pressure (ICP) as demonstrated by cranial computed tomography (CT) in at-risk emergency department patients.


METHODS
Optic nerve sheath diameters were measured on a convenience sample of adult patients presenting with suspected elevated ICP to the emergency department of a large teaching hospital over a 6-month period. A cut off for optic nerve sheath diameter of 5 mm was considered positive for elevated ICP. All patients had a subsequent cranial CT scan on the same day reported by a radiologist. Signs of elevated ICP on cranial CT include midline shift with a mass effect of at least 3 mm, sulcal effacement with evidence of significant oedema, collapse of ventricles, and cisternal compression.


RESULTS
Twenty-four patients were recruited with a sensitivity of 100% [95% confidence interval (CI), 83.8-100] and specificity of 75% (95% CI, 30.1-95.4) with a cut-off of 5 mm for optic nerve sheath diameter to predict elevated ICP on cranial CT scan. The positive predictive value for an increased optic nerve sheath diameter for elevated ICP was 95.4% (95% CI, 74.13-99.75) and negative predictive value was 100% (95% CI, 31-100). The positive likelihood ratio of a wide optic nerve sheath diameter for elevated ICP on cranial CT was calculated to be 4.00 (95% CI, 0.73-21.84).


CONCLUSIONS
This study shows that the ultrasound guided optic nerve sheath diameter is a sensitive and specific test for predicting elevated ICP. A prospective validation study across emergency departments would test applicability of this test. We propose an algorithm for incorporating ultrasound for the management of suspected intracranial hypertension in emergency departments.
Emergency Department, Northern General Hospital, Sheffield, South Yorkshire, UK. drqayyum@doctors.org.uk
Hasan
H
Qayyum
Shammi
S
Ramlakhan
D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000175:diagnosis / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D016001:Confidence Intervals; D004635:Emergency Medicine / Q000379:methods; D004636:Emergency Service, Hospital; D005260:Female; D015600:Glasgow Coma Scale; D006784:Hospitals, Teaching; D006801:Humans; D015601:Injury Severity Score; D019586:Intracranial Hypertension / Q000175:diagnosis / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D018608:Ultrasonography, Doppler / Q000379:methods*; D006113:United Kingdom