In emergency medicine, a lucid interval is a temporary improvement in a patient's condition after a traumatic brain injury, after which the condition deteriorates. A lucid interval is especially indicative of an epidural hematoma. An estimated 20 to 50% of patients with epidural hematoma experience such a lucid interval. [1] [2]
When related to haemorrhage, the lucid interval occurs after the patient is knocked out by the initial concussive force of the trauma and then temporarily recovers, before lapsing into unconsciousness again when bleeding causes the haematoma to expand past the extent for which the body can compensate. [3] After the injury, the patient is momentarily dazed or knocked out, and then becomes relatively lucid for a period of time which can last minutes or hours. [3] Thereafter there is rapid decline as the blood collects within the skull, causing a rise in intracranial pressure, which damages brain tissue. In addition, some patients may develop "pseudoaneurysms" after trauma which can eventually burst and bleed, a factor which might account for the delay in loss of consciousness. [4]
Because a patient may have a lucid interval, any significant head trauma is regarded as a medical emergency and receives emergency medical treatment even if the patient is conscious.
Delayed cerebral edema, a very serious and potentially fatal condition in which the brain swells dramatically, may follow a lucid interval that occurs after a minor head trauma. [5]
Lucid intervals may also occur in conditions other than traumatic brain injury, such as heat stroke [6] and the postictal phase after a seizure in epileptic patients. [7]
A head injury is any injury that results in trauma to the skull or brain. The terms traumatic brain injury and head injury are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injuries, there are many causes—including accidents, falls, physical assault, or traffic accidents—that can cause head injuries.
Cerebral edema is excess accumulation of fluid (edema) in the intracellular or extracellular spaces of the brain. This typically causes impaired nerve function, increased pressure within the skull, and can eventually lead to direct compression of brain tissue and blood vessels. Symptoms vary based on the location and extent of edema and generally include headaches, nausea, vomiting, seizures, drowsiness, visual disturbances, dizziness, and in severe cases, coma and death.
A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include loss of consciousness (LOC); memory loss; headaches; difficulty with thinking, concentration or balance; nausea; blurred vision; sleep disturbances; and mood changes. Any of these symptoms may begin immediately, or appear days after the injury. Concussion should be suspected if a person indirectly or directly hits their head and experiences any of the symptoms of concussion. It is not unusual for symptoms to last 2 weeks in adults and 4 weeks in children. Fewer than 10% of sports-related concussions among children are associated with loss of consciousness.
Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and, at rest, is normally 7–15 mmHg for a supine adult. The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF.
Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. Symptoms may include a severe headache of rapid onset, vomiting, decreased level of consciousness, fever, and sometimes seizures. Neck stiffness or neck pain are also relatively common. In about a quarter of people a small bleed with resolving symptoms occurs within a month of a larger bleed.
A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrounding the brain. It usually results from tears in bridging veins that cross the subdural space.
Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. Subtypes are intracerebral bleeds, subarachnoid bleeds, epidural bleeds, and subdural bleeds.
Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain and the skull. Often there is loss of consciousness following a head injury, a brief regaining of consciousness, and then loss of consciousness again. Other symptoms may include headache, confusion, vomiting, and an inability to move parts of the body. Complications may include seizures.
A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity, mechanism, or other features. Head injury is a broader category that may involve damage to other structures such as the scalp and skull. TBI can result in physical, cognitive, social, emotional and behavioral symptoms, and outcomes can range from complete recovery to permanent disability or death.
Intracerebral hemorrhage (ICH), also known as cerebral bleed and intraparenchymal bleed, is a sudden bleeding into the tissues of the brain, into its ventricles, or into both. It is one kind of bleeding within the skull and is one kind of stroke.
Cerebral contusion, Latin contusio cerebri, a form of traumatic brain injury, is a bruise of the brain tissue. Like bruises in other tissues, cerebral contusion can be associated with multiple microhemorrhages, small blood vessel leaks into brain tissue. Contusion occurs in 20–30% of severe head injuries. A cerebral laceration is a similar injury except that, according to their respective definitions, the pia-arachnoid membranes are torn over the site of injury in laceration and are not torn in contusion. The injury can cause a decline in mental function in the long term and in the emergency setting may result in brain herniation, a life-threatening condition in which parts of the brain are squeezed past parts of the skull. Thus treatment aims to prevent dangerous rises in intracranial pressure, the pressure within the skull.
