A panic attack is defined as the abrupt onset of an episode of intense fear or discomfort, which peaks in approximately 10 minutes, and includes at least four of the following symptoms:

A feeling of imminent danger or doom
The need to escape
Palpitations
Sweating
Trembling
Shortness of breath or a smothering feeling
A feeling of choking
Chest pain or discomfort
Nausea or abdominal discomfort
Dizziness or lightheadedness
A sense of things being unreal, depersonalization
A fear of losing control or "going crazy"
A fear of dying
Tingling sensations
Chills or hot flushes

Three Types Of Panic Attacks

Unexpected: The attack "comes out of the blue" without warning and for no discernible reason.
Situational: Situations in which an individual always has an attack, for example, upon entering a tunnel.
Situationally Predisposed: Situations in which an individual is likely to have a panic attack, but does not always have one. An example of this would be an individual who sometimes has attacks while driving.

Panic Disorder

Panic disorder is diagnosed when an individual suffers at least two unexpected panic attacks, followed by at least one month of concern over having another attack. Sufferers are also prone to situationally predisposed attacks.

The frequency and severity of the attacks varies from person to person, an individual might suffer from repeated attacks for weeks, while another will have short bursts of very severe attacks.

The sufferer often worries about the physical and emotional consequences of the Panic Attacks. Many become convinced that the attacks indicate an undiagnosed illness and will submit to frequent medical tests. Even after tests come back negative, a person with panic disorder will remain worried that they have a physical illness.

Some individuals will change their behavioral patterns, avoiding the scene of a previous attack for example, in the hopes of preventing having another attack.

Information provided by Anxiety Disorders Association of America.