Trigeminal Neuralgia & Bell Palsy

Meet the patient

A 62-year-old man winces as he describes electric shocks firing through his right cheek every time he shaves, eats, or steps into a cold wind. Each spasm lasts a few seconds, vanishes, and leaves him terrified of the next. Between attacks his face is normal — no numbness, no weakness. He has had three teeth extracted in the last six months; they did not help.[1]

A different patient arrives in your acute clinic at 9 am — a 34-year-old who woke with the right side of her face drooping. She cannot close her right eye, drools when she drinks, and has lost the taste on the front of her tongue. Her forehead does not move on the right when she raises her brows. The question that decides her next hour is the same one that runs the whole topic: is the forehead involved (Bell palsy — steroids) or is it spared (UMN stroke — thrombolysis pathway)?[2][3]

Two cranial nerves, one bedside decision

These are two of the commonest cranial nerve syndromes in practice, paired because both present acutely to the same clinics, both are clinical diagnoses made at the bedside, and both hinge on a single discriminator an examiner will probe relentlessly. They do not share a mechanism — and confusing them, or worse, labelling a stroke as Bell palsy, is a classic and serious error.[1]

Trigeminal neuralgia (TN, tic douloureux) is defined by its pain quality, not by any scan. The European Academy of Neurology 2019 guideline describes it as recurrent, unilateral, paroxysmal facial pain in one or more trigeminal divisions, lasting a fraction of a second to two minutes, of severe intensity, with an electric-shock, stabbing or shooting quality, precipitated by innocuous stimuli — washing, shaving, eating, a cold wind. Critically, there is no persistent neurological deficit between attacks in classical TN.[1]

Bell palsy is an acute, unilateral, peripheral (lower motor neurone) facial-nerve palsy of unknown cause that develops over under 72 hours and is not attributable to stroke, infection, tumour or trauma. The pivotal skill is distinguishing an LMN lesion (Bell — forehead and eye involved) from a UMN lesion (cortical stroke — forehead spared), because the management and urgency are entirely different. It is a diagnosis of exclusion: secondary causes of an acute LMN facial palsy must be ruled out at the bedside first.[2][3]

Classification — two diseases, three red banners

Trigeminal neuralgia sorts by aetiology into three mutually exclusive categories. Classical TN is a neurovascular conflict — a vessel (most often the superior cerebellar artery) compressing the trigeminal root at the root-entry zone with demonstrable morphological change. Secondary TN is a demyelinating plaque of MS or a tumour (meningioma, schwannoma, epidermoid) at the root or Gasserian ganglion. Idiopathic TN is the label when neither is found. By phenotype, TN is purely paroxysmal or TN with concomitant continuous pain (TN type 2) — a constant dull ache beneath the shocks that is harder to treat and carries a poorer prognosis.[1]

Facial weakness sorts by the level of the lesion — the single most important diagnostic fork. An LMN palsy (the Bell pattern) paralyses the whole ipsilateral hemiface: forehead, eye and mouth all fail, because the facial nucleus and all its peripheral branches are damaged. A UMN palsy affects only the contralateral lower face with forehead sparing, because the upper face receives bilateral cortical innervation — one intact cortex still drives the forehead after a unilateral stroke. Severity is then graded by House-Brackmann.[2]

[1]

How common, and who

Trigeminal neuralgia has an incidence of about 4 to 13 per 100,000 a year and a prevalence of roughly 0.03 percent. Peak age is over 50 (typically 50 to 70), with a slight female predominance (about 3 to 2) and a curious right-sided predominance (about 3 to 2). It is rare before 40, and onset in a younger patient should always trigger suspicion of multiple sclerosis — about 1 to 6 percent of patients with MS develop TN over a lifetime, and it may even be the presenting feature. MS-related TN is characteristically bilateral more often than classical TN.[1]

Bell palsy has an incidence of about 20 to 30 per 100,000 a year — far commoner than TN. It affects any age but peaks between 15 and 45, with roughly equal sex incidence. Recognised risk factors are pregnancy (especially the third trimester and first postpartum week, where incidence rises three- to four-fold), diabetes mellitus, hypertension, obesity, immunosuppression and a recent viral upper-respiratory infection. Both diabetes and hypertension confer a higher incidence and a worse recovery.[2][6]

