Key points
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Congenital craniofacial abnormalities are rare but often correctable causes of obstructive sleep apnea.
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Robin sequence and syndromic craniosynostosis are the most common congenital craniofacial anomalies associated with obstructive sleep apnea.
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Mandibular distraction is effective in relieving obstructive sleep apnea in properly selected patients with Robin sequence.
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Le Fort III midfacial distraction is effective in relieving obstructive sleep apnea in properly selected patients with syndromic craniosynostosis.
Video content accompanies this article at http://www.oralmaxsurgeryatlas.theclinics.com .
Introduction
Skeletal abnormalities are rare but often correctable causes of pediatric obstructive sleep apnea (OSA). Any facial abnormality that leads to airway impingement may contribute to OSA. The most common congenital craniofacial diagnoses associated with OSA are Robin sequence and syndromic craniosynostosis (SCS).
Robin sequence
Robin sequence (RS) is defined as the triad of micrognathia (small and retropositioned mandible), glossoptosis (tongue positioned superiorly and posteriorly such that it occludes the oropharynx), and airway obstruction. The incidence of RS ranges from 1:8500 to 1:14,000 live births. Although not a defining characteristic of RS, a cleft of the secondary palate is present in more than 90% of affected individuals.
The term “sequence” is applied to acknowledge a developmental progression beginning with micrognathia, which results in glossoptosis due to insufficient space in the oral cavity for normal tongue positioning ( Fig. 1 ). The malpositioned tongue, in turn, obstructs the oropharynx and may inhibit fusion of the palatal shelves creating a U- or V-shaped cleft ( Fig. 2 ). RS is not itself a syndrome; the initiating mandibular deformity can be attributed to one of more than 40 syndromic diagnoses or may be due to other extrinsic or intrinsic factors. Stickler and 22q11.2 syndromes are the most common syndromes associated with RS.
RS typically presents as airway obstruction and feeding impairment in the first few weeks of life. Some present later with failure to thrive. The airway obstruction associated with RS can often be managed with nonoperative maneuvers, including side or prone positioning, insertion of a nasopharyngeal tube or oral appliance, or continuous positive airway pressure. Many will experience mandibular catch-up growth and spontaneous resolution of the airway obstruction over the first year of life.
In infants with persistent obstruction despite nonoperative therapies, an operation is necessary. Tracheostomy is the most efficacious procedure, but is associated with significant morbidity, mortality, and social burden. Tongue-lip adhesion (TLA), which secures the anterior ventral tongue to the lower lip, thereby advancing the tongue base away from the oropharynx, is an alternative. Reported success rates range from 33% to 100%. In a 2015 analysis of TLA outcomes using polysomnographic data, Resnick and colleagues found that TLA improves but does not predictably resolve airway obstruction in patients with RS.
Mandibular distraction osteogenesis (MDO), which lengthens the mandible and brings the tongue forward, has gained popularity in treatment of infants with RS over the last decade. Compared with TLA, MDO more predictably improves breathing and avoids the need for tracheostomy in patients with RS. Success rates for MDO are 82% to 100%. Oral feeding has also been found to improve after MDO.
Surgical technique: mandibular distraction osteogenesis
Preoperative planning
The diagnosis and management of RS require a coordinated team approach, including expertise from neonatology, genetics, pulmonology, gastroenterology, oral and maxillofacial surgery, otolaryngology, plastic surgery, anesthesia, and additional consultants as necessary. As clinical examination and continuous pulse oximetry underestimate the true incidence of OSA in infants, formal polysomnography is necessary to determine the severity of the apnea and rule out central apnea as a significant contributor to the respiratory distress.
Before an operation, it is critical to determine the site of airway obstruction. Bedside laryngoscopy may be used to assess the upper airway and vocal folds. Direct laryngoscopy and bronchoscopy, typically under general anesthesia, are necessary to evaluate subglottic structures.
