B-scan measurement of optic nerve sheath diameter as a marker of elevated intracranial pressure
Keywords:B-scan ultrasound, Elevated intracranial pressure, Optic nerve sheath diameter
Background: Elevated intracranial pressure is a complication of several traumatic as well as non-traumatic medical conditions. Clinical diagnosis can be difficult as it may present with non-specific complaints such as headache, vomiting, blurred vision, vomiting and altered sensorium. The expertise to perform ophthalmoscopy is not always immediately available in emergency rooms and the access to cross sectional imaging may be limited. Distention of the optic nerve sheath is an early sign of raised ICP as it is in direct communication with the subarachnoid space. Ultrasound is a widely available tool in emergency situations which can be used to measure the optic nerve sheath diameter (ONSD).
Methods: In this prospective observational study, 36 patients suspected of having elevated intracranial pressure underwent high resolution B-scan ultrasound to measure the ONSD. Further, patients underwent CT scan of head and were evaluated for signs of raised ICT. Sensitivity and specificity of B-scan measurement of ONSD with CT scan was compared.
Results: The ONSD measurement was 88.5% sensitive (95% CI 68% to 97%) and 90% specific (95% CI 55% to 99%) with CT as the reference.
Conclusions: Bedside ultrasound B-scan measurement of the optic nerve sheath diameter provides information about raised intracranial pressure with a high sensitivity and specificity.
Sadoughi A, Rybinnik I, Cohen R. Measurement and management of increased intracranial pressure. Open Critic Care Med J. 2013;6:56-65.
Hansen HC, Helmke K. The subarachnoid space surrounding the optic nerves. An ultrasound study of the optic nerve sheath. Surg Radiol Anat. 1996;18(4):323-8.
Blaivas M, Theodoro D, Sierzenski PR. Elevated intracranial pressure detected by bedside emergency ultrasonography of the optic nerve sheath. Acad Emerg Med. 2003;10(4):376-81.
Tayal VS, Neulander M, Norton HJ. Emergency department sonographic measurement of optic nerve sheath diameter to detect findings of increased intracranial pressure in adult head injury patients. Ann Emerg Med. 2007;49(4):508-14.
Qayyum H, Ramlakhan S. Can ocular ultrasound predict intracranial hypertension? A pilot diagnostic accuracy evaluation in a UK emergency department. Eur J Emerg Med. 2013;20(2):91-7.
Goel RS, Goyal NK, Dharap SB, Kumar M, Gore MA. Utility of optic nerve ultrasonography in head injury. Injury. 2008;39(5):519-24.
Rajajee V, Vanaman M, Fletcher JJ, Jacobs TL. Optic nerve ultrasound for the detection of raised intracranial pressure. Neurocrit Care. 2011;15(3):506-15.
Soldatos T, Karakitsos D, Chatzimichail K, Papathanasiou M, Gouliamos A, Karabinis A. Optic nerve sonography in the diagnostic evaluation of adult brain injury. Crit Care. 2008;12(3):R67.
Bäuerle J, Nedelmann M. Sonographic assessment of the optic nerve sheath in idiopathic intracranial hypertension. J Neurol. 2011;258(11):2014-9.
Strumwasser A, Kwan RO, Yeung L, Miraflor E, Ereso A, Castro-Moure F, et al. Sonographic optic nerve sheath diameter as an estimate of intracranial pressure in adult trauma. J Surg Res. 2011;170(2):265-71.
Hansen HC, Helmke K. Validation of the optic nerve sheath response to changing cerebrospinal fluid pressure: ultrasound findings during intrathecal infusion tests. J Neurosurg. 1997;87(1):34-40.