Page 67 - Journal of Special Operations Medicine - Summer 2015

1,2
neurocognitive testing and clinical balance testing. It is postconcussion syndrome (PCS) compared with individu-
still unknown if asymptomatic truly means healed and ally matched non-PCS control subjects, showing that eye
without symptoms, or if it means just compensating. movement function continued to be impaired postacutely
There is also no reliable way to determine truthfulness at more than 6 months. 23
in reporting. For neurocognitive testing in military prac-
30
tice settings, it is difficult to interpret findings, as there Brahm et al. found the following visual dysfunctions
are no normative data, and tests lack face validity for in 68 military inpatients with TBI at a Veterans Affairs
the conditions faced by military populations, especially polytrauma rehabilitation center (PRC), and 124 military
in deployed settings. Balance testing is incorporated into outpatients with TBI at a polytrauma network site (PNS):
postconcussive evaluations either independently or, as subjective visual complaint (PRC 75.4%, PNS 75.8%);
mentioned, as part of a multimodal assessment. Bal- convergence insufficiency (PRC 42.6%, PNS 48.4%); ac-
ance deficits, as measured by the Balance Error Scoring commodative insufficiency (PRC 39.6%, PNS 47.5%);
System or force platform systems, have been observed pursuit/saccadic dysfunction (PRC 30.2%, PNS 23.4%);
for longer periods than appreciable cognitive test re- fixation instability (PRC 9.5%, PNS 6.5%); strabismus
sults. 4,8,12,26,36,38,52,65 In concussed athletes, evidence has (PRC 25%, PNS 7.3%); and reading difficulties (PRC
suggested recovery time disparities among the three in- 65.5%, PNS 87.1%).
dicators, thereby underscoring the importance of the
multifaceted approach. Using this approach can aid cli- Healthcare providers grossly assess eye movements non-
nicians in understanding other comorbidities that may quantitatively on physical examination (e.g., CN exami-
complicate recovery and management of mTBI. 12,37 It nation) in suspected cases of head injury. Contemporary
also underscores the importance of continuing to search research is demonstrating that these impairments are
for more accurate and reliable screening and diagnostic quantifiable at subclinical thresholds. Since 50% of the
tools. Also of importance is determining disposition for CNs relate in some way to vision, examination can di-
those who are subacute or chronic and without resolu- rectly assess not only function of the named nerves, but
tion of symptoms. How to assess, follow up, and treat brainstem function and the cortical regions through which
those returned to duty who are still functional despite these nerves and their associated white-matter tracts travel
their continued symptoms is unclear. en route to the muscles of the eyes. Such regions are nu-
merous; have connections in nearly all functional areas
Due to the complex, pervasive interconnections and inter- of the brain, including those that support spatial process-
actions between vision and cortical function, it is difficult ing and span of attention; and are frequently damaged in
to pinpoint from which areas visual deficits may arise and, mTBI. 24,28,67 In the absence of preinjury deficits, postinjury
conversely, how visual deficits impact cognitive function deficits in visual and oculomotor function, whether gross
and rehabilitation. 23–25,28,29,66–70 It has long been suspected or subtle, can be attributable with certainty to physical
that, despite negative findings with traditional neuroimag- damage to the structures affecting those functions.
ing technology, diffuse axonal damage occurs with mTBI.
A 2010 study found correlation between visual track- New understanding of the importance of visual and vi-
ing deficits and damage to white-matter tracts most as- sually mediated performance screening and what role
sociated with oculomotor function in the brain, through it might play in the rehabilitation of brain-injured pa-
fractional anisotropy measurements with diffusion tensor tients is emerging. Literature suggests that measures
imaging–enhanced magnetic resonance imaging. The cor- for assessing visual skills decrements are meaningful
relations imply that gaze error variability during visual and sensitive enough to be useful for baseline screening
24
tracking may provide a useful screening tool for mTBI. and aiding in determining progress and RTD decision-
The primary sensory modality of vision includes color vi- making. 23–25,27,28,71–73 Literature also suggests that there
sion, visual field detection, and contrast sensitivity, which are many useful training tools to improve visual, visual-
are controlled by cranial nerve (CN) II, the common vi- spatial, and visual-motor function in competitive athlete
sual pathways, and visual centers of the occipital region. populations. 73–77 A supplement to current guidelines for
Near point of convergence, rapid saccade, dynamic visual screening and treating mTBI subjects may be found in
acuity, near–far accommodation, and smooth pursuit, the examination of visual performance. 22–24,39,50,72,75,77–80
which are all measures of coordinated oculomotor func-
tion from CN III/IV/VI. Oculomotor dysfunction among Of particular interest is the visual sensory evaluation
the general population is commonly reported at between and training station technology; there are Nike Visual
20% to 30%, but as much as 90% of patients with TBI Sensory Training Stations (STSs) (Nike Inc.; www.nike
have been reported to suffer from it. 28,29 .com) residing in human performance facilities at several
SOF locations. 25,42,93 It would make sense that research
Heitger et al. found significant between-group differences should occur at those locations, given the need for re-
in oculomotor function between a group of patients with search for this population. 70–72

Postconcussion Visual Sensory Screening, Diagnostics, and Training for SOF 57