What may have caused a hematoma after a PSA nerve block?

A hematoma after a posterior superior alveolar (PSA) nerve block is most commonly caused by the needle inadvertently penetrating the pterygoid plexus of veins. This plexus is located in close proximity to the area where the PSA nerve block is administered. When the needle enters this network of veins, blood can leak into the surrounding tissue, leading to the formation of a hematoma.

Understanding the anatomy surrounding the PSA nerve block area is crucial as this is where major blood vessels are located. When the local anesthetic solution is injected, if it happens within the pterygoid plexus, it results in hemorrhaging due to the disruption of these venous vessels.

While inserting the needle into a blood vessel or the parotid gland can also cause complications, the specific risk of hematoma relates more closely to the pterygoid plexus as it is directly involved with venous bleeding. Muscle irritation, although it can lead to discomfort and other complications, would not cause a hematoma in the same way that a vascular injury would.