Trochlear nerve

The trochlear nerve is the fourth cranial nerve. It innervates the superior oblique muscle ( called with animals abdominal dorsalis) motor and also has afferent fibers from the proprioceptors ( low sensitivity ).

Course

The cranial nerve nucleus of the trochlear nerve, the trochlear nucleus nervi, located in the midbrain. The nerve occurs after crossing its efferent fibers is the only cranial nerve posteriorly from the brain stem. He leaves the cranial cavity in humans through the superior orbital fissure - in non-primate accordingly by the orbital fissure, with artiodactyls through the foramen orbitorotundum - where it passes over the tendinous communis away into the eye socket and innervated there said muscle.

The tendon of the superior oblique muscle is deflected in the eye socket by a rolling cartilage in their direction of pull. This rolling cartilage ( trochlea ) was eponymous for the nerves.

Damage

Paralysis of the trochlear nerve ( fourth nerve palsy ) leads to loss of function of the superior oblique muscle, which triggers a squint with corresponding double vision ( diplopia) and movement restrictions. The affected eye deviates in this case upward ( hypertropia ) and inward ( esotropia ). There is also a significant roll of the sagittal axis outwards ( Exzyklotropie ). Vertical diplopia occur thus in particular when you look to the opposite side and down rotatory looking in the direction of the affected eye. Therefore, the patient tilts his head compensatory often to the healthy side. This leads to a so-called ocular torticollis ( head turn or torticollis ocularis ).

In an isolated unilateral injury to the brain nerve core is to be noted that the opposite side is affected due to the intersection of the nerves of the muscle.