The trochlear nerve is a motor nerve that arises from the midbrain and is the only cranial nerve that crosses to the other side of the brain. It innervates the superior oblique eye muscle and is involved in eye movement. Lesions or damage to the trochlear nerve can cause weakness of the superior oblique muscle resulting in symptoms like hyperdeviation of the eye, limited eye movement, and double vision when looking downward. The most common causes of trochlear nerve palsy are congenital, traumatic injury, and idiopathic.

1. TROCHLEAR NERVE
30th July 2020
DR M SAQUIB
Vice Principal
MBBS,MS , FSCEH DELHI,FHVDESAI PUNE,
EX REGISTRARA JNMCH,AMU
CONSULTANT OPHTHALMOLOGIST
HOD D/O OPHTHALMOLOGY
G.S .MEDICAL COLLEGE
Founder sec: MEDICS India ,
Mail-dms2k5@gmail.com , 9634123800

2. Trochlear Nerve
▸ Motor Nerve
▸ Arise from Dorsal aspect of the Brain
(Midbrain)
▸ Only cranial Nerve to cross completely on
the other side
▸ Trochlear nerve arises from the
contralateral nucleus
▸ Longest and thinnest of all cranial nerve2

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4. Functional components
▸ Somatic Efferent
component
Eye ball movement through
superior oblique
▸ General somatic afferent
Proprioceptive impulse
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5. NUCLEUS
▸ Trochlear
Nucleus
Situated in
the
midbrain at
the level of
inferior
colliculus
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6. Connection of Nucleus
▸ Cerebral Cortex
▸ Nuclei of 3rd ,6th and 8th Cranial Nerve
▸ Superior colliculi
▸ Vertical and torsional gaze center
▸ Cerebellum
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8. Course and Distribution
▸ FASCICULAR PART •
▸ Nucles efferent fibres posteriorly
around the aqueductal gray matter
anterior medullary velum decussate
completely
▸ Pre-cavernous
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9. ▸ Intracavernous
▸ Intraorbital
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11. g
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14. Primary – Intorsion
Secondary- Depression
Tertiary- Abduction
▸ visual stability. It resists the eye’s
tendency to rotate itself involuntarily
when looking downwards or upwards.
▸ inward torsion, which maintains the
position of the eye towards the midline of
the face
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15. ▸ Hyperdeviation –Involved eye is higher as a
result of the weakness of the superior oblique
muscle .
▸ Ocular movements- Depression is limited in
adduction .Extorsion is limited
Diplopia –Homonymous vertical diplopia occur
on looking downward
Abnormal Head Posture To avoid diplopia head
takes posture towards the action of superior
oblique muscle
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17. Causes of 4th Nerve Palsy
▸ Congenital paralysis : 40%
▸ Trauma -34%
▸ Idiopathic -20%
▸ Vascular – Aneurysm
▸ Neurological - Myasthenia Gravis17

18. ▸ Superior oblique paralysis is the most
common form of paralytic squint
▸ Nuclear Lesion – when the lesion involve
the nucleus and the fibres of the nerve
within the midbrain before their
decussation ,there occurs paralysis of the
contralateral superior oblique muscle .
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20. ▸ Thanks
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