Midbrain (OMG) Flashcards
What muscles of the eye are supplied by CN IV?
Superior oblique
What muscles of the eye are supplied by CN III?
- Superior rectus
- Medial rectus
- Inferior rectus
- Inferior oblique
- Levator palpebrae superioris
- Lens and iris supplied by Ciliary ganglion
What muscles of the eye are supplied by CN VI?
Lateral rectus
Describe the light reflex.
- Photons activate OPTIC NERVE, which synapses on OLIVARY PRETECTAL NUCLEUS
- Activates parasympathetic component of CN III in EDINGER-WESTPHAL NUCLEUS
- Activates ciliary and constrictor pupilae muscles
Describe the blink reflex.
- Trigeminal nerve stimulated through mechanical receptors in eye
- Trigeminal senosry nucleus inhibits oculomotor nerve/ levator paplebrae superiorius muscle
- Stimulates facial nerve to contract orbicularis oculi
What muscles of the eye are activated by the sympathetic nervous system?
Tarsal muscles
What arteries off of the basilar artery supply the midlebrain?
Posterior cerebellar artery:
- Quadrigeminal
- Superior cerebellar artery
What structures are affected in Benedikt syndrome?
- CN III nucleus
- Red nucleus
- Corticospinals
In tegementum of midbrain/ cerebellum (median zone)
What artery is typically affected in Benedikt syndrome?
- Posterior cerebral artery
What are 3 symptoms of Benedikt syndrome?
- Drooping eyelid
- Dilated, nonresponsive pupil
- Contralateral tremor
What structures are affected in Weber syndrome?
- Substantia nigra
- Corticospinals/ corticobulbar
- Oculomotor nerve fibers
What are 4 symptoms of Weber syndrome?
- Deviation of eye downward and outward
- Drooping eyelid
- Dilated, nonresponsive pupil
- Contralateral UMN paralysis
What structure is affected in Oculomotor nerve palsy?
Oculomotor nerve rootlet
What are the 3 symptoms of Oculomotor nerve palsy?
- Deviation of eye downward and outward
- Drooping eyelid
- Dilated, non responsive pupil
What is Claude’s syndrome?
- Weber’s syndrome (SN, CS, CB, CN III) +
- Red nucleus
- Cerebellothalamic fibers
What are symptoms of Claude’s syndrome?
- Deviation of eye downward and outward
- Drooping eyelid
- Dilated, nonresponsive pupil
- Contralateral UMN paralysis
- Contralateral tremor
- Ataxia
What is Parinaud’s syndrome?
Lesion of posterior tegmentum
What is the symptom of Parinaud’s syndrome?
Conjugate upward gaze
How is the position of the eye affected in Trochlear Nerve Pathology when the eye is:
- Looking straight ahead?
- Looking towards the side of the lesion?
- Looking down?
- Head tilted toward the affected side?
Straight ahead: Contralateral eye elevated due to lack of balance of superior rectus
Toward side of lesion: Contralateral eye elevated due to lack of counter balance to superior rectus
Down: Can’t be depressed below midline
Head til: Eliminates diplopia
What is the term for patients with trochlear nerve lesions correct their vision by tilting their head toward the affected side?
Bielschowsky’s Head Tilt Test
What is Argyll-Roberston Pupil?
- Pupil reacts to accommodation/ convergance, but not light
- Pupil is a fixed size, but contracts with accommodation
What structure degenerates in Adie’s pupil?
- Ciliary ganglia or post ganlionic parasympathetic fibers
What reflex is decreased/ absent in Adie’s pupil?
- Light reflex
How is the pupil affected in Adie’s pupil?
- Delayed contraction to near vision
- Delayed dilation in dark
Describe the Decerebate position? What is lesioned?
- Lesion below red nucleus
- UE extended
- LE extended
Describe the decorticate position. What is lesioned?
- CS tract lesioned
- UE flexed
- LE extended
