Brain injury can occur in two ways:

1. a result of external events, such as a head trauma resulting from a severe blow, motor vehicle accident, or
2. a result of internal events, such as cerebral vascular accident, strokes or tumors.

The consequences of brain injury are many and complex. The structures of the brain and their role in thinking and doing may be the most complex puzzle in science. For our educational purposes, understanding how the brain functions differently after injury has much greater importance than knowing the cause or type of the injury.

There is great variation in the possible effects of a head injury on an individual. Injuries may result in some degree of impairment in the following functions:

• Memory - Memory difficulties are probably the most common characteristic of students with brain injuries, and present the greatest challenge for learning. The primary problem is a decreased ability to store information and recall it at a later time. The storage and retrieval of pre-injury memories or previously acquired knowledge may be surprisingly intact.
• Distractibility – Poor attention and concentration, often caused by poor filtering or processing of sensory information, may reduce the ability to focus long enough for learning to take place.
• Speed of Thinking –New information may take longer to process effectively.
• Communication-Language functions such as writing, reading, speaking, listening, and "pragmatics" may be impaired. Communication pragmatics problems are interrupting, talking out of turn, dominating discussions, speaking too loudly or rudely, or standing too closely to the listener.
• Spatial Reasoning refers to the ability to recognize shapes of objects, judge distances accurately, navigate, read a map, visualize images, comprehend mechanical functions, or recognize position in space. Mathematic abilities are linked to spatial reasoning.
• Conceptualization – Deficits of this type may reduce the ability to categorize, sequence, abstract, prioritize, and/or generalize information.
• Executive Functions - The ability to set goals, plan, and work methodically toward a goal, especially with any mental flexibility, may be impaired. The difficulty may show as disorganization and poor problem solving and judgment especially with time and money.
• Psychosocial - Some common types of psychosocial disabilities may appear as depression or withdrawal, poor insight, poor reality orientation, low frustration tolerance, heightened irritability, restlessness, anxiety, emotional instability, impulsiveness, poor social judgment, euphoria, apathy, fatigue, and/or poor personal hygiene.
• Movement, Vision, Hearing, and Physical Disabilities - Specific somatic impairments may be present after an injury.