Facial nerve paralysis (Bell`s palsy)

Bell`s palsy (facial palsy) is an acute nerve paralysis (CN VII) that has an incidence of ~20/100.000.

CAUSES:

Herpes virus activation (not necessarily associated with skin lesions) is probably the most common etiology.

Other conditions (e.g. herpes zoster, Lyme disease) may play an important role as well.

SIGNS & SYMPTOMS:

Usually it presents as acute unilateral facial paralysis, which includes inability to maintain a symmetric smile, inability to completely close one of the eyes, eyebrow sagging, and dropping of one corner of the mouth.

Sometimes Lyme disease related paralysis can be bilateral.

DIAGNOSIS:

Patients with typical lesions may not need further testing.

Sometimes it may be difficult to differentiate between facial palsy and more serious conditions (such as stroke or metabolic abnormalities). In such cases, further tests may be necessary (e.g. imaging with CT scan or MRI, CMP, testing for Lyme disease).

CLASSIFICATION:

A way to classify a facial nerve`s function is to use the House-Brackmann classification, as follows:

I. Normal Normal facial function in all areas
II. Mild dysfunction Gross

Slight weakness noticeable on close inspection
May have slight synkinesis
At rest, normal symmetry and tone
Motion
Forehead – Moderate to good function
Eye – Complete closure with minimal effort
Mouth – Slight asymmetry

III. Moderate dysfunction Gross

Obvious but not disfiguring difference between sides
Noticeable (but not severe) synkinesis, contracture, or hemifacial spasm
At rest, normal symmetry and tone
Motion
Forehead – Slight to moderate movement
Eye – Complete closure with effort
Mouth – Slightly weak with maximum effort

IV. Moderately severe dysfunction Gross

Obvious weakness and/or disfiguring asymmetry
At rest, normal symmetry and tone
Motion
Forehead – None
Eye – Incomplete closure
Mouth – Asymmetrical with maximum effort

V. Severe dysfunction Gross

Only barely perceptible motion
At rest, asymmetry
Motion
Forehead – None
Eye – Incomplete closure
Mouth – Slight movement

VI. Total paralysis No movement

TREATMENT:

Oral glucocorticoids are beneficial, especially when started in the first three days. Prednisone (60mg PO qDay for 5 days, with a reduction of 10mg/day for the next 5 days) is effective. In addition to prednisone, patients with House-Brackmann grade IV or above may benefit from antivirals (valacyclovir 1g TID for 7 days).

Physical therapy may also play an important role.

To reduce eye discomfort, artificial tears may be used.

Patients with incomplete recovery may benefit from botulinium toxin injections or plastic surgery.

Around 85% of the patients improve after three weeks, even without treatment. Recurrence may be seen in about 7% of patients.

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