Numb lip after a difficult lower third molar removal
A 27-year-old woman had a mesioangular impacted 38 removed under inferior alveolar nerve block and buccal infiltration 2 days ago. The surgery was prolonged, requiring a buccal flap and bone removal, and the crown was sectioned. She now reports that her right lower lip and chin feel numb and 'thick', and she has dribbled while drinking. She has no pain, no swelling, and no trismus beyond mild discomfort. Sensation to light touch on the right vermilion and chin is reduced compared with the left. The socket looks clean with a stable blood clot. She is distressed and asks whether the feeling will come back and whether anything should have been done differently.
1. What is your differential diagnosis, and how would you assess and document her nerve injury?
Read the worked answer
The distribution - lower lip and chin on the operated side, with altered light touch - fits injury to the inferior alveolar nerve, with possible involvement of the mental nerve branches. The differential includes: temporary neuropraxia from local anaesthetic or retraction and pressure during surgery, which is the most likely and usually resolves over weeks; axonotmesis from compression or traction; less commonly neurotmesis from direct trauma; and, rarely, a haematoma or infection compressing the nerve, though there is no swelling here.
Assessment: take a structured history of onset, whether numbness was present immediately after the anaesthetic wore off, and whether it is improving, static or worsening. Test light touch, pinprick and two-point discrimination on the lip, chin and buccal mucosa, and map the affected area against the contralateral side. Check for taste change if lingual involvement is suspected. Photograph or draw a diagram of the distribution and record it in the notes. Explain that most such injuries are temporary and recover, but that recovery can take months and a small proportion are permanent.
Document the consent discussion that took place pre-operatively, the surgical difficulty, and the findings today. Advise her to avoid hot food and drinks and to be careful with lip biting, and give written safety advice.
2. What is your management plan, including referral, review, and communication?
Read the worked answer
Explain the findings clearly and honestly, using plain language: the nerve has been bruised or stretched and sensation is likely to return, but this can take 6–18 months and a minority of patients have some permanent change. Avoid promising full recovery. Acknowledge her distress and offer a further appointment to discuss it.
Refer to an oral and maxillofacial unit with an interest in nerve injury, ideally within a few weeks, for assessment and consideration of microneurosurgery if there is no improvement; the timing is debated, but early referral allows assessment while intervention may still be an option. Send a referral letter with the operative details, onset, distribution and current sensory findings.
Review her in 2 weeks and then at intervals of 1–3 months, recording the mapped area each time so change is measurable. Provide written advice about lip and cheek biting, hot drinks, and eye care is not relevant here, but mouth care and avoiding trauma to the numb area are. Consider whether she needs psychological support if the injury persists. Review the case to see whether the nerve block technique, flap design or bone removal could be modified in future, and record this as a learning point; do not alter the clinical record retrospectively.