[Etiology].
The etiology of congenital myotonic levator is still unknown. However, most scholars believe that abnormal intrauterine pressure or fetal malposition is the main cause of congenital myotonic neck. The fetal malposition in the uterus or abnormal pressure on the uterine wall may cause pressure on one side of the neck and local blood circulation in the sternocleidomastoid muscle, resulting in ischemic fibrous degeneration of the muscle and causing oblique neck.
Difficult delivery and the use of forceps is one of the causes of myotonic rhomboid. This view has not been conclusively confirmed because it occurs more often in breech births, but examination of the local mass of the sternocleidomastoid muscle did not reveal signs of old hemorrhage.
It is thought that the occurrence of this condition is genetically related because 1/5 of the children have a clear family history of this condition, and such children are often combined with congenital acetabular dysplasia and other malformations.
Pathological changes
The mass in the sternocleidomastoid muscle is mainly a strip of fibrotic muscle tissue, and the bulk of the specimen resembles a soft fibrous scar with a white cut surface. Microscopic observation shows that it is composed of dense fibrous tissue with reduced muscle tissue and reduced transverse lines, and in severe cases the muscle tissue disappears and more scar tissue appears, but there is no bleeding in the muscle.
It can be divided into three pathological types according to the proportion of muscle and fibrous tissue presented.
1. Muscle type: predominantly muscle tissue, containing only a small amount of fibrous degenerated muscle tissue or fibrous tissue.
2. Mixed type: containing both muscle tissue and fibrous tissue.
3. Fibrous type: mainly fibrous tissue, containing a small amount of muscle or degenerated muscle tissue.
This typing has certain guiding significance for the determination of clinical efficacy. In general, the muscle type has better efficacy and the fiber type has poorer efficacy.
Clinical manifestations
Oblique neck deformity
After birth, the mother may find that the child’s head is tilted to the affected side, the face is rotated to the healthy side, and the lower jaw points to the healthy shoulder. Turning the head to the healthy side is obviously limited, and the symptoms should be observed carefully in milder cases. This symptom worsens as the child grows and develops.
Cervical masses
A cervical mass is usually palpable after birth or within 2 weeks of birth and is located in the middle and lower sternocleidomastoid muscle, most often on the right side. The mass is pyknotic in shape, without pressure, and usually reaches its maximum size after 1 to 2 months, after which it gradually shrinks until it disappears completely.
Facial deformity
If congenital myotonic neck is not treated effectively at an early stage, facial deformity will appear after 2 years of age. The main manifestation is facial asymmetry, the distance from the outer corner of the eye to the corner of the mouth is asymmetrical, the distance on the affected side is shortened and the healthy side grows. The affected side of the eye position plane is reduced, because both eyes are not on the same level, easy to produce visual fatigue and vision loss. The healthy side of the face is round and full, while the affected side is narrow and flat. The cervical spine may develop compensatory scoliosis. In addition, the whole face, including the nose and ears, may be asymmetrically altered.
In addition to the main manifestations mentioned above, congenital dislocation of the acetabulum and other deformities of the cervical spine may be combined with this disease.
Diagnosis
It is easy to make a clear diagnosis based on the typical clinical manifestations and physical findings.
Differential diagnosis
Attention should be paid to differentiate from the following causes of oblique neck.
Congenital bony oblique neck is mostly caused by congenital occipital and cervical deformities, including short neck deformity, skull base depression, hemivertebral deformity, atlanto-occipital fusion and dentate developmental deformity. These disorders may result in an oblique neck and facial asymmetry, but do not usually produce the typical striated contracture bands and masses of the sternocleidomastoid muscle, and x-ray examination may clarify the above diagnosis.
Pediatric cervical lymphadenitis in infancy can result in rapid onset of a squint and a neck mass, but this mass is often painful and not located within the sternocleidomastoid muscle.
Spontaneous rotational subluxation of the atlantoaxial spine can also cause a slanting neck, but this disease is often associated with a history of minor trauma or upper respiratory tract infection, and is mainly characterized by limited rotational movement of the neck and significant neck pain.
Cervical spine tuberculosis can cause the sternocleidomastoid muscle spasm and produce slanting neck, but such patients have obvious neck pain, obvious restriction of neck movement, and jaw deviation to the affected side, which can be clearly diagnosed by X-ray examination.
In addition, it should be distinguished from hysterical squint, habitual squint, injury squint, and squint caused by post-polio paralysis.
Non-surgical treatment
For children under half a year old, non-surgical treatment can achieve satisfactory results. Therefore, once the diagnosis is made, treatment should be given as soon as possible. The methods of non-surgical treatment include local hot compress, massage, bed immobilization and manual traction. The specific method of manual traction is: the mother will lay the child on her knees, so that the child’s neck is stretched back, the mother gently presses the child’s thorax with her left hand, holds the head and neck with her right hand, rotates the child’s face to the affected side as far as possible, and the occiput is rotated to the shoulder peak of the healthy side, the operation process should be gentle, so that the contracted sternocleidomastoid muscle gets a greater stretch. When the child is lying in bed, take the supine position and fix the head with a small sandbag on the face toward the affected side and the occiput toward the healthy side.
Surgical treatment]
Indications and contraindications for surgery: (1) for those who are more than half a week old and conservative treatment is ineffective; (2) for those who are under 12 years old with obvious oblique neck deformity; (3) for those who are more than 12 years old, surgery can be considered if the facial deformity is not serious; (4) for adults, because the deformity has existed for many years, after surgery, not only the facial deformity will be more obvious, but also the vision will be changed because it is not adapted to the new postoperative position, so surgery is not recommended. Therefore, surgery is not recommended.
The following surgical methods are mainly available.
Sternocleidomastoid excision is one of the more commonly used surgical methods. A transverse incision is made on the clavicle to reveal the sternal and clavicular heads of the sternocleidomastoid muscle, which are cut above the attachment point, and the surrounding fascial tissue is released.
Partial sternocleidomastoidectomy can be performed on the mass of the sternocleidomastoid muscle for those with obvious neck masses.
For adolescent patients, if the entire sternocleidomastoid muscle is scarred, the whole segment can be removed.
Sternocleidomastoid lengthening is a procedure in which the clavicular head of the sternocleidomastoid muscle is cut off and the sternal head is lengthened in a “Z” shape. The advantages of this surgery are: (1) correction of head and neck distortion and restoration of normal neck function; (2) no destruction of the normal neck triangle body shape, avoiding other surgical methods to leave the neck sunken deformity or abnormal flat deformity, making the neck beautiful and symmetrical.
Combined upper and lower sternocleidomastoid muscle release plus plication
Ferkel et al. concluded that this procedure can be used in older children or in those who have failed other procedures. The sternocleidomastoid muscle is completely severed on the mastoid side and the head side of the clavicle, and the head side of the sternum is lengthened in a “Z” shape.
Postoperative management of severe oblique neck deformity and uncooperative children requires postoperative correction with a head-neck-thorax cast to maintain the child’s posture.