Nervous System & Special Senses

Trigeminal neuralgia: diagnosis and management

Clinical Overview and When to Suspect Trigeminal Neuralgia

— Incidence ~4–13/100,000/year; peak onset age 50–70

— Female:male ≈ 3:2; right side > left

— Bilateral or <40 years old → think secondary cause (MS, tumor)

— Classic TN: neurovascular compression of the trigeminal root entry zone, typically by an aberrant loop of the superior cerebellar artery, causing focal demyelination and ephaptic transmission

— Secondary TN: multiple sclerosis plaque at the pons, cerebellopontine angle (CPA) tumor (vestibular schwannoma, meningioma, epidermoid), AVM, brainstem infarct

— Idiopathic TN: no identifiable cause on MRI

— Older adult with brief (<2 seconds to 2 minutes), stabbing unilateral facial pain

— Triggered by light touch, chewing, brushing teeth, shaving, wind, cold air

— Pain-free intervals between attacks; refractory periods after a paroxysm

— Patients often avoid eating, washing face, talking → weight loss, depression, social withdrawal

— Recurrent unilateral paroxysms in trigeminal distribution

— Severe, electric, shock-like quality

— Precipitated by innocuous stimuli to ipsilateral face

— No clinically evident neurologic deficit (if present → secondary TN)

Board pearl: A patient <40, with bilateral symptoms, sensory loss on exam, or pain lasting hours suggests an alternative diagnosis (MS, tumor, cluster, dental pathology) and mandates MRI before empiric therapy.

Definition: Trigeminal neuralgia (TN, tic douloureux) is a chronic neuropathic facial pain disorder characterized by recurrent, paroxysmal, unilateral, electric-shock–like pain in one or more divisions of cranial nerve V (V2 and V3 most common; V1 <5%).

Epidemiology:

Pathophysiology:

When to suspect on Step 3:

Diagnostic framework (ICHD-3):

Presentation Patterns and Key History

— Sudden onset and termination

— Stabbing/shock-like quality (electric, lancinating)

— Short duration (seconds to <2 minutes per paroxysm; clusters can last hours)

— Superficial (not deep, not throbbing)

— Stimulus-triggered in a trigeminal distribution

— V2 (maxillary) alone or with V3 most common (~35%)

— V3 (mandibular) alone ~20%

— V1 (ophthalmic) alone uncommon (<5%) — if present, exclude herpetic neuralgia, cluster headache

— Always unilateral in classic TN; if bilateral, suspect MS

— Light touch to nasolabial fold, upper lip, gum line, cheek

— Chewing, talking, brushing teeth, cold wind, shaving

— Patients may sit motionless during meals to avoid attacks (clue: weight loss)

— Bouts of attacks lasting weeks to months, followed by spontaneous remissions lasting months to years

— Over time, remissions shorten and attacks intensify ("crescendo" course)

— A refractory period of seconds to minutes follows each paroxysm

— Background dull, aching, burning pain between paroxysms

— Often responds less well to carbamazepine; consider neuropathic adjuncts

— Age <40, bilateral pain, sensory deficit, hearing loss, diplopia, ataxia

— Optic neuritis history, Lhermitte sign → multiple sclerosis

— Progressive numbness, hearing loss → CPA tumor

Key distinction: TN paroxysms last seconds; cluster headache lasts 15–180 minutes with autonomic features (lacrimation, rhinorrhea, ptosis); dental pain is constant and tied to a tooth, not triggered by light touch.

Cardinal pain features (the "5 S's"):

Distribution:

Trigger zones and maneuvers:

Temporal pattern:

TN with concomitant continuous pain ("TN type 2" / "atypical"):

History red flags (suggest secondary cause):

Physical Exam Findings

— Cranial nerves intact, including V1–V3 sensation, corneal reflex, and muscles of mastication

— Any objective deficit shifts the diagnosis toward secondary TN → mandates MRI

— Cranial nerve V: light touch and pinprick in all three divisions bilaterally; corneal reflex (afferent V1, efferent VII) — depression suggests CPA lesion

— Motor V: jaw deviation toward the weak side on opening (pterygoid weakness)

— Cranial nerve VII: facial symmetry — facial weakness with TN suggests CPA pathology, not classic TN

— Cranial nerve VIII: finger rub, Weber/Rinne — hearing loss → vestibular schwannoma

— Cerebellar exam: finger-to-nose, gait, tandem — ataxia suggests posterior fossa lesion or MS

— Optic nerve and visual fields: prior optic neuritis → MS

— Gently stroke nasolabial fold, gingiva, lip — reproduces paroxysm; document distribution for treatment planning

— Do not repeatedly trigger pain; one demonstration suffices

— Weight, BMI — many patients lose weight from food avoidance

— Oral exam to exclude dental caries, abscess, cracked tooth syndrome

— Temporomandibular joint palpation — exclude TMJ disorder

— Sinus tenderness, nasal exam — exclude sinusitis

— PHQ-9 and suicide risk — TN carries one of the highest suicide rates among pain disorders ("suicide disease")

— Anxiety about anticipating attacks impairs quality of life

Step 3 management: A patient presenting with classic TN symptoms but with diminished corneal reflex, V2 numbness, or facial weakness should not be started on empiric carbamazepine alone — order MRI brain with thin-cut trigeminal sequences and gadolinium before treatment to exclude tumor or demyelination.