[1]

Why they happen — two compression mechanisms

The mechanisms are entirely different, which is why the treatments — an anticonvulsant for TN, a corticosteroid for Bell palsy — are entirely different too.[1]

Classical TN — neurovascular conflict and ephaptic transmission. A blood vessel (most often the superior cerebellar artery) compresses the trigeminal nerve at the root-entry zone — the point where central myelin (oligodendrocytes) meets peripheral myelin (Schwann cells), mechanically and metabolically vulnerable to pulsatile injury. Chronic compression produces focal demyelination, so demyelinated A-beta (light-touch) fibres lie physically adjacent to demyelinated A-delta and C (pain) fibres. A touch then cross-fires ('ephaptic transmission') into the pain fibres, generating the electric-shock paroxysm — light touch felt as agony. The mechanism also explains why surgery that separates the vessel (MVD) can cure.[1]

Secondary TN comes not from a vessel but from an MS plaque at the trigeminal root, or a tumour compressing the root or Gasserian ganglion — which is why sensory loss, bilaterality or other cranial-nerve deficits exclude classical TN and mandate imaging.[1]

Bell palsy — compression neuropathy of CN VII in the fallopian canal. The facial nerve's course through the temporal bone is the longest bony canal of any cranial nerve, and its labyrinthine segment and the meatal foramen at the geniculate ganglion are the narrowest point and the site of entrapment. Inflammation and oedema of the facial nerve (most likely viral, with HSV-1 reactivation in the geniculate ganglion the leading candidate, and varicella-zoster causing Ramsay Hunt) within this narrow segment produces compression, venous congestion, ischaemia and conduction block (neuropraxia).[2]

Facial-nerve branch anatomy localises the lesion level and explains the constellation of deficits. Within the fallopian canal the nerve gives off three branches in order: the greater petrosal nerve (parasympathetic fibres for lacrimation, tested by the Schirmer test), the nerve to stapedius (which dampens the stapes; its loss causes painful hyperacusis), and the chorda tympani (taste to the anterior two-thirds of the tongue and salivation). A lesion proximal to all three reduces lacrimation, causes hyperacusis and impairs taste — the worst deficit. Hence the memory device 'Tears, Tastes, Taps'.[2]

The two clinical pictures

Trigeminal neuralgia — the pain is severe, paroxysmal, electric-shock, stabbing or shooting, lasting a fraction of a second to under two minutes. Attacks are strictly unilateral and follow one or more trigeminal divisions: V2 and V3 combined in about 60 percent, V3 alone in about 20 percent, V2 alone in about 20 percent, V1 alone in fewer than 5 percent. Bilateral disease is rare in classical TN and strongly suggests MS. The patient can usually point to a discrete trigger zone (nasolabial fold, lip, gum), and attacks are precipitated by innocuous stimuli: washing, shaving, brushing teeth, eating, talking, a cold wind. A refractory period follows each attack.[1]

Between attacks the patient is neurologically normal and pain-free. Any persisting sensory loss, allodynia, or other cranial-nerve deficit between attacks excludes classical TN and points to secondary disease. The secondary morbidity is substantial: patients lose weight and become dehydrated from food avoidance, many undergo unnecessary dental extraction for misdiagnosed toothache, and depression and isolation are common.[1]

Bell palsy — the hallmark is acute onset, over hours to under 72 hours, of unilateral facial weakness. The whole ipsilateral hemiface is involved: the forehead (cannot wrinkle or raise the eyebrow), the eye (cannot close it — lagophthalmos — and on attempted closure the globe rolls upward, the Bell phenomenon, exposing the cornea), and the mouth (drooping angle, drooling, dysarthria for labials, food trapping in the buccal sulcus). Proximal involvement adds reduced taste (chorda tympani), hyperacusis (stapedius), reduced lacrimation (greater petrosal), and sometimes a dull retro-auricular pain.[2]

