The Third, Fourth and Sixth Cranial Nerves Flashcards
3rd Cranial Nerve
Origin
Midbrain medial to crus cerebri
3rd Cranial Nerve
Nuclei
Paired Occulomotor Nuclei
Pair EW Nuclei
Single Caudal Central Nucleus
3rd Cranial Nerve
Paired Occulomotor Nuclei function
Efferents to Extra-Occular Muscles
3rd Cranial Nerve
Paired EW Nucleus function
Efferents to Ciliary and Constrictor Pupilae Muscles
Parasympathetic
3rd Cranial Nerve
Single Caudal Central Nucleus function
Supply Levator Palpebrae Superioris Muscle
3rd Cranial Nerve
Course
Emerges from Midbrain medial to Crus Cerebri
Runs in Interpeduncular Fossa
Pierces lateral wall of Cavernous Sinus
3rd Cranial Nerve
Boundaries of Interpeduncular Fossa
Anterior: Optic Chiasma
Anterolateral: Optic Tracts
Posterolateral: Crus Cerebri
Posterior: Pons
3rd Cranial Nerve
Contents of Interpeduncular Fossa
Infundibulum
Mammilary Bodies
Posterior Perforated Substance
3rd Cranial Nerve
Divisions
Upper Division
Lower Division
Ciliary Ganglion
3rd Cranial Nerve
Upper Division supplies …
Levator Palpebri Superioris
Superior Rectus
Skeletal Muscles
3rd Cranial Nerve
Lower Division supplies …
Medial Rectus
Inferior Rectus
Inferior Oblique
Skeletal Muscles
3rd Cranial Nerve
Ciliary Ganglion supplies …
Ciliary Muscles
Sphincter Pupillae
Smooth Muscles responsible for reflexes (Light and Accommodation pathways)
3rd Cranial Nerve
Roots of Ciliary Ganglion
Motor Root: EW nucleus → 3rd Nerve → Ciliary Ganglion
Sensory Root: Nasocilliary Nerve (5th Cranial Nerve branch)
Sympathetic Root: Plexus around Internal Carotid Artery supplying CM and SP
3rd Cranial Nerve
What is Oculomotor Nerve Palsy
LMNL lesion affecting Occulomotor Nerve or Nuclei in the Midbrain
3rd Cranial Nerve
Is the Lesion Ipsilateral or Contralateral?
Ipsilateral
3rd Cranial Nerve
Consequences of Oculomotor Nerve Palsy
Ptosis (paralysis of Levator Palpebrae Superioris)
Lateral/Divergent Squint (Paralysis of Adductors)
Diplopia - Double Vision
Mydriasis - Pupillary Dilatation
Loss of Accommodation and Light Reflexes
4th Cranial Nerve
Origin
Dorsal surface of Midbrain
4th Cranial Nerve
Nuclei
Trochlear Nucleus gives somatic efferent fibers to Superior Oblique
4th Cranial Nerve
Course
Emerges from Dorsum of Midbrain
Winds around Superior Cerebellar Peduncle
Pierces Lateral Wall of Cavernous Sinus
4th Cranial Nerve
Effects of Trochlear Nerve Palsy
LMNL causing Paralysis of Superior Oblique
Contralateral Convergent Squint (Eye up and Medial)
Diplopia (when going down stairs and reading books)
6th Cranial Nerve
Origin
Pontomedullary Groove between Pons and Pyramid
6th Cranial Nerve
Nucleus
Abducent Nucleus gives Somatic Efferents to Lateral Rectus
6th Cranial Nerve
Course
Nerve emerges between Pons and Pyramid
Runs upwards and forwards piercing wall of Cavernous Sinus
6th Cranial Nerve
Abducent Nerve Palsy
LMNL Paralysis of Lateral Rectus
Ipsilateral Convergent Squint
Diplopia when looking lateral