Hallmark exam finding in classic TN: a normal neurologic examination.

Targeted exam components:

Trigger zone mapping:

General exam:

Mental health screen:

Diagnostic Workup — Initial Evaluation and Imaging

— MRI brain with and without contrast, including high-resolution trigeminal sequences (FIESTA/CISS) — recommended in all patients with suspected TN per AAN/EFNS, because secondary causes are found in ~15%

— Look for: neurovascular compression of root entry zone, MS plaques in pons, CPA tumors, brainstem infarct

— MR angiography helps delineate offending vessel for surgical planning

— MRI contraindicated (non-MRI-conditional pacemaker, severe claustrophobia) — CT with contrast can detect tumors but misses MS plaques and subtle vascular compression

— CBC (baseline WBC, platelets — agranulocytosis, thrombocytopenia risk)

— CMP including sodium (hyponatremia/SIADH risk, especially with oxcarbazepine and in elderly)

— LFTs (hepatotoxicity)

— HLA-B*15:02 screening in patients of Han Chinese, Thai, Malay, Filipino, Vietnamese ancestry — strong association with carbamazepine-induced Stevens-Johnson syndrome/TEN

— HLA-A*31:01 in Northern European, Japanese, Korean populations — milder SJS risk signal

— Pregnancy test in women of childbearing age (teratogenic AEDs)

— Panoramic dental X-ray (orthopantomogram) if dental etiology suspected

— ESR/CRP if giant cell arteritis is on the differential in V1 distribution >50 years old

— Lumbar puncture only if MS workup positive on MRI

Board pearl: Always check HLA-B\*15:02 before initiating carbamazepine in at-risk Asian ancestries — its positive predictive value for SJS is high enough that the FDA mandates screening.

TN is primarily a clinical diagnosis (ICHD-3 criteria). Workup focuses on excluding secondary causes and preparing for pharmacotherapy.

Mandatory neuroimaging in nearly all patients:

When CT is acceptable:

Baseline laboratory studies (prior to starting carbamazepine/oxcarbazepine):

Adjuncts when differential remains broad:

Diagnostic Workup — Advanced and Confirmatory Studies

— 3D T2 FIESTA/CISS sequences show CSF, vessels, and the trigeminal nerve in fine detail

— 3D TOF MRA identifies the offending artery (most often superior cerebellar artery, less commonly AICA or veins)

— Findings of morphologic change (atrophy, displacement, indentation) at the root entry zone are most predictive of surgical benefit from microvascular decompression

— Empiric trial of carbamazepine — dramatic response (>50% pain reduction within days) is itself supportive of the diagnosis (often called the "carbamazepine test")

— Reassess in 4–6 weeks; if no response, reconsider diagnosis

— Trigeminal reflex testing (blink reflex, masseter inhibitory reflex) — abnormal in secondary TN, normal in classic TN; AAN class II evidence as alternative when MRI unavailable

— Not routinely required when MRI accessible

— Refer to dentistry/oral surgery if exam suggests tooth pathology — cracked tooth syndrome classically mimics V2/V3 TN and is curable

— Caution: avoid unnecessary extractions in a patient with true TN (common pitfall — patients may undergo multiple extractions before correct diagnosis)

— Full neuro-axis MRI (brain + cervical/thoracic cord), CSF oligoclonal bands, IgG index, ophthalmology for optic neuritis

— Audiometry for any hearing complaints

— Neurosurgical/otologic referral if vestibular schwannoma or meningioma identified

Key distinction: Classic TN has no objective sensory loss and normal trigeminal reflexes; secondary TN typically demonstrates abnormal blink reflex or sensory deficit and an identifiable structural lesion on MRI — this distinction drives whether to pursue surgical decompression vs treat the underlying cause.

