Journal of Rare Disorders: Diagnosis & Therapy

Keywords

Sternal cleft; PHACES syndrome; Cantrell’s Pentalogy; Paediatrics

Introduction

Chest wall malformations represent a large phenotypic spectrum. Among them, congenital sternal cleft is a rare anomaly, and have been classified as complete or incomplete, with complete cleft the rarer form. The incidence being of 1:100,000 cases per live birth, and represent about less than 1% of all chest wall deformities. [1].

In embryonic life, the sternum has its origin in the lateral plate mesoderm of either side of midline, which becomes fused by the 10th weeks. The development of the sternum appears during the 6th week of embryology as a pair of parallel mesenchymal bands of condensed mesenchyme. Cells migrate from two lateral plates on either side of the anterior chest wall to fuse in the midline by the 10th week of gestation in a craniocaudal fusion. The sternum originates as cartilage, and then multiple ossification centre’s develop in a craniocaudal sequence (Figure 1).

Figure 1 Facial and thoracic hemangiomas and superior sternal cleft with supraumbilical raphe.

This anomaly results from a failure fusion of the sternum. Very rarely, the sternal bars fail to join in the midline, which results in a complete or incomplete sternal cleft. The clinical severity of sternal cleft ranges from the benign sternal cleft to the potentially lethal ectopia cordis. Generally observed at birth and the prognostic depends mostly on associated anomalies as congenital cardiac anomalies leading to severe cardiovascular compromise during anesthesia and if pulmonary hypertension is associated then it may be difficult to maintain adequate oxygenation of arterial blood [2]. Sternal clef may be associated also with defects in the anterior chest wall such as ectopia cordis, or, Cantrell's pentalogy, with a combination of defects involving the abdominal wall, sternum, diaphragm, pericardium, and heart. It can be diagnosed in the prenatal period with three-dimensional ultrasonography.

Surgery is indicated to protect the heart and major vessels are left unprotected and may be easily injured by external trauma, and to improve respiratory dynamics and aesthetic reasons. The challenge to the anesthetist is the risk of paradoxical respiration especially if the defect is incomplete.

We report our experience in the treatment of sternal anomalies and evaluate the results and evolutions of these patients.

Materials and Method

From 1994 to 2015, we reviewed the medical records of five neonates with sternal anomalies. The majority of patients were girls (4:1). Four cases were detected in neonatal period and one in prenatal period confirmed by MRI. The mean weight at birth was 3,2 kg (2.2-4.1). Sternal anomalies types were: Upper sternal cleft in two cases; one case was an isolated anomaly, and the other was associated to PHACES syndrome (posterior fossa brain malformations, facial hemangiomas, arterial anomalies, cardiac defects, eyes abnormalities, sternal cleft, and supraumbilical raphe). Lower sternal cleft in two cases; one associated to PHACES syndrome (Figure 1), intestinal atresia and gyral pattern disorders. The other anomaly associated as part of a field defect known as Cantrell’s Pentalogy (ectopia cordis, deficiency of the anterior diaphragm, supraumbilical abdominal wall defect, defect in lower sternum, and congenital intra-cardiac anomalies). One total sternal cleft associated to Cantrell’s pentalogy. Characteristics of patients are reported in the Table 1.

Table 1: Data base of patients (ICA: internal carotid artery; ACA: Anterior Cerebral Artery; PCA: Posterior Cerebral Artery).

All patients were studied preoperatively by chest X-ray, computerized tomography, cardiologic evaluation, genetic evaluation. When the sternal anomaly was associated to hemangiomas, cerebral MRI and ophthalmic evaluation were done (Figure 2).

Figure 2 CT-scan in superior sternal cleft.

Three of them, surgical correction by primary closure was done (two upper and one complete). These patients presented retraction at the defect with inspiration and protrusion with exhalation or Valsalva maneuver.

During surgery, a cerebral and splanchnic monitoring was evaluated with the use of near infrared spectroscopy (NIRS). Postoperatively, all infants were admitted to the neonatal intensive care unit.

Surgical approach

Under endo-tracheal general, the patient was placed in decubitus position, the skin incision was vertical on the midline (Figure 3), and the pectorals muscles were dissected to expose the sternal bars and then, the medial edges of the two sternal halves were freed from the underlying pleura and pericardium. The inferior aspect of partial sternal cleft was incised, when U shaped, to make closure easier. The sternal bars were approximated on the midline by non-absorbable sutures (Figure 4).

Figure 3 Vertical incision on the midline and anatomic marks.

Figure 4 Surgical correction of sternal defect.
A. Exposition of sternal bars: The medial edges of the two sternal halves were freed from the underlying pleura and pericardium.
B. Sternal bars are re-approximated.
C. Primary closure

In complete sternal cleft was too wide or there was a mediastinal compression after sternal bar juxtaposition, we closed the defect by placing non-absorbable prostheses in multiple layers and them, the defect and the primary repair was delayed using the technique described previously.

