Extraocular muscle hypoplasia

Introduction to extraocular muscle hypoplasia Extraocular muscle dysplasia (ateliaofocularmuscles) is a congenital dysplasia in which the extraocular muscles are completely or partially undeveloped and the extraocular muscles are ectopically attached. Clinically, congenital extraocular muscles are completely or partially underdeveloped, which is mainly due to the lack of extraocular muscles in the absence of congenital extraocular muscles, and the inferior rectus muscles are congenitally absent. Congenital extraocular muscle end attachment abnormalities are more common, the most common is the oblique oblique muscle attachment abnormalities. Secondly, the medial and lateral rectus muscles are displaced downwards, and the slight displacement of the medial rectus muscle lateral displacement can only be manifested as slanting, and the large displacement can show obvious eye position deflection. basic knowledge The proportion of illness: 0.02% Susceptible people: no special people Mode of infection: non-infectious Complications: ptosis

Extraocular muscle dysplasia

(1) Causes of the disease

The true cause of congenital extraocular muscle hypoplasia is unclear.

(two) pathogenesis

From the perspective of embryonic development, the extraocular muscles are developed from the center of each mesoderm. During the period of 12 to 13 mm in the 5th week, the mesoderm condenses into a very thin cone, which is the cone of the mesodermal layer. The formation is the beginning of the development of extraocular muscles. When the embryos are 13 to 18 mm in length in the 6th week, the muscle cones are obvious. When the 6th weekend has become an individual muscle tissue, the differentiation of the extraocular muscles begins at the back of the eyelids. Pointed forward and forward, at the end of the second month of the embryo 30mm length, the muscle is composed of long cells and fibers, separated by a small number of connective tissue septum, in which the tissue in the muscle cone is in addition to the optic nerve Outside the vicinity, it is thin and loosely arranged. In the third month, the connective tissues of the eye muscles and the iliac crest continue to differentiate, and by the end of the month, the embryos are well developed, and the muscles are separated by many septums. The end of the eye is in the sclera slightly in front of the equator of the eye, and the beginning is in the optic nerve hole. At the 4th month, the extraocular muscle is similar to the adult except for its size. Therefore, in the 5th week of the embryo 4 months period Defects in the development of mesoderm can often lead to extraocular muscle hypoplasia, such as the fusion of the rectus muscle and the superior iliac muscle, the fusion of the medial rectus and the superior oblique muscle, etc., can also occur abnormalities of the extraocular muscles, single or The lack of multiple muscles.

Extraocular muscle hypoplasia prevention

There is no effective preventive measure for this disease. Early detection and early diagnosis are the key to the prevention and treatment of this disease.

Extraocular muscle dysplasia Complications

Often associated with eyelids, cornea, iris, choroid, optic nerve and other congenital abnormalities.

Symptoms of extraocular muscle hypoplasia Common symptoms Visually impaired eyeballs can not move freely with ptosis

1. Congenital total extraocular muscle deficiency: congenital panabsence of ocular muscles (congenital panabsence of ocular muscles) is a congenital anomaly in which multiple extraocular muscles are completely undeveloped, characterized by ptosis of the upper eyelid and mild eyeballs. Oblique, the eyeball is restricted in all directions, the mandible is lifted, and the EMG examination has no electromyographic reaction. Only fascial tissue or a few fibers can be found in the surgical exploration. It is generally binocular, has family heredity, and is extremely rare in clinical practice.

2. Congenital partial absence of extraocular muscles: Congenital partial absence of ocular (muscles) is a congenital anomaly of single or partial extraocular muscle hypoplasia, and the effect of the oblique position of the eye On the side, the eyeball cannot rotate in the direction of the defect muscle. The following lack of the right rectus muscle is the most common, and may also be combined with the absence of the inferior oblique muscle or the displacement of the medial rectus muscle and the congenital dysplasia of the eyeball. The clinical features of congenital absence 0f the inferior rectus muscles are as follows:

(1) An upper slant occurs from birth or a few months after birth: and as the age increases, the upper slant increases.

(2) More in the right eye: Occasionally both eyes.