High-resolution MRI trigeminal protocol is the gold standard for documenting neurovascular conflict:

When MRI is non-diagnostic but clinical suspicion remains:

Evoked potentials and electrophysiology:

Dental evaluation:

MS workup if MRI shows demyelinating lesions:

CPA tumor workup:

Risk Stratification and First-Line Management Logic

— Confirm clinical diagnosis (ICHD-3) → obtain MRI → exclude secondary cause → initiate first-line pharmacotherapy → escalate if refractory → surgical referral

— Severity and frequency of attacks — daily debilitating paroxysms warrant prompt pharmacotherapy

— Weight loss, dehydration, suicidality — urgent treatment, consider hospitalization for IV options

— Secondary etiology identified — treat underlying disease (MS DMT, tumor resection) in parallel with symptomatic therapy

— ≥50% pain reduction is realistic; complete remission is the ideal

— Maintain functional status (eating, hygiene, sleep, social engagement)

— Minimize sedation and cognitive side effects, especially in elderly

— Carbamazepine — most effective, NNT ~1.7, but worst side-effect profile

— Oxcarbazepine — comparable efficacy, better tolerability, preferred in many practices

— Lamotrigine, baclofen, gabapentin, pregabalin, phenytoin, topiramate

— Combination therapy reasonable before referring for surgery

— Inadequate response or intolerable side effects after ≥2 adequately dosed agents

— Identified neurovascular conflict on MRI in surgically fit patients

— Patient preference for definitive therapy

— Disease course: bouts and remissions; medications suppress, do not cure

— Side effects of carbamazepine: dizziness, ataxia, hyponatremia, rash, marrow suppression

— Drug interactions (carbamazepine is potent CYP3A4 inducer)

CCS pearl: On a CCS case, after confirming TN, order MRI brain with contrast, CBC, CMP, LFTs, HLA-B\*15:02 (if indicated), pregnancy test, then start carbamazepine 100–200 mg PO BID and schedule 2-week follow-up for titration and labs.

Step 3 management algorithm:

Initial decision points:

Goals of therapy:

First-line drugs (AAN/EFNS Level A):

Second-line / add-on (Level C):

When to refer for surgical evaluation:

Counseling at first visit:

Pharmacotherapy — First-Line Regimens

— Start 100–200 mg PO BID; titrate by 100–200 mg every 3 days as tolerated

— Typical effective dose 600–1200 mg/day divided BID–QID

— Maximum 1200–1600 mg/day

— Use extended-release formulation for steady levels and better tolerability

— Serum levels (4–12 mcg/mL) primarily for toxicity, not efficacy

— Side effects: dizziness, diplopia, ataxia, sedation, hyponatremia (SIADH), leukopenia/agranulocytosis, aplastic anemia, hepatotoxicity, SJS/TEN (HLA-B\*15:02), DRESS

— Drug interactions: strong CYP3A4 inducer — reduces OCPs, warfarin, DOACs, statins, immunosuppressants; autoinduction reduces its own levels over weeks

— Monitor: CBC, CMP, LFTs at baseline, 2 weeks, 1 month, then every 3–6 months

— Start 150–300 mg PO BID; titrate to 600–1800 mg/day

— Maximum 2400 mg/day

— Better tolerated; weaker CYP3A4 induction; less marrow suppression

— Higher rate of hyponatremia (up to 25%) — check sodium at 2 weeks, 1 month, then periodically

— ~25–30% cross-reactivity for rash with carbamazepine — HLA-B*15:02 screening still applies

— Take with food to reduce nausea

— Counsel about driving/falls during initiation

— Avoid abrupt discontinuation (lower seizure threshold)

— Both are teratogenic (neural tube defects, craniofacial); prescribe folic acid 4 mg/day; co-manage with neurology and MFM

— After 6–8 weeks pain-free, attempt gradual dose reduction; many patients enter remission and can be off medication for months to years

Board pearl: A patient on carbamazepine presenting with fever, sore throat, mucosal ulceration, or rash requires immediate CBC and drug discontinuation — agranulocytosis and SJS are life-threatening idiosyncratic reactions.

Carbamazepine (first-line, AAN Level A):

Oxcarbazepine (first-line alternative, AAN Level B):

Practical titration tips:

Pregnancy considerations:

When to consider taper:

Procedural and Surgical Management

— Failure or intolerance of ≥2 first-line agents at adequate doses

— Severe disease impairing nutrition, hygiene, or causing suicidality

— Patient preference for definitive therapy

— Most effective, durable therapy for classic TN with documented neurovascular conflict

— Suboccipital craniotomy; Teflon pledget placed between offending vessel and trigeminal root entry zone

— Initial pain relief 80–90%; 10-year durability 70%

— Preserves facial sensation (key advantage)

— Risks: CSF leak, hearing loss (~1–3%), facial weakness, stroke, anesthesia dolorosa (rare), perioperative mortality <0.5%

— Best candidates: younger, surgically fit, classic TN with imaging-confirmed compression

— Radiofrequency thermocoagulation of Gasserian ganglion — high initial relief; recurrence 25% at 3 years; causes sensory loss

— Glycerol rhizotomy — less precise, easier to perform

— Balloon compression — useful for V1 (preserves corneal reflex less, but effective)

— Common adverse effect: facial numbness; rare but feared: anesthesia dolorosa, corneal anesthesia with V1 lesions

— Non-invasive; targets trigeminal root

— Onset of relief delayed 4–8 weeks

— Initial response 70–80%; durability less than MVD

— Good option for poor surgical candidates and MS-related TN

— Lamotrigine and misoprostol have evidence; surgical options include percutaneous procedures and radiosurgery — MVD less effective because pathology is central demyelination, not compression

Step 3 management: Refer the young, healthy patient with classic TN and MRI-confirmed vascular compression for microvascular decompression; offer percutaneous rhizotomy or Gamma Knife to the elderly or comorbid patient who cannot tolerate craniotomy.

