Fetal Surgery for Neck Masses

Fetal cervical masses are a challenging congenital malformation to manage; they can grow rapidly, resulting in hydrops fetalis, polyhydramnios, and in-utero fetal demise (IUFD). Among affected fetuses who survive to delivery, complications such as asphyxia and death commonly result from airway compromise.[1]

Fetal cervical masses are diagnosed with antenatal ultrasonography (US); when they are identified, follow-up fetal magnetic resonance imaging (MRI) for further characterization is warranted.

Management continues to evolve, and with the introduction of the ex-utero intrapartum treatment (EXIT) procedure, survival past the neonatal period has significantly improved.[2]

Fetal cervical lesions can result from various congenital malformations, with the two most common types being cervical lymphangiomas and cervical teratomas. The incidence of cervical cystic hygromas, a lymphatic malformation, is fairly high, affecting 1 in 1000 births.[3] In fact, it has been observed in 1 in 300 spontaneous abortions.[4] Cervical teratomas, the second most common fetal neck mass, are far less common (see the image below), with an unknown incidence. 

Cervical Teratoma in an infant delivered via EXIT procedure

Other rare neck masses include thyroid malignancies and cysts, branchial cleft cysts, vascular malformations, and neuroblastomas; these are beyond the scope of this article.

Once a fetal cervical mass is identified with antenatal US, fetal MRI should be performed to help characterize the mass and, if necessary, to assist with preoperative planning. Fetal MRI is valuable in that it aids in delineating solid and cystic components, as well as identifying the presence of fat. In addition, the tracheal anatomy can be evaluated and a detailed analysis of its displacement by large cervical masses can be performed by means of MRI.[5]

Difficulty arises in defining the severity of the lesion and determining the need for an EXIT procedure. A parameter developed to define the severity of cervical masses is the tracheoesophageal displacement index (TEDI), first described by the Texas Children’s Hospital group.[6] The TEDI is based on summing the ventral and lateral displacement of the esophagus and the trachea from the cervical spine. In the Texas Children's Hospital's series of 24 patients, 100% of patients with a TEDI higher than 12 mm had a complicated airway, compared with 46% of those with a TEDI lower than 12 mm.[6]  Thus, this measurement can serve as an indicator of a potential airway obstruction.

Further studies have shown that quantifying the largest vertical pocket of amniotic fluid on MRI and its associated mass effect on the trachea can be used to identify a high-risk fetus and potential morbidity that would necessitate an EXIT procedure.[7]

There have been previous reports of successful in-utero resection of cervical masses.[8] An EXIT procedure, on the other hand, should be offered to viable fetuses with complicated airways because it provides an opportunity to manage the airway while the fetus remains on uteroplacental support.[9] Additionally, radiologic findings demonstrating polyhydramnios or a solid neck mass should prompt a pediatric surgeon to be present at the time of delivery in case a surgical airway is required if an EXIT procedure is not performed.

Contraindications for fetal surgery can be either maternal or fetal in origin. Maternal contraindications include the following:

• Frequent contractions
• Membrane rupture
• Short cervix
• Uncontrolled comorbidities that may predispose the patient to preeclampsia or HELLP (Hemolysis, Elevated Liver enzymes, Low Platelets) syndrome

Fetal contraindications include the following:

• Multiple fetal anomalies
• Chromosomal abnormalities
• Anatomic restrictions (eg, anterior-lying placenta) that may prohibit safe access

Complication prevention

Appropriate anesthesia and tocolytics are imperative for preventing uterine contractions and placental separation.

Uterine atony can lead to diffuse bleeding. Therefore, it is essential to minimize blood loss, to obtain a preoperative type and cross for 4 units of packed red blood cells (RBCs), and to monitor hematocrits, if necessary.

A special fetal uterine stapler can reduce the risk of hemorrhage.

Outcomes vary. Early neonatal death after a secured airway during an EXIT procedure may result from pulmonary hypoplasia or prematurity.[10] Outcomes depend on the location, size, and underlying etiology of the cervical mass.

Neonatal survival during an EXIT procedure is approximately 80%; mortality may result from cardiorespiratory failure, large cervical masses that consequently lead to pulmonary hypoplasia, or intubation or tracheostomy failure.[11]

Cervical teratomas frequently displace rather than invade surrounding structures; thus, resection is often feasible.

The malignant potential depends on the pathologic findings, and screening for recurrence with alpha-fetoprotein (AFP) levels should be routinely performed.

Lymphatic and vascular malformations have a much more protracted course and often necessitate multiple operations. In addition, they are associated with a higher risk of nerve dysfunction and disfigurement.[12]

Historically, developmental delay resulting from hypoxia in the perinatal period was common, but with the advent of the EXIT procedure, obvious delays appear to have been dramatically reduced.[13]

A 2015 study suggested that despite the substantial perinatal morbidity associated with fetal neck masses, long-term outcomes, both functional and cognitive, are quite good.[12]

Given that the progression of cervical masses varies, counseling parents is challenging. Masses identified early in gestation associated with hydrops carry a high risk of fetal demise, and patient counseling is of paramount importance. Patients who have masses that progress rapidly, constricting the trachea and esophagus, and who survive to a viable gestation should be offered an ex-utero intrapartum treatment (EXIT)-to-delivery procedure. Counseling should also include discussion of the fetal risk associated with EXIT-to-delivery, which may include cardiorespiratory failure, asphyxia, prematurity, mass rupture, and pneumothorax.

