A neurenteric cyst (NEC) is a rare, non-cancerous growth that forms within the central nervous system, most commonly in the spine. This congenital anomaly is a fluid-filled sac lined with tissue resembling the lining of the digestive or respiratory tract. NECs are developmental lesions, originating from an error during the earliest stages of embryonic formation. Although non-malignant, the cysts cause neurological symptoms by pressing on the spinal cord or brain structures. They account for a small fraction of all spinal axis tumors, estimated between 0.7% and 1.3% of cases.
The Embryological Origin
The formation of a neurenteric cyst traces back to a developmental mishap during the third week of human gestation. At this time, the embryo is undergoing gastrulation, establishing the three primary germ layers: ectoderm, mesoderm, and endoderm. The endoderm forms the lining of the gut and respiratory system, while the ectoderm forms the nervous system. A temporary structure, the neurenteric canal, briefly connects the embryonic gut (endoderm) to the amniotic cavity, passing through the developing notochordal plate.
A neurenteric cyst forms due to incomplete separation between the presumptive endoderm and the notochordal plate, the precursor to the vertebral column and central nervous system structures. This failure allows a small remnant of endodermal tissue to become misplaced and trapped within the developing neural canal. This misplaced tissue, composed of columnar or cuboidal epithelium, forms the cyst lining and often secretes mucus. Continuous secretion of this fluid causes the epithelial remnant to swell and form a cyst, creating pressure on surrounding neural structures.
Common Locations and Manifestations
Neurenteric cysts are most frequently found within the spinal canal, typically ventral to the spinal cord, with the lower cervical and upper thoracic regions being the most common sites. Approximately 75% of all neurenteric cysts occur in the spine. They are usually located in the intradural, extramedullary space, meaning they are inside the protective dura mater but outside the actual spinal cord tissue. A significant number of spinal cysts, around 50% of cases, are associated with bony abnormalities of the vertebrae, such as spina bifida or hemivertebrae.
The clinical presentation of a neurenteric cyst is directly related to its size and precise location, as symptoms arise from the cyst’s mass effect on the nervous system. In the spine, compression of the spinal cord or nerve roots can lead to localized or radiating pain, weakness, and sensory changes in the limbs. Patients may also experience difficulty with bladder or bowel control, known as sphincter dysfunction, due to pressure on the lower spinal nerves. The symptoms can sometimes fluctuate, which is attributed to changes in the cyst’s fluid volume, sometimes leading to an initial misdiagnosis.
While less common, neurenteric cysts can also occur within the brain, with the posterior fossa being the most frequent intracranial location. When a cyst is located in the brain, it can cause symptoms such as persistent headache, dizziness, or deficits in cranial nerves. The presentation of these cysts is often delayed until late childhood or early adulthood, despite their congenital origin.
Identifying and Managing the Cyst
The diagnostic process for a suspected neurenteric cyst relies heavily on advanced medical imaging, with Magnetic Resonance Imaging (MRI) considered the preferred technique. MRI is especially effective for clearly defining the cyst’s fluid content, its size, and its relationship to the surrounding neural structures. Computed Tomography (CT) scans may also be used to identify any associated bony abnormalities in the vertebrae that frequently coexist with the cyst. The typical appearance on MRI helps differentiate the neurenteric cyst from other cystic lesions in the central nervous system.
Surgical intervention is the standard treatment for symptomatic neurenteric cysts, aiming to alleviate pressure on the neural tissue. The primary goal is the complete excision of the cyst wall, which prevents recurrence. Total removal can be challenging because the cyst wall often adheres closely to delicate neural structures, such as the spinal cord or brainstem. If adherence is too intimate, a surgeon may leave a small remnant rather than risk causing a new neurological deficit.
When complete removal is not possible, the surgeon removes as much of the cyst as safely feasible for decompression. Even partial removal can lead to significant resolution or improvement of the patient’s neurological symptoms. Techniques like simple aspiration or fenestration, which drain the fluid but leave the secreting cyst wall, are considered temporary measures. Histopathological analysis of the removed tissue confirms the diagnosis by identifying the characteristic columnar or cuboidal epithelium lining the cyst.
Long-Term Monitoring and Prognosis
Following successful surgical treatment, the overall prognosis for patients with a neurenteric cyst is favorable, with a high likelihood of neurological symptom resolution. The long-term outlook is closely tied to the extent of the initial surgical removal. The risk of recurrence is significantly higher if the entire cyst wall was not excised, with rates reported as high as 37% after incomplete removal.
Due to the possibility of recurrence, continuous, lifelong neurological follow-up is essential post-operatively. Patients typically undergo periodic follow-up MRI scans to monitor the surgical site for fluid re-accumulation or cyst growth. The long-term outcome is also influenced by the extent of pre-existing neurological damage caused by the cyst’s initial compression.