Traumatic brain injury, or TBI, often stems from physical impacts to the head or acceleration/deceleration injuries - where the brain strikes the inside of the skull. But what about brain injury caused by a blast wave from an explosion? Should that type of brain injury be considered distinct from a TBI caused by a physical impact?

The short answer is "yes."

Blast injuries to the brain are often called "invisible injuries" because there is no evidence of an external injury on physical examination or routine medical imaging. In a blast, energy from explosive shock waves is transmitted into the brain, causing injury.

"It has become clear through clinical practice and research that this type of TBI is a unique clinical entity," said trauma surgeon Dr. Ralph DePalma.

Prior to the fall of 2022, there was no dedicated medical code for blast injury to the brain. At that time, the Centers for Disease Control (CDC) International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) code book contained eight separate codes for blast injury (or blast overpressure) to organs in the human body: the colon, rectum, ear, lung, bronchus, small intestine, fallopian tube and thoracic trachea. But nothing for the brain.

That concern drove DePalma, special operations officer for the VA Office of Research and Development (ORD), and Dr. William Rice, an occupational medicine physician with the Department of Defense (DOD), to petition the CDC Coordination and Maintenance Committee in 2020 to create a new diagnostic code for primary blast injury of the brain.

With the assistance of team members from both agencies, it took two years to achieve their goal. The 2023 ICD-10-CM code updates, effective Oct. 1, 2022, a series of codes for "S06.8A - Primary blast injury of brain, not elsewhere classified."

UNITY OF MEDICAL CODING

The ICD-10-CM is an international coding system used by physicians, hospitals and medical billers to classify and code medical diagnoses and symptoms. ICD-10 codes are used for billing and payment of medical services, and for ordering diagnostic tests, medical imaging and treatments like physical therapy. They also help facilitate medical research, disease monitoring (like COVID-19 trends) and understanding health care utilization, according to Rice. The 2022 edition of the ICD-10 code book contains over 73,000 codes.

For example, if you were in a skiing accident and broke the upper bone (thigh) in your right leg, and it did not protrude through the skin, your physician would code it: S72. 91XA unspecified fracture of right femur, initial encounter for closed fracture.

"As a practicing physician, I am aware that if you write a prescription or order a lab test, you must include an ICD-10-CM code. Now, if a veteran walks into a physician's office - outside VA - he or she can report that they had a blast exposure. With the new ICD-10 code for blast injury to the brain, a physician can bill for services and the radiologist can bill for needed specialized imaging studies," said DePalma. "It also allows the veteran to submit a more specific reimbursement claim."

TRAINING EXPOSURES

Service members (SMs) are not only exposed to blast injuries in combat, but also during training exercises. Rice, a practicing physician, cares for SMs and staff at the U.S. Army Aberdeen Proving Ground (APG), located along the Chesapeake Bay in Maryland. The proving ground was established in 1917 to support national defense during World War I.

Beginning in 1918, personnel at APG tested field artillery weapons, ammunition, trench mortars, air defense guns and railway artillery. Following World War, I, the base's mission shifted to ordinance training and munitions research and development. Today, APG is known for world-class research and development, testing and evaluation of military weapon systems and equipment.

"At a training level, some of our combat systems have a high blast overpressure exposure pattern. SMs in training can be exposed to these insults on a daily basis. In occupational medicine, we're still trying to decide what constitutes a dangerous or safe level of blast exposure," said Rice. "We are also seeking to identify occupational specialties and combat systems in which these types of exposures occur."

Blast overpressure (pressure caused by a shock wave from an explosion that is above normal atmospheric pressure) is measured in pounds per square inch (PSI) or kilopascals (kPA). Research has demonstrated that 50 kPA (7.3 PSI) of blast overpressure can rupture the eardrum and cause lung injury. Hemorrhage in the lung occurs above 100 kPA (14.5 PSI) of overpressure, said DePalma. SMs exposed to 150 kPA (21.7 PSI) of blast overpressure in the field will likely experience progressive lung injury leading to death. DOD strives to limit exposures far below these levels in training.

Blast injuries to the brain can produce a wide range of symptoms; affected people can experience difficulties with sleep and problems with vision, thinking, hearing and other sensory issues. About 20% of veterans cared for in VA report blast exposure. The average SM who experienced an explosion is exposed to a blast about three times in combat, said DePalma.

VA and DOD researchers are investigating more sensitive ways to identify brain injury from blast overpressure. Two examples are the use of special imaging to identify subtle brain damage and measuring chemicals in the blood, called biomarkers. "We are looking for better ways to protect SMs in combat and better ways to protect them in training," DePalma and Rice note.

"Given the number of service members, law enforcement officers, miners and others that are routinely exposed to blast overpressure, primary blast injury of the brain is an important issue in several respects. The new ICD-10 code for primary blast injury of the brain is necessary and appropriate to understanding, diagnosing, treating and better understanding this injury."

"Ultimately we (DOD Health Affairs) see this partnership with VA to establish this critical ICD-10 code as a mechanism to track the health and well-being of SMs who transition into the VA system of care," said Kathy Lee, director of Casualty Management in DOD Health Affairs. "Initiatives such as this supports ‘taking care of our people.'"