A Case of Paralytic Strabismus Caused by Midbrain Infarction

I. Introduction

Paralytic strabismus refers to the nerve paralysis in the muscles responsible for the movement of the eyeball for any reason, resulting in a restriction of eye movement. There are three cranial nerves involved in the extraocular muscles. Trochlear nerve, the 4th cranial nerve works on superior oblique muscle. Abducens nerve, the 6th cranial nerve adjusts external rectus muscle. Oculomotor nerve, the 3rd cranial nerve controls the rest of extraocular muscle.

Paralytic strabismus are caused by vascular risk factors such as high blood pressure, or by compressive lesions such as aneurysm in the vertebral artery, tumors, intracranial pressure, or head trauma, multiple sclerosis, and meningitis¹⁾.

Identifying the underlying causes is essential to diagnose and treat the paralytic strabismus, but It’s often impossible to determine. Initially, corticosteroids and vitamins are administered, and surgery can be considered if the symptoms do not improve after at least 6 months of observation^2,3).

In Korean medicine, there are various diseases that refer to strabismus, and depending on the severity or types of the symptoms, the name of the disease is expressed differently. Symptoms include sudden unilateral or bilateral strabismus, with vertigo, headache, nausea, and vomiting^4,5). The principle of the treatment is divided in two types with the concept of the occurring pace of the disease. If the development is fast, the principle is to subside spasm through improving blood circulation and removing cachexia. If the development is slow, improving hematological status and relaxing body muscles would be the principle of the treatment. Diagnosing etiological factor, the treatment focus would be different. For instance, If there is a disease caused by deficiency of the kidney and liver energy, the main treatment should be focused on reinforcing those organ energy. If metabolic waste is the problem, the treatment should be eliminating waste from the body⁵⁾.

There are many case reports about paralytic strabismus such as the case of Benedikt’s syndrome patient reported by Jeong et al⁶⁾, 3 cases which are treated with Homnis placenta pharmaco-acupuncture reported by Jung et al⁷⁾, or the case of a patient with midbrain and Thalamus hemorrhage reported by Lee et al⁸⁾. However, There are no studies about a case of monocular partial oculomotor nerve palsy in a patient with midbrain infarction.

This case report describes Korean medical treatment for monocular partial oculomotor nerve palsy caused by midbrain infarction.

II. Objects & Methods

III. Case Report

IV. Discussion

Strabismus is a condition in which the eyes do not properly align with each other when looking at an object. That is, the right and the left collimation axes does not face the same point⁹⁾. In previous epidemiological research, 4% of the total population has these symptoms.

Fig. 1. Progress of Eye Movement

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Strabismus is divided into paralytic strabismus and non-paralytic strabismus depending on the presence or absence of oculomotor paralysis. Paralytic strabismus is classified into lateral rectus paralysis, medial rectus paralysis, superior rectus paralysis, inferior rectus paralysis, inferior oblique paralysis and superior oblique paralysis. If one or both eyes turns inward, it is called esotropia. If one or both eyes are deviated outward, it is called exotropia. Hypertropia is a condition that the visual axis of one eye is higher than the fellow fixating eye, and hypotropia is the similar condition that the visual axis of one eye is lower¹⁰⁾.

Paralytic strabismus is divided into complete paralysis and incomplete paresis depending on the degree of paralysis. The causes include lesions of the extraocular muscles themselves or nerve paralysis. Lesions of the extraocular muscles include various physical trauma such as orbital fracture, physical impairment of eye movement due to scar formation caused by repeated muscle operations, muscle degeneration, infection, diabetes, peripheral nerve lesions due to trauma, and nucleus & nuclear lesions caused by encephalitis or cerebrovascular circulation disorder^2,3,9).

