Medulloblastoma in an adult

Clinical History

23-year-old woman with occipital throbbing headache, nausea, dizziness and vomiting for a month. She presented to the emergency department with exacerbation of symptoms, unsteady gait and positive Romberg's test.

Imaging Findings

CT without contrast shows expansive lesion located in paravermis of the right cerebellum, with well-defined margins and lobulated shape, hyperdense appearances with central cystic or necrotic areas. It shows strong enhancement. It is associated with mild dilation of both lateral ventricles as well as the third ventricle with signs of increased intracranial pressure due to a compression the fourth ventricle and the aqueduct of Sylvius.

MR: Neoformative process located in paravermis of the right cerebellum, with well-defined margins and lobulated shape, with a solid nodule in cephalic projection and basal component with large areas of necrosis. The lesion was hypointense in T1WI and hyperintense in T2WI and showed mild heterogeneous enhancement after IV administration of gadolinium. It shows restricted diffusion (hypointense on ADC and hyperintense on DWI). Associated with vasogenic oedema, mass effect and displacement of midline. In MR spectroscopy it showed increased choline peak with reduced N acetyl aspartate.

Discussion

Medulloblastoma is the most common malignant brain tumour in paediatric patients [1]. It represents 20% of childhood brain tumours and 40% of those located in the cerebellum [2] but represents less than 1% of adult primary CNS tumours [3]. The clinical presentation is related to the aggressive biologic behaviour of the tumours. The tumours grows rapidly, about 75% of patients have symptoms for less than 3 months predominantly related to increased intracranial pressure due a obstructive hydrocephalus [4]. The usual symptoms are headache (generalized or localized to the suboccipital region), nauseas, vomits and in some cases ataxia and spasticity. In addition they can present seizure activity (associated often with metastatic spread), papilloedema, nystagmus, dysdiadochokinesia, limb ataxia and acute neurological deterioration due to tumoral bleeding. The medulloblastoma in imaging studies appears as circumscribed margins round or ovoid tumours. The main location in adults is in the cerebellar hemisphere. It has been reported that findings on CT and MRI are more variables in adult cases than those seen in children. In childhood, medulloblastoma appears as a mass arising from the vermis. In CT, medulloblastoma presented as a hyperdense lesion in relation to the adjacent grey matter which relates to the histological tumour composition (round cells densely packed) [5]. In adults, medulloblastoma shows less enhancement after injection of contrast medium than it does in children, this is due at the higher prevalence of desmoplastic lesions in adults. Other features are vasogenic oedema, hydrocephalus and the presence of hypodense areas related to intratumoral cysts or necrosis. At MR imaging, the medulloblastoma is an iso to hypointense mass on T1WI and an iso to hyperintense mass on T2WI. Cystic or necrotic areas are easily detected in T2WI due to hyperintensity. They show heterogeneous enhancement after intravenous administration of contrast material. Other MRI features are zones of haemorrhage or calcification and leptomeningeal infiltration. Medulloblastoma uniformly demonstrates restricted diffusion (hyperintense) on DWI and hypointense on ADC map. MR spectroscopy shows elevated choline peaks and reduced N-acetyl aspartate and creatine peaks as it is seen in our case [4]. The treatment is the surgical extirpation trying to remove most of the tumour. In many cases it is necessary to place a ventriculoperitoneal shunt due to increased intracranial pressure by obstruction of the CSF flow in the fourth ventricle. After the surgery it is necessary to continue the treatment with radiation therapy, in some cases associated with neoadjuvant chemotherapy. The 5-year survival rates is between 50% and 70% [4].

Differential Diagnosis List

Final Diagnosis

Medulloblastoma

URL:	https://www.eurorad.org/case/13843
DOI:	10.1594/EURORAD/CASE.13843
ISSN:	1563-4086