2.2
Neuropathic Pain
Dermot Canavan
Objectives
At the end of this case the reader should appreciate that persistent neuropathic pain in the orofacial area is easily misdiagnosed as toothache.
Trigeminal neuralgia (TN) is perhaps the best known of the neuropathic disorders, and due to extensive research we now have a much clearer understanding of this complex disorder.
Introduction
A 57‐year‐old female patient was referred to the orofacial pain clinic with concerns regarding persistent pain and sensitivity around the lower left first molar tooth (LL6). The patient’s endodontist sought an opinion following completion of root canal treatment on the LL6.
Chief Complaint
The patient complained of persistent pain in the left midface area. She described episodic dull, aching discomfort in the mandible and maxilla on the left side that lasted for hours at a time. Pain intensity was mild to moderate on average and from the patient’s perspective it felt like ‘toothache coming from the lower left molar tooth’. She was also experiencing superimposed sharp shooting (lancinating) pain of increasing severity. These severe pains were relatively brief but almost ‘unbearable’. They were triggered by speech, eating, movement of the tongue and touching the lower lip on the left side. Her pain was unresponsive to ibuprofen, acetaminophen (paracetamol) and codeine. The sharp pains regularly woke the patient at night. On occasion she noticed that her left eye was tearing, she had some swelling (oedema) of the eyelids on the left side and redness of the eye (conjunctival injection).
Medical History
Her current medication regime included levothyroxine 50 mg/day for her underactive thyroid condition and esomeprazole 20 mg/day for gastric discomfort. She had suffered from recurrent migraine attacks with significant frequency during her late 20s and early 30s. The headaches gradually resolved as she got older and at the time of assessment she was headache free.
There was a positive family history of episodic migraine (her mother suffered from migraine as a young woman).
Dental History
The patient had a history of recurring toothache‐like pain in the lower left posterior quadrant when in her early 40s. Despite repeated dental visits and procedures, the toothaches continued and eventually led to the extraction of the lower second molar (LL7). Following this extraction, the episodic toothache seemed to resolve. Tooth LL6 had been root treated recently by a specialist endodontist, however the patient complained of persistent intermittent pain and sensitivity around this tooth. All of her wisdom teeth had been removed under general anaesthesia at the age of 27.
What are the important questions to ask in this scenario?
- Is there a history of trauma to the orofacial region? Traumatic injury to the orofacial area may lead to the onset of trigeminal neuropathic pain weeks, months or even years after the injury.
- When the pain is active in the symptomatic area does it extend into areas outside the orofacial region? For example, is it also experienced in the ipsilateral parietal and suboccipital areas? The trigeminal neuropathic pain disorders (including trigeminal neuralgia) are typically experienced within the area normally innervated by the trigeminal nerve. If the orofacial complaint is associated with simultaneous pain in the parietal, occipital or posterior neck area, then a broader differential diagnosis needs to be considered. Possible causes would include intraoral disease, headache disorders and cervicogenic pathology.
- Are the sharp shooting pains experienced in a fixed location or do they move to other areas in the face or head? For example, are the lancinating pains experienced in the tongue, throat or ear? Lancinating pain in the ipsilateral border of the tongue is a common feature of TN. The sharp shooting pains of TN are typically unilateral and do not extend outside the trigeminal region. More widely distributed sharp shooting pains may be associated with headache complaints or myofascial disorders.
- Are the sharp shooting pains ever triggered by certain smells or tastes? Non‐noxious stimuli like certain smells or tastes will rarely trigger pain, but there are exceptions. The lancinating pains of TN may be triggered by foods that are spicy or bitter. Strong pungent smells like paint, diesel or perfume may be quite repulsive to patients experiencing headache disorders.
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