Neurologic Assessment Note

An emerging technology that can be considered as an adjunct to neurologic assessment is ultrasound measurement of optic nerve sheath diameter (ONSD). If the patient is unconscious (i.e. does not follow commands or open eyes spontaneously), measure a baseline ONSD. There is no definite diameter that is diagnostic of increased ICP; however, an ONSD >5.2mm, especially if it increases over time, may indicate elevated ICP.5 In no circumstance should measurement of ONSD take priority over a neurologic examination, and all results must be considered in the context of the neurologic examination and overall patient status. See Appendix B for further details on using ultrasound to obtain and interpret ONSDs.

ONSD should NOT be attempted in any patient who has sustained an open globe injury where any pressure on the globe is contraindicated. As many as 30% of head injuries in combat may also have an eye injury.6