emergency medicine Emergency medicine is the medical speciality concerned with the care of illnesses or injuries requiring immediate medical attention. Emergency physicians (often called “ER doctors” in the United States) continuously learn to care for un ...

, a lucid interval is a temporary improvement in a patient's condition after a

traumatic brain injury 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 (ranging from mild traumatic brain injury TBI/concussionto severe traumatic b ...

, after which the condition deteriorates. A lucid interval is especially indicative of an

epidural hematoma Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain (dura mater) and the skull. Often there is loss of consciousness following a head injury, a brief regaining of consciousness, and then loss of conscio ...

. An estimated 20 to 50% of patients with epidural hematoma experience such a lucid interval.

Indications

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. 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. Thereafter there is rapid decline as the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in th ...

collects within the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

, causing a rise in

intracranial pressure 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. ...

, which damages

brain The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...

tissue. In addition, some patients may develop "

pseudoaneurysm A pseudoaneurysm, also known as a false aneurysm, is a locally contained hematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or sur ...

s" after trauma which can eventually burst and bleed, a factor which might account for the delay in loss of consciousness. Because a patient may have a lucid interval, any significant

head trauma 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 in ...

is regarded as a medical emergency and receives emergency medical treatment even if the patient is conscious. Delayed

cerebral edema 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 compressio ...

, 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. Lucid intervals may also occur in conditions other than traumatic brain injury, such as

heat stroke Heat stroke or heatstroke, also known as sun stroke, is a severe heat illness that results in a body temperature greater than , along with red skin, headache, dizziness, and confusion. Sweating is generally present in exertional heatstroke, ...

and the

postictal 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, nau ...

phase after a

seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...

in epileptic patients.

References

{{reflist

External links

Medpix.com discussion of lucid interval
Retrieved on February 6, 2007. Neurotrauma Medical signs

Indications

See also

References

External links