Trigeminal neuralgia

Trigeminal neuralgia, or tic douloureux, is a condition characterized by attacks of facial pain in the area of one or more branches of the trigeminal nerve. The pain is typically very severe in intensity, has a sharp, stabbing quality, and lasts for several seconds. Attacks can occur without provocation but are sometimes triggered by innocuous stimuli like chewing. It is a rare condition that typically manifests in patients above the age of 60 years and affects women more often than men. Trigeminal neuralgia is a clinical diagnosis. Neuroimaging (preferably MRI) is used for further classification. Classical trigeminal neuralgia (CTN) is caused by neurovascular compression of the trigeminal nerve root, while secondary trigeminal neuralgia (STN) is caused by an underlying condition (e.g., multiple sclerosis). If there is no identifiable cause, it is referred to as idiopathic trigeminal neuralgia (ITN). Anticonvulsants (especially carbamazepine) are the mainstay of therapy. Surgery may be indicated if pharmacological treatment is insufficient. Options include microvascular decompression (MVD) and transcutaneous procedures that aim to lesion sensory fibers of the trigeminal nerve root or ganglion.

• Sex: ♀ > ♂ (2:1)
• Peak incidence: 60–70 years

References:^[1][2]

Epidemiological data refers to the US, unless otherwise specified.

• Classical trigeminal neuralgia (CTN): caused by neurovascular compression, most often by an aberrant loop of a neighboring artery (usually the superior cerebellar artery) ^[3]
• Secondary trigeminal neuralgia (STN): caused by a major underlying neurological disease, most frequently multiple sclerosis, a tumor at the cerebellopontine angle, or arteriovenous malformation. ^[3]
• Idiopathic trigeminal neuralgia (ITN): no identifiable cause (unremarkable findings on MRI and electrophysiological tests) ^[3]

• Unilateral facial pain: paroxysmal, severe shooting or stabbing (like an electric shock), followed by a burning ache
  • Lasts several seconds; (in rare cases, several minutes) and may occur up to 100 times per day
  • Typically shoots from mouth to the angle of the jaw on the affected side ^[4]
  • Occurs either at rest or is triggered by movements such as chewing, talking, or touch (e.g., brushing teeth, washing face); becomes worse with stimulation
• Facial spasms may occur.
• Psychological distress: ranging from dysphoria to severe depression with suicidal tendencies
• Usually progressive course

References:^[5][6]

Trigeminal neuralgia is a clinical diagnosis. MRI should be performed at least once in the patient's lifetime to evaluate for structural etiology.

Diagnostic criteria

• All of the following criteria must be fulfilled: ^[3]
  • Recurring unilateral face pain in the area innervated by one or more divisions of the trigeminal nerve
  • Pain characteristics
    • Severe
    • Lasting no more than two minutes
    • Quality: sharp, shooting, stabbing, or electric shock-like
  • Triggered by innocuous stimuli in the area innervated by the affected trigeminal nerve divisions
  • Another ICHD-3 diagnosis does not better explain the symptoms.

Imaging

• MRI head without and with IV contrast and MRA
  • Indications
    • All patients with associated neurological deficits
    • In patients with a clinically established diagnosis, MRI should be performed at least once in a patient's lifetime (to identify the underlying etiology). ^[7][8][9]
  • Supportive findings ^[8][10]
    • Classical trigeminal neuralgia: vascular compression with deformation or atrophy of the trigeminal nerve root ^[3][10]
    • Secondary trigeminal neuralgia: signs of an underlying condition (e.g., demyelination plaques in multiple sclerosis, tumor at the cerebellopontine angle) ^[10]
    • Idiopathic trigeminal neuralgia: typically normal
• CT head and maxillofacial with IV contrast and CTA
  • Indication: contraindications to MRI
  • Findings: similar to those in MRI ^[8]

Patients with trigeminal neuralgia and an accompanying neurological deficit require urgent imaging studies (ideally MRI) to rule out a mass or vascular abnormalities. ^[11]

Additional investigations

• Electrophysiologic trigeminal reflex measurement ^[10][12][13]
  • Indication: differentiation of CTN from STN (if MRI is not possible)
  • Procedure: The supraorbital, infraorbital, or mental nerve is stimulated electrically and the response recorded with surface electrodes.
  • Findings
    • Classical trigeminal neuralgia: normal findings
    • Secondary trigeminal neuralgia: reflex abnormalities on the affected side (e.g., increased latency)

• Other differential diagnoses of headache, e.g., migraine, cluster headache
• Otitis media or externa
• Shingles
• Dental infection
• Sinusitis
• Glaucoma
• Temporomandibular joint dysfunction

References: ^[11]

The differential diagnoses listed here are not exhaustive.

