Non-neoplastic intracranial cystic lesions: not everything is an arachnoid cyst

Figure 1 Epidermoid cyst. MRI showing a cyst-like formation in the suprasellar and left juxtasellar region, showing a hypointense signal in a FLAIR sequence (A - arrow) and a hyperintense signal in a functional diffusion-weighted sequence (B - arrow).

Figure 2 Pineal cyst. Contrast-enhanced axial T1-weighted MRI showing a cyst-like formation in the pineal gland region, with no evidence of septations or mural nodules (arrow), with a thin, smooth line of contrast enhancement along the margin (arrowhead).

Figure 3 Neuroglial cyst. Axial FLAIR MRI sequence showing a cyst-like formation in the white matter of the right frontal lobe with signal intensity similar to that of the CSF and without surrounding edema (arrow).

Figure 4 Rathke’s cleft cyst. Contrast-enhanced sagittal T1-weighted MRI (A) and coronal T2-weighted MRI (B), showing an expansile cystic lesion extending slightly into the suprasellar region, without contrast enhancement (white arrow). Note the small intracystic nodule (arrowhead), as well as the colloid cyst in the third ventricle (black arrow).

Figure 5 Colloid cyst. Sagittal T1-weighted MRI (A) and axial T2-weighted MRI (B), showing a cyst-like formation in the anterosuperior portion of the third ventricle, with a signal that was hyperintense in the T1-weighted sequence and hypointense in the T2-weighted sequence (arrows). Note the hydrocephalus.

Figure 6 Dermoid cyst. Sagittal T1-weighted MRI sequences (A and B), showing a heterogeneous formation, with a signal that was predominantly hyperintense (arrowhead), located in the juxtasellar region. In B, hyperintense foci were also seen scattered throughout the cortical sulci (arrows), characteristic of a ruptured dermoid cyst, together with injury to the suprasellar cistern.

Figure 7 Cerebral cryptococcosis. Axial T2-weighted MRI showing hyperintense, cyst-like formations with a soap-bubble appearance, distributed throughout the basal ganglia, in the periventricular and subcortical white matter (arrows), featuring gelatinous pseudocysts.

Figure 8 Neurocysticercosis. Axial FLAIR MRI showing cyst-like formations with signal intensities similar to that of the CSF, affecting the right temporal and left occipital lobes (arrows), and containing scolices (arrowheads). There is no evidence of perilesional edema, the absence of which is characteristic of the vesicular stage.

Figure 9 Alveolar echinococcosis. Axial T2-weighted MRI (A) and contrast-enhanced axial T1-weighted MRI (B), showing multiple coalescent cyst-like lesions in the right occipital lobe, characterized by a signal similar to that of the CSF in the T2-weighted sequence and peripheral contrast enhancement (arrows).

Figure 10 Porencephalic cyst. Axial T2-weighted MRI showing a cyst-like lesion in the left occipital lobe, with a signal intensity similar to that of the CSF (arrow). Note the communication with the ventricular system (arrowhead) and that the edges of the lesion are composed of white matter.

Figure 11 Neonatal hypoxic-ischemic encephalopathy. Axial T2-weighted MRI showing multiple cysts of varying sizes, with intensity similar to that of the CSF, distributed bilaterally in the white matter (arrows). Note the dilatation of the lateral ventricles (asterisks), secondary to involvement of the cerebral parenchyma.

Figure 12 Enlarged perivascular space. Axial FLAIR MRI showing a small cyst-like lesion in the left temporal lobe with a signal similar to that of the CSF (arrow). Note the slight hyperintensity in the surrounding brain parenchyma (arrowhead).

Figure 13 Arachnoid granulations. Axial T2-weighted MRI showing rounded, cyst-like lesions, located extra-axially, with intensity similar to that of the CSF, in close proximity to the cerebellar hemispheres (arrows).

Figure 14 Mucopolysaccharidosis. T1-weighted sagittal MRI showing multiple cystic images with a signal similar to CSF, affecting the region around the corpus callosum (arrows), resulting in enlarged perivascular spaces.