Atypical presentations that mandate reclassification, not reassurance. TN with sensory loss, onset under 40, or bilaterality (secondary TN — MS or tumour, MRI mandatory); TN with a continuous background ache beneath the paroxysms (TN type 2, harder to treat); Bell palsy with complete paralysis at onset (House-Brackmann V or VI, worse prognosis); Ramsay Hunt (ear or palate vesicles, severe otalgia, facial palsy, ± hearing loss or vertigo); and bilateral facial palsy (GBS, sarcoidosis, Lyme, HIV — never Bell).[1][2]

The differential — and the mimics that bite

For trigeminal neuralgia, the consequences of mislabelling range from unnecessary dental work to a missed tumour.[1]

• Dental disease (pulpitis, apical abscess) — the pain is continuous and localised to a tooth or gum, with dental signs; not paroxysmal, not triggerable elsewhere.
• Cluster headache — strictly unilateral periorbital or temporal pain lasting 15 to 180 minutes, with prominent ipsilateral autonomic signs (lacrimation, conjunctival injection, rhinorrhoea, ptosis), in bouts.
• SUNCT or SUNA — very brief attacks (seconds) but many per day, with prominent conjunctival injection and tearing.
• Post-herpetic neuralgia — a constant, burning pain in a zoster-scarred dermatome with a clear preceding vesicular rash.
• Glossopharyngeal neuralgia — paroxysmal throat or ear pain triggered by swallowing, in the distribution of CN IX.
• Giant-cell (temporal) arteritis — in the over-50 patient: continuous temporal headache, jaw claudication, scalp tenderness, visual disturbance, raised ESR and CRP; never call it TN, and never miss it.[1]

For an acute facial palsy, exclude the secondary LMN causes before labelling it Bell.[1]

• Ramsay Hunt syndrome (herpes zoster oticus) — vesicles in the ear canal, on the pinna, or on the palate, with severe otalgia and facial palsy ± sensorineural hearing loss; worse prognosis, antivirals essential.
• Otitis media or mastoiditis — ear discharge, fever, otoscopic signs.
• Lyme disease — tick exposure, erythema migrans, often bilateral facial palsy in endemic regions.
• HIV seroconversion — a mononucleosis-like illness with facial palsy.
• Cholesteatoma — chronic otorrhoea, conductive hearing loss, otoscopic mass.
• Parotid tumour — a palpable parotid mass invading the facial nerve.
• Trauma — temporal bone fracture, Battle sign, CSF otorrhoea.[1]

The discriminator that decides everything: forehead-sparing UMN weakness (stroke) versus forehead-involving LMN weakness (Bell palsy) — a fork that decides whether the patient is fast-tracked to thrombolysis or sent home with steroids and eye care.[2]

The focused bedside assessment

In suspected TN, the history is the diagnosis. Confirm the pain quality (electric, stabbing), the duration (seconds), the distribution (a trigeminal division, strictly unilateral), and the trigger pattern (innocuous stimuli, a trigger zone). Examine for inter-paroxysm sensory loss or other cranial-nerve deficit — these exclude classical TN. Inspect the teeth, ears and temporomandibular joint to exclude local causes.[1]

In suspected Bell palsy, examine all four facial-nerve functions systematically: Motor (forehead, eye closure — can the lashes be buried?, mouth — show teeth, puff cheeks; look for lagophthalmos and the Bell phenomenon); Taste (anterior two-thirds with salt or sugar); Lacrimation (Schirmer test); and Stapedial reflex (ask about hyperacusis).[1]

Then inspect the ear canal, pinna and palate for vesicles (Ramsay Hunt — examine this in every facial palsy, since missing it changes treatment and prognosis), examine the parotid for a mass, and perform a full cranial-nerve and peripheral neurological examination to exclude limb weakness. Always check the forehead first — it decides LMN from UMN, and it is the single observation an examiner rewards. Grade severity with House-Brackmann.[2][6]

Investigations — both are clinical diagnoses

Both TN and Bell palsy are clinical diagnoses. Routine bloods and imaging are not required for a typical presentation — over-investigating a classical case is itself a pitfall. Investigation exists to exclude the secondary causes that masquerade as the common syndrome.[1][6]