Results

Surgical correction was performed in 3 of them. During primary closure, none signs of compression of the mediastinum appear. None intra-operative complications occurred. Near infrared spectroscopy stayed normal and regular all along the surgeries. Mean operative time was 120 min (100-150). In cases of upper sternal cleft, primary closure was performed at 5 and 10 week-old respectively. In complete sternal cleft, prosthetic closure was done at 14 days-old, and the primary repair was done seven months later. In cases of lower sternal cleft non-surgical correction was necessary due to asymptomatic patients and minor defect.

The mean follow-up period was 9.5 years (3.6-21 years). No complications were reported. All patients achieved good functional and cosmetic results after correction.

Discussion

Sternal cleft malformation caused by the failure of fusion of the sternal elements. The etiology is unknown, thought to arise from a failure of ventral fusion of the sternal bars during the 8th week of gestation. There is a female predominance. Alcohol intake and methylcobalamine or riboflavine deficiency is thought to be associated with sternal cleft, and studies in mice indicate anomalies in HOX b gene expression as a possible factor [3].

Sternal prenatal diagnosis is difficult with ultrasonography. Twomey considers that a thinned and sunken midline anterior chest wall with intact skin coverage but no identifiable cartilaginous sternum is diagnostic of this anomaly [4].

Sternal clefts are classified as being total or partial. The partial deformity can be superiorly or inferiorly located, with the upper sternum being the most common and almost always an isolated abnormality [5]. Occasionally it can be associated with PHACES syndrome [6]. The rare inferior variety is often associated with a thoraco-abdominal ectopia cordis, being part of a Cantrell’s Pentalogy [7].

Superior clefts have an orthotopic normal heart, normal skin coverage, and an intact pericardium. In isolated cleft, the patient is usually asymptomatic, except during cries or coughs (upper and midline thoracic depression during inspiration and a prominence during expiration) [1]. When a sternal cleft is diagnosed, associated anomalies must be searched by careful physical examination, chest X-ray and echocardiography, because the prognostic changes if the cleft had associated anomalies. Genetic evaluation can be useful [6].

When haemangioma was associated, other criteria’s of PHACES syndrome must be searched and them, a cerebral RMI and an ophthalmologic evaluation are done. A consensus statement on diagnostic criteria was published in 2009 [6].

Concerning Cantrell’s Pentalogy, the prognosis depends mainly on the cardiac anomalies [7].

Even for asymptomatic patients, sternal surgery is necessary to offer protection to the heart, to prevent recurrent respiratory infections due to the paradoxical respiratory movements, to maintain the growth potential of the chest wall and to offer a good cosmetic outcome. Chest computerized tomography or MRI is necessary preoperatively in order to confirm the presence of a sternal cleft and confirmed the variety of anomaly (presence or not of bar inferiorly) and them the repair can be planned [8].

Surgical correction is indicated to protect the heart and major vessels are left unprotected and may be easily injured by external trauma, and to improve respiratory dynamics and aesthetic reasons. Only in very minors defect, particularity in lower sternal cleft conservative treatment can be propose due to asymptomatic patients. In our series two cases of lower sternal cleft non-surgical correction was done with uneventful course.

In some cases the reduction in thoracic volume can cause cardiovascular impairment. The age of the patient is an important factor for primary repair, if possible in the neonatal age to achived primary closure. Nevertheless in some cases the reduction in thoracic volume can cause cardiovascular impairment. It is noted that after 3 months of age, the chest wall becomes relatively rigid and more complicated techniques may be required such as with the use of prostheses, partial or total thymectomy, sliding chondrotomies, and clavicle dislocation. These techniques can be an alternative to primary closure if the latter is challenging or impossible due to a stiff thorax [1].

In our patients 1 and 2, sternal surgery was accomplished at 10 weeks and 40 days respectively, by primary closure alone. For patient 4, primary closure was impossible at 14 days because of a great distance between the sternal halves, a prosthetic material was necessary, and direct approximation of the sternal halves was performed at 7 months.

Many authors agree to say that primary repair is best accomplished in the neonatal period, to take advantage of the pliability of the chest wall and less compression of underlying structures. If signs of compression of the mediastinum appear during surgery, primary repair should be abandoned for a more elaborate approach (sliding or rotating chondrotomies, pectoralis major myoplasty, clavicular fracture, or even autologous tissue flaps, myocutaneous flaps, prosthetic materials) [5,8 9].

In conclusion, congenital sternal cleft is an uncommon pathology and need a multidisciplinary approach for optimal patient outcome. They can be isolated or part of a syndrome, justifying complementary explorations. The surgical approach is not necessary in all patients. We decide the surgical treatment depend the type of sternal malformation. We can obtain best results for make the surgical approach during the neonatal period, when the chest wall is maximally flexible to make the repair easier. Furtherer, if is its necessary, we can do a prosthetic closure resolving the malformation in betters conditions.

References

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