Bell's Palsy

Definition & Epidemiology

• Incidence: ~23-25 per 100,000/year; roughly 1 in 60 persons will develop it during a lifetime
• Affects men and women roughly equally; occurs at all ages
• Risk factors: pregnancy (especially last trimester and first 2 weeks postpartum), diabetes mellitus, possibly hypertension
• Recurrence rate: ~7-8% of cases, average interval ~10 years

Pathophysiology

• HSV-1 (herpes simplex virus type 1): HSV DNA has been found in the endoneurial fluid surrounding the facial nerve and in the geniculate ganglion - HSV-1 reactivation is the leading cause in the majority of cases
• VZV (varicella-zoster virus): implicated in up to one-third of cases and is the second most common cause; when it causes vesicular lesions, the syndrome is called Ramsay Hunt syndrome rather than Bell's palsy
• Other viruses including SARS-CoV-2 and HIV seroconversion have also been implicated

Clinical Features

MRI Findings

Clinical Photographs

Differential Diagnosis

• Ramsay Hunt syndrome (VZV reactivation): severe facial palsy + vesicular eruption in external auditory canal ± ear pain ± CN VIII involvement
• Lyme disease (Borrelia burgdorferi): can cause unilateral or bilateral facial palsy; in endemic areas, accounts for ≥10% of facial palsy cases
• Sarcoidosis: can cause bilateral facial palsy; check ACE level and chest imaging
• Guillain-Barré syndrome: bilateral facial palsy possible; check CSF
• HIV seroconversion: CN VII involvement
• Diabetes, Sjögren's syndrome, amyloidosis, leprosy
• Carcinomatous meningitis (LMN pattern possible)
• Melkersson-Rosenthal syndrome: recurrent facial paralysis + facial/labial edema + fissured tongue
• Stroke/UMN lesion: forehead SPARED (upper face has bilateral cortical representation); lower face only affected; often with arm/leg weakness or aphasia
• Parotid tumors or acoustic neuroma: typically slower onset

Workup

1. Typical abrupt-onset unilateral facial palsy
2. No risk factors pointing to another cause
3. No vesicles in external auditory canal (would suggest Ramsay Hunt)
4. Otherwise normal neurological exam

• ESR/CRP, fasting glucose (diabetes)
• Lyme serology (if endemic area)
• HIV serology
• ACE level + chest X-ray (sarcoidosis)
• Lumbar puncture (Guillain-Barré)
• Gadolinium-enhanced MRI (facial nerve enhancement)

Prognosis

• ~70-80% recover completely within 1-2 months
• ~85% achieve near-normal function overall
• Most favorable prognostic signs:
  • Incomplete paralysis in the first week
  • Early recovery of some motor function within 5-7 days
  • Return of taste in the first week
• If denervation on EMG by day 10: expect long delay (months), incomplete recovery
• Recurrence: ~7-8%; average interval ~10 years

Treatment

1. Corticosteroids (first-line, strongest evidence)

• Evidence: increases return of facial function from 63% to 83% at 3 months (Goldman-Cecil); modestly shortens recovery and improves functional outcome
• Must be started early (within 72 hours of onset for best effect)
• A 2024 systematic review and meta-analysis (PMID 37940744) compared oral vs. intravenous steroids; oral route is standard first-line
• A 2025 systematic review (PMID 40741786) noted statistical fragility in some steroid-antiviral trial conclusions, worth noting for severe cases

2. Antivirals (adjunct, case-dependent)

• Antiviral monotherapy: not recommended - no benefit alone
• Combined with steroids: evidence is mixed. Most large RCTs (Sullivan et al.) show no added benefit of valacyclovir (1000 mg/day x 5-7 days) or acyclovir (400 mg 5x/day x 10 days) when added to steroids in general Bell's palsy
• Exceptions - give antivirals:
  • Vesicular lesions present (ear canal, palate) - suggests Ramsay Hunt, where antivirals ARE indicated
  • Severe/complete facial palsy (some evidence of additive benefit with valacyclovir + prednisolone in this subgroup - Hato et al.)
  • HIV or immunocompromised

3. Eye care (mandatory in incomplete eyelid closure)

• Artificial tears during the day
• Lubricating eye ointment at night
• Paper tape/eye patch to close eyelid during sleep
• Consider ophthalmology referral if corneal exposure is significant

4. No role for surgical decompression

• Evidence does not support surgical decompression; may be harmful

5. Supportive/rehabilitation

• Physiotherapy and facial muscle massage
• For permanent paralysis: cosmetic surgical procedures to restore facial symmetry

Key Distinguishing Points: LMN vs UMN Facial Palsy

Recent evidence note: A 2025 systematic review (PMID 40741786) highlights statistical fragility in steroid-antiviral combination trials for Bell's palsy - the benefit of adding antivirals to steroids may be less robust than previously thought, though this does not change current first-line steroid recommendations.

