A penetrating, or open, head injury occurs when an object pierces the skull and breaches the dura mater, the outermost membrane surrounding the brain. Severity
Brain injuries can be classified into mild, moderate, and severe categories. The Glasgow Coma Scale (GCS), the most commonly used system for classifying TBI severity, grades a persons level of consciousness on a scale of 3–15 based on verbal, motor, and eye-opening reactions to stimuli. In general, it is agreed that a TBI with a GCS of 13 or above is mild, 9–12 is moderate, and 8 or below is severe. Similar systems exist for young children. However, the GCS grading system has limited ability to predict outcomes. Because of this, other classification systems such as the one shown in the table are also used to help determine severity. A current model developed by the Department of Defense and Department of Veterans Affairs uses all three criteria of GCS after resuscitation, duration of post-traumatic amnesia (PTA), and loss of consciousness (LOC). It also has been proposed to use changes that are visible on neuroimaging, such as swelling, focal lesions, or diffuse injury as method of classification. Grading scales also exist to classify the severity of mild TBI, commonly called concussion; these use duration of LOC, PTA, and other concussion symptoms. Pathological features
Systems also exist to classify TBI by its pathological features. Lesions can be extra-axial, (occurring within the skull but outside of the brain) or intra-axial (occurring within the brain tissue).
Concussion symptoms were first described systematically in the 16th century by Berengario da Carpi.It was first suggested in the 18th century that intracranial pressure rather than skull damage was the cause of pathology after TBI. This hypothesis was confirmed around the end of the 19th century, and opening the skull to relieve pressure was then proposed as a treatment.In the 19th century it was noted that TBI is related to the development of psychosis. At that time a debate arose around whether post-concussion syndrome was due to a disturbance of the brain tissue or psychological factors. The debate continues today. Perhaps the first reported case of personality change after brain injury is that of Phineas Gage, who survived an accident in which a large iron rod was driven through his head, destroying one or both of his frontal lobes; numerous cases of personality change after brain injury have been reported since.The 20th century saw the advancement of technologies that improved treatment and diagnosis such as the development of imaging tools including CT and MRI, and, in the 21st century, diffusion tensor imaging (DTI). The introduction of intracranial pressure monitoring in the 1950s has been credited with beginning the "modern era" of head injury. Until the 20th century, the mortality rate of TBI was high and rehabilitation was uncommon; improvements in care made during World War I reduced the death rate and made rehabilitation possible. Facilities dedicated to TBI rehabilitation were probably first established during World War I.