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Posterior Superior Alveolar Nerve Block — MFDS Part 1 MCQ

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ModerateAnatomy (Head & Neck)Posterior Superior Alveolar Nerve BlockMFDS Part 1

During a conventional intraoral posterior superior alveolar nerve block, the needle is advanced upwards, inwards and backwards from the mucobuccal fold above the maxillary second molar. Which anatomical surface should the needle remain close to as it advances?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Posterior surface of the maxilla

The correct answer is B. In the conventional posterior superior alveolar nerve block, the needle is advanced upwards, inwards and backwards while remaining close to the posterior surface of the maxilla in the tuberosity region. Local anaesthetic is deposited near the posterior superior alveolar nerves before they enter the posterior maxillary foramina. The pterygoid hamulus is a landmark for palatal and pharyngeal anatomy, not this injection. The greater palatine foramen is used for a greater palatine block, whereas the infraorbital foramen is relevant to an infraorbital block. The pterygopalatine fossa is approached in a maxillary nerve block rather than a conventional PSA block. The original key was correct, but 'directed to the maxillary tuberosity' was anatomically imprecise and could encourage excessive bony contact.

Reference: Becker DE, Reed KL. Local anesthesia part 2: technical considerations, posterior superior alveolar nerve block section and Figure 1. Anesthesia Progress. 2012;59(3):127-137. https://pubmed.ncbi.nlm.nih.gov/23050753/