Normative Values for Pupillary Light Reflex Metrics Among Healthy Service Academy Cadets.

INTRODUCTION: Assessments of the pupil's response to light have long been an integral part of neurologic examinations. More recently, the pupillary light reflex (PLR) has shown promise as a potential biomarker for the diagnosis of mild traumatic brain injury. However, to date, few large-scale normative data are available for comparison and reference, particularly, in military service members. The purpose of this study was to report normative values for eight PLR measurements among healthy service academy cadets based on sex, age, sleep, race, ethnicity, anisocoria, and concussion history. METHODS: Freshmen entering a U.S. Service Academy completed a quantitative pupillometric assessment in conjunction with baseline concussion testing. PLR measurements were conducted using a Neuroptics PLR-3000 with a 121 µW light stimulus. The device measured maximum and minimum pupil diameter (mm), latency (time to maximum pupil constriction post-light stimulus [s]), peak and average constriction velocity (mm/s), average dilation velocity (mm/s), percentage pupil constriction, and T75 (time for pupil re-dilation from minimum pupil diameter to 75% maximum diameter [s]). During baseline testing, cadets also reported concussion history (yes and no) and hours slept the night before (<5.5 and ≥5.5). Normative values for each PLR measurement were calculated as mean ± SD, percentiles, and interquartile range. Mann-Whitney U tests were used to assess differences based on sex, concussion history, ethnicity, and hours slept for each PLR measurement. Kruskall-Wallis testing was used to assess differences based on age, race, and anisocoria. Alpha was set at .05 and nonparametric effect sizes (r) were calculated for statistically significant results. Effect sizes were interpreted as no effect (r < .1), small (r ≥.1-<.3), medium (r ≥.3-<.5), or large (r ≥ .5). All procedures were reviewed and approved by the local institutional review board and the U.S. Army Human Research Protection Office before the study was conducted. Each subject provided informed consent to participate in the study before data collection. RESULTS: Of the 1,197 participants baselined, 514 cadets (131 female; 18.91 ± 0.96 years) consented and completed a valid baseline pupillometric assessment. Eighty participants reported at least one previous concussion and participants reported an average of 5.88 ± 1.63 h slept the previous night. Mann-Whitney U results suggest females had larger initial (z = -3.240; P = .001; r = .10) and end pupil diameter (z = -3.080; P = .002; r = .10), slower average dilation velocity (z = 3.254; P = .001; r = .11) and faster T75 values (z = -3.342; P = .001; r = .11). Age, sleep, and race stratified by sex, also displayed a significant impact on specific PLR metrics with effect sizes ranging from small to medium, while ethnicity, anisocoria, and concussion history did not display an impact on PLR metrics. CONCLUSION: This study provides the largest population-specific normative values for eight PLR measurements. Initial and end pupil diameter, dilation velocity, and the T75 metrics differed by sex; however, these differences may not be clinically significant as small effect size was detected for all metrics. Sex, age, sleep, and race may impact specific PLR metrics and are worth consideration when performing PLR assessments for mild traumatic brain injury management.

Epidemiology of cranial infections in battlefield-related penetrating and open cranial injuries.

BACKGROUND: Penetrating brain injuries are a potentially lethal injury associated with substantial morbidity and mortality. We examined characteristics and outcomes among military personnel who sustained battlefield-related open and penetrating cranial injuries during military conflicts in Iraq and Afghanistan. METHODS: Military personnel wounded during deployment (2009-2014) were included if they sustained an open or penetrating cranial injury and were admitted to participating hospitals in the United States. Injury characteristics, treatment course, neurosurgical interventions, antibiotic use, and infection profiles were examined. RESULTS: The study population included 106 wounded personnel, of whom 12 (11.3%) had an intracranial infection. Posttrauma prophylactic antibiotics were prescribed in more than 98% of patients. Patients who developed central nervous system (CNS) infections were more likely to have undergone a ventriculostomy ( p = 0.003), had a ventriculostomy in place for a longer period (17 vs. 11 days; p = 0.007), had more neurosurgical procedures ( p < 0.001), and have lower presenting Glasgow Coma Scale ( p = 0.01) and higher Sequential Organ Failure Assessment scores ( p = 0.018). Time to diagnosis of CNS infection was a median of 12 days postinjury (interquartile range, 7-22 days) with differences in timing by injury severity (critical head injury had median of 6 days, while maximal [currently untreatable] head injury had a median of 13.5 days), presence of other injury profiles in addition to head/face/neck (median, 22 days), and the presence of other infections in addition to CNS infections (median, 13.5 days). The overall length of hospitalization was a median of 50 days, and two patients died. CONCLUSION: Approximately 11% of wounded military personnel with open and penetrating cranial injuries developed CNS infections. These patients were more critically injured (e.g., lower Glasgow Coma Scale and higher Sequential Organ Failure Assessment scores) and required more invasive neurosurgical procedures. LEVEL OF EVIDENCE: Prognostic and Epidemiological; Level IV.