If MDO is pursued, the operation can commence with or without preoperative virtual surgical planning (VSP) ( Fig. 3 ). VSP allows for the fabrication of 3-dimensionally printed cutting guides and stereolithographic models ( Fig. 4 ), aids in distraction device selection and placement, improves vector management, shortens and simplifies the operation, and may decrease injury to the inferior alveolar nerve and developing teeth.
Preparation and patient positioning
Careful perioperative airway management and preparation for a potentially difficult intubation are critical. A bronchoscopy and laryngoscopy are often performed at the beginning of the procedure, and intubation can be facilitated by the use of specialty equipment, such as an anterior commissure laryngoscope or an intubating fiberscope. Intubation can be from a nasal or oral approach; the curvature of a nasoendotracheal tube may improve stability of the tube and decrease the likelihood of accidental intraoperative extubation compared with an oroendoctracheal tube. The endoctracheal tube can be prepared in the sterile field, and the breathing circuit can be draped with a clear sterile ultrasound probe cover so that it is accessible for inspection and manipulation during the procedure. The entire face and neck are then prepared and draped.
Surgical procedure
The mandible is accessed via a 1-cm incision within a natural skin tension line 1 to 2 cm inferior to the mandibular inferior border ( [CR] ). Layered dissection is performed with identification and protection of the marginal mandibular nerve and management of the facial vessels as necessary. The mandibular angle and ramus are exposed, and the cutting guides are used, when available from preoperative VSP, to mark the planned osteotomies and device positions.
The goals in osteotomy design are to (1) minimize or avoid damage to developing teeth and the inferior alveolar nerve, (2) avoid binding of the mobilized distal segment against the proximal segment during distraction, (3) avoid bringing the coronoid process forward with the distal segment, because this could lead to impingement with the zygomatic arch during distraction, (4) provide sufficient bone in each segment for device fixation, (5) achieve the desired vector for distraction, and (6) match the distraction vector between sides. Based on these criteria, the osteotomy can be custom designed for each patient. Common osteotomy designs include linear oblique, inverted-L, and multiangular ( Fig. 5 ). The osteotomy is created with a piezo electric saw, with only a buccal corticotomy in the midportion over the inferior alveolar nerve. This technique avoids damage to the nerve and maintains continuity of the mandible for stability while the device is applied.
Either a buried internal device ( Fig. 6 ) or an external distraction device with percutaneous pins can be used. When using an internal device, the device is applied with at least 4 screws in each footplate. The turning mechanism can extend either posteriorly and emerge under the lobule of the ear ( Fig. 7 ) or anteriorly to emerge inferior the mandibular body. After application of the device, the osteotomy is completed at the remaining lingual plate with an osteotome. The operation is repeated on the contralateral side. The device is activated 1.5 to 2 mm, and the segments are observed for complete separation without tension. The wound is closed in layers, and the operation is repeated on the contralateral side.
Immediate postoperative care
Patients often remain intubated for 2 to 3 days postoperatively to allow for resolution of airway swelling that results from intubation and fluid shifts associated with the operation. A short latency period may be used, after which distraction commences at a rate of 1 to 3 mm per day. At Boston Children’s Hospital, distraction begins on the first postoperative day with 2 mm of advancement on that day and each day thereafter, separated into morning and afternoon turns. The most common end-distraction target is when the mandibular alveolar ridge is 2 to 4 mm anterior to the maxillary alveolar ridge. Once active distraction has completed, the turning arms are removed at the bedside. The average advancement is 20 mm ( Fig. 8 ).
Patients may be discharged home either during the distraction process, if appropriate, or immediately after removal of the activation arms, unless comorbidities require continued hospitalization. At Boston Children’s Hospital, a polysomnogram is repeated to confirm the resolution of OSA before discharge. Devices are removed after a 6- to 12-week consolidation period.
Potential complications
There are many opportunities for error in the surgical management of the infant with RS with MDO. These errors include the following:
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Incorrect/incomplete diagnosis. Appropriate surgical management begins with an accurate diagnosis and workup. If comorbidities that contribute to respiratory distress, such as hypotonia or central apnea, are not recognized and managed, mandibular distraction may fail to relieve the OSA.