Approach

• Manage acute pain crises, e.g., with intravenous lidocaine.
• Start regular anticonvulsant therapy.
• Consult neurology.
• Consider neurosurgical intervention for poorly-controlled persistent symptoms or intolerable treatment side effects.

Inpatient treatment may be necessary for intractable pain in an acute exacerbation. Neurology specialists can adjust antiepileptic medications, provide IV medications, and consider referral for neurosurgical intervention. ^[12]

Medical therapy ^{[6][12][14][15]}

Acute exacerbation

• Consider lidocaine infusion (only under the direction of an experienced physician) with continuous cardiac monitoring. ^[12][16]
• Further treatment options include : ^[16]
  • Phenytoin or fosphenytoin infusion
  • Oral or nasal application of lidocaine
  • Local anesthetic trigger point injection
  • Sumatriptan (SQ, nasal, or oral)

Avoid opioids as they are ineffective for managing pain from trigeminal neuralgia. ^[12]

Chronic therapy

• First-line treatment: choose from one of the following ^[12][14]
  • Carbamazepine
  • Oxcarbazepine
• Alternatives and additional considerations
  • Other anticonvulsants (e.g., lamotrigine, oxcarbazepine, baclofen, phenytoin, gabapentin) may be used on an individual basis.
  • Treatment should be initiated and supervised by neurological specialists.

Surgical therapy ^[12][14][15]

Indications

• Insufficient response to medical therapy or intolerable side effects ^[15]
• Risks and benefits in the individual patient must be carefully weighed.
• Most procedures have only been investigated in small studies in patients with CTN, and the evidence for their efficacy in patients with STN is even more limited. ^[12][14]

Microvascular decompression (MVD) ^[12][14]

• Indications: Initially established in patients with CTN and signs of neural compression, but may be considered in ITN and STN as well
• Description
  • Major neurosurgical procedure that requires a high level of expertise
  • Following a suboccipital craniotomy, the blood vessel compressing the trigeminal nerve root is identified and separated from the nerve. A piece of sponge-like material may be placed between the blood vessel and nerve. ^[17]
  • Achieves the most sustained pain relief in comparison to other invasive treatments ^[15]
• Complications include ^[15]
  • Aseptic meningitis
  • Ipsilateral hearing loss
  • Sensory loss
  • Cerebrospinal fluid leakage
  • Stroke
  • Hematomas

Percutaneous neuroablative procedures ^[6][12][15]

• Description
  • Insertion of a trocar or needle through the foramen ovale to lesion sensory fibers in the trigeminal nerve root
  • Ablation via heat (thermocoagulation), pressure (balloon compression), or chemicals (glycerol injection)
• Complications include
  • Sensory loss (in up to 50% of patients) ^[15]
  • Dysesthesia
  • Anesthesia dolorosa
  • Corneal numbness ^[18]
• Comparison to MVD
  • Craniotomy is not necessary, resulting in lower periprocedural risk.
  • Lower risk of serious complications
  • Similar rates of initial pain relief (∼ 90%)
  • Lower long-term efficacy (recurrence of pain in around 50% after 5 years) ^[14]

Gamma knife radiosurgery ^[12][15]

• Indications: Consider in patients who cannot undergo open surgery, e.g., due to frailty or those who are anticoagulated.
• Description: Stereotactic application of high-intensity gamma rays to damage the trigeminal ganglion
  • Pain relief may be delayed (∼ 1 month).
• Complications include:
  • Sensory loss
  • Paresthesia
  • Recurrence of pain in around 50% of patients 3 years after treatment ^[15]

• Evaluate for accompanying neurological deficits.
• Obtain urgent neuroimaging if indicated.
• Treat acute pain.
• Initiate anticonvulsant therapy.
• Refer to an outpatient neurological specialist.
• Order an outpatient brain MRI if not already obtained.
• Consider inpatient treatment for intractable pain.