From a maternal standpoint, depending on placental location, a classic hysterotomy may be required, prohibiting the possibilities of future vaginal deliveries. Additionally, the risk of uterine dehiscence and rupture in subsequent pregnancies is not trivial; such events have been reported to occur after 14% of EXIT procedures.[14]  Therefore, all mothers should be counseled with regard to the associated risks.

The EXIT procedure requires careful planning with a multidisciplinary team that typically includes two pediatric/fetal surgeons, one obstetrician, one neonatologist, one ultrasonographer, one otolaryngologist, and one nurse scrub. In view of the risk that the fetus will require a tracheostomy during an EXIT procedure, the multidisciplinary team needs to be prepared to perform additional high-risk procedures if necessary to establish an airway. To ensure maternal safety during the procedure, adequate attention to uterine relaxation is paramount. Additionally, the multidisciplinary team should be prepared for the need for additional surgical procedures (eg, mass removal).

A direct laryngoscope, rigid and flexible bronchoscopes, and a tracheostomy kit should be immediately available. Case reports have demonstrated the use of a video laryngoscope to assist with visualizing the vocal cords and prevent the need for tracheostomy when oral intubation cannot be performed with direct laryngoscopy.[15, 16]

A uterine stapler with absorbable staples (US Surgical Corporation, Norwalk, CT) is used to minimize blood loss during the hysterotomy.

Anesthesia

Inhaled anesthetics, particularly isoflurane,[17, 18] are necessary for uterine relaxation and uteroplacental gas exchange, which have been demonstrated to be normal up to 54 minutes on uteroplacental support during EXIT delivery.[19]

Alpha-adrenergic agonists are frequently required to maintain maternal blood pressure, given that high levels of isoflurane, which are needed for uterine relaxation, often result in hypotension.

In addition, nitroglycerin can assist with uterine relaxation. Activation of guanylyl cyclase leads to increased levels of cyclic guanosine monophosphate (cGMP) and decreased levels of intracellular calcium, resulting in uterine relaxation.[20] Typically, a fetal cocktail consisting of a paralytic and a narcotic is injected into the fetus intramuscularly.

Positioning

The patient is typically placed in the supine position on the operating room table. Occasionally, the patient may be placed in a lithotomy position to increase the space available to operating room staff.

After birth, follow-up computed tomography (CT) or magnetic resonance imaging (MRI) should be performed to confirm the diagnosis. Surgical management can be elective once an airway is established.

Postnatal management depends on the type, size, and location of the lesion. Cervical teratomas are frequently resected in the neonatal period to minimize the risk of malignant transformation. Because these lesions may involve the thyroid gland, care should be taken during the dissection, and consultation with an endocrinologist for hypothyroidism may be required postoperatively. Vascular malformations are frequently managed medically, whereas lymphatic malformations benefit from sclerotherapy, surgical resection, or both.

No definitive management strategy has been delineated for fetuses identified with cervical masses and hydrops early in gestation. One current practice is to offer an ex-utero intrapartum treatment (EXIT)-to-airway procedure for viable fetuses with a concerning airway.[21]  Antenatal imaging findings that predict the need for an EXIT-to-airway procedure include the following[22] :

• Location of the mass
• Presence of an invasive component into the airway
• Relationship to the airway

During the procedure, all necessary personnel should be present in the operating room.

EXIT deliveries can lead to tremendous blood loss, in that tocolytics and inhaled anesthetics are used to obtain uterine atony, which, in turn, maintains placental blood flow. To minimize blood loss during the hysterotomy, a specific uterine stapler device with absorbable staples (US Surgical Corporation, Norwalk, CT) is required.

It is paramount to preserve placental blood flow, which requires profound uterine relaxation and caution when entering the uterus. With anterior placentas, a posterior uterine incision is frequently required in an attempt to avoid placental injury and chorioamniotic separation, which can disrupt uteroplacental gas exchange. Additionally, caution should be taken to minimize manipulation of the umbilical cord, which may result in vessel spasm and compromised blood flow. Amnioinfusion with normal saline is employed to reduce the risk of decelerations and fetal distress.

With the fetus still on placental support, the head and one arm are exposed through the uterine incision. A pulse oximeter is then placed on the fetal hand to continuously monitor fetal oxygenation.

At this point, the mass and the airway are evaluated with direct laryngoscopy. If endotracheal intubation is not possible, bronchoscopy may be attempted. If this is unsuccessful, the next step is tracheostomy.

Rarely, resection of the mass during the EXIT procedure is needed to establish an airway. All equipment, including the laryngoscope, must be sterile to minimize the chances of maternal infection.

Once the airway is established, the fetus is delivered and the umbilical cord divided. The uterus and the abdominal wall are closed in the same technique as a cesarean section.

Esophageal and tracheal obstruction are common complications, leading to polyhydramnios, hydrops fetalis, and in-utero fetal demise (IUFD). Perinatal complications include asphyxia and death.[23, 24] The diagnosis of a fetal cervical lesion is not to be taken lightly, in that it carries an estimated IUFD rate of 20%.[25]  However, when an EXIT procedure involves a multidisciplinary team, the perinatal outcome is improved and the safety of both mother and fetus enhanced.