The extraocular muscles consist of four rectus muscles and two oblique muscles, and there are three cranial nerves involved in the extraocular muscles. Trochlear nerve, the 4th cranial nerve works on Superior Oblique muscle. Abducens nerve, the 6th cranial nerve adjusts external rectus muscle. Oculomotor nerve, the 3rd cranial nerve controls the rest of extraocular muscle. The 3rd, 4th, and 6th cranial nerves are paralyzed by various causes and are known to have various clinical manifestations of paralysis. According to reports, the overall incidence of the cranial nerve paralysis was abrupt in the abducens nerve, followed by oculomotor nerve and trochlear nerve²⁾.

Oculomotor nerve is the 3rd cranial nerve that controls the rest of extraocular muscles except for the lateral rectus and superior oblique. It controls the eye movement and the contraction of the pupil¹¹⁾. Oculomotor nerve palsy is caused by congenital or head trauma, vascular disease, aneurysm, tumor, diabetes, inflammatory disease, etc. The nucleus of the oculomotor nerve is located in the midbrain, so midbrain damage such as infarction, hemorrhage, and tumors can cause nerve paralysis. If the midbrain is damaged, It may cause the symptoms related to the eye, and also cause headache, nausea, vertigo, vomiting, rigorous hemiplegia or tremor. However, depending on the area of damage to the midbrain, the oculomotor nerve palsy may occur without ataxia^12,13). In the case of a single oculomotor nerve palsy, limited adduction, upshoot and downshoot movement and ptosis may occur. In addition, diplopia and visual impairment could appear. If the inner fibers of the nerve are damaged, the pupil expands and the light reflexes and the control reflexes would disappear. However, sympathetic light reflexes of the opposite eye would be normal^11,12,14). In most cases, when the lesion occurs in the nerve nucleus or nerve fibers, bilateral ocular motility disorders such as ptosis or bilateral upward gaze disorder may occur. Therefore, when a complete or partial oculomotor nerve palsy occurs, it is thought to be caused by subarachnoid space, spongy area, aneurysm occurring in the posterior segment of the eye, tumor, inflammation or muscle disease, or peripheral neuropathy. In rare cases, however, some of the neuromuscular complexes may be damaged, resulting in paralysis of some of the extraocular muscles dominated by oculomotor nerve, or if the nerve fibers are damaged while driving through the midbrain, only some of the nerve-dominated muscles are paralyzed^15-17). These partial paralysis occurring in some muscles are due to the three-dimensional arrangement of oculomotor nerve nuclei, and therefore, eye movement paralysis can occur in various forms^18-21).

This case is considered to be rare because this patient had paralytic strabismus without intracranial hypertension, rigorous hemiplegia, or ataxia, and also the cranial nerve is partially paralyzed so the discomfort only appears when he is gazing to the left.

Many books such as Young Chu or Zhu Bing Yuan Hou Lun mentioned the causes, types, features, characteristics, and treatments of strabismus. In Korean medicine, strabismus is caused by a lack of organ energy, which makes bad energy enter to the body and damage the eyes²⁾. Park et al⁵⁾ reviewed about causes and treatments of strabismus. In this review, strabismus is mainly caused by trauma, pathogenic energy or factors, metabolic waste, and lack of organ energy. The target and method of the treatment would be different depending on the diagnosis. For instance, If there is a disease caused by deficiency of the kidney and liver energy, the main treatment should be focused on reinforcing those organ energy. If metabolic waste is the problem, the treatment should focus on eliminating waste from the body.

This patient is 59-year-old male person with slightly obese body types. He suddenly developed diplopia on December 11, 2018, so he was hospitalized in the Neurology Department of General Hospital on December 12, 2018. He was diagnosed with midbrain infarction so he took the conservative treatment for 7 days. On December 19, 2018, He started Korean medical treatment.

Initially, the patient had limited Rt. eye movement so there was no voluntary Rt. eye movement from center to inside. As the patient's gaze moved from the right to the left, the diplopia phenomenon became apparent, making it impossible for the patient to walk without an eye patch on his Rt. eye.

The treatment was mainly performed in 2 ways, herbal medicine and acupuncture.

