😐nerve injury

Bell's Palsy

Bell's palsy is acute unilateral facial nerve paralysis of unknown cause, resulting in weakness of all facial muscles on the affected side. It is the most common cause of facial paralysis and must be distinguished from stroke, which spares the forehead.

Anatomical Basis

The facial nerve (CN VII) travels through the narrow facial canal in the temporal bone. Inflammation causes nerve edema within this confined space, leading to compression and dysfunction. Because it is a lower motor neuron lesion, all facial muscles on that side are affected, including the forehead (unlike stroke).

Relevant Structures

Facial nerve (CN VII)Facial canal (temporal bone)Geniculate ganglionStylomastoid foramenParotid glandFacial muscles of expression

Mechanism

Exact cause unknown, but viral reactivation (HSV-1) is suspected. The nerve becomes inflamed and edematous within the bony facial canal, causing compressive ischemia and demyelination. Associated with herpes simplex, pregnancy, diabetes, and upper respiratory infections.

Clinical Presentation

•Acute onset unilateral facial weakness (hours to 1-2 days)
•Inability to close the eye, raise the eyebrow, or smile on affected side
•Forehead involvement (distinguishes from stroke)
•May have pain behind the ear before weakness
•Taste disturbance (anterior 2/3 of tongue)
•Hyperacusis (sounds seem loud) if stapedius affected
•Decreased tearing or excessive tearing

Physical Examination

→Complete unilateral facial weakness (forehead, eye, mouth all affected)
→Inability to wrinkle forehead (LMN lesion)
→Bell's phenomenon: Eye rolls upward when attempting to close (normal reflex)
→Incomplete eye closure with lagophthalmos
→Mouth droops on affected side, drools from corner
→Assess for vesicles in ear canal (Ramsay Hunt if present)

Treatment

✓Corticosteroids: Prednisone 60-80mg daily for 7 days, started within 72 hours
✓Antivirals: Valacyclovir often added, though benefit uncertain
✓Eye protection: Artificial tears, lubricating ointment at night, taping eye closed
✓Eye patch or moisture chamber for severe lagophthalmos
✓Physical therapy may help during recovery
✓Surgical decompression rarely indicated

Prognosis

Excellent: 70-85% recover completely without treatment, >95% with steroids. Most recovery occurs within 3 weeks, complete recovery by 3-4 months. Poor prognosis: complete paralysis, no recovery at 3 weeks, older age, diabetes.

Study Tips

💡LMN lesion = entire face (including forehead); UMN = forehead spared (bilateral cortical innervation)
💡Bell's phenomenon is normal - eye rolls up when closing, exposed in Bell's palsy
💡Ramsay Hunt = Bell's palsy + herpes zoster oticus (worse prognosis)
💡Main emergency is corneal exposure - protect the eye!

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Bell's Palsy FAQs

Common questions about this condition

The forehead muscles receive bilateral upper motor neuron input from both cerebral hemispheres. A unilateral stroke (UMN lesion) leaves the contralateral input intact. Bell's palsy affects the lower motor neuron (facial nerve itself), paralyzing all ipsilateral facial muscles including the forehead.

Both cause facial paralysis, but Ramsay Hunt syndrome is caused by varicella-zoster virus reactivation in the geniculate ganglion. It presents with vesicles in the ear canal (zoster oticus), more severe paralysis, and has worse prognosis. It requires antiviral treatment.

All Clinical Cases

🤚 Carpal Tunnel Syndrome 🦴 Scaphoid Fracture 😐 Bell's Palsy 👋 Radial Nerve Injury (Wrist Drop)🩹 Inguinal Hernia (Direct and Indirect)🧠 Middle Cerebral Artery Stroke 🏃 Anterior Cruciate Ligament (ACL) Tear 🦴 Thoracic Outlet Syndrome 🚨 Acute Compartment Syndrome 🦴 Hip Fracture (Femoral Neck and Intertrochanteric)