(3) Most of the visual acuity is amblyopia or severe visual acuity.

(4) The upper slope is generally greater than 50: those with horizontal strabismus are more common, and the external slope is 20.

(5) There is no obvious compensatory head position.

(6) can be combined with abnormal eye development: as the sag is drooping, the cleft palate widens.

(7) Other extraocular muscle abnormalities can be seen during operation. For example, the inner and outer rectus muscle attachment points move down, the muscle bundle is widened, and the inferior oblique muscle attachment point is absent in the lower rectus muscle and the inferior oblique muscle.

(8) The pulling test is that the superior rectus muscle is obviously contracted and hyperthyroidized, so that the eyeball cannot be turned down or only reaches the midline.

(9) Surgical exploration: no muscle tissue or only a few fibers adhered from the lower edge of the cornea to the vortex vein.

3. Congenital extraocular muscle attachment abnormality: Congenital abnormal attachment of the ocular muscles is a variation of the attachment position of single or multiple extraocular muscles. The abnormality of the extraocular muscles is caused by abnormality. The common cause of eye deflection is that the extraocular muscle end often has different degrees of positional variation, which is a common cause of clinical imbalance caused by muscle imbalance. Significant end ectopic can lead to obvious Eye movement disorders, generally more than the rectus end of the attachment point, but the oblique muscle variation is large, often occurs wide attachment.

The extra muscle bundle of the superior oblique muscle can extend to the epiphyseal plate and the tendon wall attached to the nasal side of the eyeball or below, or the tendon of the superior rectus or lateral rectus muscle.

The scleral end of the inferior oblique muscle has the most variation, often between the lateral rectus and the inferior rectus, or has a common total attachment to the lateral rectus. Wilson reported that one patient had an abnormally overlapping inferior oblique muscle.

The temporal ectopic position of the superior rectus muscle forms V external oblique, the nasal displacement can be merged with the medial rectus muscle tendon, and the internal and external rectus muscle attachment points move down. It is common in patients with missing inferior rectus muscle, due to internal and external straight The muscle is displaced and the upper slope is lighter.

Examination of extraocular muscle hypoplasia

No special laboratory tests are required.

Ultrasound and CT scans help to determine the location and extent of extraocular muscle deficiency.

Diagnosis and differentiation of extraocular muscle hypoplasia

diagnosis

The diagnosis of congenital extraocular muscle dysplasia is difficult. If the absence of rectus muscle can be combined with the abnormality of the extraocular muscle attachment point or the absence of other extraocular muscles, there is no obvious clinical feature except for the absence of the inferior rectus muscle. Ultrasound and CT examination can help preoperative diagnosis of extraocular muscle deficiency. For example, the common inferior rectus muscle deficiency can be under the surface anesthesia. The rectus muscle can be clamped with the gums to understand the presence or absence of subconjunctival muscle tissue. Sometimes extraocular muscle development is found at the time of surgery. Therefore, the final diagnosis is based on surgical exploration.

Differential diagnosis

1. Congenital extraocular muscle extensive fibrosis: This disease is rare, family inheritance, is a dominant genetic disease, manifested as ptosis of both eyes, eyes fixed in the downward gaze position, eye movement (upper, lower rotation and level Rotation) is significantly restricted, there is adhesion between the extraocular muscles, the eyeball fascia and the eyeball, the traction test is positive, most or all of the extraocular muscles are fibrosis, the elasticity of the bulbar conjunctiva is reduced and the mandible is lifted, the head is tilted backwards, etc. .

2. Congenital lower rectus muscle completely paralyzed: The superior rectus muscle is highly contracted, and the disease is not easy to distinguish from the congenital lower rectus muscle. The discriminating point of this disease does not increase with age, and there is obvious compensation. Head position, therefore, the possibility of congenital absence of the inferior rectus muscle should be considered during surgery.

3. Vertical retreat syndrome: Under the disease, the rectus muscle may have a certain degree of motor restriction. When the eyeball rotates to the iliac crest, the eyeball retreats and the cleft palate is reduced, which may be differentiated from the absence of the inferior rectus muscle.

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