When to refer for procedures:

Microvascular decompression (MVD) — Jannetta procedure:

Percutaneous ablative procedures (better for elderly, frail, MS-associated TN):

Stereotactic radiosurgery (Gamma Knife):

For MS-associated TN:

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher sensitivity to AED side effects: falls, sedation, confusion, hyponatremia

— Start low, go slow: carbamazepine 100 mg PO at bedtime, titrate weekly

— Prefer extended-release formulations

— Polypharmacy review — carbamazepine reduces serum levels of warfarin, DOACs, statins, calcium channel blockers, levothyroxine

— Check sodium within 1–2 weeks of initiation — older adults are at highest risk of severe hyponatremia (especially on thiazides or SSRIs)

— Screen for driving safety, fall risk, cognitive baseline (Mini-Cog or MoCA) before starting

— Gabapentin and pregabalin require renal dose adjustment (CrCl-based); accumulation causes myoclonus, sedation, confusion

— Oxcarbazepine active metabolite (MHD) cleared renally — reduce by 50% if CrCl <30 mL/min

— Carbamazepine itself is largely hepatically metabolized; modest dose reduction

— Carbamazepine, oxcarbazepine, lamotrigine are hepatically metabolized

— Avoid carbamazepine in active hepatitis or severe cirrhosis

— Gabapentin and pregabalin are renally cleared and are safer in liver disease

— Monitor LFTs more frequently (monthly initially)

— In hospice or severely frail patients, low-dose gabapentin or baclofen may be safer than carbamazepine

— Percutaneous rhizotomy can be performed under local with minimal sedation — option in those unfit for craniotomy

— Long-term carbamazepine accelerates vitamin D metabolism → osteomalacia/osteoporosis — supplement vitamin D 1000–2000 IU/day; DEXA in long-term users

Key distinction: In an elderly patient newly started on oxcarbazepine who develops lethargy and confusion at 2 weeks, check a sodium level first — hyponatremia is far more common than primary CNS toxicity in this scenario.

Elderly patients (the most common TN demographic):

Renal impairment:

Hepatic impairment:

Frailty and end-of-life considerations:

Bone health:

Special Populations — Pregnancy, Pediatrics, MS, and Post-Herpetic Overlap

— Carbamazepine: Category D — neural tube defects (~1%), craniofacial abnormalities, fingernail hypoplasia, developmental delay

— Oxcarbazepine: similar concerns, less data

— Lamotrigine has the best safety profile among AEDs in pregnancy — preferred if pharmacotherapy is essential

— Folic acid 4 mg/day preconception and through first trimester for any woman on AEDs

— Vitamin K 10 mg/day in last month of pregnancy if on enzyme-inducing AEDs (carbamazepine) to reduce neonatal hemorrhage

— Co-manage with neurology and maternal-fetal medicine; enroll in AED pregnancy registry

— Surgical options (MVD, percutaneous rhizotomy) deferred until postpartum when possible

— Carbamazepine, oxcarbazepine, gabapentin compatible with breastfeeding; monitor infant for sedation

— Rare; consider secondary causes (tumor, AVM, MS) — MRI mandatory

— Carbamazepine remains first-line; pediatric dosing 10–20 mg/kg/day divided BID

— 2–5% of MS patients develop TN; often bilateral or recurrent

— Lamotrigine and misoprostol have unique evidence in MS-related TN

— Optimize disease-modifying therapy

— Surgical: prefer Gamma Knife or percutaneous procedures over MVD (no vascular conflict)

— V1 distribution after herpes zoster ophthalmicus; continuous burning pain, not paroxysmal

— Treat with gabapentin/pregabalin, TCAs, topical lidocaine — carbamazepine less effective

— Prevent with recombinant zoster vaccine (Shingrix) in adults ≥50

Board pearl: A 28-year-old woman with new bilateral V2 pain, intermittent diplopia, and prior optic neuritis has MS until proven otherwise — order MRI brain and cervical spine with contrast before starting any AED.

