Chiasmal gliomas: appearance and long-term changes demonstrated by computerized tomography

Abstract

A survey of 22 cases showed the broad spectrum of lesions collectively termed "chiasmal gliomas." Three computerized tomography (CT) patterns were diagnostic: a tubular thickening of the optic nerve and chiasm, a suprasellar tumor with contiguous optic nerve expansion, and a suprasellar tumor with optic tract involvement. Globular suprasellar tumors lacking these features required a histological examination for diagnosis. Tumor growth was documented by CT in only three chiasmal gliomas; all were the globular type. Failing visual function did not reflect chiasmal tumor growth, and stable vision did not exclude it. Both patients with tubular optic nerve thickening and two of three patients with unilateral optic nerve expansion had neurofibromatosis. Five tumors became smaller after irradiation. Complications of radiation therapy included calcification of lenticular nuclei and remote infarcts. In patients who underwent biopsy, the CT appearance did not differentiate juvenile pilocytic astrocytoma from anaplastic astrocytoma. Thus, CT guides the diagnosis and neurosurgical treatment of chiasmal gliomas, establishing the need for biopsy or ventricular shunting.

Current Management of Low-Grade Astrocytomas of Childhood

“…Some authors [74] have maintained that the majority of these lesions are not tumors at all, but hamartomas with limited growth potential. Most mo dern workers, however, agree that although these lesions may remain indolent for years, and even spontaneously regress [75], they are neoplasms which not infrequently enlarge and may result in death [76][77][78][79]. The advent of CT scanning and, more recently, MR1 has made it clear that the distinction between low-grade astrocytomas of the optic chiasm and those of the hypothalamus is large ly artificial and of no clinical importance, and they will be considered together in this review.…”

“…Le sions with thickening of the optic nerves or streaking along the optic radiations, especially in the setting of neurofibromatosis, are presumed to be chiasmatic gli omas and do not require pathologic confirmation. Globular suprasellar masses without clear-cut features demand surgical exploration [79]. Surgery to debulk the mass is occasionally of benefit, especially if there is a large cystic component, and radical operations have been carried out safely [23], Biventricular shunting procedures are occasionally required for hydrocephalus [74,76,80].…”

Carboplatin and vincristine chemotherapy for children with newly diagnosed progressive low-grade gliomas

“…Radiotherapy may result in objective shrinkage of low-grade gliomas and there is some evidence to indicate that it will increase the duration of progression-free survival in patients with residual tumor after surgery. [3,4,22,23,26] However, there has been significant reluctance to use radiotherapy in very young children. This is because of the vulnerability of the immature nervous system to therapeutic doses of radiation and the tendency of low-grade gliomas, especially in very young children, to infiltrate the central nervous system extensively, which results in the requirement of large radiotherapy volumes.…”

Correcting Finger Counting to Snellen Acuity

“…In one of these publications, "Chiasmal gliomas and long-term changes demonstrated by computerized tomography," Dr. Hoyt's group tracked the change in size of chiasmal glioma by computed tomography (CT) scans and correlated them with changes in visual acuity. 4 In one of 22 patients included in the study, CT-documented tumor growth was noted alongside a loss in visual acuity over 4 years. In the initial publication, the change was recorded as a drop from 20/100 to CF 10 ft, two visual acuities recorded in two different modalities.…”