Anesthesia · patient case question
Which complication is LEAST likely to follow an inferior alveolar nerve block?
Patient case: An Extraction, a Block, and a Drooping Eyelid
Patient: 45-year-old female
Chief Complaint: Extraction of tooth #19.
Background: No medical history of note. No known drug allergies, though she reports her mother 'reacts to penicillin.'
Medications: None
Vital Signs: BP 120/76 mmHg · HR 74 bpm · RR 16 · T 98.4°F
Findings: An inferior alveolar nerve block is administered. Within minutes she is unable to close her right eye and the right corner of her mouth droops. Lip and tongue numbness on that side is profound.
Show answer and explanation
Correct answer: C. Infection
- A. TRISMUS is common. The needle traverses the medial pterygoid muscle; haemorrhage into the muscle, or irritation from the solution, produces spasm and restricted opening — typically appearing 1 to 6 days after the injection.
- B. PARAESTHESIA occurs in roughly 1 in 20,000 to 1 in 800,000 blocks, most often affecting the LINGUAL nerve, and is more frequently reported with 4% solutions (articaine, prilocaine). Most cases resolve within 8 weeks.
- C. CORRECT — this is the LEAST likely. INFECTION after an IAN block is rare, because the needle passes through non-contaminated tissue with a sterile single-use needle and the local anaesthetic solution itself is mildly bacteriostatic. It happens only where the needle is contaminated or passes through an infected area.
- D. HAEMATOMA occurs when the pterygoid venous plexus or the inferior alveolar vessels are punctured. It is more visible after a posterior superior alveolar block, but it certainly occurs with the IAN block.
Note: Practical points: aspirate in two planes before injecting, never inject into an area of active infection, and warn patients about post-injection trismus so they do not attribute it to the extraction.