Retrocerebellar arachnoid cyst with syringomyelia: a case report.

Association of syringomyelia with retrocerebellar arachnoid cysts is rare. A case of 14 year old female is being reported, who presented with hydrocephalus caused by a large midline retrocerebellar infravermal arachnoid cyst leading to obstruction of the outlet foramina of the fourth ventricle. There was associated syringomyelia. The pathogenesis of syringomyelia is discussed. The need to evaluate cervical spinal cord by taking T1 weighted sagittal sections in all the patients of large posterior fossa mass lesions causing obstruction to the outlet foramina of the fourth ventricle has been stressed, in order to detect associated syringomyelia.