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B29. Symptoms of peripheral and central facial palsy

From greek.doctor

Facial nerve palsy is a peripheral (nuclear) or central (supranuclear) lesion of the facial nerve. In the cases where this lesion is idiopathic and peripheral, the condition is called Bell’s palsy.

The upper half of facial muscles are innervated by fibres from both hemispheres. These are the muscles for movement of forehead and eyelid. The lower half is innervated only from the contralateral hemisphere. As such, a peripheral palsy will affect both the upper and lower facial muscles, while a central palsy will affect only the lower facial muscles.

Etiology

Bell’s palsy is caused by idiopathic inflammation of CN VII in the facial canal. It might be due to viral infection, especially HSV.

Clinical features

Peripheral lesion

Symptoms of peripheral facial palsy are ipsilateral to the lesion and affect both the lower and upper half of the face. Symptoms include:

  • Motor symptoms
    • Frowning, eye-closing, blinking is impaired
    • Inability to close the eye
    • Drooping corner of mouth
    • Disappearance of nasolabial fold
  • Pain behind the ear
  • Hyperacusis
  • Abnormal lacrimation
  • Abnormal taste

If Lyme disease is the cause, the facial palsy may be bilateral.

Central lesion

Symptoms of central facial palsy are contralateral to the lesion and affect only the lower half of the face. Symptoms include:

  • Drooping corner of mouth
  • Disappearance of nasolabial fold

Diagnosis and evaluation

To evaluate for the motor symptoms, ask the patient to grin with teeth, close their eyes, and wrinkle the forehead. The tympanic membrane and ear canal should be evaluated for herpes blister by otoscope. If peripheral facial palsy is the only symptom, Bell’s palsy is assumed, and no further investigation is needed. If other symptoms are present, investigate with MRI or LP to look for other causes.

Treatment

In most cases Bell’s palsy resolves completely in a few weeks without treatment. Corticosteroids hasten the resolution if given within the first 3 days of symptoms. Acyclovir can be used if viral etiology is suspected.

To prevent atrophy the patient should do physiotherapy of the face. To prevent keratitis if the patient can’t close the eye completely, artificial eye drops must be used to prevent dry eyes.