Acquired cerebellar tonsillar herniation and syringomyelia associated with posterior fossa mass lesions is an exception rather than the rule. In the present article, we describe the neuroimaging findings in a case of 28-year-old female patient presented with a history of paraesthesia involving right upper limb of 8-month duration. Magnetic resonance imaging showed a giant retrocerebellar arachnoid causing tonsillar herniation with cervical syringomyelia. The findings in the present case supports that the one of the primary mechanism for the development of syringomyelia may be the obstruction to the flow of cerebrospinal fluid causing alterations in the passage of extracellular fluid in the spinal cord and leading to syringomyelia.

Arachnoid cysts are benign congenital lesions of the central nervous system accounting for 1% of all intracranial masses. Intraventricular location of arachnoid cyst especially in the fourth ventricle is rare. Fenestration or marsupialization of these "innocent-looking" benign cysts can lead to dreadful life-threatening complications. We report a rare case of development of malignant irreversible global cerebral edema in a 21-year-old lady following surgical decompression of fourth ventricular arachnoid cyst.

The rarity of the tubercular involvement of the clivus makes the preoperative diagnosis difficult. We report a case of a 40-year-old man who presented with right-sided trigeminal neuralgia without any other neurological symptoms or deficits. Postcontrast images showed a dural-based lesion in the region of the clivus which was isointense on T1 images and hypointense on T2 images and the lesion was enhancing after contrast administration suggestive of a tumor. The patient underwent surgical excision of the lesion and the histopathological examination was suggestive of tuberculosis. The patient completed the course of antitubercular therapy and recovered well. Tuberculosis of the clivus region runs an indolent course and following appropriate treatment these patient do well.

Pilocytic astrocytoma (PA) is a subset of gliomas characterized by a benign course with an excellent prognosis and rarely metastasizing or spreading along the neuraxis. We report a case of a 56-year female with intraventricular dissemination of pilocytic astrocytoma in an adult and discuss the clinical significance diagnosis and management including the peculiar pattern of dissemination of the pilocytic astrocytoma. The course of the disseminated disease may not be as good as that of patients with localized recurrence or totally resected primary disease and can vary from rapid progression to prolonged stabilization.