Optic chiasmatic-hypothalamic gliomas: is tissue diagnosis essential?

Background: Optic chiasmatic-hypothalamic gliomas are sellar-suprasellar lesions with variable radiological features. The advocated treatment is mainly primary radiotherapy without a histological diagnosis. However, in developing countries, like India infective granulomas (tuberculomas) in the suprasellar region radiologically can mimic optic chiasmatic-hypothalamic gliomas. Hence primary radiotherapy without histological confirmation may have deleterious consequences.

Aim: The aim of the paper was to analyze the sensitivity and specificity of magnetic resonance imaging (MRI) in these lesions and to analyze the feasibility of primary radiotherapy.

Patients And Methods: The magnetic resonance imaging (MRI) characteristics of 24 patients with either histologically proven optic chiasmatic "pilocytic astrocytoma" or radiologically suspected optic chiasmatic-hypothalamic gliomas were analyzed. They were grouped into three groups on the basis of radiological features and treated with a suspected diagnosis. The final diagnosis was correlated with preoperative diagnosis, and the feasibility of managing these lesions without a histopathological confirmation is discussed.

Results: The three radiological groups were: Group-1 solid tumors with or without microcysts in 9 patients (histology: 8 pilocystic astrocytomas and 1 tuberculoma); Group-2 mixed tumors with solid and cystic components in 9 patients (histology: 7 pilocytic astrocytomas and 2 craniopharyngiomas); Group-3 ring enhancing lesions in 6 patients (all the 6 patients initially received antituberculous treatment, in 3 patients the lesion resolved and in the remaining 3 patients the lesion was subjected to biopsy as it did not resolve, the biopsy was suggestive of pilocytic astrocytoma). Thus, MRI was shown to have a sensitivity of 83.33% and a specificity of 50% for diagnosing optic chiasmatic-hypothalamic gliomas.

Conclusions: Various lesions like craniopharyngiomas, tuberculomas can mimic optic chiasmatic-hypothalamic gliomas radiologically, and it is not possible to diagnose them with certainty on the basis of radiological findings alone. Biopsy and tissue diagnosis should always be sought before instituting radiotherapy or chemotherapy for optic chiasmatic-hypothalamic gliomas.