Pregnancy:

Lactation:

Pediatric TN:

Multiple sclerosis–associated TN:

Postherpetic trigeminal neuralgia (different entity):

Complications and Adverse Outcomes

— Weight loss and malnutrition from food avoidance — track BMI, prealbumin if severe

— Dehydration from inability to drink

— Poor oral hygiene from avoidance of brushing → caries, periodontal disease

— Depression, anxiety, suicidal ideation — TN has one of the highest suicide rates among pain disorders ("the suicide disease")

— Social withdrawal and occupational impairment

— Carbamazepine:

– Hyponatremia/SIADH (10–15%; severe in 1–2%)

– Aplastic anemia (rare, ~1:200,000) and agranulocytosis

– SJS/TEN — risk highest in first 8 weeks; HLA-B*15:02

– DRESS syndrome — rash, fever, eosinophilia, multiorgan involvement

– Hepatotoxicity — monitor LFTs

– Osteopenia with chronic use

– CYP3A4 induction → contraceptive failure, anticoagulant failure

— Oxcarbazepine: hyponatremia (more common), rash

— Gabapentinoids: sedation, peripheral edema, weight gain, misuse potential

— Baclofen: sedation, withdrawal seizures if abruptly stopped

— MVD: CSF leak, meningitis, hearing loss, cerebellar injury, stroke, death (rare)

— Percutaneous ablative procedures: facial numbness (common, expected), anesthesia dolorosa (painful numbness; very difficult to treat), corneal anesthesia → neurotrophic keratitis, masseter weakness

— Gamma Knife: facial numbness (~20% at 3 years), delayed onset

— 10-year recurrence after MVD ~30%

— Higher after percutaneous procedures and radiosurgery

— Recurrent disease may respond to medications again, repeat procedure, or alternative surgery

Step 3 management: A patient 1 week post-percutaneous rhizotomy presents with eye redness, decreased vision, and corneal opacity — suspect neurotrophic keratitis from corneal anesthesia → urgent ophthalmology consult, lubricating drops, and possibly tarsorrhaphy.

Disease-related complications:

Medication-related complications:

Procedure-related complications:

Recurrence:

When to Escalate Care — Inpatient and Consultation Triggers

— Status trigeminus / refractory crisis — continuous severe paroxysms preventing eating, drinking, sleeping

— Suicidal ideation related to pain — psychiatric admission for safety

— Severe hyponatremia (Na <125) from carbamazepine/oxcarbazepine — admit for sodium correction

— Suspected SJS/TEN, DRESS, or aplastic anemia — burn unit or ICU-level care

— New focal neurologic deficits suggesting acute structural cause (tumor hemorrhage, stroke)

— IV fosphenytoin 15 mg PE/kg load over 30 minutes — can abort severe paroxysms within hours; cardiac monitoring required

— IV lidocaine infusion (1.5–5 mg/kg over 30–60 minutes with telemetry) — second-line abortive

— Bridge to oral carbamazepine/oxcarbazepine

— Treat dehydration with IV fluids; nutrition consult

— Neurology — diagnosis confirmation, treatment optimization, MS workup

— Neurosurgery — procedural candidacy, MVD planning

— Pain medicine — multimodal regimens, refractory cases

— Psychiatry — depression, suicidality screening and management

— Ophthalmology — V1 procedures, corneal anesthesia

— Dentistry/oral surgery — exclude dental etiology before procedures

— Nutrition — significant weight loss

— No improvement after 2–4 weeks of titrated first-line therapy → add second agent or switch

— Two failed monotherapies → surgical/procedural referral

— Intolerable side effects despite dose adjustment

CCS pearl: Admit a patient with severe TN crisis unable to maintain hydration → order IV fluids, IV fosphenytoin load, neurology consult, MRI brain with contrast, telemetry, and PHQ-9/suicide screen, then transition to oral oxcarbazepine before discharge with 2-week neurology follow-up.

Indications for hospitalization:

Acute inpatient management of TN crisis:

Specialty consultations:

Outpatient escalation criteria:

Key Differentials — Other Facial Pain Syndromes

— Paroxysmal pain in throat, tonsillar fossa, ear, base of tongue

— Triggered by swallowing, coughing, talking, yawning

— Can cause bradycardia, syncope (vagal coactivation)

— Treatment: same first-line (carbamazepine, oxcarbazepine)

— Severe unilateral periorbital/temporal pain lasting 15–180 minutes, occurring in clusters

— Autonomic features: lacrimation, conjunctival injection, ptosis, miosis, rhinorrhea, nasal congestion, restlessness

— Male predominance, circadian pattern

— Treatment: high-flow O₂, subcutaneous sumatriptan; prevention with verapamil

— Shorter (2–30 minutes), more frequent (>5/day) than cluster

— Absolute response to indomethacin (diagnostic)

— Very brief (5–240 seconds) unilateral V1 attacks with autonomic features

— Triggered cutaneously like TN but with autonomic signs

— Treatment: lamotrigine, IV lidocaine

— Key feature distinguishing from TN: prominent ipsilateral autonomic symptoms

— Continuous, dull, poorly localized pain not in nerve distribution

— No triggers, no paroxysms

— Treatment: TCAs, SNRIs, CBT — not carbamazepine

— Continuous burning, allodynia after shingles

— Treatment: gabapentin/pregabalin, TCAs, topical lidocaine

Key distinction: Autonomic features (tearing, rhinorrhea, ptosis) point to trigeminal autonomic cephalalgias, not TN — and a >5-minute attack essentially excludes classic TN.

