Radiological Case of the Month FREE

Figure 1. The chest radiograph shows partially opaque right hemithorax and displacement of the heart and mediastinal structures to the left side. Segmentation anomalies are present in the upper thoracic spine.

Figure 2. Sagittal T₂-weighted magnetic resonance image shows a high-signal mass in the right hemithorax communicating with an extradural cystic lesion via the anomalous upper dorsal vertebra (arrow). An intramedullary cystic component is also present and extends cranially and caudally. The thecal sac is indented anteriorly by the extradural mass. The subdiaphragmatic extent of the cyst is not visualized on this image.

Figure 3. Axial T₂-weighted magnetic resonance images demonstrate cord expansion (arrows) caused by the intramedullary component of the lesion.

Figure 4. Axial T₂-weighted magnetic resonance images demonstrate mediastinal shift caused by the lesion and filling of the right hemithorax by a homogenous high-signal mass.

The imaging features are indicative of a large neurenteric cyst with extradural and intraspinal components.

Surgery was performed on the sixth day after the magnetic resonance scan. The mediastinal component of the cyst was aspirated and dissected. The inferior extent of the cyst was a blind tube on the antimesenteric border of the proximal jejunum. A short section of jejunum was resected.

Postoperatively, repeated chest drainage for a right chylothorax was necessary. At age 12 months the patient is well and her neurological status is being followed up as she is awaiting neurosurgical excision of the intraspinal component of the lesion.

Neurenteric cysts are rare intraspinal masses that arise during notochord development and represent persistence of the embryonic communication between the primitive foregut and the spinal canal.¹ The cysts are well delineated, thin-walled, fluid-filled masses containing elements derived from endodermal cells.² The fluid within them is nearly identical to cerebrospinal fluid or is milky or mucinous.¹ Neuroenteric cysts lie ventral to the spinal cord and associated anomalies of vertebral segmentation are common. Patients presenting later in life may exhibit no bony abnormality other than pressure erosion of adjacent vertebra. The expected location of cysts is at the cervicothoracic junction or the region of the conus.^1,3 Only 10% to 15% of the cysts occur intracranially.⁴

The clinical presentation depends on the location and size of the cyst. The lesions are sometimes diagnosed antenatally,^5- 6 but most patients present in the first decade of life with signs of cardiorespiratory embarrassment. Some present in adolescence, with pain or signs of myelopathy secondary to an intraspinal mass effect.⁷

Accurate anatomical information, particularly regarding the spinal component, is a prerequisite to surgery and magnetic resonance imaging is the modality of choice.

Accepted for publication February 9, 1998.

Reprints: Louise E. Sweeney, FFRRCS(Ire), FRCR, Royal Belfast Hospital for Sick Children, 180 Falls Rd, Belfast BT12 6BE, Northern Ireland.