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Nonrecognition of concomitant airway lesions. Similar to incomplete diagnosis, failure to address other contributing airway lesions, including laryngomalacia, may lead to an unsatisfactory outcome.
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Airway mismanagement. Intubation may be difficult in the patient with RS and requires special expertise and equipment.
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Incomplete osteotomy. If the mandibular osteotomy is incomplete, the segments will not move as expected and the distraction process will halt prematurely. It is imperative to evaluate all areas of the osteotomy and test the mobility of the segments intraoperatively.
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Damage to teeth and nerves. Developing teeth and the inferior alveolar nerve are at risk during the mandibular osteotomy. This risk may be minimized with VSP. The marginal mandibular branch of the facial nerve must also be recognized and protected during the dissection.
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Device detachment. The bone of the mandible may be narrow and poorly calcified, particularly in neonates. Careful application of bone screws and assessment of the device stability intraoperatively are important to minimize the risk of device detachment during distraction or consolidation.
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Device malfunction. The distraction device may fail to operate properly during the distraction or consolidation phases, or components may break. This may require additional operations to repair or exchange devices, particularly when internal devices are used.
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Pin scars. When external devices are used, unsightly pin scars may result from movement of the percutaneous pins through the skin during distraction.
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Infection. Subcutaneous infections, particularly at the site of emergence of the distractor activation mechanism when internal devices are used, are common. Diligent wound care is crucial, and perioperative antibiotics are often necessary. Infection may occasionally dictate early removal of distraction devices. Osteomyelitis is exceedingly rare.
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Nonunion. A nonunion can occur if bone consolidation within the distraction gaps and fusion of the proximal and distal mandibular segments are inhibited. This can occur if the distraction rate is too fast, if a comorbidity decreases bone turnover, or may be idiopathic.
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Premature consolidation. An inadequate rate of distraction may lead to premature consolidation. This may necessitate a repeat operation.
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Disruption of future growth. The effect of distraction on future mandibular growth is unknown. Some patients will require repeated distraction; this may be due to disruption of growth by the first procedure or an inherent mandibular growth abnormality.
“Pearls and pitfalls”
Experience with patients with RS has led to improvement in management. Recommendations based on this experience include the following:
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Always perform a direct laryngoscopy and bronchoscopy before pursuing mandibular distraction or any other operation intended to relieve airway obstruction. Lack of recognition of concomitant airway lesions may lead to an operative failure.
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Preoperative polysomnography, when available, may help in determining the best management plan. The presence and degree of obstruction cannot be adequately evaluated by bedside examination and monitoring.
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Engage in preoperative discussion with the anesthesia provider, with particular focus on the following:
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Airway management plan
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Expected and allowable blood loss
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Avoidance of neuromuscular blockade to facilitate monitoring for the marginal mandibular nerve
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During the preparation and drape, apply a clear sterile ultrasound probe cover over the endotracheal tube and breathing circuit to allow them to be visualized during the procedure. The ability of team members to visualize and manipulate the endotracheal tube and breathing circuit throughout the case has reduced accidental intraoperative extubation, particularly during head turns.
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When planning the mandibular osteotomy, leave sufficient proximal bone for device application. Placement of the osteotomy proximal to the mandibular canal is ideal for protection of the inferior alveolar nerve and may be achievable in older children, but is usually impossible in infants. The osteotomy typically overlaps the inferior alveolar nerve canal in younger patients to provide adequate proximal bone for device fixation.
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When the osteotomy overlaps the inferior alveolar nerve canal, the nerve can be preserved by identifying its location on preoperative imaging and performing only a buccal corticotomy over this area with a piezo electric saw. The separation of the proximal and distal segments is completed later by driving an osteotome along the lingual cortex. Using this technique, the nerve is typically seen within the osteotomy gap ( Fig. 9 ) and will elongate during the distraction process.
