Keywords
neurenteric cysts - intramedullary - spinal - endodermal cysts - enterogenous cysts
Introduction
Neurenteric cysts, also referred to as endodermal or enterogenous cysts, are rare and benign congenital lesions of the central nervous system (CNS) characterized by an epithelial lining of endodermal origin. They predominantly affect the spinal canal and cord, with spinal neurenteric cysts being more common than their intracranial counterparts.[1] Typically, these cysts are associated with various congenital abnormalities, such as vertebral dysgenesis, meningomyeloceles, and malformations of the respiratory or enteric tracts. However, isolated cases without concurrent bone or soft tissue abnormalities are exceedingly rare, making up less than 100 reported instances.[2]
[3]
Intriguingly, most of these cysts are located ventrally in the intradural, extramedullary compartment of the cervicothoracic junction of the spinal cord.[4]
[5]
[6]
[7] Only a small percentage, fewer than 5%, have been identified as intravertebral, and an even smaller proportion, also fewer than 5%, manifest as intramedullary cysts, with or without accompanying malformations.[8]
[9]
[10] In our extensive literature review, we identified only very few reported cases of intramedullary neurenteric cysts in an isolated form[2]
[11]
[12] ([Table 1]).[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26] Given the extraordinary rarity and unique characteristics of these cases concerning patient age, lesion location, and clinical presentation, we aim to present a comprehensive account of an isolated intramedullary neurenteric cyst. This report provides a thorough description of the case, elucidates its magnetic resonance imaging (MRI) features, and delves into the treatment-related considerations. Notably, complete cyst removal is the treatment of choice, although some cases have presented challenges due to strong adhesions to surrounding structures, impeding complete resection.
Table 1
Summary of isolated intramedullary neurenteric cyst cases described in the literature
|
Study
|
Age/sex
|
Location of cyst
|
MRI findings
|
CT/X-ray findings
|
Surgical removal
|
|
Riviérez et al[6]
|
46 y/F
|
L1–L2
|
Wall-enhancing cyst; T1: isointense to CSF; T2: hyperintense
|
Normal
|
Total
|
|
Singhal et al[17]
|
67 y/M
|
T7
|
Faint enhancement; T2: hyperintense
|
None mentioned
|
Total
|
|
Lippman et al[7]
|
68 y/F
|
T10–T11
|
Nonenhancing cyst; T1: hypointense to spinal cord; T2: hyperintense
|
Normal
|
Subtotal
|
|
Reinders et al[18]
|
38 y/F
|
T8–T9
|
Nonenhancing cyst; T2: hyperintense
|
None mentioned
|
Subtotal
|
|
Agrawal et al[19]
|
3 mo/M
|
T1–T7
|
Nonenhancing cyst; T1: hypointense; T2: hyperintense
|
Normal X-ray
|
Total
|
|
de Oliveira et al[20]
|
6 y/M
|
C4–C7
|
Nonenhancing hypointense; T1: hypointense; T2: hyperintense
|
None mentioned
|
Total
|
|
6 y/F
|
C7–T1
|
Nonenhancing; T1 and T2: mixed signal
|
None mentioned
|
Total
|
|
3 wk/M
|
T10
|
Nonenhancing; T1: hypointense; T2: hyperintense
|
None mentioned
|
Total
|
|
Rotondo et al[21]
|
67 y/F
|
T10–T11
|
Nonenhancing cyst; T2: hyperintense
|
Normal
|
Total
|
|
53 y/F
|
T12–L1
|
Nonenhancing cyst; T1: hypointense; T2: hyperintense
|
Normal
|
Total
|
|
61 y/F
|
T12–L1
|
Nonenhancing cyst; T1: hypointense; T2: hyperintense
|
Normal
|
Total
|
|
Menezes and Traynelis 2006[27]
|
6 y/M
|
C2–C3
|
Nonenhancing cyst; T1:iso-hyperintense; T2: hyperintense
|
Normal X-ray
|
Subtotal
|
|
Nagi et al[22]
|
40 y/F
|
C3–C4
|
Nonenhancing cyst; T1: hypointense; T2: hyperintense
|
Normal X-ray
|
Total
|
|
Muzumdar et al[23]
|
12 y/M
|
C2–C3
|
Enhancing cyst; T1: mixed; T2: hyperintense
|
Normal X-ray
|
Total
|
|
Cai et al[24]
|
3 y/F
|
C7–T1
|
Nonenhancing cyst; T1: isointense; T2: hyperintense
|
None mentioned
|
Total
|
|
Takahashi et al[25]
