28: Facial and Trigeminal Neuropathy

Question 1

Facial nerve carries what fiber bundles, and what do they innervate?

Answer 1

1. Motor fibers (muscles of facial expression; posterior belly of digastric, stapedius, stylohyoid)
2. Parasymp motor fibers (mucosa of soft palate; salivary and lacrimal glands)
3. Taste (anterior 2/3 of tongue)
4. Parasymp sensory fibers (visceral sensation from salivary glands and nasal and pharyngeal mucosa)
5. Somatic sensory fibers (small part of external auditory meatus and skin of ear)
6. Proprioceptive sensory afferents

Question 2

The facial nerve within the bony facial canal gives off what branches after passing through the geniculate ganglion?

Answer 2

Parasymp fibers given off to the greater and lesser petrosal nerves (bound for the pterygopalatine and otic ganglia)

Question 3

What supplies taste fibers to the anterior 2/3 of the tongue? What else does this nerve supply?

Answer 3

Chorda tympani nerve;
parasymp fibers to the submandibular and sublingual salivary glands

Question 4

After the stylomastoid foramen, what muscles are supplied by the facial nerve prior to innervating the muscles of facial expression?

Answer 4

Stylohyoid and the posterior belly of the digastric muscles

Question 5

Peripheral branches of the facial nerve?

Answer 5

Temporal, Zygomatic, Mandibular, Buccal, Cervical

Question 6

Some facial nerve-innervated muscles?

Answer 6

Frontalis; orbicularis oculi; nasalis; levator labii superioris;
zygomaticus; orbicularis oris; mentalis

Question 7

What are the three sensory nuclei?

Answer 7

1. Main sensory nucleus (mid-upper pons): light touch
2. Nucleus of the spinal tract of V (pons to upper cervical cord): pain and temperature
3. Mesencephalic nucleus of V (lower midbrain): proprioception from facial muscles

Question 8

What is the trigeminal ganglion known as?

Answer 8

Semilunar or gasserian ganglion

Question 9

Three major peripheral nerve divisions of the trigeminal nerve?

Answer 9

1. Ophthalmic
2. Maxillary nerve
3. Mandibular (has motor fibers supplying muscles of mastication, anterior belly of digastric, mylohyoid, tensor tympani muscles)

Question 10

Muscles of mastication?

Answer 10

Masseter, temporalis, medial and lateral pterygoid muscles

Question 11

What increases risk of Bell’s palsy?

Answer 11

HTN, DM, pregnant women

Question 12

What else can cause unilateral facial nerve dysfunction?

Answer 12

Herpes zoster involving the geniculate ganglion (Ramsay Hunt); lymphoma; leprosy; cerebellopontine angle tumors, MS, stroke

Question 13

What is a consequence of aberrant reinnervation after Bell’s palsy?

Answer 13

Synkinesis of facial movements (e.g. closing eyes can lead to movement of the lips due to involvement of orbicularis oculi and oris)

Question 14

What is the most common cause of hemifacial spasm?

Answer 14

Aberrant blood vessel lying in contact with the facial nerve near its exit zone from the brainstem

Question 15

Trigeminal neuropathy most often seen with what pathology?

Answer 15

Connective tissue disorders, like Sjogren or SLE

Question 16

What facial nerve peripheral branches, when stimulated on NCS, innervate what muscles?

Answer 16

Temporal (frontalis);
Zygomatic (nasalis);
Buccal (orbicularis oris);
Mandibular (mentalis);
Cervical (platysma)

Question 17

What characteristic differentiates hemifacial spasm from blepharospasm and other central movement disorders?

Answer 17

MUAPs firing repetitively at high rates (80-150 Hz), often in irregular bursts