Indications for MRI in TN — any atypical feature: sensory loss in the trigeminal distribution, onset under 40, bilaterality, non-response to adequate carbamazepine, deafness or any other cranial-nerve deficit, or progression to continuous pain. High-resolution CISS or FIESTA cisternal sequences demonstrate the neurovascular conflict and exclude an MS plaque or a CPA tumour.[1]

Indications for imaging or bloods in facial palsy — the AAO-HNS guideline recommends no routine imaging or electrophysiology for a typical Bell palsy. Reserve MRI (internal auditory meatus and parotid) and bloods for slow progression beyond three weeks, no recovery by three to six months, recurrent or bilateral palsy, other cranial-nerve signs, a parotid mass, severe otalgia with vesicles (Ramsay Hunt), or clinical suspicion of a secondary cause. Targeted bloods: Lyme serology (endemic regions), glucose or HbA1c, HIV, ACE (sarcoid), autoimmune screen; check ESR and CRP if giant-cell arteritis is possible.[2][6]

Electroneurography (ENoG) and EMG assess severity and prognosis by comparing the compound muscle action potential amplitude between sides. Degeneration exceeding 90 percent within the first two weeks predicts a poor outcome. ENoG is not needed for a typical mild palsy that begins to recover within three weeks.[2]

House-Brackmann facial-nerve grading (reproduced verbatim)

The international standard for grading facial-nerve function, reproduced accurately:[1]

• Grade I — Normal: normal facial function in all areas.
• Grade II — Mild dysfunction: slight asymmetry on close inspection; at rest, normal symmetry and tone; forehead movement moderate to good; eye closure complete with minimum effort; slight mouth asymmetry.
• Grade III — Moderate dysfunction: obvious but not disfiguring asymmetry; symmetrical at rest; forehead movement slight to moderate; eye closure with effort; noticeable but not disfiguring mouth movement.
• Grade IV — Moderately severe dysfunction: obvious disfiguring asymmetry; symmetrical at rest; no forehead movement; incomplete eye closure; asymmetric mouth movement.
• Grade V — Severe dysfunction: only barely perceptible movement; asymmetry at rest; no forehead movement, no eye closure, slight mouth movement.
• Grade VI — Total paralysis: no movement.[1]

Grades IV to VI at onset define the severe subgroup in which early aggressive treatment and close ophthalmic follow-up matter most.[2][6]

Trigeminal neuralgia — the carbamazepine ladder

[1]

Neither TN nor Bell palsy is a time-critical ABC resuscitation, but several acute priorities must be recognised at first contact, and missing them causes preventable harm.[1][2]

• Eye protection in Bell palsy — institute immediately at first contact, before the patient leaves the room. Lubricating drops hourly by day, ointment at night, and eyelid taping or a moisture chamber overnight prevent exposure keratopathy, corneal ulceration and blindness — the single most preventable complication of Bell palsy.
• Forehead sparing or any limb weakness — treat as possible acute stroke: fast-track to stroke imaging and thrombolysis. Do not label it Bell palsy, do not give steroids, do not delay.
• Ramsay Hunt syndrome — start urgent high-dose antivirals (aciclovir or valaciclovir) plus corticosteroids without waiting for confirmation; delay worsens an already-poor prognosis.
• Carbamazepine toxicity in TN — check sodium (symptomatic SIADH hyponatraemia) and look for rash (Stevens-Johnson — stop immediately; the HLA-B*1502 allele confers high risk in Han Chinese and Thai populations, where screening is recommended).
• Severe TN — may cause dehydration and weight loss from food avoidance; escalate the medication, support nutrition.[1]

The medical ladder

First-line: carbamazepine. Start 100 to 200 mg once or twice daily and titrate every few days to a maintenance of 600 to 1200 mg a day in divided doses (maximum 1600 mg a day). About 70 percent of patients obtain initial relief, often dramatic — a response that is itself nearly diagnostic. Monitor serum sodium (SIADH hyponatraemia), full blood count (leucopenia, aplastic anaemia), rash (Stevens-Johnson), and the clinical effects of drowsiness, ataxia, diplopia; carbamazepine is a potent CYP3A4 inducer with many interactions (including the oral contraceptive pill).[1]

