Trochlear Nerve (CN IV)
7,818 views
Cranial Nerves
- Olfactory Nerve (CN I)
- Optic Nerve (CN II)
- Oculomotor Nerve (CN III)
- Trochlear Nerve (CN IV)
- Trigeminal Nerve (CN V)
- Abducens Nerve (CN VI)
- Facial Nerve (CN VII)
- Vestibulocochlear Nerve (CN VIII)
- Glossopharyngeal Nerve (CN IX)
- Vagus Nerve (CN X)
- Accessory Nerve (CN XI)
- Hypoglossal Nerve (CN XII)
Trochlear Nerve (CN IV)
Subscribe to watch this premium Trochlear Nerve (CN IV) mnemonic in the Cranial Nerves playlist.
Subscribe to watch this premium mnemonic
Summary
The trochlear nerve, also known as cranial nerve number 4 or the 4th cranial nerve, is a motor nerve that controls eye movement - specifically by innervating the superior oblique muscle. Since it controls eye movement, the trochlear nerve is also a major motor component of the vestibulo-ocular reflex, used to stabilize our gaze in response to head movements. The nerve originates in the midbrain and exits the skull to enter the eye socket through a cranial foramen called the superior orbital fissure.
Key Points
- Trochlear Nerve (Cranial Nerve IV)
- Nerve Type
- Motor
- Function
- Eye movement
- Innervates superior oblique muscle to abduct, depress, and internally rotate eye
- Test function via six cardinal positions of gaze test (tracking H-shape)
- Damage typically leads to vertical diplopia, which worsens when the patient looks down (compensated by tucking chin and tilting head away from affected side)
- Eye movement
- Nerve Entry/Exit
- Nerve exits the dorsal midbrain near the inferior colliculus
- Only cranial nerve that crosses over (decussates) before reaching its target (superior oblique)
- Nerve originates in nucleus of the trochlear nerve
- Nerve exits the dorsal midbrain near the inferior colliculus
- Cranial foramen
- Superior orbital fissure
- Reflexes
- Vestibulo-ocular reflex (efferent motor)
- Responsible for adjusting and stabilizing vision in response to vestibular balance
- Vestibulo-ocular reflex (efferent motor)
- Nerve Type