The facial nerve (VII) originates in the brainstem and has both motor and sensory functions. It exits the skull through the internal acoustic meatus and travels through the facial canal. It gives off several branches that innervate the muscles of facial expression and the parotid gland. The chorda tympani and greater petrosal nerves carry parasympathetic and special sensory fibers. Injury at different points along the nerve can cause distinct functional deficits, such as loss of taste, tearing with smiling (crocodile tears), or hypersensitivity to sound.

1. Facial nerve

2. Introduction
• VII
• second pharyngeal arch
• Motor:
• Sensory
• Special sensory
• Parasympathetic

3. Intracranial
• UMN - 1ry motor cortex FL
• Descend ipsiL
• nucleus at dorsal Pons
• 2 parts :
• dorsal – upper face- both hemispheres
• Ventral – lower face – contraL hemisphere
• 2 roots : motor and sensory

4. Intra-temporal
• internal acoustic meatus
• facial canal
• stylomastoid foramen.

5. Extracranial
• Branches :
• Post auricular :
• Branch to post belly of the digastric muscle
• stylohyoid muscle
• Parotid gland
• Temporal
• Zygomatic
• Buccal
• Marginal mandibular
• Cervical

7. Parasympathetic/Special sensory
Greater petrosal nerve.
• immediately distal to the geniculate ganglion
• combines with the deep petrosal N to form nerve of pterygoid canal
• through the pterygoid canal to enter the pterygopalatine fossa, and synapses with
the pterygopalatine ganglion
• mucous glands of the oral cavity, nose and pharynx, and the lacrimal gland

8. Parasympathetic/Special sensory
• Chorda tympani
• Facial canal travel thr middle ear
• Exit petrotympanic fissure
• Enter infratemporal fossa
• Combine lingual N – submandib gang
• 2/3 of the tongue and taste.
• Parasympathetic : submandibular and sublingual glands

9. Intracranial Injury
• Muscles of facial expression
• Chorda tympani – altered salivation and loss of taste on the ipsilateral 2/3 of the
tongue.
• Nerve to stapedius – ipsilateral hyperacusis.
• Greater petrosal nerve – ipsilateral reduced lacrimal fluid production.

10. Extracranial injury
• distal to the stylomastoid foramen.
• Only the motor function : muscles of facial expression.

12. Crocodile tears
• Bogorad syndrome
• PH of FN
• different theories
• Diagnosis by exclusion
• Slit lamp
• Schirmer's test
• treatment = severity
• Botox

13. Hyperacusis
• unusual tolerance
• Less data
• Tinnitus
• 1.5-hydroxytryptamine (5-HT) dysfunction
• 2.neurotransmitters
• 3.auditory efferent dysfunction
• Desensitization