Neurology · MU Sofia

15. Facial nerve: anatomy, physiology, examination, syndromes

Covers the anatomy and functions of the facial nerve, including its motor, sensory taste, and parasympathetic roles, followed by a clinical examination sequence covering inspection, facial muscle testing, taste, and the corneal reflex. Compares peripheral (LMN) and central (UMN) facial palsy, with Bell's palsy, their clinical features, and the reason forehead movement is spared in central lesions, then briefly notes hemifacial spasm and facial synkinesis.

Inside: 1 section · 16 flashcards · 2 min

Topic 15 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 285 words (2 min of reading), with 16 flashcards.

In this note

  1. Facial nerve - anatomy, physiology, examination, syndromes

Facial nerve - anatomy, physiology, examination, syndromes

Anatomy

The facial nerve (CN VII) is a mixed cranial nerve with motor, sensory, parasympathetic, and special sensory (taste) functions.

Functions

  • Motor
  • Innervates muscles of facial expression: Frontalis. Orbicularis oculi. Orbicularis oris. Buccinator. Platysma
  • Sensory: Taste from the anterior 2/3 of the tongue (via chorda tympani)
  • Parasympathetic
  • Stimulates: Lacrimal gland. Submandibular gland. Sublingual gland
  • Reflexes
  • Corneal reflex: efferent limb (blinking)

Physiology

The facial nerve is responsible for: Facial expression. Eye closure. Smiling. Frowning.Taste from anterior tongue. Autonomic (Tear and saliva production)

Examination

1. Inspection

  • Observe: Facial symmetry. Nasolabial folds. Forehead wrinkles. Drooping of mouth corner

2. Motor Examination

  • Ask the patient to:
  • Upper Face: Raise eyebrows. Wrinkle forehead
  • Eyes: Close eyes tightly
  • Lower Face: Smile. Show teeth. Puff out cheeks. Whistle. Look for asymmetry or weakness.

3. Taste Examination: Test sweet, salty, sour, and bitter substances on the anterior 2/3 of the tongue (rarely performed clinically).

4. Corneal Reflex

  • Afferent: CN V1. Efferent: CN VII
  • Normal response: Bilateral blinking

Facial Nerve Syndromes

1. Peripheral Facial Palsy (LMN Lesion)

  • Causes: Bell's palsy (most common). Infection. Trauma. Tumors
  • Clinical Features: Ipsilateral paralysis of the entire half of the face. Inability to wrinkle forehead. Inability to close eye. Drooping mouth corner. Loss of nasolabial fold. Hyperacusis (sometimes). Decreased tearing/salivation. Loss of taste (anterior 2/3 tongue)
  • Bell's Palsy: Acute idiopathic peripheral facial nerve paralysis.

2. Central Facial Palsy (UMN Lesion)

  • Cause: Lesion above the facial nucleus (e.g., stroke).
  • Clinical Features: Contralateral weakness of the lower face only. Forehead movements preserved. Eye closure preserved
  • Reason: The upper facial muscles receive bilateral cortical innervation.

Other Facial Nerve Disorders

Hemifacial Spasm: Involuntary contractions of facial muscles. Usually unilateral

Facial Synkinesia: Abnormal associated facial movements after nerve regeneration.. Eye closure causes mouth movement

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