INTRODUCTION
Congenital muscular torticollis (CMT) is among the most common musculoskeletal deformities in children and is characterized by a persistent head tilt toward the affected side, with the chin rotated toward the opposite direction [
1]. The prevalence of CMT in neonates has historically ranged from 0.3% to 2.0% [
1,
2]. Although the clinical features of CMT are well known, no consensus exists regarding the cause of this disorder. Possible etiologies include birth trauma, intrauterine malpositioning, a hereditary component, neurogenic disorders, infection, and sequelae of intrauterine or perinatal compartment syndrome [
3-
5].
The treatment strategies used for CMT include observation, orthosis application, an active home exercise program, stretching exercises, Botox injections, manual myotomy, and various surgical procedures [
3,
6]. Stretching exercises are sufficient for primary treatment in approximately 90% of cases, while surgical resection of the affected sternocleidomastoid muscle (SCM) is recommended for resistant cases (i.e., no response or improvement after at least 6 months of physiotherapy) [
3,
7].
In this study, we analyzed various clinical factors in patients with CMT who were treated with surgical resection. Numerous studies have explored the causes of CMT, but no definitive causes have been established. Therefore, we investigated the cause of CMT in patients with severe CMT that required surgery, and sought to identify different possible causes of CMT from those that were proposed in previous studies.
DISCUSSION
CMT is defined as unilateral shortening or contracture of the SCM caused by fibrosis of unknown cause in newborn infants or young children. The shortening of the SCM on the involved side results in an ipsilateral head tilt and contralateral rotation of the chin. This limits head mobility in both rotation toward the affected side and lateral flexion toward the other side. Although several theoretical proposals have been made, uncertainties remain regarding the actual etiology of CMT [
11].
Many studies have been performed to identify the causes of CMT. An abnormal fetal presentation and resultant birth trauma were initially considered to be the cause of CMT. Abnormal presentations include breech presentation and transverse lie presentation. Breech presentation is characterized by entrance of the fetus’s buttock or feet into the pelvis. Transverse lie presentation is characterized by orientation of the fetal shoulder towards the maternal pelvis. Birth trauma was historically believed to result in hematoma formation in the SCM, leading to fibrous contracture of the muscle [
12]. However, this theory does not explain the occurrence of CMT after cesarean sections [
4,
13]. Later suggestions include hereditary factors, neurogenic disorders, infection, and sequelae of intrauterine or perinatal compartment syndrome [
5,
11]. However, these hypotheses were mainly studied from the 1930s to 1950s. The most recent case report advocating for the hereditary hypothesis was published in 1997 [
4]. Overall, the etiology of CMT remains unclear.
To the best of our knowledge, the actual incidence of oligohydramnios, abnormal fetal presentation, and birth-related injury has not been established. The reported rates of oligohydramnios in the general population are influenced by inconsistencies in diagnostic criteria, the population analyzed, the threshold used, and the gestational age at the time of the ultrasound examination [
14]. One study reported that oligohydramnios (defined as an amniotic fluid index of ≤5 cm) occurs in about 1%–5% of pregnancies at term [
14]. In our study group, oligohydramnios was noted in 5.9% of patients. Considering the incidence of oligohydramnios in the general population, the incidence of oligohydramnios among the patients with CMT in our study was rather high. Reported rates of abnormal fetal presentation are also influenced by variations in the population studied and the gestational age at the time of the ultrasound examination. Generally, 3%–4% of fetuses are breech at term, and approximately 1 in 300 fetuses has a transverse presentation at delivery [
15-
18]. The rates of abnormal fetal presentations in our study group were 16.6% for a breech presentation and 0.2% for a transverse presentation, which are markedly higher than the reported rates in the general population. The overall incidence of birth injuries is roughly 2.0% and 1.1% in singleton vaginal deliveries of fetuses in a cephalic position and in cesarean deliveries, respectively [
19,
20]. In the present study, clavicle fractures and cephalohematomas were reported in 1.3% and 0.4% of patients, respectively. Based on data obtained from large case series, the incidence of clavicle fractures due to birth trauma ranges from 0.5% to 1.6% [
21-
23]. Cephalohematoma is estimated to occur in 1%–2% of all deliveries [
19]. Although some limitations prevent a direct comparison of the reported incidence in this study with that in the general population, we can suggest that the incidence of several factors potentially associated with torticollis during the past few decades was not particularly high (e.g., oligohydramnios and birth injury). However, 16.6% of the patients with CMT were in the breech position; this is a much higher rate than that observed in the general population (3%–4%). Therefore, we can hypothesize that the breech position seems to exert a significant influence on shortening and fibrosis of the SCM.