Second-line or add-on agents when carbamazepine is ineffective, poorly tolerated, or loses efficacy over time: oxcarbazepine (less hepatic induction but its own hyponatraemia risk), lamotrigine (titrate slowly to avoid Stevens-Johnson), gabapentin and pregabalin (especially in MS-related TN), baclofen (a GABA-B agonist, especially in MS and as an add-on), and phenytoin. Combination therapy is common in refractory cases.[1]

The surgical ladder

When an adequate medical trial fails or side-effects are intolerable, three families of procedures are available, in roughly escalating invasiveness.[1]

• Microvascular decompression (MVD, Jannetta procedure) — a posterior fossa craniotomy that physically separates the offending vessel from the trigeminal root with a small Teflon pad. It is the only procedure that treats the cause, giving the best and most durable relief (about 90 percent immediate, roughly 70 percent pain-free at five years, 60 percent at ten years). Risks: ipsilateral hearing loss (up to 10 percent — the commonest significant complication), facial numbness or weakness, CSF leak, meningitis, cerebellar injury, stroke, and death under 1 percent.
• Gamma knife stereotactic radiosurgery — a non-invasive, single-fraction high-dose (75 to 90 Gy) radiation to the root-entry zone. Effective but with delayed onset (weeks to months), facial numbness in a minority, and recurrence over years. Suits the patient who declines or cannot tolerate craniotomy.
• Percutaneous procedures on the Gasserian ganglion via the foramen ovale — radiofrequency thermocoagulation, percutaneous balloon compression (Mullan), and glycerol rhizolysis. Chosen for the frail and elderly; they give immediate relief but reliably produce facial numbness and have a higher recurrence than MVD.[1]

[1]

Bell palsy — the evidence-based bundle

Oral prednisolone is the cornerstone. Give 60 mg once daily for 5 days, then taper over 5 days (for example 50, 40, 30, 20, 10 mg on successive days), started within 72 hours of onset. This raises complete recovery from about 80 percent (untreated) to about 94 percent, confirmed in the Scottish SCOPE trial (Sullivan, NEJM 2007), the Swedish trial (Engstrom, Lancet Neurology 2008), and the Cochrane review (Madhok, 2016).[2][3][4]

Antivirals (aciclovir or valaciclovir) alone are no better than placebo, and the added benefit over steroids alone is small and not statistically robust in pooled analyses (Gagyor, Cochrane 2015). The AAO-HNS guideline therefore recommends antivirals not be offered as sole therapy, but they may be added to steroids for severe palsy (House-Brackmann IV to VI), Ramsay Hunt syndrome (where valaciclovir 1 g three times daily for 7 to 10 days is essential), or immunocompromise.[4][5][6]

Eye protection — mandatory, non-negotiable, for every patient. Lubricating drops hourly by day (preservative-free for frequent use), ointment at night, and taping the eyelid shut or a moisture chamber overnight; for severe lagophthalmos, a temporary tarsorrhaphy or botulinum-toxin-induced ptosis protects the cornea until recovery. Neglect of eye care is the classic, preventable cause of corneal blindness.[6]

Supportive measures — facial physiotherapy and massage or exercises to maintain muscle tone and reduce contracture; reassurance that the outlook is good; and psychological support for the disfigurement and anxiety of an acute facial palsy.[2]

The subtypes and scenarios that bite

TN in multiple sclerosis — patients are younger, the TN may be bilateral, and MRI shows a demyelinating plaque at the trigeminal root-entry zone. Carbamazepine remains first-line, but the response is less durable, and the surgical preference shifts toward percutaneous procedures and gamma knife rather than MVD (the conflict is a plaque, not a vessel).[1]

