Brain injury
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, 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 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 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 injuries have a mortality rate of 40% whereas severe diffuse injuries have a mortality rate of 25%. 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 his or her 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 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 and an absence of spontaneous breathing when the lungs are filled with carbon dioxide.
Cognitive effects
, and issues with both long- and short-term memory, are common with brain damage, as is temporary aphasia, or impairment of language. Tissue damage and loss of blood flow caused by the injury may cause both of these issues to become permanent. Apraxia, the impairment of motor coordination and movement, has also been documented.Cognitive effects can depend on the location of the brain that was damaged, and certain types of impairments can be attributed to damage to certain areas of the brain. Larger lesions tend to cause worse symptoms and more complicated recoveries.
Brain lesions in Wernicke's and Broca's areas are correlated with language, speech and category-specific disorders. Wernicke's aphasia is associated with word retrieval deficits, unknowingly making up words, and problems with language comprehension. The symptoms of Wernicke's aphasia are caused by damage to the posterior section of the superior temporal gyrus.
Damage to Broca's area typically produces symptoms like omitting functional words, sound production changes, alexia, agraphia, and problems with comprehension and production. Broca's aphasia is indicative of damage to the posterior inferior frontal gyrus of the brain.
The impairment of a cognitive process following a brain injury does not necessarily indicate that the damaged area is wholly responsible for the process that is impaired. For example, in pure alexia, the ability to read is destroyed by a lesion damaging both the left visual field and the connection between the right visual field and the language areas. However, this does not mean one with pure alexia is incapable of comprehending speech—merely that there is no connection between their working visual cortex and language areas—as is demonstrated by the fact that people with pure alexia can still write, speak, and even transcribe letters without understanding their meaning.
Lesions to the fusiform gyrus often result in prosopagnosia, the inability to distinguish faces and other complex objects from each other. Lesions in the amygdala would eliminate the enhanced activation seen in occipital and fusiform visual areas in response to fear with the area intact. Amygdala lesions change the functional pattern of activation to emotional stimuli in regions that are distant from the amygdala.
Other lesions to the visual cortex have different effects depending on the location of the damage. Lesions to V1, for example, can cause blindsight in different areas of the brain depending on the size of the lesion and location relative to the calcarine fissure. Lesions to V4 can cause color-blindness, and bilateral lesions to MT/V5 can cause the loss of the ability to perceive motion. Lesions to the parietal lobes may result in agnosia, an inability to recognize complex objects, smells, or shapes, or amorphosynthesis, a loss of perception on the opposite side of the body.
Psychological effects
There are documented cases of lasting psychological effects as well, such as emotional changes often caused by damage to the various parts of the brain that control emotions and behaviour. Individuals may experience sudden, severe mood swings that subside quickly. Emotional changes, which may not be triggered by a specific event, can cause distress to the injured party and their family and friends. Brain injuries increase the risk of developing depression, bipolar disorder and schizophrenia. The more severe a brain injury is the likelier it is to cause bipolar disorder or schizophrenia; the correlation between brain injuries and mental illness is stronger in female and older patients. Often, counseling in either a one-on-one or group setting is suggested for those who experience emotional dysfunction after their injury.Any type of acquired brain injury can result in changes in personality, including, with regards to the Big Five personality traits, increased neuroticism, decreased extraversion and decreased conscientiousness. If the patient is aware of the change in his or her cognitive capacity, personality and mental state after an injury, he or she might feel disconnected from his or her pre-injury identity, leading to irritability, emotional distress and a disrupted concept of self.