What are the diagnostic steps and treatment options for trigeminal neuralgia?

Diagnosing Trigeminal Neuralgia

The diagnosis of trigeminal neuralgia is made almost entirely based on the patient's clinical history, with MRI serving a supportive role to identify underlying causes and guide treatment decisions rather than to confirm the diagnosis itself. 1, 2

Clinical Diagnostic Criteria

The diagnosis relies on identifying the following characteristic features in the patient's history:

• Unilateral brief electric shock-like pains that are abrupt in onset and termination, lasting seconds to minutes 2, 3
• Pain distribution limited to one or more branches of the trigeminal nerve (most commonly V2 and V3 divisions) 1, 3
• Trigger factors including light touch stimuli such as washing the face, cold wind, eating, brushing teeth, or talking 1, 3
• Paroxysmal attacks that recur throughout the day with pain-free intervals between episodes 1
• Pain severity described as moderate to very severe, often frightful in intensity 1

Important clinical distinction: Some patients present with Type 2 trigeminal neuralgia, characterized by more prolonged continuous pain between the sharp shooting attacks, which may be of more central origin and responds less well to treatment. 1

Neurological Examination

• In classical trigeminal neuralgia, the neurological examination is typically normal 2
• Examine for light touch-evoked pain in the affected trigeminal distribution 1
• In secondary trigeminal neuralgia, focus on identifying signs of multiple sclerosis or cerebellopontine angle tumors 2
• Sensory changes are rare but should be documented if present 1

Imaging Protocol

MRI with contrast of the trigeminal ganglion is the gold-standard imaging modality and should be performed prior to any interventional procedures. 1, 2, 4

Specific MRI Sequences Required:

• 3-D heavily T2-weighted MRI sequences to visualize the trigeminal nerve and potential neurovascular compression 1
• MR angiography (MRA) combined with high-resolution MRI, which achieves sensitivities of 97-100% and specificities of 100% for detecting neurovascular contact 1
• Pre- and post-contrast imaging to identify and characterize lesions along the entire course of the trigeminal nerve 1
• Thin-cut high-resolution techniques through the brainstem, cisternal segment, Meckel's cave, and peripheral branches 1

Critical Imaging Interpretation Caveat:

MRI is supportive rather than diagnostic for trigeminal neuralgia—both false-positive and false-negative studies occur when assessing neurovascular contact, with congruence rates between imaging and surgical findings ranging from 83-100%. 1 The imaging must be interpreted in the context of the clinical presentation and symptom location. 1

Imaging Findings by Etiology:

• Classical trigeminal neuralgia: Neurovascular compression of the trigeminal nerve root entry zone, with the symptomatic nerve often measuring smaller than the contralateral side 1, 5
• Secondary trigeminal neuralgia: Tumors (mostly benign), multiple sclerosis plaques, or other structural lesions 1, 5
• Idiopathic trigeminal neuralgia: No identifiable cause on imaging 5

Differential Diagnoses to Exclude

Critical time-sensitive exclusion: In patients over age 50 with temporal region pain, immediately check ESR and C-reactive protein to rule out giant cell arteritis, which can cause blindness if untreated. 1

Other conditions to differentiate:

• SUNCT/SUNA syndromes: Shorter attacks (seconds), up to 200 daily, with prominent autonomic features (tearing, conjunctival injection, rhinorrhea) and no refractory period between attacks 1
• Glossopharyngeal neuralgia: Same characteristics as trigeminal neuralgia but pain located deep in the ear, back of tongue, tonsils, or neck; may cause syncope 1
• Post-stroke facial pain: Continuous pain with dysesthesia, associated with other neurological deficits 1
• Persistent idiopathic facial pain: Non-anatomical distribution, continuous pain without the paroxysmal quality 1

Advanced Imaging Techniques (Optional)

• Diffusion tensor imaging (DTI) can detect microstructural tissue changes in symptomatic nerves and may help guide treatment decisions 1, 5
• MR neurography is emerging as useful for characterizing peripheral trigeminal neuropathy 1, 5

Treatment Overview

First-Line Medical Treatment:

Carbamazepine remains the primary drug of choice, starting at 200 mg twice daily and increasing by 200 mg weekly as needed, with maximum doses of 1200 mg/day. 1, 6 Oxcarbazepine is equally effective with fewer side effects. 1

Alternative Medical Options:

• Lamotrigine, baclofen, gabapentin, and pregabalin have evidence supporting their use as second-line or add-on therapy 1, 7

Surgical Considerations:

Obtain neurosurgical consultation early when medical management fails or side effects become intolerable. 1

• Microvascular decompression is the only non-ablative procedure and first-line surgery for patients with documented neurovascular compression, offering 70% pain-free rates at 10 years, though it carries 0.4% mortality and 2-4% risk of hearing loss 1, 2
• Percutaneous ablative procedures (radiofrequency thermocoagulation, glycerol rhizotomy, balloon compression) are recommended for elderly patients or those with major comorbidities 1, 2
• Gamma knife radiosurgery is an alternative for patients unsuitable for other procedures 2, 8