Operation "NeuroTeam": rendering the absolute best care for the most deserving patients under the most difficult conditions.

The tenets of neurosurgery worldwide, whether in the civilian or military sector, espouse vigilance, the ability to adapt, extreme ownership, and, of course, an innate drive for developing a unique set of technical skills. At a time in history when the complexity of battlefield neurotrauma climaxed coupled with a chronic shortage of military neurosurgeons, modernized solutions were mandated in order to deliver world-class neurological care to our servicemen and servicewomen. Complex blast injuries, as caused by an increased incidence of improvised explosive devices, yielded widespread systemic inflammatory responses with multiorgan damage. In response to these challenges, the "NeuroTeam," originally a unit of two neurosurgeons as deployed during Operation Desert Storm, was redesigned to instead pair a neurosurgeon with a neurointensivist and launched itself during two specialized missions in Operations Iraqi Freedom and Enduring Freedom. Representing a hybridized version of present-day neurocritical care teams, the purpose of this unit was to optimize neurosurgical care by focusing on interdisciplinary collaboration in an Echelon III combat support hospital. The NeuroTeam provided unique workflow capabilities never seen collectively on the battlefield: downrange neurosurgical capability by a board-certified neurological surgeon within 60 minutes from the point of injury paired with a neurocritical care-trained intensivist. This also set the stage for intraoperative telemedicine infrastructure for neurosurgery and optimized the ability to evaluate, triage, and stabilize patients prior to medical evacuation. This novel military partnership ultimately allowed the neurosurgeon to focus on the tenets of the craft and thereby the dynamic needs of the patient first and foremost. Since the success of these missions, the NeuroTeam has evolved into a detachable unit, the "Head and Neck Team," comprising neurosurgeons, otolaryngologists, and ophthalmologists, supported by a postinjury hospital unit, which includes an embedded neurocritical care physician. The creation and evolution of the NeuroTeam, necessitated by a shortage of military neurosurgeons and the dangerous shift in military wartime tactics, best exemplifies multidisciplinary collaboration and military medicine agility. As neurocritical care continues to evolve into a highly complex, distinct specialty, the lessons learned by the NeuroTeam ultimately serve as a reminder for civilian and military physicians alike. Despite the conditions and despite one's professional ego, patients with highly complex morbid neurological disease deserve expert, multidisciplinary management for survival.

Proposal of a Management Algorithm to Predict the Need for Expansion Duraplasty in American Spinal Injury Association Impairment Scale Grades A-C Traumatic Cervical Spinal Cord Injury Patients.

Expansion duraplasty to reopen effaced subarachnoid space and improve spinal cord perfusion, autoregulation, and spinal pressure reactivity index (sPRX) has been advocated in patients with traumatic cervical spinal cord injury (tCSCI). We designed this study to identify candidates for expansion duraplasty, based on the absence of cerebrospinal fluid (CSF) interface around the spinal cord on magnetic resonance imaging (MRI), in the setting of otherwise adequate bony decompression. Over a 61-month period, 104 consecutive American Spinal Injury Association Impairment Scale (AIS) grades A-C patients with tCSCI had post-operative MRI to assess the adequacy of surgical decompression. Their mean age was 53.4 years, and 89% were male. Sixty-one patients had falls, 31 motor vehicle collisions, 11 sport injuries, and one an assault. The AIS grade was A in 56, B in 18, and C in 30 patients. Fifty-four patients had fracture dislocations; there was no evidence of skeletal injury in 50 patients. Mean intramedullary lesion length (IMLL) was 46.9 (standard deviation = 19.4) mm. Median time from injury to decompression was 17 h (interquartile range 15.2 h). After surgery, 94 patients had adequate decompression as judged by the presence of CSF anterior and posterior to the spinal cord, whereas 10 patients had effacement of the subarachnoid space at the injury epicenter. In two patients whose decompression was not definitive and post-operative MRI indicated inadequate decompression, expansion duraplasty was performed. Candidates for expansion duraplasty (i.e., those with inadequate decompression) were significantly younger (p < 0.0001), were AIS grade A (p < 0.0016), had either sport injuries (six patients) or motor vehicle collisions (three patients) (p < 0.0001), had fracture dislocation (p = 0.00016), and had longer IMLL (p = 0.0097). In regression models, patients with sport injuries and inadequate decompression were suitable candidates for expansion duraplasty (p = 0.03). Further, 9.6% of patients failed bony decompression alone and either did (2) or would have (8) benefited from expansion duraplasty.

The Expanding Role of Quantitative Pupillometry in the Evaluation and Management of Traumatic Brain Injury.

Traumatic brain injury is a rapidly increasing source of morbidity and mortality across the world. As such, the evaluation and management of traumatic brain injuries ranging from mild to severe are under active investigation. Over the last two decades, quantitative pupillometry has been increasingly found to be useful in both the immediate evaluation and ongoing management of traumatic brain injured patients. Given these findings and the portability and ease of use of modern pupillometers, further adoption and deployment of quantitative pupillometers into the preclinical and hospital settings of both resource rich and medically austere environments.