Introduction and purpose

Ependymomas are the most common type of tumor in the posterior fossa that required surgical attention in children [1]. Many children are presently extubated in the operating room (OR), immediately afterwards in the recovery room (RM), or intensive care unit (ICU) and may have multiple difficulties. The surgery is sometimes long and the numerous adjacent structures can be injured which can adversely impact the immediate postoperative course. We noted that the immediate postoperative management of these patients was variable and wanted to optimize their course. At our institution we have developed a protocol which allows for the child to have recovered from the anesthetic and become hemodynamically stable. After a child has passed through the immediate postoperative period of a day or so from their ependymoma surgery, they enter a second significant phase of their care. Extra attention is necessary because of the diverse potential problems with vocal cord function and swallowing as a consequence of tumor resection. Timing of the management may be important to minimize complication of aspiration and respiratory distress.

Materials and methods

Because of the large volume of our neurosurgical service, we have had the opportunity to develop a team approach to address the later phase of postoperative ICU care of children with ependymoma. Our team consists of a neurosurgeon, an otolaryngologist, an intensivist, a speech pathologist/swallowing specialist, and a radiologist. From our early experience, a protocol has been developed. First the neurosurgeon who did the resection gives their best estimate to the team of the areas affected by the surgery. Then the intensivist prepares the patient for extubation when medically stable, usually the first postoperative day. The child must be breathing spontaneously and be completely awake. The child is kept intubated until the otolaryngologist is at the bedside with a flexible fiberoptic nasopharyngolaryngoscope and light source. After topical anesthetic and lubrication are applied to the scope and nasal cavity, the scope is passed through the nose and positioned just above the larynx. Looking at the vocal cords the endotracheal tube is removed. Vocal cord function and sensation is then evaluated. If there is a unilateral vocal cord paralysis from a CN injury, the child is observed to see if they can tolerate the airway restriction and secretions, and usually do not require a tracheotomy. If there is a bilateral vocal cord paralysis (usually secondary to nuclear swelling or trauma) the child is usually reintubated and observed for several more days to see if there is transient brainstem swelling that might go down on steroids. The child is then re-extubated, and if both cords are paralyzed in an airway obstructive position, the child is then tracheotomized. After the child is either successfully extubated or tracheotomized they then receive a modified barium swallow with both a radiologist and a speech pathologist specially trained in swallowing disorders present. If the child has contrast penetration with significant aspiration, a gastrostomy tube is placed.

Results

The new system of integrated care was initiated and all parties agreed to participate. All services were alerted to the cases before the children had surgery so availability could be assured. Only two pediatric neurosurgeons performed the posterior fossa surgeries on 45 consecutive children in one institution. There were no operative deaths. The intensivists kept the patients sedated and paralyzed overnight the day after the surgery to optimize their medial condition after this major surgery. The neurosurgeons conferenced with the otolaryngologist and discussed the extent of the surgery and the possible injury to important structures such as nuclei, ganglion, and nerve roots. This information aided in the evaluation of the vocal cord function. The next morning the children were awakened, the paralytic stopped, and they were weaned off the ventilator quickly. In the afternoon, with the children completely awake, they were vigorously suctioned both through the nose into the pharynx and through the endotracheal tube. Topical anesthetic gel was placed in the nose. Once the airways were suctioned clear and the nose numbed, a flexible 4-mm fiberoptic telescope was passed through the nose and place just above the vocal cords. The tube was removed and the movement of the vocal cords evaluated as well as the ability of the child to clear the secretion from the pyriform fossa. If both cords or only one functioned well and the pyriforms were clear of pooled secretions the child was left extubated and observed in the ICU for the rest of the day, then transferred to the floor if stable. If both cords were impaired in their movement or there was substantial pooling of secretions the child was reintubated and observed for another 24 h and extubation was attempted again. The thought was that the added time might allow for postoperative swell to subside. Tracheotomy was reserved for those with inadequate vocal cord function to allow for an adequate airway or for those children who had pooling of secretion so severe and such diminished vocal cord sensation that the otolaryngologist felt that there was significant risk of respiratory distress or aspiration pneumonia in the future. In those children that later continued to have some difficulty with swallowing and the risk of feeding was unclear, a speed pathologist and radiologist performed a modified barium swallowing study immediately to determine if a gastrostomy tube or altered feeding techniques were required. Forty-five patients underwent posterior fossa surgery at our institution and have been managed by our team. Nine have had sufficient vocal cord dysfunction to required immediate tracheotomy. Eleven have required a gastrostomy. None have developed respiratory distress and none have developed aspiration pneumonia.

