IS case 456: Pontine glioma
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
History
Patient is a 9-year-old female presenting with a one week history of drooling, slurred speech and ataxia.
Findings
CT and MR displayed a large expansile lesion within the pons, with areas of central necrosis. The mass resulted in marked expansion of the pons with compression of the fourth ventricle, effacement of the adjacent cisterns and partial encasement of the basilar artery.
Diagnosis
Pontine glioma
Discussion
Brainstem gliomas account for approximately 15% of all pediatric CNS neoplasms, with a peak incidence between the ages of 3 and 10 years of age. The majority of these tumors are astrocytomas. The tumor tends to infiltrate the brainstem causing expansile enlargement. Because of the location of the tumor, characteristically patients present with cranial nerve palsies, nausea/vomiting, bulbar signs and ataxia. Chemotherapy and radiation therapy are the mainstays of treatment. Because of its location surgery is uncommonly an option and for children the median survival rate is less than 1 year. Because of the slow growth of these tumors, hydrocephalus is uncommon. Hemorrhage occur in approximately 25% of cases.
On CT, brainstem gliomas appear as low attenuation lesion with expansion of the brainstem. Brainstem gliomas may be isodense on CT, in which case expansion of the brainstem may be the only sign. Enhancement of brainstem gliomas is extremely variable and with increasing enhancement over time.
The preferred imaging tool for diffuse brainstem gliomas is MR with contrast and thin sagittal T2WIs. On MR, brainstem gliomas appear low signal on T1WI images. T2WI images are best to evaluate the extent of the tumor, because the hyperintense signal of the tumor contrasts sharply with the low signal of the normal surrounding white matter. Proton MR spectroscopy can be helpful in differentiating brainstem gliomas from viral pontomesencephalitis.
Regardless of the imaging technique, findings which are suggestive of brainstem gliomas are: expansion of the brainstem; effacement of adjacent cisterns; exophytic growth, which occurs in 60% of cases; engulfment of the basilar artery by the ventral portion of the pons; and alteration of the normal forth ventricle contour by mass effect, without invasion of the ventricle itself.
Differential diagnosis when considering a brainstem glioma should include: brainstem encephalitis, tuberculoma, brain stem hamartoma (NF1), acute disseminated encephalomyelitis, histiocytosis and vascular malformation.
References
- Castillo M. The Core Curriculum: Neuroradiology. Lippincott Williams & Wilkins; Philadelphia, 2002.
- Hargrave D, Bartels U, Bouffet E. Diffuse brainstem glioma in children: critical review of clinical trials. Lancet Oncol. 2006 March; 7(3):241-248. PMID: 16510333
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