Sensation and Motor Face Pathways Flashcards
Dermatomal Pattern of the head/neck
Pain and Temp Pathway - Face
- Receptor -> trigeminal ganglion -> Pons -> descends as Spinal Trigeminal Tract (as far as upper cervical levels); Other cranial nerve receptors run this tract as well
- All pathways synape with secondary neuron in spinal trigeminal nucleus -> Decussation -> ascending brain stem as ventral trigeminal tract (Gives off trigeminoreticular and trigeminomesencephalic pain pathways) -> Ventral posteriormedial nucleus of the thalamus
- Synapse with tertiary neuron -> exits thalamus and travels to the posterior limb of the internal capsule
- Synapse within the cortex of the postcentral gyrus
Crude Touch and Pressure Pathways - Face
- Thought to be part of the spinal trigeminal pathway with pain and temp
- May split and run bilaterally
Prprioception, Fine Touch, Vibration - Face
- Receptor in the face -> trigeminal ganglion (and CNs) -> Enter Pons
- Synapse with main sensory trigeminal nucleus -> Decussation -> Ascend the brain stem as ventral trigeminal tract -> Ventral Posteriormedial nucleus of the thalamus
- Synapse with teritary neuron -> Posterior Limb of Internal Capsule -> Synapse with Postcentral Gyrus
Blink Reflex
- One eye is touched, both blink
- Main sensory trigeminal nucleus sends a split signal (internucial axons) to both facial motor neurons causing the eyes to blink.
- Indicated whether someone may have injury to brainstem/pathway
Facial Loss Possible Causes
- Unilateral jaw pain: Cancer/Metastatic Disease
- Loss of sensation of entire face/possible blindness: Herpes zoster (shingles)
- Unilateral face loss of sensation if lesionin nucleus at the pons/medulla: Stoke or M.S,.
- Contralateral face loss of sensation if lesion is after decussation in tracts of the midbrain: Stroke or M.S.
What is the pathway involving the head and face called?
Corticobulbar pathway
Trigeminal Motor Pathway
- Muscles: Mastication (Temporalis, Masseter, Pterygoids)
- UMN travel bilaterally to the Trigeminal Motor Nucleus of the Pons
- Sends out LMN to muscles
Facial Nerve Motor Pathway
- Muscles: Facial Expression
- UMN travel from motor cortex to the Facial Motor Nucleus (UMN bilaterally; ipsilateral: only upper face; contralateral: upper and lower face)
- LMN exit nucleus to muscles
Bell’s Palsy
- Damage to CN 7
- Rapid development of weakness of upper and lwoer parts of one side of face (24-48 hours)
- May be preceded by ear pain/retroauricular (due to referral patterns)
- Associated with Lyme’s Disease
- With paralysis, may lose ipsilateral taste and tear production
Glossopharyngeal and Vagus Pathway
- Run same pathway of each other
- Muscles: Larynx and Pharynx
- UMN travels to the nucleus ambiguous in the medulla
- LMN exits and we have CNs
Spinal Accesory Pathway
- Muscles: SCM and Trapezius
- UMN travels (bilateral, ipsilateral, contrlateral) to spinal accersory nucleus in the upper cervical spinal cord
- LMN exit the spinal cord as the Accessory Nerve. This nerve ascends the vertebral canal through the foramen magnum and then exits the skull through the jugular foramen.
Hypoglossal Nerve Pathway
- Muscles: Tongue (contralateral)
- UMN moves contralateral to Hypoglossal Nucleus in the medulla
If the tongue deviates to the left, what are possible injuries?
Right UMN or LMN on left
Extra-Ocular Motor Pathway Basics
- NOT ASSOCIATED WITH MOTOR CORTEX
- Located in the frontal lobe
- Involves 3 CNs: Oculomotor, Trochlear and Abducens
Extra-Ocular Motor Pathway
- UMN comes from gaze center located in the frontal lobe
- Oculomotor: ipsilateral: Inferior oblique, inferior rectus and medial rectus; contralateral: superior rectus; bilaterally: levator palpebrae
- Trochlear: contralateral: superior oblique
- Abducens: ipsilateral: lateral rectus
Control of Horizontal Gaze
- UMN from frontal lobe
- Travels contralateral to the Reticular Formation in the Pons -> Synapses and sends signal to the abducens nucleus -> sends LMN out ipsilateral for abducens and sends out internucial neuron (medial longitudional tract) to the contralateral oculomotor nucleus (sends LMN to medial rectus on ipsilateral)
What muscles create intorsion vs extorsion?
Intorsion: superior rectus, superior oblique
Extorsion: inferior rectus, inferior oblique
Spinal Cord Pathway Cross section Basics
- Inside to outside: Cervical, Thoracic, Lumbar, Sacral
- Reversed in the doral column
General Pathway through internal capsule
Medial: Head and face pathways; axons from thalamus to cortex; Corticobulbar
Lateral: Body pathways; axons from motor corticies to the cerebral peduncles; Corticospinal tract
This lady was asked to close her eyes tightly and show her teeth. What’s wrong with this patient?
Left Facial Periperal Nerve Damage