Discussion

We feel that this team approach and delayed evaluation is necessary for three reasons. The first reason for concern is because of potential disruption to the function the larynx cranial nerve X nuclei [2] and then subsequently the function of the superior laryngeal nerve and recurrent nerve root or trauma to the recurrent laryngeal nerve itself. The nuclei provide motor and sensory input into the larynx. If injured the cords can be spastically dysfunctional, weak, or frankly paralyzed, any of which can lead to life-threatening airway obstruction, aspiration, and pneumonia. Obstruction of the airway is an immediate indication for a tracheostomy. Sensory disruption to the superior larynx and vocal cords is equally dangerous. In this case the larynx cannot detect swallowed material before it passed through the cords and into the tracheal and lungs [3]. Potentially worse is motor dysfunction with an insensate larynx [4]. Thus, all the oral salivary fluid and feeds will go directly into the lungs and precipitate a very serious aspiration pneumonia that can be either immediately fatal or cause death years later. A tracheostomy may be necessary for protection of the lungs [5]. This is why working with a radiologist and speech pathologist with special swallowing training is required and a formal barium swallow study before feeding is necessary to make this determination of “whether it is safe to feed this child.”

The second reason for this modified approach is the possible disruption of swallowing functions, which involve many more brain stem nuclei and CN roots. The sequelae of dysphagia (swallowing dysfunction) include respiratory disorders (from aspiration), dehydration, and malnutrition. Any of these factors or combination of factors can be lethal. Aspiration pneumonia resulting from swallowing deficits is a major cause of morbidity and mortality in children after posterior fossa tumor resection [6] Swallowing is far more complex than the physician may perceive.

Swallowing refers to the entire act of deglutition from placement of food in the mouth (oral preparatory stage) through the oral cavity (oral stage), pharynx (pharyngeal stage), and esophagus (esophageal stage) and ending with entrance of food into the stomach. Swallowing can be disrupted at many levels and for many reasons. One of the most common etiologies of dysphagia is neurologic disorders [7]. Neural control of swallowing involves the brainstem, specifically two areas of the medulla: (1) the nucleus of the tractus solitaries and the adjacent reticular formation and (2) the nucleus ambiguous [8–10]. The nucleus of the tractus solitaries is composed of general visceral afferent fibers of cranial nerves VII, OX, and X, including the superior laryngeal nerve and is the first synaptic relay for multiple inputs affecting heart rate, blood pressure, respiratory drive, taste reception, and deglutition. The nucleus ambiguous is composed of special visceral efferent fibers of cranial nerves IX, X, and XI innervating the muscles of the pharyngeal and larynx.

Swallowing can be divided into four stages. The following is a brief overview of the physiology and neurophysiology of swallowing function. The oral preparatory stage involves mastication (with semi-solid or solid food) and bolus formation, rendering food into an appropriate consistency for swallowing. Neurologic control of mastication and bolus formation includes cranial nerve V, VII, and XII. The motor nucleus of the trigeminal (V) innervates the muscles of mastication . The efferent fibers of cranial nerve VII are responsible for innervations of the labial and buccinators muscles. The hypoglossal (XII) innervates the tongue, which in mastication is responsible for moving the material laterally to the posterior teeth and bolus formation.

The oral stage follows mastication and involves transporting the bolus to the posterior area of the oral cavity. This is accomplished by tongue contacting the hard palate and stripping the bolus back. Once again, neurologic control of the oral phase depends primarily on cranial nerve XII, which controls the intrinsic and extrinsic muscles of the tongue.

