Uncommon presentation of medulloblastoma

Medulloblastoma commonly occurs in children as a midline posterior fossa mass arising from the vermis, which appears as a hyperdense, homogeneously enhancing mass on CT scan and is associated with the clinical profile of posterior fossa syndrome. This unique clinico-radiological pattern is considered 'typical', but then medulloblastomas do not follow the typical clinico-radiological pattern in a significant number of cases.

Out of the 42 cases of medulloblastoma operated on at SGPGIMS from 1988 to 1998, 29 cases were retrospectively and 13 cases were prospectively studied to detect the atypical clinico-radiological features. The typical radiological feature of a hyperdense homogeneously enhancing mass was seen in only 23 of the 42 patients, while 5 patients had hypodense nonenhancing masses, 13 had cystic changes, and 6 patients had calcifications in their tumours. Three patients presented with tumours in a very unusual location, i.e. the cerebellopontine angle cistern.

During follow-up, which ranged from a minimum period of 1 year to a maximum of 9 years, patients came back with metastases at very unusual sites. There were 5 cases of metastases in the frontal and subfrontal area (developed between 5 months and 5 years following surgery), and 1 patient developed a cervical intramedullary metastasis. Two patients developed abdominal metastases and ascites 2 years after definitive surgery and ventriculo-peritoneal shunting. Each of these 2 patients, however, had received a full course of craniospinal irradiation following surgery. Thus, we had a number of cases with an unusual clinical, radiological and metastatic pattern.