Page 54 - JSOM Winter 2023

ensure early detection and treatment. Moreover, the proposed to psychotherapy and cognitive rehabilitation may be effec-
classification system does not account for the possibility that tive in treating Operators with both blast-induced mTBI and
85
symptoms may emerge weeks to years after RBE, resulting in chronic symptoms from RBE. As we await disease- modifying
misattribution of symptoms to other sources. We therefore an- therapies, these multidisciplinary treatment programs may
ticipate that this diagnostic classification system will require currently be the most effective way to treat Operators who
iterative revisions as more information about the temporal experience cognitive, psychological, and physical symptoms
dynamics of rBBI becomes available and as new tools are de- after blast exposure. However, randomized controlled trials in
veloped to measure concurrent exposures. large numbers of SOF personnel have not yet been performed.
Hence, multidisciplinary, individualized treatment programs
Proposal for a Diagnostic Risk Assessment Matrix require further evaluation before they can be endorsed by clin-
Once individual Operators are classified into one of the above ical guidelines.
four groups, we advocate for the implementation of a Risk
Assessment Matrix to guide symptom monitoring and treat- Third, when assessing responses to therapy, there are likely
ment (Figure 2). This Risk Assessment Matrix is designed to to be differences in brain monitoring protocols that are even-
facilitate the realization of two goals: tually translated to clinical care for rBBI and single, blast-
induced mTBI. For example, rBBI may be associated with a
1. Individualized care: rBBI symptoms exist on a continuum specific combination of blood biomarkers that are expressed
and therefore require an individualized approach in which chronically. 88,89 Studies of blunt TBI in civilians indicate that
Operators are monitored with direct comparison to base- blood tau and neurofilament light are elevated in the sub-
line assessments performed at the time of selection. acute and chronic stages of injury, as compared to ubiquitin
2. Operational flexibility: While Operators exposed to high C-terminal hydrolase L1, which becomes elevated in the blood
numbers of blasts during training will have access to diag- acutely, and glial fibrillary acidic protein, which is elevated
nostic monitoring protocols, Operators who experience rBBI acutely, declines subacutely, but may rise again starting six
while deployed may have limited access to medical care. months post-injury. 90,91 Determining the temporal dynamics of
these blood biomarkers is critically important for their clinical
Thus, the Risk Assessment Matrix must provide guidance translation as measures of brain injury and brain healing.
about optimal clinical management that accounts for these
constraints. This Risk Assessment Matrix could provide an Fourth, just as blunt TBI can cause chronic brain inflammation
early clinical guide that will be refined as additional evidence and contribute to neurodegeneration, the effects of rBBI may
becomes available. be long-lasting and progressive. 34,35,92 Early detection and treat-
ment of rBBI, before it becomes irreversible, is a major moti-
FIGURE 2 Repeated blast brain injury (rBBI) risk assessment matrix. vation for developing a diagnostic test for rBBI. Regardless of
how diagnostic information about rBBI is ultimately used to
rBBI No rBBI inform clinical care, a reliable diagnostic test will empower
high uncertain Operators, team leaders, commanders, and U.S. Special Oper-
Symptomatic
(treat) (monitor) ations Command leadership to make more informed decisions
Asymptomatic moderate low about combat readiness and capacity for peak performance.
(frequent monitoring) (monitor)
In this proposed Risk Assessment Matrix, medical care for Operators Conclusions
is individualized based on the presence or absence of cognitive, physi-
cal, and psychological symptoms, as well as on the presence or absence Historically, a diagnostic test for rBBI has been elusive due
of objective changes in neuroimaging or blood biomarkers. to a variety of barriers, including the pathophysiologic com-
rBBI = repeated blast brain injury. plexity of blast overpressure, which exerts both focal and dif-
fuse effects on brain structure and function. Moreover, SOF
Clinical Management of rBBI personnel experience a myriad of additional exposures during
training and combat, such that rBBI symptoms may be diffi-
Once an Operator is diagnosed with rBBI, what is the appro- cult to distinguish from those related to blunt head trauma,
priate clinical management to optimize brain healing? We pro- combat stress, or exposure to heavy metals, high altitudes, div-
pose four guiding principles, recognizing that it is premature ing, aircraft vibrations, and acceleration-deceleration forces on
to recommend specific clinical guidelines. fast-moving Naval Special Warfare Combatant-craft Crewmen
boats. To address this complex, multidimensional problem,
First, management strategies will likely differ depending on we advocate for the development of a multimodal diagnostic
where the diagnosis is made. For Operators diagnosed with battery that will integrate data from cognitive performance,
rBBI during training, it may be possible to reduce or eliminate psychological health, physical symptoms, blood measures, and
further blast exposure for a period of time that allows the brain brain imaging to detect and monitor the trajectory of rBBI
to heal, adapt, or compensate for the injury. For Operators throughout an Operator’s career. Such a test must be specific
diagnosed with rBBI after being exposed to repeated blasts for rBBI and deployable to combat zones. We propose that this
during combat and other deployment settings, optimal man- diagnostic test will provide the foundation for a Risk Assess-
agement will depend upon the operational requirements of the ment Matrix to guide decision-making about symptom mon-
mission and the potential risks to the mission if an Operator itoring and treatment. A diagnostic testing battery will also
were to be temporarily sidelined. provide new targets for therapies aimed at preventing or alle-
viating symptoms caused by rBBI. A reliable diagnostic test for
Second, proof-of-principle evidence suggests that multidisci- rBBI will thus promote SOF brain health, combat readiness,
plinary treatment programs with individualized approaches and quality of life.

52 | JSOM Volume 23, Edition 4 / Winter 2023