Ramsay Hunt syndrome (herpes zoster oticus) — reactivation of varicella-zoster virus in the geniculate ganglion, producing vesicles in the ear canal, on the pinna or on the palate, severe otalgia, an LMN facial palsy, and sometimes sensorineural hearing loss, tinnitus and vertigo. Treat with high-dose antivirals (aciclovir 800 mg five times daily, or valaciclovir 1 g three times daily for 7 to 10 days) plus corticosteroids, started as early as possible. Prognosis is worse than Bell palsy — about 70 percent recovery of facial function, lower if treatment is delayed.[2][6]

Bilateral facial palsy — this is never Bell palsy and mandates investigation. Think Guillain-Barre syndrome (ascending weakness, areflexia, CSF albuminocytologic dissociation), sarcoidosis (Heerfordt syndrome — uveitis, parotitis, fever, raised ACE), Lyme disease (the commonest cause of bilateral facial palsy in endemic regions — tick exposure, erythema migrans), and HIV seroconversion. Investigate rather than treat empirically with steroids alone.[2]

Bell palsy in pregnancy — commoner in the third trimester and the first postpartum week, often more severe. Treat with prednisolone within 72 hours (benefit outweighs late-pregnancy risk; avoid the first trimester on teratogenicity grounds), institute strict eye protection, and screen for hypertension, pre-eclampsia and gestational diabetes.[2]

Recurrent facial palsy or Melkersson-Rosenthal syndrome — a triad of recurrent facial palsy, recurrent facial or lip swelling (cheilitis granulomatosa) and a fissured (scrotal) tongue; a granulomatous disorder that may respond to steroids and prophylaxis in recurrent cases.[2]

How these conditions harm — complications and pitfalls

TN complications arise from both disease and treatment. The disease causes depression, weight loss, dehydration and social isolation; rarely, unremitting TN pain is a risk factor for suicide, which is why refractory TN is a neurosurgical urgency. Carbamazepine carries SIADH hyponatraemia, drowsiness, ataxia, leucopenia, aplastic anaemia and Stevens-Johnson syndrome. The surgical risks of MVD — hearing loss, facial numbness or weakness, CSF leak, meningitis, cerebellar injury, stroke, death under 1 percent — must be discussed in consent.[1]

Bell palsy complications centre on the eye and on aberrant regeneration. Exposure keratopathy and corneal ulceration are preventable with eye care and a recognised, avoidable cause of blindness. Synkinesis and aberrant regeneration — misdirection of regrowing axons to the wrong branches — produce crocodile tears (the eye waters when eating) and mouth-eye synkinesis (the mouth corner moves on blinking). Hemifacial spasm and permanent contracture are late sequelae.[2]

The classic pitfalls examiners probe and that cause real harm: labelling dental pain or atypical facial pain as TN (unnecessary dental extraction); missing MS or a tumour in young-onset or bilateral TN (delayed imaging); labelling a UMN (forehead-sparing) weakness as Bell palsy and missing a stroke (the most dangerous error — delays thrombolysis); missing Ramsay Hunt by not examining the ear (denying the patient essential antivirals); calling bilateral facial palsy 'Bell palsy' and missing GBS, Lyme or sarcoid; giving antivirals without steroids, or delaying steroids beyond 72 hours; and neglecting eye care at any point.[1][2]

Prognosis and disposition

Bell palsy prognosis. About 70 to 85 percent recover fully without any treatment. Early prednisolone within 72 hours raises complete recovery to about 94 percent. Recovery typically begins within three weeks and is complete by three to six months. Poor prognostic factors: complete paralysis at onset (House-Brackmann V or VI), age over 60, diabetes, pregnancy, severe retro-auricular pain, hyperacusis, complete loss of taste (a proximal lesion), no recovery by three weeks, and ENoG showing more than 90 percent degeneration within the first two weeks.[2]

Ramsay Hunt has a worse prognosis — about 70 percent recovery of facial function, lower still if treatment is delayed beyond 72 hours; hearing loss may be permanent. Trigeminal neuralgia is chronic and relapsing-remitting: medical control is initially good but efficacy often wanes over years (tachyphylaxis), and many patients eventually need surgery. Microvascular decompression gives the most durable relief (about 70 percent pain-free at five to ten years); percutaneous procedures and gamma knife have higher recurrence.[1]

