NIMG-86. THE STORY OF BITHALAMIC GLIOMAS: A SPECIAL EMPHASIS ON MASS INTERMEDIA Free

To describe the pattern of spread of bithalamic tumors and possibly tailor the existing treatment modalities.

Bilateral thalamic tumors are different from their counterparts presenting as unilateral thalamic gliomas. These are known to have poor prognosis, irrespective of their histopathology. There are two views regarding the origin. According to one view, bithalamic tumors arise on one side of thalamic nuclei and spread to the other side with time, while according to another view they arise by sprouting of tumors from the subependymal region of the third ventricle.

We retrospectively studied the MR Imaging of 9 patients with gliomas involving thalamus bilaterally. We used FLAIR sequence in all 9 cases, in order to select a point of origin and locate massa intermedia. Additional data such as demographic details, the presence of obstructive hydrocephalus and tumoral enhancement patterns were also noted.

The median age of the patients (3F, 6M) was 16 y/o. Six out of 9 patients had hydrocephalus, with massa intermedia noted in 6 cases whereas it was not appreciated in 3 cases due to the tumor size. Bilateral involvement of the thalamus was noted in 7 patients on their initial scan, 1 patient had tumor confined to the cavum velum interpositum, which caused the abnormal signal in the thalamus bilaterally and 1 patient had left sided unilateral glioma which later progressed to the right side.

Bithalamic tumors share a poor prognosis. Massa intermedia seems to be a possible route of spread of tumor from one thalamus to the other and subependymal region of the third ventricle may be contributing. These views open a newer channel for prophylactic radiation covering MI and third ventricle to prevent the intact thalamus and hence improve the prognosis of the patients.