Brain injury, also known as brain damage or neurotrauma, is the destruction or degeneration of brain cells. It may result from external trauma, such as accidents or falls, or from internal factors, such as strokes, infections, or metabolic disorders. Traumatic brain injury (TBI), the most common type of brain injury, is typically caused by external physical trauma to the head. Acquired brain injuries occur after birth, in contrast to congenital brain injuries that patients are born with. In addition, brain injuries can be classified by timing: primary injuries occur at the moment of trauma, while secondary injuries develop afterward due to physiological responses. They can also be categorized by location: focal injuries affect specific areas, whereas diffuse injuries involve widespread brain regions. The symptoms and complications of brain injuries vary greatly depending on the area(s) of the brain injured, the individual case, the cause of the injury and whether the person receives treatment. People may suffer from headaches, vomit or lose consciousness (potentially falling into a coma or a similar disorder of consciousness) after a brain injury. Long-term cognitive impairment, disturbances in language and motor skills, emotional dysfunction and changes in personality are common. Treatments for brain injuries include preventing further injuries, medication, physical therapy, psychotherapy, occupational therapy and surgery. Because of neuroplasticity, the brain can partially recover function by forming new neural connections to compensate for damaged areas. Patients may regain adaptive skills such as movement and speech, especially if they undergo therapy and practice.
Classification
Focal and diffuse Focal brain injuries affect only a single area of the brain; they result from direct force to the head and manifest as haemorrhages, contusions, and subdural and epidural haematomas. Diffuse brain injuries cause widespread damage to all or many areas, and are caused by diffuse axonal injuries, hypoxia, ischaemia and vascular injuries. If both are severe, focal brain injuries are deadlier than diffuse ones; severe focal and diffuse injuries have mortality rates of 40% and 25% respectively. Although, diffuse brain injuries more often result in long-term neurological and cognitive deficits.
Primary and secondary Primary brain injuries, most of which are traumatic brain injuries, occur directly because of mechanical forces that deform the brain. Secondary brain injuries result from conditions, such as hypoxia, ischaemia, oedema, hydrocephalus and intracranial hypertension, that may or may not be the aftereffects of primary brain injuries.
Signs and symptoms Symptoms of brain injuries vary based on the severity of the injury, the area of the brain injured, and how much of the brain was affected. The three categories used for classifying the severity of brain injuries are mild, moderate and severe.
Severity of injuries
Mild brain injuries When caused by a blow to the head, a mild brain injury is known as a concussion. Symptoms of a mild brain injury include headaches, confusion, tinnitus, fatigue and changes in sleep patterns, mood or behavior. Other symptoms include trouble with memory, concentration, attention or thinking. Because mental fatigue can be attributed to many disorders, patients may not realise the connection between fatigue and a minor brain injury.
Moderate/severe brain injuries Cognitive symptoms include confusion, aggression, abnormal behavior and slurred speech. Physical symptoms include a loss of consciousness, headaches that worsen or do not go away, vomiting or nausea, convulsions, brain pulsation, abnormal dilation of the eyes, inability to wake from sleep, weakness in extremities and a loss of coordination.
Symptoms in children Young children could be unable to communicate their physical states, emotions and thought processes, so parents, physicians and caregivers may need to observe their behaviours to discern symptoms. Signs include changes in eating habits, persistent anger, sadness, attention loss, losing interest in activities they used to enjoy, or sleep problems.
Complications
Physiological effects Physiological complications of a brain injury, caused by damage to the neurons, nerve tracts or sections of the brain, can occur immediately or at varying times after the injury. The immediate response can take many forms. Initially, there may be symptoms such as swelling, pain, bruising, or loss of consciousness. Headaches, dizziness and fatigue, which can develop as time progresses, may become permanent or persist for a long time. Brain damage predisposes patients to seizures, Parkinson's disease, dementia and hormone-secreting gland disorders; monitoring is essential for detecting the development of these diseases and treating them promptly. Diffuse brain injuries, brain injuries that result in intracranial hypertension and brain injuries affecting parts of the brain responsible for consciousness may induce a coma, a prolonged period of deep unconsciousness. Severe brain injuries may cause a persistent vegetative state in which a patient displays wakefulness without any awareness of their surroundings. Brain death occurs when all activity of the brain is deemed to have irreversibly ceased. The prerequisite for considering brain death is the presence of an injury, bodily status (e.g. hyperpyrexia) or disease that has severely damaged the entire brain. After this has been confirmed, the criteria for ascertaining brain death are an absence of brain activity 24 hours after a patient has been resuscitated, an absence of brainstem reflexes (including the pupillary response and gag reflex) and an absence of spontaneous breathing when the lungs are filled with carbon dioxide.
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