Evaluation & Management of an Infant with a Small Jaw

In this episode of BackTable ENT, Dr. Shah discusses mandibular distraction in infants with Dr. Brianne Roby, director of the ENT and Plastic Surgery Fellowship at the University of Minnesota.

First, the doctors discuss the difference between micrognathia and retrognathia, two terms that are commonly and incorrectly interchanged. Micrognathia refers to an infant having a small mandible, while retrognathia means the infant’s mandible is normal sized, but just recessed.
Dr. Roby usually makes the distinction through physical examination by feeling the angle and body of the mandible. In infants with retrognathia, she is able to feel a long body and defined angle in the mandible. She notes that diagnosis of micrognathia will most likely be postnatal, as obtaining a perfect sagittal view for measurement of inferior facial angle in a prenatal ultrasound is very difficult. However, she notes that polyhydramnios, or excess accumulation of amniotic fluid, is a significant indicator of an underdeveloped fetal jaw.

In her initial evaluation of an infant with micrognathia, she first confirms that the infant is stable and in optimal position. Then, she examines the infant for other comorbidities and syndromic developments. Although Stickler syndrome is the most common syndrome associated with micrognathia, Pierre-Robin sequence and Treacher Collins syndrome can also cause micrognathia. Before scoping the infant, she prefers to familiarize herself with the infant’s anatomy and feeding/breathing patterns first. In order to do this, she collaborates with the NICU staff and encourages them to informally document the infant’s behavior. Then, she will insert a bedside flexible scope through the infant’s nose to confirm that the infant has glossoptosis and not just a benign enlarged tongue base. She emphasizes that a surgeon should always confirm that there are no other airway malformations before performing surgery to place a mandibular distractor. Besides glossoptosis, other important indicators for mandibular distraction are airway obstruction and feeding difficulties. Dr. Roby only performs mandibular distractions on babies that are gestationally full term (37-38 wks) and weighing over 2 kg.

Next, Dr. Roby shares her tips for mandibular distraction surgery. Her general approach is to secure the airway first and then insert the distractor. She emphasizes that preparation for airway emergencies is the most important intraoperative consideration. She prefers to have an experienced anesthesiologist on hand and multiple methods to secure an infant’s airway, including nasotracheal intubation, oral intubation, a Glidescope, a Telescope, flexible fiberoptic nasal intubation, a tracheostomy set, and manual ventilation. The longer time it takes to secure an infant’s airway, the higher the risk of spontaneous laryngospasm and bleeding. For this reason, she keeps a paralytic prepared just in case laryngospasm occurs. When it is time to insert the distractor, she uses the infant’s submandibular gland as a landmark for the mandible.

The otolaryngologist can either place an internal or external distractor. For an internal distractor, the plates and screws are placed under the skin so only the distraction arm is visible. This device can only distract in one direction, so it is commonly used in Pierre-Robin sequence infants. External distractors contain hardware that must be inserted externally and can distract in multiple directions. Dr. Roby prefers to place an internal distractor to minimize scarring and maximize parent and nurse comfort.

After the distractor is placed, it must be rotated daily to open the mandible. Dr. Roby turns the pins twice a day by 2 mm; she does 1 mm in the morning and 1 mm in the night. Her goal is to achieve a 12-14 mm distraction and a slight underbite in most infants. After achieving this distance, the plates have to be left in for 10 weeks in order for the bone to harden. After 10 weeks, she removes the distractor and observes the infant for improvement in feeding.

Finally, Dr. Roby discusses special considerations for syndromic infants. Stickler syndrome infants share the same success rate for mandibular distraction as non-syndromic kids. Treacher Collins infants may present with abnormal mandible anatomy that prevents the feasibility of mandibular distraction, so surgeons should wait until their jaws are more developed until performing surgery. In Treacher Collins infants that are able to undergo mandibular surgery, there is a higher likelihood that they will need a gastrostomy tube and a tracheostomy if surgery fails. Finally, in infants with Nager syndrome, a tracheostomy may be preferred over distraction.