Hyperventilation Induced Syncope: Differential Feature of Head-up Tilt Table Test with Transcranial Doppler in Patient with Hyperventilation Syndrome from True Syncope

The causes of a transient loss of consciousness (TLOC) are divided into syncope, epileptic seizures, cerebrovascular diseases and functional disorders such as hyperventilation (HV) syndrome, psychogenic pseudosyncope. The differential diagnosis of TLOC is may be difficult due to lack of history, misleading features, or confusion over the definition of syncope. We have experienced a rare case of HV syncope that TLOC developed after HV from mental stress, and differentiated by head-up tilt table test with transcranial doppler.