Transsphenoidal encephalocele in a neonate.

Transsphenoidal encephaloceles have often been attributed to persistence of the craniopharyngeal canal. The craniopharyngeal (or transsphenoidal) canal is a vertical midline defect in the skull base. Its diameter is usually less than 1.5 mm. The defect extends from the floor of the sella turcica to the nasopharynx. Only rarely are craniopharyngeal canals visible on radiographs of the skull.

The etiology of the craniopharyngeal canal is unknown, although two theories have been proposed to explain its origin. According to the more widely accepted theory, which was proposed by Currarino et al in 1985, the canal is formed by a vertical defect in the basisphenoid and carries the remnant of the stem of Rathke's pouch. This remnant extends through the sphenoidal synchondrosis, between the presphenoid and postsphenoid. It traverses the floor of the sella and through the undersurface of the sphenoid bone. (1) In this way, the canal connects the pituitary fossa to the nasopharynx cavity. The other theory was published in 1950 by Arey, who wrote that the canal is a remnant of a vascular channel formed during osteogenesis. (2)

Transsphenoidal masses are extremely rare. They represent the least common form of basal encephaloceles, which themselves account for only 10% of all encephaloceles (i.e., 1 in 40,000 live births). (3) Transsphenoidal encephaloceles contain mature neuroglial cells with a varying degree of gliosis, in which astrocytes have divided and formed fibrillary networks called glial scar tissue. Meningeal tissue may also be present in the encephalocele.

The transsphenoidal type of mass is often large enough to cause feeding or nasal respiratory dysfunction. Newborns present with symptoms such as mouth breathing, nasal obstruction, snoring, and nasal discharge or cerebrospinal fluid leak. The encephaloceles appear as soft, compressible, bluish or red masses. They can enlarge with crying, with Valsalva's maneuver, or with compression of the jugular veins (Furstenberg's sign). Ocular hypertelorism and an increase in bitemporal diameter are common in patients with encephalocele. In addition, approximately 25% of patients have a cleft palate, which can occur when the mass is large enough. (4) The workup of these patients includes a complete head and neck evaluation in addition to nasal endoscopy.

We evaluated a 4-day-old boy who presented with grunting, flaring, and severe retractions. Fiberoptic nasopharyngoscopy detected a large soft-tissue mass in the nasopharynx and laryngeal edema; vocal fold mobility was normal.

Barium swallow imaging indicated mild esophageal dysmotility, nasopharyngoscopy identified a pulsatile midline mass in the nasopharynx, and bronchoscopy detected severe laryngomalacia and mild compression of the left mainstem bronchus. Axial computed tomography (CT) demonstrated a bone defect in the middle portion of the sella turcica (figure, A). High-resolution midsagittal T2-weighted magnetic resonance imaging (MRI) showed that a mass traversed the sella turcica and that a larger portion of the encephalocele obstructed the airway (figure, B). The bony defect might have represented the craniopharyngeal canal through which the encephalocele traversed. Axial T2-weighted MRI further elucidated the nasopharyngeal mass (figure, C).

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CT followed by MRI is the preferred radiographic study for encephalocele. CT allows for an assessment of the bone anatomy and intraorbital distance. It can also demonstrate a fluid-filled cyst, soft-tissue mass, distortion of the crista galli, and enlargement of the foramen cecum. MRI can better delineate the contents of the sac and assess brain abnormalities. (5)

The goal of surgical treatments is to resect the encephalocele while causing as little damage to vital nervous tissue as possible and to close the defect in the dura and any large bony defects. Surgical indications for transsphenoidal encephalocele are controversial because vital brain structures, including the hypothalamic-pituitary system and the anterior cerebral arteries, are often present in the herniated tissue. Our patient underwent extended lateral rhinotomy, septoplasty, endoscopic stalk ligation, and transoral resection of the encephalocele with a microdebrider. Postoperative endocrine evaluation revealed no hypothalamic dysfunction, and the patient was able to bottle-feed without any signs or symptoms of respiratory distress or nasal airway obstruction.

References

(1.) Currarino G, Maravilla KR, Salyer KE. Transsphenoidal canal (large craniopharyngeal canal) and its pathologic implications. AJNR Am J Neuroradiol 1985;6:39-43.

(2.) Arey LB. The craniopharyngeal canal reviewed and reinterpreted. Anat Rec 1950;106:1-16.

(3.) Hengerer AS, Yanofsky SD. Congenital malformations of the nose and paranasal sinuses. In: Bluestone CD, Stool SE, Kenna MA, eds. Pediatric Otolaryngology. Philadelphia: W.B. Saunders; 1996:831-42.

(4.) Brown K, Brown OE. Congenital malformations of the nose. In: Cummings CW, ed. Pediatric Otolaryngology Head & Neck Surgery. 3rd ed. St. Louis: Mosby; 1998:92-8.

(5.) Mylanus EA, Marres HA, Vlietman J, et al. Transalar sphenoidal encephalocele and respiratory distress in a neonate: A case report. Pediatrics 1999;103:e12.

Kailash Narasimhan, BA; James Coticchia, MD

From the Department of Otolaryngology, Case Western Reserve University School of Medicine, Cleveland (Mr. Narasimhan), and the Department of Otolaryngology, Wayne State University School of Medicine, Detroit (Dr. Coticchia).