The postictal state is the altered state of consciousness after an epileptic seizure. It usually lasts between 5 and 30 minutes, but sometimes longer in the case of larger or more severe seizures, and is characterized by drowsiness, confusion, nausea, hypertension, headache or migraine, and other disorienting symptoms. Additionally, emergence from this period is often accompanied by amnesia or other memory defects. It is during this period that the brain recovers from the trauma of the seizure.
Second-impact syndrome (SIS) occurs when the brain swells rapidly, and catastrophically, after a person suffers a second concussion before symptoms from an earlier one have subsided. This second blow may occur minutes, days or weeks after an initial concussion, and even the mildest grade of concussion can lead to second impact syndrome. The condition is often fatal, and almost everyone who is not killed is severely disabled. The cause of SIS is uncertain, but it is thought that the brain's arterioles lose their ability to regulate their diameter, and therefore lose control over cerebral blood flow, causing massive cerebral edema.
Post-traumatic epilepsy (PTE) is a form of acquired epilepsy that results from brain damage caused by physical trauma to the brain. A person with PTE suffers repeated post-traumatic seizures more than a week after the initial injury. PTE is estimated to constitute 5% of all cases of epilepsy and over 20% of cases of acquired epilepsy.
Post-traumatic seizures (PTS) are seizures that result from traumatic brain injury (TBI), brain damage caused by physical trauma. PTS may be a risk factor for post-traumatic epilepsy (PTE), but a person who has a seizure or seizures due to traumatic brain injury does not necessarily have PTE, which is a form of epilepsy, a chronic condition in which seizures occur repeatedly. However, "PTS" and "PTE" may be used interchangeably in medical literature.
Kernohan's notch is a cerebral peduncle indentation associated with some forms of transtentorial herniation. It is a secondary condition caused by a primary injury on the opposite hemisphere of the brain. Kernohan's notch is an ipsilateral condition, in that a left-sided primary lesion evokes motor impairment in the left side of the body and a right-sided primary injury evokes motor impairment in the right side of the body. The seriousness of Kernohan's notch varies depending on the primary problem causing it, which may range from benign brain tumors to advanced subdural hematoma.
Traumatic brain injury can cause a variety of complications, health effects that are not TBI themselves but that result from it. The risk of complications increases with the severity of the trauma; however even mild traumatic brain injury can result in disabilities that interfere with social interactions, employment, and everyday living. TBI can cause a variety of problems including physical, cognitive, emotional, and behavioral complications.
Midline shift is a shift of the brain past its center line. The sign may be evident on neuroimaging such as CT scanning. The sign is considered ominous because it is commonly associated with a distortion of the brain stem that can cause serious dysfunction evidenced by abnormal posturing and failure of the pupils to constrict in response to light. Midline shift is often associated with high intracranial pressure (ICP), which can be deadly. In fact, midline shift is a measure of ICP; presence of the former is an indication of the latter. Presence of midline shift is an indication for neurosurgeons to take measures to monitor and control ICP. Immediate surgery may be indicated when there is a midline shift of over 5 mm. The sign can be caused by conditions including traumatic brain injury, stroke, hematoma, or birth deformity that leads to a raised intracranial pressure.
Computed tomography of the head uses a series of X-rays in a CT scan of the head taken from many different directions; the resulting data is transformed into a series of cross sections of the brain using a computer program. CT images of the head are used to investigate and diagnose brain injuries and other neurological conditions, as well as other conditions involving the skull or sinuses.; it used to guide some brain surgery procedures as well. CT scans expose the person getting them to ionizing radiation which has a risk of eventually causing cancer; some people have allergic reactions to contrast agents that are used in some CT procedures.
A sports-related traumatic brain injury is a serious accident which may lead to significant morbidity or mortality. Traumatic brain injury (TBI) in sports are usually a result of physical contact with another person or stationary object, these sports may include boxing, gridiron football, field/ice hockey, lacrosse, martial arts, rugby, soccer, wrestling, auto racing, cycling, equestrian, roller blading, skateboarding, skiing or snowboarding.