This study will enroll patients meeting Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for post-traumatic stress disorder (PTSD). Following an initial screening visit, clinical assessment, and enrollment, subjects will be randomized into treatment and placebo arms. Both cohorts will undergo a pre-intervention functional magnetic resonance imaging (fMRI) of their brain. Treatment subjects will receive unilateral two-level stellate ganglion block via ultrasound-guided injection of anesthetic (bupivacaine) into the cervical sympathetic tissue; placebo subjects will receive an identical volume of saline via the same procedures. At approximately 4 weeks post-procedure, both cohorts will then undergo a post-intervention clinical assessment. Finally, both cohorts will undergo a post-intervention fMRI of their brain.