The severity of traumatic brain injury after head injury is difficult to assess because specific measures of the presence and severity of such injuries have been unavailable. Computed tomographic scans reveal a brain injury in 8% to 22% of patients with minor head injuries. Magnetic resonance imaging is more sensitive but availability is limited. Single photon emission computed tomographic scans demonstrate abnormalities in more than 50% of patients, but this measure of regional blood flow is not necessarily related to structural damage of the brain. There is a major need for a biological marker for the severity of traumatic brain injury, especially in mild injury in the medical-legal context in which it may be desirable or necessary to prove that disability or neuropsychological impairment after a traumatic event is really due to the head injury. The need for an early prognostic indicator exists so that therapies can be selected.
Biochemical markers of brain lesions and/or ischemia quantify secondary cerebral injury, identify toxic mediators, optimize target-controlled therapy or neuroprotective agents, and possibly to facilitate economical and/or ethical decision making. Problems in relying on biochemical markers, such as S100, neuron specific enolase (NSE), aldolase C40, glial fibrillary acid protein (GFAP), creatine kinase (CK), adenylate kinase (AK), myelin basic protein (MBP), and τ, include the following: (1) No currently used markers are unique to the brain. (2) Sex, age, species variability, and possibly neurological disease influence production of a marker. (3) Type and extent of the injury and localization of the marker in the cell affect marker release. Moreover, several markers are physiologically released. (4) Concentrations of biochemical markers found are dependent on rate of diffusion and CSF (cerebrospinal fluid) volume and flow. (5) Kidney and liver function affect clearance of the biochemical markers and little is known about their clearance from the CSF. (6) Assay properties need to be standardized to avoid variations.
Romner B. Traumatic Brain Injury—Biochemical Markers. Arch Neurol. 2000;57(8):1234. doi: