Everyone from school is aware of 12 pairs of cranial nerves. They occupy key positions in the functioning of the nervous system. Any violation in their work entails a violation of the work of the whole organism. So the block nerve belongs to the fourth pair.
Location in the brain
It is difficult to understand what and where is located without anatomical preparations. Therefore, you need to read a detailed description of the location of the nerves. So, the fourth pair is the only one that goes to the back of the brain stem. At the level of the lower mounds of the roof of the midbrain are the nuclei of the block nerve. Looking forward, they are located forward from the central gray matter. In relation to the nuclei of the oculomotor nerve, the nuclei of the block nerve are located below.
The block nerve forms a cross on a gray plate called the brain sail, which forms the lid of the ventricle. After the nerve exits through the midbrain to the bottom of the lower mounds. Each pair goes around the leg of the brain on the side. There, the block nerve penetrates the gap between the temporal lobe of the cerebral hemisphere and the brain stem. After moving forward, it penetrates through the medulla into the outer wall of the cavernous sinus. There, through the upper orbital fissure, it reaches the orbit and extends to the superior oblique muscle of the eye.
Block nerve: functions, interaction with other pairs of nerves
The main task of the fourth pair of cranial nerves is to provide eye movement forward and down. Normally, the eyeball has several axes of rotation. In total, six muscles are involved in this process. So they distinguish between turning the eyes to the temples, to the nose, rising up and down. An important feature of human eyes is their joint movement, since normally a person cannot look with his eyes in different directions. So, oculomotor, block and abducent nerves are included in the general group of oculomotor nerves. Failure in the work of any participant causes visual impairment. Thus, we can draw the following conclusions:
- isolated eye movements are not possible;
- both eyes move at the same time;
- a pair of oculomotor muscles is always reduced.
Research Methodology
To determine whether a particular pair of cranial nerves is functioning properly, doctors use special research methods. To do this, they check whether a person has double vision. The width of the palpebral fissures, the size of the pupil, and the position of the eyeball are carefully examined. An important diagnostic test is the pupil’s response to light. For this patient, they are asked to close their eyes with their palms and abruptly remove them, looking at the light. To study the convergence of the eyes, an ordinary hammer is used. He is brought closer to the bridge of the nose, checking the convergence of apples. Accommodation is tested even easier: the patient closes his eyes, the second looks first at a distant object, then at a close one.
Block nerve damage: symptoms and treatment
Since the main function of the fourth pair of cranial nerves is motor, the first and main symptom is paralysis. There is a deviation of the eyeball up and in. This is clearly seen when the patient is walking up the stairs. Another symptom is double vision, since desynchronization forces you to project an image on different parts of the retina.
With the defeat of all the oculomotor nerves, the following picture is observed: the eye does not move, the pupil is wide, does not respond to light. If this is observed in both eyes, then we can talk about damage to the nuclei of nerves.
Most often, this is a consequence of the development of diseases such as neurosyphilis, meningitis, a sign of aneurysm, thrombosis and others. Therefore, for treatment, it is important to eliminate the root cause of the condition.
To date, there are no effective methods of treating oculomotor nerves. According to the data, physiotherapy is successfully used, its only drawback is the slow effect or its complete absence. In order for the block nerve to start functioning again, electrical stimulation is often used.
In any case, treatment should be carried out only by a doctor. In case of damage to cranial pairs of nerves, it is better to use an integrated approach that includes several techniques. It is important not to start the disease process, since during development, damage to the nerve nuclei will begin, which at times reduces the chances of recovery.