What is panic disorder?
Panic disorder is a fairly common condition in which a person has uncomfortable episodes of fear or anxiety that occur suddenly (often without warning). The attacks--called panic attacks--can last from minutes to hours. They may occur only seldom, or quite frequently. The cause, or "trigger," for these attacks may not be obvious right away.

What happens during a panic attack?
Panic attacks are often associated with physical symptoms such as shaking, a feeling your heart is pounding or racing, sweating, chest pain, shortness of breath, a feeling of choking, nausea, cramping, diarrhea, dizziness, an out-of-body sensation (a feeling of being apart from oneself), tingling in the hands, chills or hot flashes, and headache. A person may also have an extreme fear of losing control, going crazy or dying during a panic attack. It is very rare for a person to have all of these symptoms at once, although the presence of at least 4 symptoms strongly suggests the diagnosis of panic disorder.

http://familydoctor.org/handouts/137.html