Syncope: Diagnosis
Syncope can generally be categorized as being metabolic, vasomotor, cardiac, or neurological in nature. For our purposes we will focus on neurological causes for syncope, which are relatively rare.

There are only four neurological conditions that cause syncope, and none are particularly common:

• Vertebrobasilar transient ischemic attacks (TIAs): Blood flow to the vertebrobasilar arteries, located in the back of the neck near the spinal column, is interrupted. The vertebrobasilar arteries supply blood to the consciousness center of the brainstem.
  
• Subclavian steal syndrome: Involves a blockage in the subclavian artery; during physical exertion when there is an increased demand for blood flow, the subclavian artery cannot keep up, and blood is re-routed from one of the arteries that supplies blood to the brain.
  
• Normal pressure hydrocephalus: This an accumulation of excess fluid in the brain and it typically affects elderly patients.
  
• Seizure disorders: A seizure is a sudden disruption of the brain's normal electrical activity accompanied by altered consciousness. There are more than 20 different seizure disorders, the most notable being epilepsy.
  

Your doctor will conduct a careful physical examination, measuring your blood pressure and heart rate while lying down and standing up. In the vast majority of patients with syncope, neurological causes can be ruled out after a thorough physical exam.

In some cases an electrocardiogram (EKG or ECG) may be used to test for abnormal heart rhythms. Additional tests, such as an exercise stress test, Holter monitor (used to record your heart rhythm over a 24-hour period), or an echocardiogram may be needed to rule out other cardiac causes of syncope.

A CT scan or an MRI may be used to further evaluate suspected neurological causes.