Block nerve

The nerve block (n. Trochlearis) motor, thin, leaves the midbrain behind the plate of the quadruple, near the bridle of the upper cerebral sail. Then the nerve passes from the lateral side of the brain leg, passes between it and the temporal lobe of the cerebral hemisphere, goes in the thickness of the lateral wall of the cavernous sinus and penetrates the orbit through the upper orbital fissure. In the eye socket, he goes to the upper oblique muscle of the eye, which is innervated.

[1], [2], [3]

Important features of the IV pair of cranial nerves (block)

• The only cranial nerve that emerges from the dorsal surface of the brain.
• Crossed cranial nerve. The nucleus of the nerve block innervates the contralateral superior oblique muscle.
• Very long and thin nerve.

1. The nucleus of the block nerve is located at the level of the lower hills, ventral to the Sylvian aqueduct. It lies caudal to the nuclear complex of the third pair of cranial nerves, merging with it.
2. The bundle consists of axons that curved posteriorly around the Sylvian aqueduct and intersect with polyosti in the upper cerebral sail.
3. The nerve leaves the brain stem on the dorsal surface, caudal to the lower hills, bending laterally, goes forward under the free margin of the namet, and passes between the posterior cerebral and upper cerebellar arteries (similar to III CHN). Further passes through the dura mater and enters the cavernous sinus.
4. The intracavernous part passes in the lateral wall of the sinus, below the III CH and above the I branch of the trigeminal nerve. In the anterior part of the cavernous sinus, the nerve rises and passes through the upper orbital fissure above and the lateral ring Zinn.
5. The intraorbital part nnerverves the upper oblique muscle.

Special tests for the diagnosis of lesions of the nerve block

The three-step Parks test is very useful for diagnosing a lesion of the nerve block:

• First: assess which eye is hypertropic in the primary position. Hypertension of the left may be associated with weakness of one of the four muscles: lowering the left eye (upper oblique or lower line) or lifting the right eye (upper straight or lower oblique);
• second: determine where there is more hypertrophy of the left eye - when looking to the right or left. An increase when looking to the left implies either the left lower line, or the right lower oblique. A magnification when viewed to the right implies either the left upper oblique or right upper line;
• third: the Bielschowsky head tilt test identifies the paretic muscle. The patient, fixing the object directly in front of him at a distance of 3 m, tilts his head to the right, then to the left. An increase in left eye hypertrophy when tilting to the left implies a left
  upper oblique muscle, and a decrease in the left eye hypertrophy when tilted to the right is the left lower line.

Double test with a Maddox wand

• The red and green Maddox sticks with vertical cylinders are placed in front of the eyes.
• Each eye will distinguish between a luminous horizontal line.
• In the presence of cyclodeaviation, the line distinguished by the paretic eye will be inclined and therefore - differ from that seen by the other eye.
• Then one Maddox stick is rotated until the lines are merged (overlapped).
• Rotation can be measured in degrees and show the magnitude of cyclodeaviation.
• Unilateral lesion of the nerve block is characterized by cyclodeaviation less than 10.