Neurenteric cysts can occur anywhere throughout the neuraxis and have various synonyms,they are typically located ventral to the cervical or thoracic spinal cord, these benign lesions rarely occur intracranially,embryopathogenesis of neurenteric cysts is still unclear and various hypotheses have been proposed.Clinically,neurenteric cysts may present with symptoms related to mass effect, or they can be asymptomatic and incidentally discovered[4, 5].
Radiological characteristics of intracranial neurenteric cysts are quite variable depending on protein content of the cystic fluid. The CT appearance is variable with neurenteric cysts previously reported as hypodense or hyperdense depending on protein content. As with CT, the MRI appearance is variable and depends on the protein content within the cyst. Typically, neurenteric cysts with low protein content are isointense to slightly hyperintense relative to cerebral spinal fluid on T1WI, while cysts with higher protein content are more hyperintense on T1WI. T2WI and FLAIR signal intensities can be variable, but are more commonly hyperintense in signal[6–8]. Typically, the cysts rarely show rim enhancement by contrast medium. These findings highlight the variability in imaging characteristics displayed by neurenteric cysts, which is likely a reflection of the range in protein level of the cyst contents.
Skull osteomas are benign bone-forming neoplasms that can occur in any part of the skull. Most osteomas are asymptomatic, and some are accidentally found in imaging examinations. Only 4%-10% of osteomas may cause clinical symptoms, especially when the lesion penetrates skull base, which may cause headache, frontal sinusitis or chronic sinusitis. If the osteoma produces compression effect or penetrates into the skull to form pneumocephalus and mucous cysts, surgical treatment is necessary,ongoing advancements in endoscopic surgery have allowed less invasive surgical approaches to be adopted for removal than open surgery.If the time is long enough, the osteomas can recur, and the tumor grows faster after incomplete resection. There is no report of malignant transformation of skull base osteoma.
No cases of intracranial neurenteric cysts accompanied by skull base osteoma have been reported,and the relationship between these two lesions is unclear, which may be a coincidence,the cause for the formation of pneumocephalus is considered to be that the osteoma penetrates the dura, which makes the dura mater lose its integrity, and the air from the sinuses can then enters the skull.
The first-line treatment for neurenteric cysts and osteomas is complete surgical resection ,as both of these the diseases are not sensitive to radiotherapy or chemotherapy. If the mass is large or is causing symptoms,not only radical but also subtotal resection can lead to good control of disease opening on to good postoperative course and outcome. Total resection of the cyst wall can cure the disease. If the cyst wall can not be completely removed during the operation, the cyst wall should be removed as much as possible, which can reduce the recurrence rate that may occur several years after surgery.Therefore, a long-term follow-up lasting even more than ten years after surgery is recommended. During the operation, the contents of cyst can be sucked out in advance to achieve the purpose of volume reduction, avoiding the overflow of the contents caused by the rupture of the capsule cavity,which may help reduce the occurrence of aseptic meningitis[11, 12].