Tinnitus After IANB — ORE Part 1 MCQ

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HardPharmacology & TherapeuticsTinnitus After IANBORE Part 1

Immediately after an inferior alveolar nerve block, a patient reports sudden unilateral ringing in the ear. There is no rash, wheeze, facial swelling, fever or ear pain. What is the most likely cause?

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Correct answer: D — Inadvertent intravascular injection of local anaesthetic affecting cochlear circulation

Explanation lettering: C = shown as A · D = shown as C · A = shown as D

A is correct. The immediate onset after an inferior alveolar nerve block strongly indicates an injection-related vascular event. The pterygoid venous plexus and vessels adjacent to the mandibular foramen can be entered inadvertently; vascular delivery of local anaesthetic can plausibly produce transient cochlear/auditory disturbance. The revised answer deliberately avoids claiming a specific, proven retrograde route to the internal auditory artery. Allergy would usually produce cutaneous, respiratory or cardiovascular features rather than isolated tinnitus. Direct cochlear-nerve trauma is anatomically implausible because cranial nerve VIII is remote from the IANB needle path. Middle-ear infection does not arise immediately after injection. Vasoconstrictor effects may cause palpitations, tremor or anxiety, but isolated tinnitus is less well explained without intravascular delivery.

Reference: Brizuela M, Daley JO. Inferior Alveolar Nerve Block. StatPearls, updated 2025; section on complications/anatomy notes the pterygoid venous plexus should be avoided to reduce inadvertent vascular injection. https://pubmed.ncbi.nlm.nih.gov/33232038/