BACKGROUND: Rare reports in the literature have documented the presence of a cyst at the tip of the cerebellar tonsil in @entity1 with @entity1645 . The current study aimed to better elucidate these cysts and identify their etiology via a histological and radiologically analysis. @entity1 AND METHODS: We prospectively reviewed all new @entity1645 ( @entity1645 ) @entity1 who presented to our clinic during a 2-year period. This was a pediatric cohort made up of 340 @entity1 aged 3 to 18  years. Specifically, all @entity1 were screened for @entity63 or cystic lesions of the @entity3976 on MRI. RESULTS: Out of 340 @entity1 , 2.9  % were found to have signal changes on MRI consistent with @entity63 or cysts in the cerebellar tonsils. Of the 340 @entity1 , 20  % underwent posterior fossa decompression. Of the 67 @entity1 , @entity63 was observed in 10.4  % and @entity76 were seen in 6  %. Four of the seven operative @entity1 with @entity63 and concomitant @entity1644 and three of these @entity1 with @entity5326 concomitant @entity1644 and @entity76 underwent subpial dissection of some cerebellar tonsil to ensure that CSF egress from the fourth ventricle to the cervical subarachnoid space, and this transected tissue was also sent for histological analysis. Three of the four @entity1 found to have intraoperative @entity5326 were noted to have tonsillar @entity63 changes on preoperative imaging in this same region. For both @entity63 and @entity76 , histologically, the tissue demonstrated loss of Purkinje cells with concomitant Bergmann gliosis. The @entity63 and cystic tissues were virtually the same, histologically. CONCLUSIONS: Based on our findings, @entity63 and cysts in @entity1 with @entity1645 can often be seen radiologically. Histologically, these @entity63 and cystic tissues are the same. Moreover, we document @entity1 where @entity63 lesions progressed to cysts, radiologically. Taken together, @entity63 and cysts are on a continuum and represent chronic compression of this herniated part of the cerebellum.

Evolution of @entity63 to @entity76 in the XXXX : radiological, surgical, and histological evidence.

@entity1 :: ('9606', 'Species') :: ['children', 'patients', 'PATIENTS'] @entity3976 :: ('MESH:D004677', 'Disease') :: ['herniated cerebellar tonsils'] @entity1644 :: ('MESH:D013595', 'Disease') :: ['syringomyelia'] @entity63 :: ('MESH:D007511', 'Disease') :: ['cerebellar tonsillar ischemia', 'ischemia', 'ischemic'] @entity1645 :: ('MESH:D001139', 'Disease') :: ['CM-I', 'Chiari I malformation'] @entity76 :: ('MESH:D002526', 'Disease') :: ['cystic cerebellar tonsils', 'cerebellar tonsillar cysts'] @entity5326 :: ('MESH:D014067', 'Disease') :: ['tonsillar cysts']
@entity1645 :: (MESH:D001139,Disease) :: ['Chiari I malformation']