Glossopharyngeal neuralgia (CN IX):

Cluster headache:

Paroxysmal hemicrania:

SUNCT/SUNA:

Trigeminal autonomic cephalalgias overlap:

Atypical facial pain / persistent idiopathic facial pain:

Postherpetic neuralgia (V1 zoster):

Key Differentials — Non-Neurologic and Structural Mimics

— Cracked tooth syndrome — sharp pain on biting, often V2/V3 distribution, may be triggered by cold

— Pulpitis, periapical abscess, atypical odontalgia

— Pitfall: patients undergo multiple extractions before correct TN diagnosis; conversely, true dental pathology is missed in patients labeled TN

— Always perform panoramic radiograph and dental exam in V2/V3 pain

— Pain on chewing, TMJ clicking, limited opening, tenderness at preauricular area

— Continuous aching, not paroxysmal

— Treatment: bite splint, NSAIDs, jaw rest

— Constant facial pressure, postnasal drip, nasal congestion

— Not triggered by light touch

— Age >50, temporal headache, jaw claudication, scalp tenderness, vision loss

— Elevated ESR/CRP — start prednisone immediately if suspected, then temporal artery biopsy

— Sialolithiasis — pain with eating, swelling

— Progressive facial numbness, hearing loss, ataxia

— MRI diagnostic; neurosurgical referral

— Younger patient, bilateral or alternating sides, other neurologic findings

— Especially in Southeast Asian patients; persistent unilateral ear pressure, epistaxis, V2/V3 involvement, cervical lymphadenopathy

— Immunocompromised, diabetes — V1 pain with CN VI palsy (Gradenigo)

Board pearl: A patient with apparent "TN" who has had multiple dental extractions without relief should prompt re-evaluation with MRI and reconsideration of classic TN vs persistent idiopathic facial pain — empiric extractions are a recognized pitfall.

Dental pathology (the most common mimic and misdiagnosis):

Temporomandibular joint (TMJ) disorder:

Sinusitis (especially maxillary):

Giant cell arteritis:

Salivary gland disease:

CPA tumors (vestibular schwannoma, meningioma, epidermoid):

Posterior fossa demyelination (MS):

Nasopharyngeal carcinoma:

Petrous apicitis, skull base osteomyelitis:

Long-Term Plan — Maintenance, Tapering, and Secondary Prevention

— Once pain controlled, maintain lowest effective dose

— Reassess every 3–6 months for efficacy, side effects, lab monitoring

— Trial gradual taper after 6–8 weeks of pain freedom — many patients enter remission and can be medication-free for months to years

— Taper carbamazepine by 100–200 mg every 1–2 weeks

— Counsel patient that pain may recur and prompt restart is appropriate

— If monotherapy partial response, add a second-line agent (lamotrigine, baclofen, gabapentin) before referring for surgery

— Reduce primary agent toward minimum effective dose

— Avoid known triggers when possible (cold wind → scarves; light touch → soft toothbrush, lukewarm water)

— Soft diet during exacerbations

— Stress reduction, sleep hygiene — stress and fatigue lower attack threshold

— Treat depression and anxiety aggressively — SSRIs, SNRIs (duloxetine may also help neuropathic pain), CBT

— Address dental and oral hygiene during pain-free intervals

— Recombinant zoster vaccine (Shingrix) in adults ≥50 to prevent postherpetic V1 neuralgia (a separate entity but coexists)

— Replace combined OCPs with non-hormonal contraception or higher-estrogen formulations

— Adjust warfarin/DOAC dosing with INR monitoring (DOACs largely contraindicated with carbamazepine)

— Re-verify levels of immunosuppressants, antiepileptics, antiretrovirals

— Vitamin D 1000–2000 IU/day; calcium per RDA; DEXA in long-term users >65 or with risk factors

Step 3 management: At every TN follow-up, document pain frequency/severity, weight/BMI, mood/PHQ-9, side effects, sodium and CBC, medication interactions, and willingness to attempt taper — these are the high-yield outpatient longitudinal items.

Maintenance pharmacotherapy:

Combination therapy:

Lifestyle modifications:

Comorbidity management:

Vaccination:

Drug interaction surveillance for carbamazepine users:

Bone health:

Follow-Up, Monitoring, and Counseling

— 2 weeks after initiation: efficacy, side effects, check sodium, CBC, LFTs

— 1 month: dose optimization, repeat labs

— 3 months: stability assessment, taper discussion if pain-free

— Every 6 months thereafter: labs, weight, mood, drug interaction review

— CBC, CMP (Na, Cr), LFTs at baseline → 2 weeks → 1 month → every 3–6 months

— Hold drug for WBC <3000, ANC <1500, platelets <100,000, AST/ALT >3× ULN, Na <130

