Known or suspected traumatic brain injuries may be treated therapeutically by administering a therapeutically effective dose of resibufogenin. A preferred method for determining if a patient has a traumatic brain injury includes obtaining a body specimen from the patient, determining the concentration of marinobufagenin in the body specimen, comparing the concentration of marinobufagenin to the concentration in such body specimens in normal patients, and if the marinobufagenin concentration is substantially above the concentration of a normal patient, concluding traumatic brain injury exists. In a preferred embodiment, a substantial elevation is deemed to be an increase of about 30 percent above the marinobufagenin concentration of a normal patient. The body specimen may be blood, urine, or cerebrospinal fluid. If a substantial elevation is deemed to exist, the magnitude of the departure from the concentration of a normal patient may be employed in determining the timing and nature of treatment provided to the patient. The method may be repeated at predetermined intervals to monitor changes in the marinobufagenin with time.