What are the pathological factors and symptoms of paralytic strabismus?

Strabismus caused by paralysis of the nerve nuclei, nerves and extraocular muscles that control eye muscle movement is called paralytic strabismus. It is divided into two types: congenital and acquired. So what are the causes and clinical symptoms of paralytic strabismus?

1. Causes and risk factors

1. Intracranial diseases

Virus or bacteria-induced encephalitis, meningitis, anterior horn poliomyelitis, peripheral neuritis, etc. can lead to ophthalmoplegia.

2. Tumor

Intracranial, intraorbital, or nasopharyngeal tumors compress the nerve nuclei, nerves, or eye muscles themselves that control the extraocular muscles, causing paralysis of the eye muscles.

3. Vascular disease

Skull base aneurysm, hypertensive arteriosclerosis, intracranial hemorrhage, etc. can often cause ophthalmoplegia.

4. Trauma

Head trauma damages the nerves that control the extraocular muscles and causes paralysis of the extraocular muscles.

5. Toxins

Acute carbon monoxide poisoning or lead poisoning damages the nervous system and can cause eye muscle paralysis.

6. Vitamin B deficiency

It can cause polyneuritis and may also lead to dysfunction of the III, IV, and VI cranial nerves. The same degree of injury can cause extraocular muscle paralysis.

2. Clinical symptoms

1. Eye deviation and eye movement disorder

When one of the extraocular muscles is paralyzed, its antagonist muscle is relatively too strong, and the eye deviates in the direction opposite to the action of the paralyzed muscle. Rotation in the direction of action of the paralyzed muscle is limited. If the lateral rectus muscle is paralyzed, the eyeball's outward rotation is restricted and it becomes internally biased; if the medial rectus muscle is paralyzed, the inward rotation is restricted and it becomes externally biased.

2. Double vision

Due to the destruction of fusion function, diplopia occurs, one object is seen as two objects, orientation disorder, dizziness and nausea, and unstable gait. When one eye is covered, the symptoms are significantly alleviated or disappear.

3. Compensatory head position

To overcome the interference of diplopia, the patient automatically tilts the head to the side where the paralyzed muscle acts, and at the same time rotates the face to overcome the diplopia caused by paralysis of the internal and external rectus muscles; or lifts or retracts the chin, and slightly turns the face to overcome the diplopia caused by paralysis of the upper and lower rectus muscles; or tilts the head toward the shoulder and rotates the chin and face to overcome the diplopia caused by paralysis of the upper and lower oblique muscles. Its purpose is to achieve binocular single vision and avoid diplopia.

4. The second oblique angle is greater than the first oblique angle

When looking with the affected eye, the cerebral cortex needs to strengthen the nerve impulses to the paralyzed muscle. This impulse is also transmitted to the partner muscle of the paralyzed muscle at the same time, causing the healthy eye to deviate significantly.