Childhood cerebellar vermian oligodendroglioma.

HS Bhatoe, GU Deshpande 
 

Correspondence Address:
H S Bhatoe

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Oligodendrogliomas are seen generally in the supratentorial compartment. Posterior fossa is rarely the site of such tumours and cerebellar location is distinctly rare in childhood. We present our experience with one child with cerebellar vermian tumor.



A 4 year old boy was admitted in Feb 94 with 6 month history of intermittent headache, progressive unsteadiness and episodic vomiting. There was no history of any limb weakness or visual disturbances. Clinical examination revealed papilloedema, left sided 6th nerve paresis and truncal ataxia. Plain CT brain revealed a high attenuating lesion occupying the cerebellar vermis and projecting into the fourth ventricle, causing obstructive hydrocephalus. There was no calcification and the tumour enhanced densely with intravenous contrast [Figure 1]. Child was operated in prone position. The tumour was exposed by a suboccipital craniectomy with removal of posterior rim of foramen magnum. Cerebellar vermis was split revealing solid, relatively avascular tumour arising in the cerebellar vermis and projecting into the fourth ventricle, with clear zone of demarcation from the cerebellar tissue. Gross total excision was achieved. Postoperative recovery was uneventful. Histopathology [Figure. 2] revealed classical picture of oligodendroglioma with sheets of small cells containing dark nuclei and abundant clear cytoplasm. Cells were separated by delicate vascular meshwork and varying degrees of microcystic changes were seen. There was no pleomorphism, mitotic activity or calcification. The tumour was negative for GFAP. Child was given craniospinal irradiation (3500 rad cranial and 3000 rad spinal). He remained well for three years after surgery till he was lost to follow up. Repeat CT done one year after surgery had not revealed any evidence of recurrence.



Posterior fossa is an extremely rare site for oligodendrogliomas. In a review of 200 cases of oligodendroglioma, Ernest et al[1] reported 14 cases (7%) in the posterior fossa location (5 in cerebellar vermis, 4 in fourth ventricle, 3 in the cerebello pontine angle and 3 in cerebellar hemispheres). Mansuy et al[2] in a review of cases found only three in the posterior fossa. Recently, Westergaard et al[3] reported two cases in posterior fossa in a series of 96 cases of oligodendroglioma. From India, Dharmarajan et al[4] reported two adult cases of cerebellar oligodendroglioma.









Literature on posterior fossa oligodendrogliomas in children is extremely sparse. Two of the three cases of Mansuy et al were children aged 6 and 9 years respectively.[2] In a series of childhood oligodendrogliomas reported by Dohrmann et al,[5] one of the 12 cases had brainstem involvement. Packer et al[6], reported their experiences with four children with high-grade oligodendrogliomas of the posterior fossa.



From the available clinical profiles of posterior fossa oligodendrogliomas of the childhood, it appears that the lesion may have a relatively long course. The two cases reported by Mansuy et al[2] had cerebellar signs for two years. One of the children reported by Packer et al[8] had a 10-year-history of hydrocephalus, previously shunted. Clinical picture is that of a posterior fossa mass lesion with raised intracranial pressure. CT findings have been described by Packer et al.[6] One of their patients had hyperdense, two had isodense and one had hypodense lesion on plain scan. All showed contrast enhancement and hydrocephalus was a constant finding. Calcification is not found in subtentorial oligodendrogliomas; perhaps such tumours progress more rapidly than the supratentorial ones.[2]



Because of low incidence of oligodendrogliomas in the posterior fossa during childhood, there has been little reference to longevity with such tumours after treatment. All four children reported by Packer et al[6] had high grade tumours. Three of these received only local radiotherapy after surgery and had metastatic disease at a median of 11 months post treatment. One child treated with craniospinal irradiation remained disease free for 15 months after diagnosis. Whereas one patient reported by Krueger and Krupp[7] lived for 15 years after surgery.



The limited number of cases available suggests that oligodendroglioma of posterior fossa may be high grade or low grade. Whether the biological behaviour of cerebellar oligodendrogliomas in children follows that of the supratentorial tumours is not yet clear. Therefore, we suggest that all children with these tumours independent of the histologic characteristics should receive both local and craniospinal irradiation after surgery till the biological behaviour of these tumours becomes more clear with addition of more cases.

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