Some patients with Post Traumatic Stress Disorder (PTSD) respond only partially to medication. This study is a pilot study investigating whether blocking the SPG helps reduce the symptoms of PTSD. This study does not involve treatment with medications. It is a proof of principal study.

The sphenopalatine ganglion (SPG) is a collection of neurons involved in autonomic regulation (which refers to bodily processes that are automatic like heart rate and blood pressure). Blocking the SPG is used to treat disorders, such as migraines or cluster headaches (short, severe headaches that occur together). The procedure will be performed by a doctor who specializes in ear, nose throat surgery. The block consists of the injection of a numbing agent (similar to the type used by dentists) to the SPG. After the SPG block, we will follow patients for 8 weeks to see how they feel.

Inclusion Criteria:

• Participants with a principal diagnosis of PTSD on stable dose of psychiatric medication or in stable psychotherapy for at least 3 months, who experience residual symptoms.
• Participants who understand all study procedures and can undergo informed consent

Exclusion Criteria:

• Participants with a medical disorder, for whom study participation could be deleterious (neurologic, cardiac, renal or infectious disease)
• Pregnant or breast feeding participants
• Participants who are on an anticoagulant, such as warfarin, or otherwise have a medical condition that increases bleeding risk