What is the recommended workup and treatment for a patient presenting with symptoms of trigeminal neuralgia?

Trigeminal Neuralgia Workup

Diagnostic Approach

Diagnose trigeminal neuralgia by clinical history alone: sudden, unilateral, severe, brief stabbing paroxysmal pain in one or more trigeminal nerve branches, triggered by innocuous stimuli (talking, chewing, light touch), with mandatory pain-free refractory periods between attacks. 1, 2

Key Clinical Features to Elicit

• Pain character: Electric shock-like, lancinating attacks lasting seconds to minutes—not continuous pain 1, 3
• Refractory periods: Mandatory pain-free intervals between attacks that distinguish this from other facial pain syndromes 3, 2
• Distribution: V2 (maxillary) and V3 (mandibular) branches most commonly affected 2
• Trigger zones: Small perioral and nasal areas where minimal stimulation precipitates attacks 2, 4
• Unilateral presentation: Pain confined to one side of the face 1, 4

Physical Examination

• Neurological exam: Typically normal between attacks 4
• Motor assessment: Check for weakness in muscles of mastication—rare finding that suggests secondary cause 2
• Sensory testing: Sensory deficits in trigeminal distribution require urgent imaging to rule out secondary causes 3
• Trigger point identification: Gentle palpation of perioral and nasal regions 2

Mandatory Imaging

Obtain MRI with high-resolution thin-cut sequences through the trigeminal nerve in all suspected cases to identify neurovascular compression, exclude secondary causes (multiple sclerosis, tumors), and guide treatment decisions. 2

Specific MRI Protocol

• 3D heavily T2-weighted sequences combined with MRA to characterize neurovascular compression (83-100% congruence with surgical findings) 2
• Pre- and post-contrast imaging to identify secondary causes such as tumors or multiple sclerosis plaques 2
• Look for: Neurovascular compression at trigeminal nerve root entry zone, demyelinating plaques in brainstem or trigeminal pathway, space-occupying lesions 3, 2

Critical Differential Diagnoses to Exclude

Trigeminal Autonomic Cephalgias (SUNCT/SUNA)

• Distinguishing features: Prominent autonomic symptoms (tearing, conjunctival injection, rhinorrhea, nasal blockage, facial redness), up to 200 attacks daily with NO refractory period between attacks 1, 3, 2
• Pain pattern: Rapid attacks lasting seconds to several minutes, mainly in V1 and V2 distributions 3

Giant Cell Arteritis

• Critical in patients over 50 with temporal region pain—requires urgent treatment to prevent blindness 1, 2

Post-Herpetic Neuralgia

• Distinguishing features: Continuous burning pain (not paroxysmal) at site of previous herpes zoster eruption, with allodynia and hyperalgesia 1, 3

Glossopharyngeal Neuralgia

• Pain location: Deep ear, back of tongue, tonsils, neck—NOT V2/V3 distribution 3
• Triggers: Swallowing, coughing, touching the ear 3
• Associated symptom: May cause syncope 3, 2

Persistent Idiopathic Facial Pain

• Distinguishing features: Continuous, non-anatomical pain without paroxysmal attacks or characteristic triggers 1, 3

Classification After Workup

• Classical TN: Paroxysmal attacks with refractory periods, MRI shows neurovascular compression 1, 5
• Type 2 TN: Prolonged continuous pain between sharp shooting attacks, may originate from central mechanisms 3
• Secondary TN: Caused by multiple sclerosis, tumor, or other structural lesion 4, 6
• Idiopathic TN: No identifiable etiology on imaging 4

Red Flags Requiring Urgent Action

• Continuous pain or ability to trigger attacks repeatedly without pain-free intervals: Prompts MRI evaluation to rule out secondary causes 3
• Sensory deficits: Requires urgent imaging 3
• Age over 50 with temporal pain: Consider giant cell arteritis 1, 2
• Bilateral symptoms: Highly unusual, suggests alternative diagnosis or multiple sclerosis 6

Initial Treatment After Diagnosis

Start carbamazepine as the gold standard first-line treatment, beginning at 200 mg twice daily (400 mg/day), increasing by up to 200 mg/day at weekly intervals until pain control is achieved, with maximum dose of 1200 mg/day. 1, 2, 7

Alternative First-Line Agent

• Oxcarbazepine: Equally effective with fewer side effects 1, 2, 8

When to Consider Surgical Referral

• Early neurosurgical consultation when pain control becomes suboptimal despite medication optimization or medication side effects become intolerable 1, 2
• Microvascular decompression is preferred surgical option for patients with documented neurovascular compression on MRI without significant comorbidities (70% pain-free at 10 years) 1, 2