Disposition and follow-up. Review Bell palsy at one to two weeks (assess for eye complications and early recovery) and again at three months — refer to a specialist if there is no recovery by three months, as the diagnosis should then be reconsidered and further imaging obtained. For TN, titrate the medication against pain and side-effects, and refer to a neurologist or neurosurgical MDT for refractory or atypical disease. Refer all Ramsay Hunt patients urgently to ENT and ophthalmology.[1]

Special populations

Pregnancy — Bell palsy is commoner in the third trimester and early postpartum, often more severe; treat with prednisolone within 72 hours (benefit outweighs risk in late pregnancy; avoid the first trimester on teratogenicity grounds), institute strict eye protection, and screen for pre-eclampsia and gestational diabetes. TN in pregnancy is managed medically (carbamazepine has teratogenic concerns — discuss with neurology and obstetrics; lamotrigine may be preferred).[2]

Diabetes mellitus — confers both a higher incidence and a worse recovery in Bell palsy; monitor blood glucose when prescribing corticosteroids. TN management is unchanged, but comorbidity affects surgical risk for MVD.[2]

Children — Bell palsy is treated with steroids in the same 72-hour window per AAO-HNS; always consider Lyme disease in endemic paediatric cases. TN is rare in children and should prompt an MS evaluation and MRI.[6]

Elderly — Bell palsy recovery is slower and less complete; favour less-invasive TN procedures (percutaneous, gamma knife) over craniotomy where comorbidity is high. Screen for giant-cell arteritis in the older patient with facial or jaw pain — it mimics TN and is treatable with steroids, not surgery.[1]

Immunocompromised (HIV) — facial palsy may occur at seroconversion or with opportunistic infection (CMV, Ramsay Hunt, toxoplasmosis); investigate the cause and add antiviral cover more readily.[1]

Resource-limited settings — carbamazepine and generic prednisolone are cheap and universally available, and are the backbone of management. Eye-protection education is the single highest-yield low-cost intervention. Access to MRI, MVD and gamma knife is limited, so medical management predominates and surgery is reserved for the few refractory cases who can access it.[1][2][6]

Evidence, guidelines and regional deltas

Trigeminal neuralgia is guided by the European Academy of Neurology guideline (Bendtsen, 2019) — the contemporary reference standard. It distinguishes classical TN (neurovascular conflict with morphological change) from secondary TN (MS or tumour) and idiopathic TN, recommends carbamazepine or oxcarbazepine first-line, notes the limited randomised evidence for add-on agents, and places MVD, gamma knife and percutaneous procedures for refractory disease, with MVD offering the most durable relief where a clear conflict is demonstrated.[1]

Bell palsy evidence rests on three landmark randomised trials and two Cochrane reviews. The Scottish SCOPE trial (Sullivan, NEJM 2007) — a factorial double-blind trial of prednisolone, aciclovir, both, and placebo in 551 patients — showed early prednisolone within 72 hours improves recovery and antivirals alone do not. The Swedish trial (Engstrom, Lancet Neurology 2008) replicated the benefit of prednisolone and found valaciclovir added no significant benefit. The Cochrane reviews (Madhok 2016, Gagyor 2015) confirmed steroids help (NNT about 11) and antivirals add at most marginal benefit.[2][5]

[3]

Regional practice diverges by resources. In high-income settings, MRI to confirm neurovascular conflict and access to MVD and gamma knife are routine for refractory TN. In India and other low- and middle-income countries, cost and access favour long-term medical therapy (carbamazepine and generic prednisolone are cheap and ubiquitous), with surgery reserved for the few, and eye-protection education prioritised for Bell palsy as the highest-yield low-cost intervention.[1]

Controversies an examiner may probe: whether antivirals add meaningful benefit to steroids in Bell palsy (the pooled effect is small); the role and timing of facial-nerve decompression surgery in severe Bell palsy (some advocate middle-fossa decompression for ENoG-greater-than-90-percent degeneration within 14 days, but it remains controversial and not standard); the optimal surgical choice and timing in TN (MVD versus gamma knife versus percutaneous); and whether atypical TN or TN type 2 should be managed differently from classical TN.[1][6]

