Hard Cranial Nerves

CN V

Trigeminal

Motor to muscles + general sensory. It does not provide motor to glands or special sensory.

What muscles does the trigeminal nerve innervate?

Muscles of mastication: masseter, temporalis, medial pterygoid, lateral pterygoid. Also mylohyoid, anterior belly of digastric, tensor tympani, and tensor veli palatini.

CN V — What sensory structures/areas does it supply?

General sensation from the face, scalp, cornea, nasal/oral cavities, teeth, anterior 2/3 of tongue (general sensation), and dura mater.

CN V — What are its three major divisions?

V1 ophthalmic, V2 maxillary, V3 mandibular. V1 and V2 are sensory; V3 carries both sensory and motor fibers.

CN V — Is the motor nucleus controlled bilaterally or unilaterally by the cortex?

Bilateral cortical input

CN VII

Facial Nerve

CN VII — What modalities does the facial nerve carry?

Motor to muscles + motor to glands + sensory + special sensory.

CN VII — What muscles does it innervate?

Muscles of facial expression, plus stapedius, stylohyoid, and posterior belly of digastric.

CN VII — What glands does it innervate?

Lacrimal gland and submandibular and sublingual salivary glands.

CN VII — What sensory/special sensory information does it carry?

General sensation from a small portion of the external ear; taste from the anterior 2/3 of the tongue.

CN VII — What is the cortical input pattern to the facial motor nucleus?

Bilateral input to the upper face; primarily contralateral/unilateral input to the lower face.

CN VII — Why can a cortical lesion cause lower facial weakness while forehead movement is spared?

The upper facial motor nucleus receives bilateral cortical input, while the lower facial motor nucleus receives predominantly contralateral cortical input.

CN VIII

Vestibulocochlear

CN VIII — What modality does the vestibulocochlear nerve carry?

Special sensory only.

CN VIII — What are the two sensory systems carried by CN VIII?

Cochlear = hearing; vestibular = balance/equilibrium.

CN VIII — What structures does it serve?

The cochlea for hearing and the vestibular apparatus for balance.

CN VIII — Does it carry motor fibers?

No. CN VIII is a pure special sensory nerve.

CN VIII — Is there a cortical UMN input pattern to its nucleus?

N/A. It is sensory rather than a motor cranial nerve.

CN IX

Glossopharyngeal

CN IX — What modalities does the glossopharyngeal nerve carry?

Motor to muscles + motor to glands + sensory + special sensory.

CN IX — What muscle does CN IX innervate?

Stylopharyngeus — elevates the pharynx during swallowing.

CN IX — What gland does it innervate?

Parotid gland for parasympathetic salivation.

CN IX — What general sensory information does it carry?

Sensation from the oropharynx, tonsillar region, middle ear, and posterior 1/3 of the tongue.

CN IX — What special sensory information does it carry?

Taste from the posterior 1/3 of the tongue.

CN IX — What visceral sensory information does it carry?

Information from the carotid sinus and carotid body, including blood pressure and blood chemistry information.

CN IX — Is the motor nucleus controlled bilaterally or unilaterally?

Bilateral cortical input.

CN X

Vagus

CN X — What modalities does the vagus nerve carry?

Motor to muscles + motor to glands + sensory + special sensory.

CN X — What major muscles does it innervate for speech/swallowing?

Most muscles of the soft palate, pharynx, and larynx.

CN X — What is an important exception in the pharynx?

Stylopharyngeus is CN IX, not CN X.

CN X — What muscles are especially important for voice?

The intrinsic muscles of the larynx, which control vocal fold movement

CN X — What glands/viscera receive parasympathetic input from CN X?

Parasympathetic innervation to organs of the thorax and much of the abdomen, including the heart, lungs, and gastrointestinal tract.

CN X — What sensory information does it carry?

Sensory information from areas of the pharynx, larynx, external ear, and visceral organs.

CN X — What special sensory information does it carry?

Taste from a small region of the epiglottis/base of tongue.

CN X — Is its motor cortical input bilateral or unilateral?

Predominantly bilateral cortical input, especially for the motor nucleus involved in pharyngeal/laryngeal function.

CN XI

Accessory

CN XI — What modality does the accessory nerve carry?

Motor to muscles only.

CN XI — What muscles does it innervate?

Sternocleidomastoid and trapezius.

CN XI — What does the sternocleidomastoid do?

Helps with head rotation and flexion.

CN XI — What does the trapezius do?

Helps with shoulder elevation/shrugging and scapular movement.

CN XI — Does it carry sensory or glandular fibers?

No. It is classified as a motor nerve.

CN XI — What is the cortical input pattern?

Predominantly bilateral cortical input is typically described for the spinal accessory motor nucleus.

CN XII

Hypoglossal

CN XII — What modality does the hypoglossal nerve carry?

Motor to muscles only

CN XII — What muscles does it innervate?

Intrinsic and extrinsic muscles of the tongue, except palatoglossus, which is innervated by CN X.

CN XII — Why is CN XII important for speech and swallowing?

Tongue movement is essential for speech articulation, bolus manipulation, and swallowing.

CN XII — Does it carry sensory or glandular fibers?

No. It is a motor nerve.

CN XII — Is its motor nucleus controlled bilaterally or unilaterally?

Predominantly contralateral/unilateral cortical input.

CN XII — Why is the UMN input pattern clinically important?

A unilateral cortical lesion can cause weakness of the tongue, particularly affecting movement toward the side opposite the lesion.