In a 61‑year‑old woman with left mandibular pain that is predominantly constant with fluctuations, triggered by brushing teeth and with pain‑free intervals, what is the most likely diagnosis and the appropriate diagnostic and therapeutic plan?

Trigeminal Neuralgia Type 2 (Atypical Trigeminal Neuralgia)

Based on the clinical presentation of predominantly constant left mandibular pain with fluctuations, triggered by tooth brushing with pain-free intervals, the most likely diagnosis is trigeminal neuralgia Type 2 (also called atypical trigeminal neuralgia or trigeminal neuralgia with concomitant pain). This variant differs from classical trigeminal neuralgia by having more prolonged background pain between the sharp shooting attacks 1.

Why This Diagnosis Fits

The key distinguishing features in this case point away from classical trigeminal neuralgia and toward Type 2:

• Predominantly constant pain with fluctuations - Classical TN presents with purely paroxysmal attacks lasting seconds to minutes with complete pain-free intervals, while Type 2 has persistent background pain 1
• Triggered by tooth brushing - This light touch trigger is characteristic of trigeminal neuralgia variants 1
• Pain-free intervals exist but are not complete - The "predominantly constant" descriptor suggests ongoing discomfort rather than the complete refractory periods seen in classical TN 1
• Unilateral mandibular location - Consistent with third division trigeminal nerve involvement 1

Critical Differential Diagnoses to Exclude

Before confirming TN Type 2, you must rule out these conditions that can mimic or coexist:

1. Dental Pathology (FIRST PRIORITY)

• Obtain intraoral X-rays or CBCT to exclude abscess, periapical pathology, or crown/post complications 2
• Recent case reports show odontogenic pain can perfectly mimic TN for years 2
• Examine for percussion sensitivity, thermal testing abnormalities

2. Post-Traumatic Trigeminal Neuropathic Pain

• Inquire specifically about any dental procedures in the past 3-6 months (extractions, root canals, implants) 1
• This presents as continuous burning/tingling pain and is managed differently than TN 1

3. Temporomandibular Disorder (TMD)

• At 61 years old, TMD remains common but typically presents with jaw movement-related pain, not tooth brushing triggers 3, 4
• Palpate masticatory muscles and assess jaw range of motion

4. Giant Cell Arteritis (RED FLAG in >50 years)

• Check ESR and CRP immediately - this is a medical emergency 1, 5
• Ask about temporal headache, visual changes, jaw claudication with chewing, scalp tenderness
• GCA can present as tooth/jaw pain and is easily confused with TMD in this age group 5

Diagnostic Workup

Immediate Steps:

1. Detailed pain history focusing on:

   • Exact quality during attacks vs. background pain
   • Duration of individual pain episodes
   • Complete list of triggers beyond tooth brushing
   • Any sensory changes (numbness, tingling)

2. Physical examination:

   • Light touch testing in all three trigeminal divisions to identify trigger zones 1
   • Look for sensory deficits (rare in TN but suggests secondary cause) 1
   • Palpate temporal arteries and check for tenderness

3. Laboratory:

   • ESR and CRP to exclude giant cell arteritis 1

4. Imaging:

   • MRI brain with focus on posterior fossa - This is mandatory to exclude secondary causes including tumors, multiple sclerosis, and to assess for neurovascular compression 1, 6
   • The 2022 ACR guidelines emphasize imaging the entire trigeminal nerve course from brainstem to peripheral branches 6
   • Dental imaging (CBCT) if any suspicion of odontogenic source 2

Therapeutic Plan

First-Line Medical Management:

Start carbamazepine as the primary drug of choice, though oxcarbazepine has equal efficacy with fewer side effects 1. The evidence strongly supports anticonvulsants as first-line therapy.

Specific dosing approach:

• Begin carbamazepine 100-200 mg twice daily, titrate up to 600-1200 mg/day in divided doses
• Alternative: Oxcarbazepine 300 mg twice daily, titrate to 600-1800 mg/day (better tolerated) 1
• Monitor for side effects: dizziness, drowsiness, hyponatremia (especially with oxcarbazepine)

Second-line options if inadequate response:

• Lamotrigine (particularly effective for Type 2 TN with constant pain component) 1
• Gabapentin or pregabalin (some evidence from cohort studies) 1
• Baclofen as adjunct therapy 1

When to Consider Neurosurgical Referral:

Obtain neurosurgical consultation early if:

• Inadequate pain control despite optimal medical therapy
• Intolerable medication side effects
• Patient preference for definitive treatment 1

The only non-ablative surgical option is microvascular decompression, which addresses neurovascular compression but requires posterior fossa surgery 1. Type 2 TN may have more central origin and potentially less favorable surgical outcomes compared to classical TN 1.

Critical Pitfalls to Avoid:

1. Do not perform irreversible dental procedures (extractions, root canals) without confirming odontogenic source - this is a common error that leads to unnecessary procedures and persistent pain 7, 2

2. Do not miss giant cell arteritis - In patients >50 years with new-onset facial/jaw pain, always check inflammatory markers. Untreated GCA causes permanent vision loss 1, 5

3. Do not delay MRI - Secondary causes (tumors, MS) must be excluded before labeling as primary TN 1, 6

4. Recognize that Type 2 TN has worse prognosis than classical TN - Set realistic expectations about treatment response and consider earlier surgical consultation 1