Furthermore, in some cases, patients who were not reported to have experienced birth trauma had bony hypertrophy or severe tissue adhesion, which is usually seen on the fracture site of clavicle after healing. It is possible that those patients might have experienced birth trauma, such as clavicle fractures, but the parents were not aware of the birth trauma when we interviewed them. This consideration suggests that the incidence of birth trauma could have been underestimated, and this possibility should be investigated in further studies.
In our study, the bulky specimen, which patients’ parents usually referred to as a “mass,” was seen in the form of an asymmetric marked thickening and internal low signal alteration on magnetic resonance imaging. Fibromatosis can also be confirmed by biopsy. Patients with CMT can benefit from a surgical intervention when a bulky specimen or fibrous band on the neck is palpated with the head tilted toward the affected side, shortening of the ipsilateral SCM is detected, or deficits are found in passive neck rotation or lateral flexion. Because age at the time of surgery is believed to be the most important factor influencing the outcome of surgery and complications of resistant CMT, surgical treatment is recommended at 1–4 years of age [
24]. For various reasons, however, some patients with CMT do not undergo surgical treatment despite meeting the clinical criteria. In the present study, 66.0% of patients underwent a surgical intervention before the age of 4 years, 24.2% between the age of 5 and 10 years, 7.0% between the age of 11 and 20 years, and 2.9% after the age of 20 years. Additionally, surgical resection of the affected SCM is recommended when no response or improvement is seen after at least 6 months of physiotherapy [
3,
7]. In our study, the average duration of preoperative rehabilitation was 6 months; however, some patients underwent surgery after more than 8 years of rehabilitation. There are many possible reasons for delayed surgery. The patient’s guardian may refuse the invasive treatment, and the clinician or guardian may not be aware that a surgical intervention can be helpful if the patient’s symptoms do not improve after at least 6 months of physiotherapy. After birth, if a guardian tries to tilt the baby’s neck and a bulky specimen of the neck is suspected, the guardian usually starts by visiting the rehabilitation medicine department, and then physiotherapy is performed first if a diagnosis is made. Patients who initially had a bulky specimen or a difference of more than 20° at the initial visit to the plastic surgeon, rather than in their visit to the rehabilitation medicine department, proceeded to surgery without any physiotherapy because physiotherapy results in minimal improvements in such patients. The variation in the duration of physiotherapy reflects differences in when the rehabilitation department transfers the care of the patient to the plastic surgery department.
Our experience indicates that surgical treatment for neglected CMT effectively achieves a satisfactory ROM of the neck and improves secondary skeletal deformities, including spinal deformities. Our center previously reported favorable results in patients older than 8 years old with recurrent or neglected CMT who underwent conventional unipolar resection with or without acellular dermal matrix grafting [
9]. Therefore, clinicians should not hesitate to recommend surgical treatment for neglected CMT in older patients.
There are several limitations of this study. We directly compared the results of this study with data in the general population. Additionally, the results include several factors that may be influenced by the development and accessibility of the healthcare system. Because some patients’ medical records were lacking, we had to obtain additional information by interviewing the patients or their guardians, which may have reduced the accuracy of the information. Additionally, we only investigated patients who had undergone surgery. Considering that 90% of patients are treated primarily through stretching exercises, the results of this study are not representative of all patients with CMT.
Although the exact etiology of CMT is still unknown, we identified the incidence of several possible causes of torticollis. The incidence of oligohydramnios and birth injury was not remarkably high. However, because fetal malpositioning, especially the breech position, can cause torticollis, more studies are needed on this cause-and-effect relationship based on ultrasound examinations of fetuses in the breech position. Whether the position of the tilted head of the fetus in utero is associated with the later occurrence of torticollis on the affected side also remains unclear. This study also revealed that many patients with CMT requiring a surgical intervention missed the optimal timing for surgery after a relatively long duration of rehabilitation. Clinicians and patients require more consultations and education about the treatment schedule of CMT.