|
8 y/M
|
T5
|
Nonenhancing cyst; T2: hyperintense
|
None mentioned
|
Biopsy and cyst aspiration
|
|
Ziu et al[26]
|
36 y/M
|
T11–T12
|
Faint wall-enhancing cyst; T1: hypointense; T2: hyperintense with hypointense inclusion
|
|
Total
|
|
Balasubramaniam et al[13]
|
21/M
|
D12–L1
|
Hyperintense
|
Not available
|
Partial
|
|
Jhawar et al[11]
|
3 y/M
|
Cervicothoracic junction
|
Hyperintense cyst, no enhancement, and fluid–fluid level
|
Not available
|
Complete
|
|
Vachhani and Fassett[9]
|
35 y/F
|
T12–L1
|
Cysts are hyperintense and display minimal or no enhancement on T1 postcontrast imaging
|
Not mentioned
|
Partial
|
|
Novegno et al[15]
|
31/F
|
T11–T12
|
Hyperintense cyst on T2
|
Not available
|
Fenestration
|
|
Can et al[12]
|
29/M
|
C5–T1
|
Hyperintense cyst on T2
|
Not available
|
Complete
|
|
Joshi et al[16]
|
8 y/M
|
D3–D6
|
Hyperintense on T2
|
Not done
|
Complete
|
|
Diyora et al[14]
|
2 mo
|
Cervicothoracic junction
|
Isointense on T1-weighted images and hyperintense on T2-weighted images
|
Not available
|
Partial
|
|
Present case
|
33 y/M
|
C1–T4
|
Nonenhancing cyst, T2: hyperintense
|
Normal
|
Total
|
Abbreviations: CSF, cerebrospinal fluid; CT, computed tomography; MRI, magnetic resonance imaging.
Case Report
Presentation and Examination
A 33-year-old male patient presented with a 6-month history of progressive weakness in the left upper limb, accompanied by pain and numbness in the left upper arm and shoulder for the last month. His medical history was unremarkable. Neurological examination revealed significant atrophy of the left upper limb muscles, reduced strength in the left upper limb, mild spastic paraparesis in both legs, bilateral Babinski sign, and normal rectal tone and perianal sensation. Sensory testing indicated limited light touch and pinprick sensations in both legs, while proprioception remained intact. No cutaneous abnormalities were observed. Plain X-ray images of the thoracolumbar spine yielded normal findings. MRI revealed an elongated, lobulated segmental cystic intramedullary space-occupying lesion with marked signal heterogeneity in the cervicodorsal spinal cord, extending from the cervicobulbar junction to the T4 level. Postcontrast images demonstrated intense enhancement in the solid tumoral tissue between the C4 and C6 levels, with regions of low signal intensity on T2-weighted images that displayed a “cap sign” due to hemosiderin staining, as well as evidence of focal subacute hemorrhage in the caudal portion of the intramedullary tumor ([Fig. 1]).
Fig. 1 MRI of the cervicothoracic spine (A: sagittal and B: axial images) depicting an elongated/lobulated, segmental, sharply marginated, expansile cystic intramedullary space-occupying lesion with marked signal heterogeneity in the cervicodorsal spinal cord, extending from the cervicobulbar junction to the T4 vertebra level.
Surgical Treatment
Surgical intervention involved a C7–D1 laminectomy. An examination of local bone, soft tissues, and meningeal layers revealed no abnormalities. However, the spinal cord exhibited swelling, prompting a myelotomy. This procedure unveiled a purple-gray cystic tumor that appeared encapsulated and separate from the surrounding normal tissue. After aspiration of 3 mL of milky-white fluid, complete removal was achieved. Subsequent microbial culture and cytological tests on the liquid yielded negative results.
Pathological Examination
The cyst was encased in a thick fibro-membranous covering, containing occasional neuroglial tissue, along with rows of ciliated columnar and mucinous epithelial cells ([Fig. 2]). The final diagnosis confirmed the presence of a neurenteric cyst.
Fig. 2 Histopathological examination revealing rows of ciliated columnar and mucinous epithelial cells, indicative of a spinal neurenteric cyst.