Herbal medicine treatment can be performed using Bianzheng Lunzhi - Korean medicine diagnosing tool - based on the comprehensive body condition. It also intended to recover the normal condition by removing pathogenic Qi and smoothly circulating the vital energy. If extraocular muscles are injured, Huafengdan could be chosen. In case of removing of metabolic waste, zhengrongtang could be used for strabismus²²⁾.

However, in this case, the patient was exposed to excessive drinking, constant overwork and stress. His personality was rapid and easily angered. His face and eyes were red, and his body was hot. He was also suffering from hypertension and hyper-lipidemia so he was taking the medication. Therefore, the perception of Korean medicine, this patient was judged to have a lot of heat in the liver so Saengkankunbi-tang is intended to remove the heat of the liver through urinating, and vitalize hyperactive liver. The patient took Saengkankunbi-tang 2 times a day for 17 days. After that, the patient didn’t want any more herbal medicine treatment, so the treatment was suspended. Kim²³⁾ has made Saengkankunbi-tang for Liver function normalization through comforting stomach and spleen, smoothing urination, normalizing gall bladder function. A study reported by Hwang et al²⁴⁾ have shown that Saengkankunbi-tang has a significant effect in preventing hyperlipidemia caused by long-term alcohol administration, and the role of Saengkankunbi-tang in the management of hyperlipidemia can be also expected. However, it was difficult to observe the long-term effects of herbal medicines.

Based on the previous studies, neighboring acupuncture points or remote acupuncture points could be chosen for acupuncture treatment. In terms of using remote acupuncture point, Jung et al²⁵⁾ reported a case of exotropia treated by Saam small intestine tonifying acupuncture. Choi et al²⁶⁾ also reported a case of abducens nerve paralysis treated by Saam stomach tonifying acupuncture. In other cases, neighboring acupuncture points are also used for treatment²⁷⁾. BL1, GB1, ST2, TE23, GB41 are all located around the eyes and effective for eye dryness, pain, cloudy cornea and conjunctiva²⁸⁾. Additionally, electro-acupunctures could be another option for treatment. Previous studies have used neighboring acupuncture points for electro-acupunctures but recent studies suggest to perform electro-acupunctures directly on paralyzed ocular muscles^29-31). In this study, LI4, ST1, EX-HN4, GB1, TE23, BL2, GB20 are used to help the circulation of Qi and blood around the eyes.

On December 19, 2018, the adduction range was significantly impaired to 14㎜ in the Rt. eye movement. The patient appealed severe diplopia when gazing to the left. However, on January 28, 2019, the distance of Rt. eye movement increased to 20㎜ and diplopia symptoms are relieved to moderate so the patient was able to walk without wearing an eye patch. On February 27, 2019, the distance of rightward movement increased to 22㎜ but the rate of improvement was slower than the beginning of treatment, and diplopia remained similar. On March 22, 2019, As Rt. eye movement and diplopia were improved, the discomfort was almost lost when looking near, but the patient still complained of diplopia when looking far. The distance of rightward movement increased to 25㎜. On April 5, compared with March 22, Rt. eye movement was similar, but diplopia was slightly improved.

In conclusion, during 15 weeks of treatment, the range of adduction of the Rt. eye was continuously increased through the Korean medicine treatment, and the moving distance of the Rt. eye increased by 11㎜ compared to the initial treatment and the diplopia symptoms also improved.

Through this case, we can confirm that Korean medicine treatment is helpful for the improvement of paralytic strabismus caused by midbrain infarction, which suggests the possibility that a good progress can be expected when Korean medicine treatment is attempted for symptoms of oculomotor nerve palsy. However, it is difficult to generalize the treatment effects of this case because there is only one case and the treatment was not completed. The overall results were thought to be contributed mainly by acupuncture treatment, as herbal medicine was administered only in the early stages of treatment. More case reports and systematic research such as RCTs are expected to be needed in the future.

V. Conclusion

In this study, we reported a case of paralytic strabismus caused by midbrain infarction. The patient was treated with Korean medicine and the symptomatic improvement was confirmed without any side effects. Therefore, it can be used as a basis for the Korean medical treatment and research of paralytic strabismus in the future.