What is the most likely diagnosis in a diabetic, hypertensive female with right‑sided facial weakness causing mouth deviation to the right and tearing of the right eye?

Most Likely Diagnosis: Bell's Palsy (Acute Idiopathic Peripheral Facial Nerve Palsy)

This diabetic, hypertensive female presenting with right-sided mouth deviation and ipsilateral eye tearing most likely has Bell's palsy—an acute unilateral peripheral facial nerve paralysis that affects the entire right side of the face, including the forehead, and causes incomplete eye closure leading to reflex tearing. 1

Key Diagnostic Features Supporting Bell's Palsy

Clinical Presentation Pattern

• Complete hemifacial weakness involving the right forehead distinguishes this from stroke, which would spare forehead movement due to bilateral cortical innervation of the frontalis muscle 2, 3
• Mouth deviation to the right indicates weakness of the left facial muscles, causing the mouth to be pulled toward the stronger (right) side—this is characteristic of peripheral facial nerve palsy 1, 2
• Excessive tearing (epiphora) occurs paradoxically in Bell's palsy due to incomplete eye closure causing corneal irritation and reflex lacrimation, combined with dysfunction of parasympathetic fibers controlling tear drainage 1, 2

High-Risk Population Factors

• Diabetes and hypertension are established risk factors for Bell's palsy, with diabetic patients showing increased susceptibility to facial nerve compression 4, 1
• The American Academy of Otolaryngology-Head and Neck Surgery explicitly identifies diabetes, chronic hypertension, obesity, and pregnancy as conditions that increase Bell's palsy risk 4

Critical Differential Diagnosis: Excluding Stroke

Why This Is NOT a Stroke

• Stroke causes central facial weakness that spares the forehead—if this patient cannot raise her right eyebrow or wrinkle her right forehead, stroke is effectively ruled out 2, 3
• Stroke typically presents with additional neurologic deficits including dizziness, dysphagia, diplopia, limb weakness, or other cranial nerve involvement 2, 3
• The pattern of complete hemifacial weakness including forehead involvement is pathognomonic for peripheral (lower motor neuron) facial nerve pathology 1, 2

Red Flags That Would Suggest Stroke Instead

• Forehead sparing (ability to raise eyebrow on affected side) 2, 3
• Presence of limb weakness, sensory changes, or ataxia 3
• Involvement of other cranial nerves (diplopia, dysphagia, dysarthria) 2, 3
• Gradual onset over hours rather than acute onset within 72 hours 2, 3

Diagnostic Approach Algorithm

Step 1: Confirm Peripheral Pattern (5 minutes)

• Test forehead function: Ask patient to raise both eyebrows and wrinkle forehead—inability on right side confirms peripheral lesion 1, 2
• Assess complete facial movement: Test eye closure, smile, cheek puffing—all should be weak on right side 1, 2
• Document rapid onset: Symptoms should have developed over less than 72 hours 1, 2

Step 2: Exclude Other Causes (10 minutes)

• Screen for stroke features: Check for limb weakness, speech difficulties, gait abnormalities, other cranial nerve deficits—all should be absent 2, 3
• Look for vesicular rash in ear canal or periauricular area (Ramsay Hunt syndrome) 3
• Ask about trauma or recent ear surgery 2, 3
• Assess for bilateral involvement—extremely rare in Bell's palsy and suggests Lyme disease, sarcoidosis, or Guillain-Barré syndrome 2, 3

Step 3: Avoid Unnecessary Testing

• Do NOT order routine laboratory tests or imaging for typical Bell's palsy presentation—this only delays treatment without improving outcomes 1, 3
• Do NOT obtain MRI or CT unless atypical features are present (gradual onset, other cranial nerve involvement, recurrent episodes, or no recovery after 3 months) 1, 3
• Do NOT perform electrodiagnostic testing for incomplete facial paralysis 1

Immediate Management Within 72 Hours

Corticosteroid Therapy (MANDATORY)

• Prescribe prednisolone 50 mg once daily for 10 days (no taper needed) OR prednisone 60 mg once daily for 5 days followed by 5-day taper 1
• Treatment MUST begin within 72 hours of symptom onset—after this window, steroids provide no benefit 1
• Diabetes is NOT a contraindication to corticosteroid therapy; the benefit outweighs the risk of temporary hyperglycemia 1
• Evidence shows 83% complete recovery at 3 months with prednisolone versus 63.6% with placebo (NNT = 6) 1

Diabetes Management During Steroid Therapy

• Monitor capillary blood glucose every 2-4 hours during the first few days of treatment 1
• Increase basal insulin dose and add or increase prandial insulin to counter steroid-induced hyperglycemia 1
• For patients on oral agents, add NPH insulin concurrent with morning steroid dose (peaks 4-6 hours later, matching hyperglycemic effect) 1

Eye Protection (CRITICAL to Prevent Permanent Corneal Damage)

• Lubricating ophthalmic drops every 1-2 hours while awake 1
• Ophthalmic ointment at bedtime for sustained moisture retention 1
• Eye taping or patching at night with careful instruction on proper technique to avoid corneal abrasion 1
• Sunglasses outdoors to protect against wind and debris 1
• Urgent ophthalmology referral if severe impairment with complete inability to close eye 1

Antiviral Therapy (Optional, Minimal Benefit)

• Do NOT prescribe antivirals alone—they are completely ineffective as monotherapy 1
• May add valacyclovir 1000 mg three times daily for 7 days to steroids within 72 hours, but benefit is small (96.5% recovery versus 89.7% with steroids alone) 1
• The large BELLS trial showed no statistically significant advantage of adding acyclovir (71.2% recovery with acyclovir versus 75.7% without, P=0.50) 1

Follow-Up and Referral Triggers

Mandatory Reassessment Points

• At 3 months: Refer to facial nerve specialist if recovery is incomplete 1
• At any time: Refer immediately for new or worsening neurologic findings 1
• At any time: Refer to ophthalmology for development of ocular symptoms (pain, vision changes, redness) 1

Expected Recovery Timeline

• Most patients begin showing improvement within 2-3 weeks 1
• Complete recovery typically occurs within 3-4 months for most patients 1
• Approximately 70% of patients with complete paralysis recover fully within 6 months, while those with incomplete paralysis have up to 94% recovery rates 1
• 30% may experience permanent facial weakness with muscle contractures 1

Common Pitfalls to Avoid

Diagnostic Errors

• Failing to test forehead function leads to misdiagnosis—always confirm complete hemifacial weakness including forehead 1, 2
• Assuming all facial weakness is Bell's palsy—30% have identifiable causes requiring different management 2, 3
• Missing bilateral involvement—this is never idiopathic Bell's palsy and requires extensive workup for Lyme disease, sarcoidosis, or Guillain-Barré syndrome 2, 3

Treatment Errors

• Delaying corticosteroids beyond 72 hours eliminates their effectiveness 1
• Prescribing antivirals alone is completely ineffective and delays appropriate steroid treatment 1
• Inadequate eye protection can lead to permanent corneal damage—this is the most preventable complication 1
• Withholding steroids due to diabetes—the benefit far outweighs the risk of temporary hyperglycemia, which can be managed 1

Follow-Up Errors

• Failing to refer at 3 months delays access to reconstructive options and psychological support 1
• Ordering unnecessary imaging or labs in typical presentations only delays treatment without improving outcomes 1, 3