1 - Cranial Nerves Flashcards by John Castillo

What Cranial Nerves exit the midbrain?

What Cranial Nerves exit the pons?

What Cranial Nerves exit the medulla?

What cranial Nerves exit the spinal cord?

Midbrain: III, IV

Pons: V, VI, VII, VIII

Medulla: IX, X, XII

Spinal Cord: XI

How well did you know this?

Not at all

Perfectly

CN II exit from CNS? (important regions from table)

Thalamus, Hypothalamus

Pretectal Area, Superior Colliculus

How well did you know this?

Not at all

Perfectly

What are the two exceptions to the rule that CN nuclei are the same level as the nerve entry/exit?

2/4 Trigeminal Nuclei

Spinal Trigeminal Nucleus extends caudally (to cervical spinal cord)

Mesencephalic Trigeminal Nucleus extends into midbrain

How well did you know this?

Not at all

Perfectly

What is the general location of sensory vs motor of CN nuclei?

Sensory = Lateral

Motor = Medial

How well did you know this?

Not at all

Perfectly

What is unique about CN II?

What is it formed by?

Where do they project to?

Only cranial nerve that is a CNS pathway, not a peripheral nerve

Formed by axons of retinal ganglion cells

- - -

Project to suprachiasmatic nucleus of hypothalamus, superior colliculi, and lateral geniculate nucleus of thalamus

How well did you know this?

Not at all

Perfectly

What is the importance of the pretectal area?

Important for relay in pupillary light reflex pathway

How well did you know this?

Not at all

Perfectly

Two Components and of CN III (Oculomotor)?

Nuclei?

Somatic Motor:

All extraocular muslces (ex. sup oblique/lat rectus), Levator palpebrae superior

Oculomotor Nucleus

- - -

Visceral Motor (via Ciliary Ganglion)

Parasympathetic innervaion of pupil constrictor and ciliary muscles

Edinger-Westphal Nucleus

How well did you know this?

Not at all

Perfectly

Pupullary Reflex Pathway

Sensory Input?

Key Region?

Motor Output?

Sensory Input: CN II (light hits eye)

Key Region: Pretectal Area (between superior colliculus and thalamus)

Relays bilaterally to preganglionic parasympathetics neurons in Edinger-Westphal Nucleus; contralateral projection is through post. commissure (mediates consenual light response)

Motor Output: Edinger-Westphal Nucleus to ciliary ganglion to pupillary constrictor

How well did you know this?

Not at all

Perfectly

Direct and Consensual Response: Oculomotor Lesion

Pupil will not constrict on side of lesion

How well did you know this?

Not at all

Perfectly

Direct and Consensual Response: Horner’s Syndrome

Pupil can not dilate on impaired side

Other Symptoms: Ptosis, Anhydrosis

*Lesion of Sympathetics = Deficit in Dilation*

How well did you know this?

Not at all

Perfectly

Direct and Consensual Response: Afferent Nerve defect

Sensory Loss

Impaired direct and consensual response on affected side.

Normal response on unaffected side.

How well did you know this?

Not at all

Perfectly

Direct and Consensual Response: Benign Anisorcoria

Pupil Asymmetry; no clinical pathology

How well did you know this?

Not at all

Perfectly

Clinical: Unilateral LMN Lesion of CN III

Common Causes?

Complete Loss of Function = “Down and Out” Eye

Ptosis = eyelid droop

Blown Pupil, no response to light (loss of parasympathetic constrictor)

Common Causes: Diabetes, tumors, compression of Posterior Communicating Artery, uncal herniation

How well did you know this?

Not at all

Perfectly

What is unique about CN IV (Trochlear)

Main role?

Only CN to exit dorsal surface

Function: Innervates Superior Oblique (contralateral to nucleus) – Fibers will decussate

How well did you know this?

Not at all

Perfectly

Clinical: Unilateral LMN Lesion of CN IV

Loss of Function?

Common Causes?

Loss of Function: Elevation and Extorion of affected eye–causes diplopia; clinical sign of Head Tilt

Common Causes: Head trauma (nerve vulnerable to shearing injury), tumor of midbrain/tectum, diabetes

How well did you know this?

Not at all

Perfectly

Trigeminal Nerve (CN V) Components

Somatic Sensory:

Touch, pain, temperature, joint position, vibration

Face, mouth, anterior 2/3 of tongue (not taste), nasal sinuses, meninges (related to Migraines)

Branchial Motor: Muscles of mastication, tensor tympani, tensor veli palatini, mylohyoid, anterior digastric

How well did you know this?

Not at all

Perfectly

Trigeminal Sensory Nuclei

Location

Input

Output

Location: Lateral mid-Pons

Input: large diameter sensory fibers from face; analogous to dorsal column; discriminative touch, vibration, proprioception

Output (Trigeminal Lemniscus): Second order neurons, crosses and joins medial lemniscus, projects to VPM of thalamus

Trigeminal (CN V) Sensory Nuclei: Spinal Trigeminal Nucleus

Input

Output

Spinal Trigeminal Nucleus

Located laterally from mid-pons to upper cervical spinal cord, w/input from small diameter sensory fibers (crude touch, pain, temperature)

Spinal trigeminal tract carriers descending sensory fibers

Output (Trigeminothalamic tract): Second order neurons, joins anterolateral system

Topographic Representation of Face

Face represented in “onion skin” pattern

Concentric rings centered around mouth

Trigeminal Sensory Nuclei: Mesencephalic Trigeminal Nucleus

Location?