Postoperative Course
The patient's recovery following surgery was uneventful. Upon discharge, neurological examination indicated moderate improvement in paraparesis. The patient improved symptomatically in the postoperative period and did not agree to get postoperative imaging due to financial constraints in the subsequent follow-up visits.
Discussion
Neurenteric cysts involving the spinal cord account for 0.7 to 1.3% of all spinal cord tumors and typically manifest in the second decade of life, with a higher incidence in males.[8.9.11.12] Histopathologically, these cysts are characterized by a true cyst structure with various epithelial linings. They are often filled with milky, xanthochromic, or transparent fluid, believed to contribute to cyst growth.
Pathogenesis and Presentation
These cysts are thought to originate from developmental abnormalities related to the notochord, involving persistent communication between the gut and dorsal skin. While the precise embryological errors leading to neurenteric cyst formation remain elusive, several hypotheses have been proposed.[13]
[14] Neurenteric cysts are typically large at the time of diagnosis and can displace the spinal cord dorsally. Isolated spinal neurenteric cysts, particularly those without associated dysraphic abnormalities, tend to present in later childhood and young adulthood. Clinical symptoms are often subtle, including localized back or neck pain, with motor weakness and myelopathy signs emerging later in the course. Periodic rupture of cyst contents into the subarachnoid space and cyst enlargement are potential reasons for the clinical exacerbations and remissions observed in some cases.
Imaging Characteristic
The imaging appearance of spinal neurenteric cysts can be challenging to distinguish, especially in cases of intramedullary and isolated presentation. Diagnosis is considered when imaging studies reveal a lobulated intradural extramedullary or, infrequently, an intramedullary cystic mass with extramedullary–subdural exophytic expansion, often accompanied by anterior spina bifida or vertebral anomalies.[15]
[16] MRI is the preferred diagnostic modality, providing crucial insights into the relationship between the cyst and the spinal cord. Neurenteric cysts typically exhibit signal characteristics that are isointense to hyperintense relative to cerebrospinal fluid (CSF) on T1-weighted images and isointense or slightly hyperintense to CSF on T2-weighted images. These signal features correspond to the high-protein fluid within the cyst, which is often described as milky or mucinous. Importantly, neurenteric cysts do not enhance with contrast and lack a mural nodule, distinguishing them from neoplastic lesions. Other nontumor cystic entities, such as teratomas, teratoid tumors, and ependymal cysts, may have similar appearances to neurenteric cysts and do not necessarily enhance after contrast administration. Computed tomography (CT) can be useful for identifying associated bone anomalies.[17]
Treatment Options
Surgical removal is the preferred treatment for spinal neurenteric cysts. A conservative “wait-and-see” approach is not advisable due to the risk of irreversible neurological deficits resulting from chronic nerve root and spinal cord compression or cyst rupture. The extent of surgical resection depends on the cyst's location. Extramedullary cysts are typically amenable to complete resection due to the clear dissection plane between the lesion and neural elements. In cases of intramedullary cysts, where the cyst may be firmly adherent to surrounding structures, a more conservative approach is recommended to avoid postoperative morbidity. Treatment options for intramedullary cysts can range from cyst aspiration to subtotal resection, with or without cyst marsupialization and cysto-subarachnoid shunting. Simple aspiration is less favored due to the risk of cyst recurrence. Subtotal resection has demonstrated positive outcomes, while the use of marsupialization and/or cysto-subarachnoid shunting remains a subject of debate among experts.
Conclusion
In the cases discussed in this report, the definitive diagnosis of neurenteric cysts was established through histological examination. The uniqueness of these cysts' intramedullary location in the lower thoracic spine, the advanced age of the patients (in their sixth and seventh decades), their isolated presentation without associated malformations, and the absence of radiologically distinctive features posed challenges in making accurate preoperative diagnoses.
Regarding treatment, cases where the cyst is strongly adherent to the spinal cord may require a more careful, piecemeal resection due to the potential risk of spillage of caustic cyst contents into the subarachnoid space. To mitigate this risk, it is advisable to aim for complete resection while avoiding the spillage of cyst contents into the subarachnoid space. If a clear dissection plane is not identified, or if the cyst wall is strongly adherent to surrounding structures, a subtotal removal is recommended to achieve favorable immediate and long-term outcomes while preventing further injury to the spinal cord. However, in such cases, vigilant radiological follow-up is crucial to monitor for potential cyst recurrence.