The pharyngeal stage of swallowing is a reflex act which has a twofold purpose: (1) guiding the bolus through the pharynx into the esophagus and (2) protection of the airway. During this phase, food is transported from the oropharynx through the pharynxesophageal junction without penetration into the nasopharynx or larynx. As the bolus moves toward the esophagus, there is excursion of the hyoid and larynx. The larynx closes to prevent laryngeal penetration and aspiration. Laryngeal closure occurs at three levels (superior to inferior): deflection of the epiglottis, adduction of the false vocal folds, and adduction of the true vocal folds [11]. Hyolaryngeal excursion contributes to opening of the upper esophageal sphincter so that the bolus can pass into the esophagus. The nucleus ambiguous (fibers of cranial nerves IX, X, and XI) is responsible for motor control of the pharyngeal muscles, laryngeal muscles, and the superior esophagus [10].

The esophageal stage of swallowing is a reflexive phase which involves the descent of the bolus of food down the esophagus via peristaltic action and relaxation of the lower esophageal sphincter. The upper esophagus contains striated muscle and is under the same neural control as the pharynx.

Swallowing is initiated by sensory impulses transmitted as a result of stimulation of receptors on the tonsils, soft palate, base of the tongue, and posterior pharyngeal wall. Sensory (afferent) impulses reach the brainstem primarily through the seventh (CN VII), ninth (CN IX), and tenth (CN X) cranial nerves (CN) while the motor (efferent) function is mediated through the ninth (CN IX), tenth (CN X), 12th (CN XII) cranial nerves any of which can be injured by ependymoma surgery. The trigeminal CN (CN V) contains both sensory and motor fibers that innervate the face, which is important in chewing.

CN VII, the facial, contains both sensory and motor fibers important for sensation of oropharynx and taste to anterior 2/3 of tongue. CN IX, the glossopharyngeal, contains both sensory and motor fibers important for taste to posterior tongue, sensory, and motor functions of the pharynx. CN X, the vagus, contains both sensory and motor fibers important for taste to oropharynx and sensation and motor function to larynx and laryngopharynx. CN X is very important for airway protection. CN XII, the hypoglossal, contains motor fibers that primarily innervate the tongue.

The properly functioning coordinated innervation of the swallowing mechanism via the CN nuclei and cranial nerves then play a critical role in swallowing phases. The oral preparatory phase movement patterns depend on lip closure, facial tone that helps with labial seal. Lateral jaw movements, rotary, lateral tongue movements, and anterior pulling of soft palate are essential. The bolus rests against the back of the tongue, which is elevated to keep material in the oral cavity. In the oral phase, an intact labial seal is important, as well as adequate anterior to posterior tongue movement of bolus and depends on functioning CN nuclei and CNs.

The pharyngeal phase begins with the triggering of the swallowing response at the anterior tonsilar arch causing elevation and retraction of the velum and complete closure of the velopharyngeal sphincters to prevent material from entering the nasal cavity. This subsequently initiates pharyngeal peristalsis to pick up the bolus as it passes the anterior tonsilar arch and carry it by sequential peristaltic (squeezing) action of the pharyngeal constrictors into and through the pharynx to the cricopharyngeal sphincter at the top of the esophagus. Cricopharyngeal sphincter opening is reflexive requiring to CNs and relaxation occurs at the time when the bolus reaches the posterior pharyngeal wall at the level of the larynx and prior to reaching this sphincter.

Proper cranial nerve function is necessary to elevate and for closure of the larynx at all three sphincters (epiglottis/aryepiglottic folds, false vocal folds, and true vocal folds) to prevent material from entering the airway (aspiration).

The cricopharyngeal sphincter relaxes reflexively to allow material to pass from the pharynx into the esophagus.

Gastric emptying can be problematic if there have been vagal nuclear or CN X injury. Delayed emptying can lead to overflow reflux and emesis with aspiration.

Conclusion

Our experience shows that a team approach is critical to successful management of children after posterior fossa surgery. It is important to delay extubation for a day until the child is stabilized. Then the vocal cords should be evaluated with fiberoptic endoscopes at extubation to determine their level of function. Finally, after the airway is secured a modified Barium Swallow is necessary to rule out aspiration. This team approach and methods eliminate respiratory distress and aspiration pneumonia from the postoperative consequences of posterior fossa tumor surgery.