— Numeric Rating Scale (NRS) for pain at each visit

— Pain frequency diary

— PHQ-9 at every visit; C-SSRS if depression positive

— BMI, weight trajectory

— Disease is chronic-relapsing, not curable but manageable

— Importance of medication adherence — abrupt discontinuation can lower seizure threshold and trigger pain return

— Recognize red-flag side effects: rash, fever, mouth sores, bruising, jaundice, severe dizziness, confusion

— Carry a medication list to all providers given multiple interactions

— Pre-op: realistic expectations, recurrence risk, sensory changes

— Post-op: wound care, signs of CSF leak (clear nasal drainage, postural headache), meningitis

— Continue AEDs initially post-op; taper after sustained pain freedom

— Counsel about sedation, dizziness during titration; state DMV reporting rules vary

— Facial Pain Association, peer support groups — addresses isolation common in TN

CCS pearl: Schedule routine follow-up at 2 weeks after starting carbamazepine for CBC, BMP, LFTs, sodium check, and pain reassessment — neglecting this visit on a CCS case forfeits points for monitoring.

Visit cadence:

Laboratory monitoring on carbamazepine:

Functional and quality-of-life metrics:

Patient education and self-management:

Counseling specific to surgical patients:

Driving safety:

Support resources:

Ethical, Legal, and Patient Safety Considerations

— Carbamazepine consent should specifically address SJS/TEN, agranulocytosis, aplastic anemia, hyponatremia, hepatotoxicity, teratogenicity

— Document HLA-B*15:02 testing decision in at-risk populations; failure to test before prescribing is a recognized standard-of-care lapse and medicolegal exposure

— Provide written medication guides

— Carbamazepine reduces efficacy of combined oral contraceptives, patches, rings, progestin implants, and emergency contraception (levonorgestrel)

— Recommend copper or levonorgestrel IUD or depot medroxyprogesterone acetate as preferred contraception

— Document discussion before prescribing in any reproductive-age female

— Preconception counseling for women on AEDs; switch to lamotrigine before conception when feasible

— Document risk-benefit discussion; enroll in AED pregnancy registry (ethically beneficial for future patients)

— TN carries elevated suicide risk; standard of care includes routine PHQ-9 and C-SSRS screening

— Positive screen → safety plan, means restriction, psychiatric referral, possibly involuntary hold if imminent risk

— Disclose risks: stroke, hearing loss, facial numbness, anesthesia dolorosa (specific, devastating)

— Discuss alternatives including continued medical therapy

— At hospital discharge: medication reconciliation must flag carbamazepine drug interactions with any new medications (warfarin, DOACs, statins, immunosuppressants, antiretrovirals)

— Communicate dose, monitoring plan, and follow-up to PCP within 48–72 hours

— Counsel and document sedation risk during titration; some states require reporting for impaired drivers

Board pearl: Prescribing carbamazepine to a woman of reproductive age without contraceptive counseling and pregnancy planning is a recognized safety/standard-of-care failure — a high-yield Step 3 ethics/safety vignette.

Informed consent for high-risk medications:

Contraceptive counseling (a Step 3 favorite):

Pregnancy and shared decision-making:

Suicide risk and mandatory action:

Surgical consent for MVD and ablative procedures:

Transitions of care safety:

Driving and occupational safety:

High-Yield Associations and Rapid-Fire Facts

— Peak age 50–70; female > male; right > left

— Bilateral TN <40 yo → multiple sclerosis until proven otherwise

— Superior cerebellar artery is the most common offending vessel

— Root entry zone at the pons — site of demyelination

— V2 + V3 distribution most common (~35% combined)

— Blood dyscrasias (aplastic anemia, agranulocytosis)

— Ataxia, Nausea, Arrhythmia (AV block), Neural tube defects, Aplastic anemia, SJS/SIADH

Key distinction: Seconds-long shocks triggered by touch = TN; minutes-to-hours with autonomic features = trigeminal autonomic cephalalgia; constant burning post-zoster = postherpetic neuralgia — different drugs, different management.

Demographics:

Anatomy:

First-line drug: Carbamazepine (Level A); oxcarbazepine (Level B alternative)

Pharmacogenomics: HLA-B\*15:02 → SJS/TEN with carbamazepine in Han Chinese, Thai, Malay, Filipino, Vietnamese ancestry

Carbamazepine adverse effects mnemonic — "BANANAS":

Oxcarbazepine signature side effect: hyponatremia (up to 25%)

Imaging of choice: MRI brain with high-resolution trigeminal sequences (FIESTA/CISS) + MRA

Surgical gold standard: Microvascular decompression (Jannetta) — best durability for classic TN

Best for elderly/frail: Percutaneous procedures (RF rhizotomy, balloon, glycerol) or Gamma Knife

Best AED in pregnancy: Lamotrigine

MS-associated TN: treat with lamotrigine, optimize MS DMT, prefer Gamma Knife over MVD

