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Head injury is an injury occurring to any part of the head such as the scalp, skull bone, blood vessels, brain, etc. It may lead to a minor injury such as a small bump on the scalp or bruising of the skin, to a severe injury such as skull fracture, brain injury, or bleeding inside the head.
Head injury is caused by a sudden blow, or push to the head, usually occurring during an incident of a road traffic accident, fall, or physical assault.
When the head injury causes damage to the brain it is called traumatic brain injury (TBI). The damage to the brain caused by TBI may also range from mild form such as concussion to a severe form such as diffuse axonal injury (DAI).
In India and the world, TBI is the leading cause of disability, death, and socio-economic loss. It is estimated that in India, about 15 to 20 lakh people get injured every year, and out of that, about 10 lakh people succumb to death. The commonest cause of TBIs in India is road traffic accidents accounting for 60% of the cases.
The treatment and prognosis of the head injury (natural course of the disease) depend on the severity and the type of injury. Due to the high rate of disability and fatality associated with the traumatic brain injury all head injuries need to be evaluated and managed accordingly.
Worldwide and in India, TBI remains the leading cause of disability, death, and socio-economic loss. In India, it is estimated to affect about 15 to 20 lakh people every year, out of which about 10 lakh people eventually die. The commonest causes of TBI in India are:
Road traffic accident accounting for 60% of injuries,
Fall from height seen in 20%-25% cases
Physical violence is seen in 10% of cases.
Alcohol involvement has been found to be a significant common factor amongst cases of TBI, seen present among 15%-20% cases at the time of injury.
The head injury or traumatic brain injury is caused by a sudden blow or impact caused by striking of a penetrating or blunt but usually hard object to head or vice versa. It is also caused by striking of the brain against the covering of bony walls, often in the opposite direction of the force called a counterblow or counter-coup injury. Sometimes, the TBI is also associated with the fracture of the skull bone.
The TBI can be classified into the following two types:
Primary injury: is the brain injury that develops immediately after the impact. It may involve bruising of the brain, bleeding within or along the surface of the brain, tearing of brain nerve fibers, or fracture of skull bones.
Secondary injury: this injury develops after some time following an impact as a reactive process. Here, the brain tissue swells and gets compressed within the enclosed bony skull resulting in a deficiency of oxygen-rich blood. This type of injury could be more damaging than the primary injury.
The brain remains covered by hard bony walls along with cushioning provided by the cerebrospinal fluid surrounding the brain. However, a significant impact caused by a fast-moving object or quick movement of the head against a hard object or surface can cause significant head injury resulting in brain damage.
It has been found that the threshold of intracranial pressure (ICP) to cause brain injury is around 26psi, where no or minor injury occurs below this range. A severe or fatal injury occurs above 35 psi which is just around the average pressure kept in the car tires to keep them inflated adequately.
The common causes of head injury or TBI are as follows:
Road traffic accident(RTA): commonest cause in India.
Fall from height: such as fall from the bed, stairs, in the bathroom, and others. It’s a common cause of head injury seen in young children and older adults.
Physical assault: fights, gunshot injury, domestic violence, elder or child abuse.
Sports injury: common in high impact sports like boxing, rugby, cricket, football, skateboarding, and others.
In newborns and small children, another type of injury is also common which occurs due to the vicious shaking of the head.
The mode of the injury and the nature of impact can result in different types of brain injuries which further determines the prognosis and treatment of the condition. There could be the following types of TBI:
Concussion: it is a mild type of TBI that usually causes temporary symptoms with no permanent brain damage. However, if a second concussion occurs in close succession to the first, then it can cause permanent damage to the brain and even death in some cases. The concussion can be caused by injuries ranging from bump, blow or jolt on the head to RTA, sports injury, blast injury, and others. The affected person may suddenly lose consciousness for a brief period or develop altered awareness. He may typically have difficulty in understanding his surroundings or situations and thus termed as being ‘dazed’.
Contusions: contusions are bruises that develop in the brain tissue. They are produced when trauma causes rupture of the very small blood vessels that lie within the brain tissue. This can be seen in the brain immediately under the site of impact termed as coup injury or exactly opposite to the impact called a counter-coup injury.
Coup and countercoup injury: these injuries involve the site just beneath the impact and the site exactly opposite to the impact and thus named accordingly. These injuries occur due to sudden deceleration which causes the brain to hit the bony walls of the skull several times. This can be seen in contusions, subdural hemorrhage, or in shaken baby syndrome.
Hematoma: this injury occurs due to the rupture of the blood vessel inside the cranium causing oozing of blood which forms a clot within the brain tissue or along the surface of the brain.
• Intraparenchymal hematoma: when the blood accumulates within the brain tissue it is called an intraparenchymal hematoma.
• Epidural hematoma: when the blood gets accumulated between the outer protective sheath, called dura and the overlying skull bone it is called an epidural hematoma. This typically occurs with rupture of the dural blood arteries usually caused by fracture of the overlying skull bone. The hematoma occupies the epidural/extradural space and exerts pressure on the underlying brain producing symptoms.
• Subdural hematoma: the blood accumulates beneath the dura and over the subarachnoid space which covers the brain. The blood collected in this space exerts significant pressure on the underlying brain. Usually occurs due to tear in the veins that run from the brain to dura. It is considered to be more dangerous than an epidural hematoma. Commonly seen in elderly people following an episode of fall.
• Subarachnoid hemorrhage: the bleeding occurs with subarachnoid space which is seen in close proximity to the underlying brain parenchyma. Normally the subarachnoid space is filled with a thin layer of CSF which provides a cushion to the brain.