Cinacalcet

Drug Class & Overview

Chemical Structure

• A 3-trifluoromethyl group (shown in red below)
• A naphthalene moiety (shown in blue)
• One chiral center with R-absolute configuration - the R-enantiomer is the pharmacologically active form

Mechanism of Action

CaSR Pharmacology

1. CaSR is expressed on parathyroid chief cells (and also kidney, thyroid C-cells, bone)
2. Cinacalcet binds to the transmembrane domain of CaSR (allosteric site), distinct from the Ca²⁺ binding site
3. This increases CaSR sensitivity to extracellular Ca²⁺ - i.e., it lowers the set-point for Ca²⁺-mediated PTH suppression
4. Result: PTH secretion is suppressed at prevailing (or even low-normal) calcium concentrations
5. Downstream: serum PTH falls → serum Ca²⁺ falls → serum phosphate falls

Pharmacokinetics (ADME)

Approved Indications

1. Secondary hyperparathyroidism (SHPT) in CKD patients on dialysis - primary use
2. Hypercalcemia in parathyroid carcinoma - reduces unresectable hypercalcemia
3. Hypercalcemia in primary hyperparathyroidism (PHPT) - for patients who are NOT surgical candidates

Important: Cinacalcet is NOT recommended in CKD patients not on dialysis - in pre-dialysis CKD, it causes marked hypocalcemia (62% develop serum Ca²⁺ < 8.4 mg/dL vs. 6% on placebo), creating a safety concern. (Brenner & Rector's The Kidney)

Dosing

Clinical Evidence: The EVOLVE Trial

• Primary outcome: Composite of death, nonfatal MI, hospitalization for unstable angina, heart failure, or peripheral vascular event
• ITT result: Nonsignificant 7% reduction in primary outcome (HR 0.93; 95% CI 0.85-1.02; p = 0.11)
• Age-adjusted result: Nominally significant reduction (HR 0.88; 95% CI 0.79-0.97; p = 0.008)
• Key confound: Cinacalcet group was older (median 55 vs. 54 years) AND a substantial proportion of placebo patients crossed over to cinacalcet commercially
• Positive findings despite primary endpoint miss:
  • Significantly reduced parathyroidectomy rates
  • Significantly reduced calciphylaxis rates
  • 16% lower hazard of non-atherosclerotic cardiovascular events
  • Lowers FGF23, which independently correlates with CV death reduction

Adverse Effects

• Serum Ca²⁺ and phosphate: within 1 week of starting/dose change
• PTH: within 4 weeks of starting/dose change
• Stop or reduce dose if PTH < 150 pg/mL

Drug Interactions

Cinacalcet vs. Etelcalcetide (IV Calcimimetic)

Place in Therapy

SHPT Management Ladder (CKD on Dialysis):
1. Dietary phosphate restriction
2. Phosphate binders (sevelamer preferred)
3. Active vitamin D analogues (calcitriol, paricalcitol)
   → BUT: raise Ca and PO₄ → worsen vascular calcification
4. Cinacalcet (or etelcalcetide)
   → Lowers PTH + Ca + PO₄ simultaneously
   → Especially preferred when:
      - Hypercalcemia or hypercalcemic tendency
      - Hyperphosphatemia
      - High risk for vascular calcification
5. Parathyroidectomy
   → For refractory cases (iPTH > 1000, failed medical Rx,
      calciphylaxis, persistent hypercalcemia)

• Patient has marginal or frank hypercalcemia (vitamin D analogues would worsen it)
• Patient has hyperphosphatemia (cinacalcet lowers phosphate too)
• As an adjunct to low-dose active vitamin D (cinacalcet upregulates CaSR expression, increasing vitamin D efficacy)
• To avoid or delay parathyroidectomy
• Parathyroid carcinoma (controlling hypercalcemia in unresectable disease)
• PHPT in surgical non-candidates