What causes a hematoma during a PSA injection?

• A. Injecting in the pterygoid plexus during a PSA injection
• B. Hitting a nerve
• C. Syringe contamination
• D. Inadequate local anesthetic concentration

Answer: (A)

During a PSA injection, a hematoma happens when the needle punctures the pterygoid venous plexus, a network of veins in the infratemporal region that runs near the vessels and nerves you’re targeting to reach the posterior superior alveolar nerve. If one of these veins is torn, blood leaks into the surrounding facial tissues, producing swelling and a bruise. The anatomy places veins close to the injection path, so careful needle control and aspiration before depositing anesthesia help reduce the risk. Hitting a nerve would mainly cause sensory disturbances, syringe contamination isn’t related to bleeding, and inadequate anesthetic concentration affects effectiveness, not bleeding.