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'' | ''Synonym: 4th cranial nerve'' | ||
==Definition== | ==Definition== | ||
The '''trochlear nerve''' is the 4th | The '''trochlear nerve''' is the 4th [[Corpus:Cranial nerve|cranial nerve]] and carries somatomotor fibers. Together with the [[corpus:oculomotor nerve|oculomotor nerve]] and the [[corpus:abducens nerve|abducens nerve]], it is responsible for the movement of the [[Corpus:Eyeball|eyeball]] and innervates the [[corpus:superior oblique muscle|superior oblique muscle]].<dcembed ratio="16x9" caption="3D model of the base of the skull with passage points, the trochlear nerve is labeled No. 19"><dcEmbedUrl src="https://sketchfab.com/3d-models/schadelbasis-mit-durchtrittsstellen-8c43adc85da745af85707649e4b37283"></dcEmbedUrl></dcembed> | ||
==Course== | ==Course== | ||
The trochlear nerve is the only | The trochlear nerve is the only cranial nerve that originates on the dorsal side of the [[Corpus:Brain|brain]]: its origin is caudal to the [[corpus:inferior colliculi|inferior colliculi]] in the tectum of the [[corpus:mesencephalon|mesencephalon]]. The nerve is also remarkable in other respects: | ||
*It is the weakest cranial nerve | *It is the weakest cranial nerve — measured by the number of [[corpus:axon|axons]]. | ||
*It has the longest intracranial course of all cranial nerves. | *It has the longest intracranial course of all cranial nerves. | ||
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==Nucleus area== | ==Nucleus area== | ||
The core area of the trochlear nerve is called the [[corpus:nucleus nervi trochlearis|nucleus nervi trochlearis]] and is located at the level of the inferior colliculi in the mesencephalon. The | The core area of the trochlear nerve is called the [[corpus:nucleus nervi trochlearis|nucleus nervi trochlearis]] and is located at the level of the inferior colliculi in the mesencephalon. The fibers from the nuclei on both sides cross over to the opposite side. | ||
==Clinic== | ==Clinic== | ||
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*Lack of internal rotation | *Lack of internal rotation | ||
The symptoms consist of oblique, vertical double images with a maximum when looking nasally and downwards. The greatest strabismus deviation occurs when the head is tilted to the diseased side. A conspicuous elevation of the affected eye becomes visible, which is known as the [[corpus:Bielschowsky phenomenon|Bielschowsky phenomenon]]. The patient compensates by tilting the head to the opposite side | The symptoms consist of oblique, vertical double images, with a maximum when looking nasally and downwards. The greatest strabismus deviation occurs when the head is tilted to the diseased side. A conspicuous elevation of the affected eye becomes visible, which is known as the [[corpus:Bielschowsky phenomenon|Bielschowsky phenomenon]]. The patient compensates by tilting the head to the opposite side — a torticollis opticus develops. | ||
[[Tag:Corpus]] | [[Tag:Corpus]] | ||
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[[Kategorie:Nerve]] | [[Kategorie:Nerve]] | ||
[[Kategorie:Head]] | |||
Aktuelle Version vom 29. Juli 2024, 15:17 Uhr
Synonym: 4th cranial nerve
Definition
The trochlear nerve is the 4th cranial nerve and carries somatomotor fibers. Together with the oculomotor nerve and the abducens nerve, it is responsible for the movement of the eyeball and innervates the superior oblique muscle.
Course
The trochlear nerve is the only cranial nerve that originates on the dorsal side of the brain: its origin is caudal to the inferior colliculi in the tectum of the mesencephalon. The nerve is also remarkable in other respects:
- It is the weakest cranial nerve — measured by the number of axons.
- It has the longest intracranial course of all cranial nerves.
In its course, the trochlear nerve runs laterally past the crura cerebri and breaks through the dura mater dorsolateral to the oculomotor nerve, at the anterior edge of the tentorium cerebelli. It then runs in the lateral wall of the cavernous sinus and passes through the superior orbital fissure into the orbit. In the orbit, it runs laterally and cranially past the annulus tendineus communis, the origin of the eye muscles.
Innervation
The trochlear nerve supplies the superior oblique muscle.
Nucleus area
The core area of the trochlear nerve is called the nucleus nervi trochlearis and is located at the level of the inferior colliculi in the mesencephalon. The fibers from the nuclei on both sides cross over to the opposite side.
Clinic
Trochlear nerve palsy results in the loss of the superior oblique muscle. As a result, the function of the antagonistic inferior oblique muscle predominates. The following disorders of ocular motility can be observed:
- Lack of lowering of the eyeball during adduction and elevation of the bulb
- Slight nasal strabismus deviation in abduction
- Lack of internal rotation
The symptoms consist of oblique, vertical double images, with a maximum when looking nasally and downwards. The greatest strabismus deviation occurs when the head is tilted to the diseased side. A conspicuous elevation of the affected eye becomes visible, which is known as the Bielschowsky phenomenon. The patient compensates by tilting the head to the opposite side — a torticollis opticus develops.