Demographics and clinical characteristics of acute traumatic brain injury patients in the different Neuroimaging Radiological Interpretation System (NIRIS) categories

Highlights

• Patients in Neuroimaging Radiological Interpretation System 0 were younger.

• Motor vehicle accidents and falls from height were the most common mechanisms.

• Glasgow Coma Scores were lower in Neuroimaging Radiological Interpretation System 4.

• Imaging elements were different in each category.

• Mortality increased with increasing Interpretation System severity.

Abstract

Purpose

To characterize the demographics, clinical and imaging findings, and outcomes of traumatic brain injury (TBI) patients in each of NeuroImaging Radiological Interpretation System (NIRIS) categories.

Material and methods

We considered all consecutive patients transported to Stanford Hospital's emergency department by ambulance or helicopter between November 2015 and April 2017. We retained adult patients (> 18 years old) for whom a trauma alert was triggered and who underwent a non-contrast head computer tomography (CT) because of suspected TBI. We reviewed the non-contrast CT scans in these patients for the NIH TBI common data elements (CDEs). We recorded, then assessed differences in terms of demographics, clinical characteristics, imaging CDEs, and outcomes in patients from the different NIRIS categories.

Results

In all, 1152 patients were included in this study. Patients with NIRIS 0 imaging findings were significantly younger than patients in other NIRIS categories (P < 0.001). Motor vehicle accidents and falls from height were the most common mechanisms of injury across NIRIS categories. GCS scores decreased with increasing NIRIS category imaging findings and were significantly lower in patients with NIRIS 4 imaging findings (P < 0.001). Significant differences in NIRIS categories were observed for all imaging CDEs (P < 0.001), in agreement with the definition of the different NIRIS categories. Mortality increased progressively with increasing NIRIS severity.

Conclusions

TBI patients in different NIRIS categories have different clinical characteristics, hospital courses and outcomes. This natural history assessment of patients from different NIRIS categories could thus serve as a reference standard for future TBI clinical trials.

Introduction

An estimated 10 million people worldwide are affected every year by a new traumatic brain injury (TBI) event [1]. In the United States alone, there are more than 2.5 million emergency department (ED) visits for TBI yearly [2], [3], [4]. This number of ED visits has increased steeply over the last few decades [5], primarily as a result of increased occurrences of mild TBI and/or concussions. As a disease process rather than a single event, TBI increases long-term mortality and is associated with increased incidences of neurodegenerative and psychiatric diseases [6]. Thus, accurate and timely identification of the injury severity is paramount for mitigating associated symptoms and disease processes, and ultimately preventing poor clinical outcomes.

The Glasgow Coma Scale (GCS) is the primary clinical classification system used to assess TBI severity in patients. GCS separates TBI into three broad categories: mild (GCS scores of 13–15), moderate (9–12), and severe (< 9) [7]. However, patients with the same GCS scores were found to have quite different TBI injuries in several clinical trials, illustrating the limited ability of GCS to stratify TBI patients in terms of the pathophysiology of their injury [8]. Yet, the different pathophysiologic mechanisms of TBI are responsible for neurological deficits and the target of therapeutic interventions [9], [10]. In addition, GCS may be difficult to interpret in some trauma patients. For instance, changes in respiratory pattern or brainstem reflexes, which reflect the severity of coma, are not accounted for in the calculation of GCS [11].

Imaging classification systems were developed to improve stratification of TBI patients. The most commonly used are the Marshall score [12] and the Rotterdam score [13]. Both scoring systems are used as independent predictors of patient outcomes. However, Marshall and Rotterdam scores are meant to predict early death in patients with moderate and severe TBI [14], [15]. Recently, a new classification system, the NeuroImaging Radiological Interpretation System (NIRIS), was developed to predict TBI patient outcomes and management, including discharge from the ED, follow-up brain imaging, admission, need for intensive care unit, neurosurgical procedure (ventricular drain, burr hole, craniotomy/craniectomy, surgical drainage/evacuation of hematoma), as well as death [16].

The clinical characteristics and natural history of TBI patients in the different NIRIS categories are poorly known. The goal of this study was to close this gap in knowledge by assessing the demographics, clinical and imaging findings, and outcomes of TBI patients in each of the NIRIS categories.