Page 89 - JSOM Fall 2025

Real-time Reduction in Optic Nerve Sheath Diameter
Following Hypertonic Saline Bolus in a Patient with
Penetrating Traumatic Brain Injury

A Case Report

Maya Alexandri, JD, MD *; Tanner M. Smith, DO ;
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Christopher A. Mitchell, MD, RDMS ; Chelsea Ausman, MD, RDMS ; Dan Brillhart, MD 5
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ABSTRACT
The Joint Trauma System Clinical Practice Guideline on Trau- casualties with severe TBI compare favorably to those of their
matic Brain Injury Management in Prolonged Field Care rec- civilian counterparts for an array of reasons, including aggres-
ommends the use of ultrasound measurement of optic nerve sive and immediate prehospital care at point of injury. Given
2,3
sheath diameter (ONSD) in the neurologic assessment of un- the risks of near-peer large scale combat operations and irreg-
conscious patients without ocular injury. This recommendation ular warfare, more soldiers are likely to receive prehospital
is well-founded in the literature, and support is growing for neurocritical care for TBI as part of prolonged field care, and
use of ONSD measurement for monitoring of neurocritical pa- Special Operations Forces (SOF) medics must be prepared to
tients, especially in resource-limited and austere environments, provide that care.
including military theaters of operation. Our patient presented
as a level 1 trauma patient with a penetrating traumatic brain As explained by the Joint Trauma System Clinical Practice
injury (TBI). ONSD measurements taken before, during, and Guideline (JTS CPG) for Traumatic Brain Injury Management
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after administration of a 250mL bolus of 3% hypertonic sa- in Prolonged Field Care, TBI can cause primary and secondary
line showed a downward trend in ONSD measurement, from injury. The primary injury occurs with the traumatic event;
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5.4 to 4.8mm in the right eye, and 7.6 to 6.3mm in the left the secondary injury is the sequelae of increased intracranial
eye, within 20 minutes. Our review of the literature identi- pressure (ICP). Because secondary TBI can include a range
3
fied studies in which ONSD decreased following treatment of of insults, including ischemia and herniation, rapid diagnosis
symptomatic hyponatremia with 3% hypertonic saline, as well and intervention are necessary. The JTS CPG recommends
4–6
as cases in which ONSD decreased in real time following lum- serial measurement of optic nerve sheath diameter (ONSD)
bar puncture and external ventricular drain placement. Many with ultrasound “as an adjunct to neurological assessment” in
studies also demonstrate the usefulness of ONSD for screening unconscious patients who do not have ocular injury. 3
and monitoring of patients with TBI. Ours is the first reported
instance of which we are aware showing real-time reduction in The optic nerve is well-suited for this purpose because it is
ONSD following treatment with 3% hypertonic saline in a pa- a central nervous system white matter tract, residing in the
tient with a penetrating TBI. ONSD measurement has poten- subarachnoid space, surrounded by cerebral spinal fluid and
tial for neurocritical monitoring in austere, resource-limited enwrapped in a sheath composed of dura mater. 4,5,7,8 Although
environments, including prolonged field care. Further study is the mechanism remains incompletely understood, increases in
needed to interrogate the accuracy and reliability of ONSD ICP in the subarachnoid space are detectable almost simul-
measurement as a tool for assessing treatment efficacy in pa- taneously in the ONSD, 4,5,9–13 and multiple studies have cor-
tients with TBI, both blunt and penetrating. related increases in ONSD with elevated ICP in a near linear
relationship. 4–6,10,11,13–15 Ultrasound assessment of ONSD may
Keywords: penetrating traumatic brain injury; elevated be of benefit in patients suffering from acute traumatic head
intracranial pressure; optic nerve sheath diameter; ultrasound; injury. Consistent with the JTS CPG recommendations,
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3% hypertonic saline; case report many studies have concluded that serial ONSD measurements
may assist both with screening and triage 5,9,11,13 and monitor-
ing and prognostication. 4,12,13,16–18 As in other resource-limited
and austere environments, ONSD measurement may be par-
Background
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ticularly useful in military theaters of operation for many
Over 500,000 soldiers have been diagnosed with traumatic reasons, including: ONSD measurement is non-invasive and
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brain injury (TBI) since the year 2000. Survival rates of combat safe in patients without ocular injury; ONSD measurement
*Correspondence to Department of Emergency Medicine, Carl R. Darnall Army Medical Center, 36065 Santa Fe Ave, Fort Hood, TX 76544 or
maya.alexandri.mil@army.mil
1 CPT Maya Alexandri is an advanced emergency medicine ultrasound fellow at the Department of Emergency Medicine, Carl R. Darnall Army
Medical Center, Fort Hood, TX. CPT Tanner M. Smith and COL Christopher A. Mitchell are affiliated with the Department of Emergency
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Medicine, Carl R. Darnall Army Medical Center, Fort Hood, TX. MAJ Chelsea Ausman is affiliated with the 67th Forward Resuscitative Surgical
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Detachment, Rhine Ordnance Barracks, Rhineland-Palatinate, Germany. LTC Dan Brillhart is the director of the advanced emergency medicine
ultrasound fellowship at the Department of Emergency Medicine, Carl R. Darnall Army Medical Center, Fort Hood, TX.
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