Input

Output

Location: Laterally from mid-pons to midbrain long lateral edge of periaqueductal grey

Input: Cell bodies of large diameter sensory fibers that convery priprioceptive sensation – “centrally located sensory ganglion”

Output: Descends to trigeminal motor nucleus, mediates jaw-jerk reflex

Trigeminal Motor Nucleus

Contain LMN for branchiomotor functions of Trigeminal

Receives proprioceptive sensory input for jaw-jerk reflex (absent with UMN injury)

Clinical: Trigeminal Neuralgia (tic douloureux)

Chronic pain condition

Type 1: Typical Form - extreme sporadic burning or shock-lik pain; may repeat in short intervals

Type 2: Atypical Form - constant aching, burning, or stabbing pain (lower intensity that Type 1)

Pain can be incapacitating

Cause: May be from nerve compression/inflammation

Clinical: Trigeminal Disorders - Shingles

Cause: Herpes Zoster (chicken pox virus), virus reemerges (usually older adults), as shingles rash

Postherpetic Neuralgia: Severe pain in area which has shingles rash

Vision loss possible if eye affected

Vaccine available (rec’d for adults 50+)

Clinical: Trigeminal Disordrs - Sensory Loss

Peripheral lesion

CNS Lesion in Lateral Pons, Medulla

If Spinothalamic fibers in the anterolateral system are also injured – ipsilateral sensory loss in face, contralateral sensory loss in body

CN VI (Abducens) Type

Type: **Somatic Motor** - lateral rectus (abduction of eye)

Clinical: Unilateral LMN Lesion of CN VI (Abducens)

Lateral gaze paralysis Inability to abduct affected eye At Rest: Medial Strabismus (cross eye), horizontal diplopia

CN VII (Facial) Types? (4)

**Branchiomotor:** Muscles of face, stapedius, post. digastric, stylohyoid muscles--**Facial Expression** **Parasympathetics:** Sublingual, Submandibular, Lacrimal **Visceral (Chem) Sensory:** Ant. 2/3 tongue Taste **Somatic Sensory:** Portion of outer ear

CN VII (Facial) Nuclei (4x)

**Facial Nucleus:** LMN innervating muscles of face (branchiomotor) **Superior Salivatory Nucleus:** Salivary and Lacrimal glands (parasympathetics) **Spinal Trigeminal Nucleus:** Somatic sensation from outer ear **Solitary Nucleus:** Visceral (chemical) sensation from ant. 2/3 tongue

Corneal Reflex Afferent Limb Efferent Limb

Afferent Limb: Trigeminal Nerve (ophthalmic division), **Chief Sensory/Spinal Trigeminal Nuclei** **Note: Blink can be invoked by visual stimuli--input is CN II in this case** Efferent Limb: Facial Nucleus and Nerve, Orbicularis Oculi Muscles

Clinical: Unilateral LMN Lesion of CN VII

**Ipsilateral Face Weakness from UMN lesion** **- - -** **Bell's Palsy** (most common) Ipsilateral weakness, loss of taste sensation from ant. ipsilateral tongue Hyperacusis, ear pain Drooling Dry eyes, mouth "Crocodile Tears" due to recovery of paraysmpathetics "Synkinesis", or abnormal movements of face

CN VIII (Vestibulocochlear) Type?

Somatic Sensory

CN IX (Glossopharyngeal) Components (4x)

**Branchiomotor:** Stylopharyngeus **Parasympathetics:** Parotic Gland **Somatic Sensory:** Touch, pain, temperature from posterior 1/3 of tongue, pharynx, **middle ear**, portion of outer ear **Visceral Sensory:** Baro- and chemo-receptors in carotid body, taste receptors in posterior 1/3 of tongue

CN IX (Glossopharyngeal) - Nuclei

**Branchiomotor:** LMNs in **Nucleus Ambiguus** **Parasympathetic:** Preganglionic neurons in inferior salivatory nucleus **Somatic Sensory:** Spinal trigeminal nucleus **Visceral Sensory:** Baro- and chemo-receptors: Caudal solitary nucleus Taste Receptors: Rostral solitary nucleus

CN X (Vagus) - Types

**Branchiomotor:** Muscles of pharync and larynx (speech and swallowing) **Parasympathetic:** Major portion of nerve, heart, lungs, digestive tract **Somatic Sensory:** Pharynx, larynx, meninges, portion or outer ear **Visceral Sensory:** Baro-and chemo-receptors in **aortic arch,** cardiorespiratory and digestive systems; taste receptors in epiglottis, posteriorpharynx

CN X (Vagus) - Nuclei

Branchiomotor: LMNs in nucleus ambiguss Parasympathetic: Preganglionic neurons in dorsal motor nucelus of vagus Somatic Sensory: Spinal trigeminal nucleus Visceral Sensory: Baro-and chemo-receptors: Causal solitary nucleus Taste receptors: Rostral solitary nucleus

Clinical: Unilateral lesion of Nucleus Ambiguus

Ipsilateral paralysis of the soft palate, pharynx, and larynx **Uvula** will deviate **away** from lesion Symptoms: Dusphonia (difficulty speaking), Dyspnea (difficulty breathing), Dysphagia (difficulty swallowing) Gag reflex diminished/absent **ipsilaterally**; afferent in CN IX, efferenct from nucleus ambiguss

CN XI (Accessory) - Type

Branchiomotor: Trapezius, Sternocleidomastoid

Clinical: Unilateral LMN Lesion of CN XI

Paresis/Paralysis of the **ipsilateral sternocleidomastoid** and **ipsilateral trapezius** Patient **unable** to turn their head away from side of lesion **Ipsilateral shoulder drop**, may have difficulty raising ipsilateral arm above horizontal

CN XII (Hypoglossal) - Type

Somatic Motor: Intrinsic and extrinsic muscles of tongue (except palatoglossus)

Clinical: Unilateral LMN Lesion of CN XII

Ipsilateral tongue weakness--**tongue deviates TOWARD lesion** Ipsilateral fasciculations, Atrophy