Prodrome in the context of "Postherpetic neuralgia"

Schizophrenia is a mental disorder characterized variously by hallucinations (typically, hearing voices), delusions, disorganized thinking or behavior, and flat or inappropriate affect. Symptoms develop gradually and typically begin during young adulthood and rarely resolve. There is no objective diagnostic test; diagnosis is based on observed behavior, a psychiatric history that includes the person's reported experiences, and reports of others familiar with the person. For a formal diagnosis, the described symptoms need to have been present for at least six months (according to the DSM-5) or one month (according to the ICD-11). Many people with schizophrenia have other mental disorders, especially mood, anxiety, and substance use disorders, as well as obsessive–compulsive disorder (OCD).

About 0.3% to 0.7% of people are diagnosed with schizophrenia during their lifetime. In 2017, there were an estimated 1.1 million new cases and in 2022 a total of 24 million cases globally. Males are more often affected and on average have an earlier onset than females. The causes of schizophrenia may include genetic and environmental factors. Genetic factors include a variety of common and rare genetic variants. Possible environmental factors include being raised in a city, childhood adversity, cannabis use during adolescence, infections, the age of a person's mother or father, and poor nutrition during pregnancy.

Syncope (syncope), commonly known as fainting or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from low blood pressure. There are sometimes symptoms before the loss of consciousness such as lightheadedness, sweating, pale skin, blurred vision, nausea, vomiting, or feeling warm. Syncope may also be associated with a short episode of muscle twitching. Psychiatric causes can also be determined when a patient experiences fear, anxiety, or panic; particularly before a stressful event, usually medical in nature. When consciousness and muscle strength are not completely lost, it is called presyncope. It is recommended that presyncope be treated the same as syncope.

Causes range from non-serious to potentially fatal. There are three broad categories of causes: heart or blood vessel related; reflex, also known as neurally mediated; and orthostatic hypotension. Issues with the heart and blood vessels are the cause in about 10% and typically the most serious, while neurally mediated is the most common. Heart-related causes may include an abnormal heart rhythm, problems with the heart valves or heart muscle, and blockages of blood vessels from a pulmonary embolism or aortic dissection, among others. Neurally mediated syncope occurs when blood vessels expand and heart rate decreases inappropriately. This may occur from either a triggering event such as exposure to blood, pain, strong feelings or a specific activity such as urination, vomiting, or coughing. Neurally mediated syncope may also occur when an area in the neck known as the carotid sinus is pressed. The third type of syncope is due to a drop in blood pressure when changing position, such as when standing up. This is often due to medications that a person is taking, but may also be related to dehydration, significant bleeding, or infection. There also seems to be a genetic component to syncope.

Koplik's spots (also Koplik's sign) are a prodromic viral enanthem of measles manifesting two to three days before the measles rash itself. They are characterized as clustered, white lesions on the buccal mucosa (opposite the upper 1st & 2nd molars) and are pathognomonic for measles. The textbook description of Koplik spots is ulcerated mucosal lesions marked by necrosis, neutrophilic exudate, and neovascularization. They are described as appearing like "grains of salt on a reddish background", and often fade as the maculopapular rash develops. As well as their diagnostic significance, they are important in the control of outbreaks. Their appearance, in context of a diagnosed case, before they reach maximum infectivity, permits isolation of the contacts and greatly aids control of this highly infectious disease.

Nobel laureate John F. Enders and Thomas Peebles, who first isolated the measles virus, were careful to collect their samples from patients showing Koplik's spots.

Apophenia (/æpoʊˈfiːniə/) is the tendency to perceive meaningful connections between unrelated things.

The term (German: Apophänie from the Greek verb: ἀποφαίνειν, romanized: apophaínein) was coined by psychiatrist Klaus Conrad in his 1958 publication on the beginning stages of schizophrenia. He defined it as "unmotivated seeing of connections [accompanied by] a specific feeling of abnormal meaningfulness". He described the early stages of delusional thought as self-referential over-interpretations of actual sensory perceptions, as opposed to hallucinations.