Glossopharyngeal neuralgia: triggered by swallowing; can cause syncope/bradycardia

Postherpetic V1 neuralgia: continuous burning, treat with gabapentin/pregabalin, prevent with Shingrix

Suicide disease: routine PHQ-9 + C-SSRS screening

Drug interactions of carbamazepine: strong CYP3A4 inducer → contraceptive failure, warfarin/DOAC underdosing

Bone health: chronic AED use → osteomalacia; supplement vitamin D

TN attack duration: seconds to <2 minutes (key distinguishing feature)

Board Question Stem Patterns

— 62-year-old woman, recurrent unilateral electric-shock pain in right cheek lasting seconds, triggered by brushing teeth and cold air, normal neuro exam → Diagnosis: trigeminal neuralgia → Next step: MRI brain with contrast → Treatment: carbamazepine

— 32-year-old woman with bilateral facial pain, prior episode of optic neuritis, mild ataxia → Diagnosis: MS-associated TN → MRI brain/cord with contrast

— Patient of Han Chinese ancestry scheduled to start carbamazepine → Next step: order HLA-B\*15:02 testing before initiation

— Elderly woman on oxcarbazepine presents with lethargy, confusion at 3 weeks → Next step: check serum sodium (SIADH)

— Patient on carbamazepine x 3 weeks with fever, mucosal ulcers, rash → discontinue, CBC, dermatology — SJS

— Woman on combined OCP started on carbamazepine, presents with pregnancy → counseling failure: carbamazepine reduces OCP efficacy; should have been on IUD or DMPA

— Healthy 55-year-old with classic TN, failed carbamazepine and oxcarbazepine, MRI shows SCA loop compressing trigeminal root → Microvascular decompression

— 82-year-old frail patient, intolerant of carbamazepine, severe TN → Percutaneous radiofrequency rhizotomy or Gamma Knife, not MVD

— Patient with paroxysmal pain triggered by swallowing with syncope → Glossopharyngeal neuralgia

— Pain on chewing, clicking, limited jaw opening → TMJ disorder, not TN

— Unilateral periorbital pain lasting 90 minutes with tearing and ptosis → Cluster headache, treat with O₂ and sumatriptan

— Woman with TN planning pregnancy → switch from carbamazepine to lamotrigine, add folic acid 4 mg/day

— Post-rhizotomy patient with painful facial numbness → anesthesia dolorosa, very difficult to treat

Step 3 management: Recognize the classic stem trio — older adult + seconds-long electric facial pain + light-touch trigger + normal exam → MRI → carbamazepine → 2-week labs follow-up. Anything that deviates (young age, bilateral, sensory loss, autonomic features, prolonged duration) signals an alternative pathway.

Classic TN stem:

Secondary TN clue:

Drug safety stem:

Hyponatremia stem:

Aplastic anemia/SJS stem:

Drug interaction stem:

Surgical referral stem:

Elderly procedural choice:

Glossopharyngeal mimic stem:

Mimic stem — TMJ:

Mimic stem — cluster:

Pregnancy planning stem:

Anesthesia dolorosa stem:

One-Line Recap

Trigeminal neuralgia is paroxysmal unilateral facial pain in a trigeminal distribution, most often caused by superior cerebellar artery compression at the root entry zone, diagnosed clinically with MRI to exclude secondary causes, treated first-line with carbamazepine or oxcarbazepine, and definitively managed with microvascular decompression in suitable surgical candidates.

— Recurrent seconds-long, electric-shock unilateral V2/V3 pain triggered by light touch, chewing, cold wind, with a normal neurologic exam

— MRI brain with high-resolution trigeminal sequences in all patients to exclude MS, CPA tumor, vascular malformation

— Red flags for secondary TN: age <40, bilateral pain, sensory deficit, other cranial nerve findings

— Carbamazepine (most effective, NNT ~1.7) or oxcarbazepine (better tolerated)

— Screen HLA-B\*15:02 in at-risk Asian ancestries before carbamazepine

— Monitor CBC, sodium, LFTs at 2 weeks, 1 month, then every 3–6 months

— Counsel on contraception, teratogenicity, and CYP3A4 drug interactions

— After failure of ≥2 adequately dosed agents, refer for procedure

— Microvascular decompression = most durable, preferred in young/fit patients with imaging-confirmed compression

— Percutaneous rhizotomy or Gamma Knife for elderly, frail, or MS-associated TN

— Screen for depression and suicidality ("suicide disease") at every visit

— Attempt drug taper after 6–8 weeks of pain freedom

— Address bone health, drug interactions, contraception, and pregnancy planning as part of comprehensive Step 3 management

Board pearl: Anything that breaks the classic profile — bilateral, young, sensory loss, autonomic features, or attacks lasting minutes — should redirect you away from primary TN and toward MS, a structural lesion, or an alternative facial pain syndrome.

Diagnosis:

First-line therapy:

Refractory disease and surgery:

Longitudinal care: