Anatomical Implications of Chiari I and Basilar Invagination (Type B) in the IV Ventricle and Cisterna Magna

Efficacy of foramen magnum decompression with and without cranioplasty in a rat model of Chiari-like malformation

“…In human medicine, the anatomical boundaries of the cisterna magna are defined with the upper limit as the lower part of the cerebellum, the inferior border as the upper limit of C1, the anterior border as the inferior medullary velum and medulla, and the posterior border as the occipital bone [7]. Based on these findings, we established a new boundary for the cisterna magna in veterinary medicine, which, to the best of our knowledge, has not yet been defined.…”

“…Based on these criteria, the volume of the cisterna magna was measured. In rat CLM models with cerebellar herniation through the foramen magnum, the volume of the desired CSF space, the cisterna magna, was calculated by subtracting the volume occupied by the herniated cerebellum from the total cisterna magna volume [7].…”

“…These boundaries delineated the total cisterna magna. In instances of cerebellar herniation, the space occupied by the herniated cerebellum was excluded from the total cisterna magna space, and the remaining space was identified as the free area of the cisterna magna (hereinafter referred to as the cisterna magna) for comparison in this study [7] (Figs 6A, B, C).…”

“…Although the features of the cisterna magna are less understood in veterinary medicine, recent studies in human medicine have suggested that headaches, a primary clinical symptom of CM1, may be linked to an anatomical feature known as a limited cisterna magna [7]. Located at the craniospinal junction, the cisterna magna lies inferior to the cerebellum and medulla and dorsal to the upper cervical spinal cord [8].…”

“…Like other cranial cisterns, the cisterna magna maintains a wide CSF compartment, regulating rapid pressure changes within the cranial and spinal compartments during physiological and pathological events [8]. However, in CM1, decreased posterior cranial fossa volume leads to herniation of the cerebellar tonsils, which invade the cisterna magna space, disrupting CSF flow and leading to clinical symptoms [7].…”