Neuroimaging Features of Ectopic Cerebellar Tissue: A Case Series Study of a Rare Entity

Coronal (A–C) and axial (D–F) T2-weighted and sagittal T1-weighted (G) MR images of patient 2 at 25 months of age show triangular-shaped ectopic cerebellar tissue on consecutive slices (A–F, arrows). Note the thin stalk connecting the ectopic cerebellar tissue with the brain stem (G, arrow).

Axial T1- (A and F) and T2- (B and G) weighted, axial DWI (C and H), ADC (D and I), and coronal T2- (E) and T1- (J) weighted MR images and maps of patient 3 at 13 years of age (upper row, arrows) and 18 years of age (lower row, arrows). The patient had a history of global developmental delay with intellectual disability, right sensorineural hearing loss, and simple febrile seizures. MR imaging shows well-defined ectopic cerebellar tissue in the right cerebellopontine angle (A–D, arrows), which was stable on follow-up MR imaging (E–H, arrows). Note the thin stalk connecting the ectopic cerebellar tissue with the middle cerebellar peduncle (E and J, arrows).

Coronal (A–D) and sagittal T2-weighted (E–G) MR imaging of patient 4 at 32 months of age shows a distorted/dysmorphic superior portion of the right cerebellar hemisphere, which also shows folial and sulcal anomalies. The dysmorphic superior portion also displaces the adjacent vermis. Ectopic cerebellar tissue (A–G, arrows) is connected to the cerebellum. Its MR signal is isointense with the cerebellum, and its morphology is elongated with irregular borders. Additional brain malformations included temporal lobe dysgyria and malrotated hippocampi (not shown).

Follow-up coronal and sagittal T1-weighted MR imaging of patient 4 at 6 years of age shows a stable imaging pattern of the ECT (arrows) with respect to the already-described findings in Fig 4.

Sagittal T1- (upper row) and T2-weighted (lower row) MR images of patient 5 at 3 years of age show a thin stalk arising from the pontomesencephalic junction below the right inferior colliculus dorsolaterally, which extends to triangular-shaped ectopic cerebellar tissue (A–F, arrows) superior to the right anterior cerebellar lobe, with an arachnoid cyst (A–F, asterisks) posteriorly. The sagittal oblique reformat T1-weighted MR imaging shows the continuous stalk (G, arrows) between the triangular-shaped ECT and the brain stem. The findings were unchanged 1 year later (not shown).

Sagittal T1-weighted (A), sagittal FLAIR (B), sagittal T2-weighted (C), sagittal contrast-enhanced T1-weighted (D), axial T2-weighted (E and F), and coronal T1-weighted (G and H) MR images of patient 6 at 17 months of age show ECT connected with the brain stem by a thin stalk (A–H, arrows). Most interesting, the MR imaging appearance of ectopic cerebellar tissue in this patient is almost identical to the MR imaging findings of patient 2.