• Intraventricular hemorrhage: here the bleeding occurs within or extends into the ventricles present inside the brain. The ventricles are CSF filled spaces which are involved in the production and circulation of the CSF. This type of hemorrhage may cause obstruction of the CSF flow resulting into dilation of the ventricles causing increased pressure within the brain.
Edema: any traumatic brain injury can lead to edema or swelling in a focal or diffuse area of the brain. The edema causes brain tissue to swell which in turn presses against the bone within the limited enclosed space of the cranium.
Diffuse axonal injury: is an injury that damages the long connecting fibers of the brain cells called axons. This type of injury typically occurs during high-speed motor accidents. Here, the high-speed impact causes the brain tissue to move backward and forward quickly within the enclosed bony skull. This results in the tearing of these nerve fibers resulting in loss of function.
DAI most commonly presents as a severe brain injury causing death in about 25% of people. A severe brain injury is one where a special neurological scale, called the Glasgow coma scale (GCS) gives value below 8. DAI should be considered in all patients with GCS below 8 for over 6 hours.
Skull fractures: is a condition where the bony protection around the brain gets broken. It is a condition that can be commonly associated with significant brain injury especially in small children with the softer skull bone.
The skull fractures can be of following types:
• Undisplaced fracture: where the fractured bones remain in its original place and just develops a break within it.
• Displaced fracture: where any part of fractured bone displaces from its original location.
• Depressed fracture: is a type of displaced fracture where a part of the bone gets significantly depressed towards the brain and tends to press upon the underlying brain. This fracture needs to be surgically treated.
• Open fracture: is a fracture where the skin develops a break and the bone gets exposed.
• Skull base fracture: fracture of the part of the skull bone which acts as the floor of the skull. It is the part of the bone on which your brain rests. This is one of the most serious fractures. In this type of fracture, a person may develop leakage of CSF which may come out of nose or ear as thin clear fluid. These people may develop a black eye or bruises around the ear depending on the location of the fracture.
The TBI is described as mild, moderate, and severe on the basis of a special neurological evaluation scale called the Glasgow coma scale (GCS). The GCS suggests the severity of the brain injury by assessing a person’s consciousness according to certain set guidelines.
The GCS gives scoring by assessing three findings during neurological examination:
1. Eye-opening (E): 4 for spontaneous eye-opening, 3 for eye-opening to voice, 2 for eye-opening on induction of pain, 1 for none.
2. Verbal Response (V): 5 for normal conversation, 4 for oriented conversation, 3 for words, but with no coherence, 2 given for ability to produce sounds with loss of ability to form words, 1 for none.
3. Motor Response (M): 6 for normal, 5 for localized to pain, 4 for withdrawal to
pain, 3 for decorticate posture, 2 for decerebrate posture.
The traumatic brain injury is classified according to GCS as follows:
1. Mild: when the GCS is between 13 to 15.
2. Moderate: when the GCS is between 8 to 12.
3. Severe: when the GCS is below 8.
The symptoms of a head injury may vary according to the severity, the type, and location of the injury. It may be mild just to cause a bump or bruise on the head or may be severe enough to cause fracture of the bone or cause traumatic brain injury with symptoms as follows:
• Changes in consciousness and awareness: such as being dazed, confused, disoriented, or loss of consciousness for few seconds to several minutes.
• Nausea and vomiting
• Feeling of tiredness, drowsiness or “tired” eyes
• Sleep problems: such as difficulty in falling asleep or sleeping more than usual.
• Sensory problems: such as blurring of vision, ringing in ears, alteration in smell or taste perception, increased sensitivity to light.
• Mental and cognitive problems: problems in memory and/concentration, mood swings, or feeling of depression or anxiety.
A person with moderate TBI may present with the following symptoms in addition to any of the above-mentioned symptoms of mild TBI.
• Persistent headache or headache worsening with time
• Loss of consciousness lasting for several minutes to hours or inability to awaken from sleep.
• Repeated vomiting
• Seizures following injury
• Weakness/ numbness in limbs, fingers or toes
• Loss of coordination or balance
• Dilatation of one or both pupils
• Clear fluid coming out of nose
• Clear fluid or blood coming out of the ear
• State of profound confusion or disorientation
• Agitation, irritation, aggressiveness or unusual behavior
• Slurring of speech
These can be as follows:
• Frontal lobe: emotional and behavioral changes, decreased mental abilities, loss of memory, paralysis on one side of the body, loss of vision, alteration, or loss of sense of smell.
• Parietal lobe: problems with the hand and eye coordination, problems with reading, writing, naming things or performing mathematical problems, decreased or lack of awareness of several body parts, changes in sense of touch or temperature.
• Occipital lobe: problems in vision such as defects in vision, blurred vision, hallucination.
• Temporal lobe: memory problems (short and long term), problem in understanding language and speaking, a problem with recognizing faces, or identifying/naming objects, development of aggressive behavior, or seizure.
• Brainstem: problem in breathing or swallowing, problems in balance, feeling dizzy, and nauseated.
• Cerebellum: problem in walking, maintaining balance or loss of coordination, development of tremors (shaking of body parts), or dizziness.
All head injuries need to be assessed properly, especially in cases of children, old age, significant impact, loss of consciousness, vomiting, changes in awareness, or development of confusion or disorientation.
Usually, traumatic brain injuries are emergencies and the person is directly brought into the emergency department of the hospital. In the emergency room, a quick history about the injury and mode of injury is taken, followed by physical and neurological examination especially using the Glasgow coma scale (GCS) to assess the severity of the brain injury and to determine the expected course of the disease.
The treatment of head injuries depends on the type and severity of the injury. The severity of the head injury is determined by the clinical examination and imaging tests.
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