Hematoma can occur if needle penetrates pterygoid plexus of veins during which injection?

• A. Inferior alveolar nerve block
• B. PSA injection
• C. Infraorbital block
• D. Mental foramen injection

Answer: (B)

The risk of a hematoma here comes from the proximity of the pterygoid venous plexus to the path of a posterior superior alveolar (PSA) injection. The pterygoid plexus lies in the infratemporal fossa near the posterior aspect of the maxilla, and the PSA nerve branches travel close to this venous network as they enter the maxilla. If the needle advances too posteriorly or medially during a PSA block and punctures those veins, blood can escape into the surrounding tissues, forming a hematoma in the cheek or infratemporal region. This is why PSA injections are classically associated with hematoma risk. The other injections target sites farther from the pterygoid plexus: the inferior alveolar block is aimed at the mandibular canal, the infraorbital block at the infraorbital canal, and the mental foramen injection at the anterior mandible, making vascular puncture of the pterygoid plexus much less likely.