CHAPTER 32: NEUROLOGICAL OUTCOME SCALE FOR TRAUMATIC BRAIN INJURY (NOS-TBI)

Description

The Neurological Outcome Scale for Traumatic Brain Injury (NOS-TBI) is a standardized assessment tool of neurological function that is based on the National Institutes of Health Stroke Scale (NIHSS) that has been uniquely modified to take into account the specific neurological deficits that may occur with head injury (Rosenfeld, 2012). The scale contains domains that are similar to the NIHSS such as level of consciousness, best gaze, visual field, facial palsy, motor arm and motor leg assessment; as well the inclusion of new items such as olfaction, pupillary response, and auditory functioning (McCauley et al., 2013). The NOS-TBI contains 15 items which have 23 components (i.e., some items have multiple modules) and takes approximately 15 minutes to complete. During assessment the clinician notes the presence or absence of certain responses to varying stimuli. An example item includes level of consciousness in which the subject is observed through examination, his or her level of arousal is then scored as (0) alert, (1) not alert, but arousable with minimal stimulation, (2) not alert, requires repeated stimulation to attend, or (3) coma—responds only with reflex motor or autonomic effects or totally unresponsive. Each item is rated by level of impairment from 0 to 5 (varies) with higher scores representing more impairment (Wilde, McCauley, Kelly, Levin, et al., 2010).

Psychometrics

Statistical properties of the NOS-TBI were established by Boake et al., (2010) in which test-retest reliability scores obtained over 2 consecutive days performed by the same rater were significant at r = 0.97. Internal consistency for all items was also significant at α = 0.94; however, several test items had low correlations from 0.34 to 0.84. Convergent validity displayed moderate to significant correlations with the Disability Rating Scale at 0.75, the Supervision Rating Scale at 0.59, and the Rancho Los Amigos Scale at –0.60. A research study of individuals who had sustained a TBI (n = 50) with a mean Glasgow Coma Scale score of 6 (which only tests for rudimentary eye, verbal, and motor responses) found that the most common anomalies discovered using the NOS-TBI were impaired olfaction, present in 76% of subjects, language impairment (46%), disorientation (42%), impairment in gross motor functioning (30% to 38%), facial paresis (30% to 34%), and sensory functioning (14% to 28%) (Wilde, McCauley, Kelly, Weyand, et al., 2010). Another study demonstrated good-to-excellent concurrent validity with other outcome measures at 3, 6, and 12 months post-injury where correlations ranged from 0.44 to 0.70 with the Glasgow Outcome Scale and its extended version, the Disability Rating Scale, and the Neurobehavioral Rating Scale-Revised (McCauley et al., 2013). The same study showed that NOS-TBI scores changed significantly between 3 and 6 months, which was contrary to the Glasgow measures, suggesting that the NOS-TBI was more sensitive to change over the 3- to 6-month time period (McCauley et al., 2013).

Advantages

The NOS-TBI is a relatively quick outcome measure that has a fair amount of research in support of its use in clinical practice. Adapted from the NIHSS, it can be completed in less than 15 minutes. The NOS-TBI incorporates elements of a clinical neurological examination not seen in other TBI-specific assessments and due to its increased complexity, may play an important contribution when used in conjunction with other scales such as the Glasgow Coma Scale for initial stratification of injuries based on severity as well as for outcome assessment (Rosenfeld, 2012). The NOS-TBI is also included as part of several larger measures such as the National Institute of Neurological Disorders and Stroke and the Federal Interagency Common Data Elements Initiative for TBI also suggesting widespread use and acceptance (McCauley et al., 2013).

Disadvantages

Administration of the measure to severely injured or those in the sub-acute phase of recovery can be difficult and although there is a fair amount of research supporting the assessment, the NOS-TBI lacks an amount of peer-reviewed literature especially not involving the authors, directly or indirectly (Wilde, McCauley, Kelly, Levin, et al., 2010).

Administration

During assessment the clinician assess gross neurological functioning relative to an individual’s motor and sensory function where each of the 23 items are rated on the subject’s ability to respond to certain stimuli or perform basic movements. Test items are scored along a variable scale (0 to 5) where 0 represents alert or no impairment and 5 represents coma. The total score for the NOS-TBI is the sum of the scores for items 1 to 13, whereas items 14 and 15 are considered supplemental and do not factor into the total score, a UN item score is also possible which is considered as untestable (i.e., limb is missing or joint is fused) (McCauley et al., 2010).

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