The mnemonics, and the mantra

[2] [1]

The mantra: forehead spared equals UMN equals stroke; forehead involved equals LMN equals Bell palsy — and protect the eye before the patient leaves the room. For TN, carbamazepine first, Jannetta if refractory, MRI if young, bilateral, or there is sensory loss.[1][2]

[1]

Ward-round test — three stems, thirty seconds each

Stem 1 — electric shocks on shaving (answer)

A 62-year-old man has seconds-long electric-shock pains in the right cheek every time he shaves or eats, for three months. Between attacks he is neurologically normal. What is the diagnosis, the first drug with its starting dose, and what feature would mandate an MRI? Model: This is classical trigeminal neuralgia — paroxysmal, electric-shock, V2 or V3 pain, seconds, triggered by innocuous stimuli, no inter-paroxysm deficit. First-line is carbamazepine 100 to 200 mg once or twice daily, titrated to 600 to 1200 mg a day; about 70 percent respond. Check sodium (SIADH), FBC and rash (Stevens-Johnson, HLA-B*1502 in Han Chinese and Thai). MRI is mandatory if there is sensory loss, onset under 40, bilaterality, deafness, non-response to carbamazepine, or progression to continuous pain — any of which suggests secondary TN (MS plaque or tumour).[1]

Stem 2 — the face that will not move (answer)

A 34-year-old woman woke with a right facial droop, cannot close her right eye, and has lost taste on the front right of her tongue. Her right forehead does not move. What is the diagnosis, the drug, the dose, the window, and the single most important non-drug measure? Model: This is Bell palsy — an acute unilateral LMN facial (VII) palsy; the forehead and eye involvement confirms LMN. The drug is prednisolone 60 mg once daily for 5 days, then taper over 5 days, started within 72 hours of onset (raises complete recovery from about 80 to about 94 percent). The single most important non-drug measure is mandatory eye protection — lubricating drops hourly by day, ointment and taping or a moisture chamber at night — to prevent exposure keratopathy and corneal blindness. Examine the ear for vesicles (Ramsay Hunt needs urgent antivirals added).[2][3]

Stem 3 — the forehead that is spared (answer)

A 68-year-old with a right-sided facial droop can still wrinkle both eyebrows. The right lower face is weak and the right arm will not lift. What is the diagnosis, and what do you do in the next 15 minutes? Model: This is NOT Bell palsy — the forehead is spared, which means a UMN lesion, and with ipsilateral arm weakness this is an acute stroke until proven otherwise. Do not give steroids, do not label it Bell. Fast-track to stroke imaging (CT then CTA or MRI) and activate the thrombolysis pathway per local protocol. This is the single bedside fork that decides the whole topic — forehead spared equals UMN equals stroke.[2]

References

1. [1]Bendtsen L, Zakrzewska JM, Abbott J, et al. European Academy of Neurology guideline on trigeminal neuralgia Eur J Neurol, 2019.PMID 30860637
2. [2]Madhok VB, Gagyor I, Daly FD, et al. Corticosteroids for Bell's palsy (idiopathic facial paralysis) Cochrane Database Syst Rev, 2016.PMID 27428352
3. [3]Sullivan FM, Swan IRC, Donnan PT, et al. Early treatment with prednisolone or acyclovir in Bell's palsy N Engl J Med, 2007.PMID 17942873
4. [4]Engström M, Berg T, Stjernquist-Desatnik A, et al. Prednisolone and valaciclovir in Bell's palsy: a randomised, double-blind, placebo-controlled, multicentre trial Lancet Neurol, 2008.PMID 18849193
5. [5]Gagyor I, Madhok VB, Daly F, et al. Antiviral treatment for Bell's palsy (idiopathic facial paralysis) Cochrane Database Syst Rev, 2015.PMID 26559436
6. [6]Baugh RF, Basura GJ, Ishii LE, et al. Clinical practice guideline: Bell's palsy Otolaryngol Head Neck Surg, 2013.PMID 24189771