Presentation
Headache.
Patient Data
There is evidence of a prior right frontal craniotomy below which is a sharply demarcated cyst lesion creating smooth scalloping against the adjacent brain parenchyma, but no significant mass effect is noted. Although the lesion is favored to be extra-axial, the parenchyma grey-matter surrounding the cyst is indistinct. There is no scalloping of the calvaria.
The cystic lesion has increased in size when compared to the images from 5 years ago, and now causes compression of the lateral ventricle and early subfalcine herniation.
Right frontal redo craniotomy with overlying staples, soft tissue swelling subcutaneous emphysema. There is a prominent air-fluid level intraparenchymal blood at the anterolateral margin of the surgical bed. A small amount of blood pools at the dependent aspect of the right frontal fluid collection. There is 8 mm left which shift of the septum pellucidum. There is mild sulcal effacement of the right cerebral hemisphere. The basal cisterns are not effaced. The grey-white matter differentiation is preserved.
Right frontal craniotomy. A large cystic space that follows CSF signal on all sequences demonstrates similar dimensions when compared to the previous CT brain, although has distinctly enlarged when compared to the more distant CT brain from years ago. This lesion demonstrates a gently lobulated margin with some thin non-enhancing septations noted superiorly. A small volume of non-enhancing material lies dependently within. Inferiorly, this cystic lesion appears to abut white matter of the deep right frontal lobe with no intervening cortex. There is no associated enhancing components to this cystic structure. No communication with the right lateral ventricle. Increased size results in a progressive mass effect, with partial effacement of the right lateral ventricle as well as subfalcine herniation and mild right uncal herniation. No evidence of entrapment of the left lateral ventricle. Remote from this cystic lesion, the remainder of the intracranial structures have a normal appearance. The optic nerve sheaths are noted to be symmetrically mildly CSF distended.
Case Discussion
Central nervous system neurenteric cysts are congenital rare lesions that are more frequently seen involving the spine. Cases like this one, in a supratentorial location, are even rarer. On imaging, they usually have non-CSF signal characteristics on MRI. In this instance, the MRI appearances are following resection, and therefore cannot be taken as typical.
The patient underwent further surgical resection of the frontal cystic lesion.
Histology
The two specimens show similar features and are described together. Examined at multiple levels, the sections show cyst wall lined with pseudostratified ciliated columnar epithelium with fine intracytoplasmic brown pigment, mixed with goblet cells and cells with PASD positive granules. No complete epithelial excrescences are present. The underlying connective tissue also shows brown pigment. No pituitary tissue is identified. The cells show patchy positive staining for CDX2 and SOX10, and are negative for EMA and Transthyretin. In the context of the intra-axial site of the frontal lobe cyst the features are most in keeping with the neuro-enteric cyst. No atypical features are identified.
Final diagnosis:
Benign developmental cyst in keeping with a neurenteric cyst.
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