Transient facial weakness is a potential complication of which mandibular block if anesthetic diffuses into the parotid gland?

• A. Inferior alveolar nerve block
• B. Posterior superior alveolar injection
• C. Incisive block
• D. Infraorbital block

Answer: (A)

Transient facial weakness occurs when local anesthetic diffuses into the parotid gland, where the facial nerve (cranial nerve VII) runs and gives its branches. If the anesthetic reaches the gland, it can temporarily block these facial nerve fibers on the same side, leading to unilateral facial weakness that resolves as the drug wears off.

This is most likely with an inferior alveolar nerve block because its injection path is closest to the parotid region. The parotid gland sits over the rami of the mandible and the facial nerve branches traverse it, so solution that spreads into or around the parotid can affect the nerve. The other blocks target areas farther from the parotid, making parotid diffusion and facial nerve involvement much less probable.