Analysis of the optic chiasmal lesions by MRI

Objective: To analyze the MRI findings of the optic chiasmal lesions, and to evaluate the value of MRI in demonstrating the optic chiasmal lesions. Methods: MRI findings in 117 cases of optic chiasmal lesions confirmed by clinical data or pathology were analyzed retrospectively. There were 54 males and 63 females, with the age from 9 months to 67 years, mean 37.4 years. Results: There were 24 (20.5%) cases with direct involvement of the optic chiasms. 11 of them were gliomas of the optic chiasm which showed enlargement or mass of the optic chiasms with involvement of optic nerves and/or optic tracts. Diffuse enlargement of optic chiasm with inflammation of adjacent structures, particularly meninges, was found in 5 cases of inflammation. Metastases were found in 5 cases, of which optic chiasm involved by retinoblastoma spreading along optic nerves were found in 4 cases, and linear enhancement of optic chiasm was found in 1 case. Circumscribed enhancement of the optic chiasm with mass of optic nerve was found in 1 meningioma. Abnormal shape of optic chiasm with encephalomalacia of the frontal lobe was found in 1 case of trauma. Irregular enlargement of the optic chiasm showing short T1 and long T2 signal was found in 1 case of intrachiasmal hemorrhage. The displacement of the optic chiasms compressed by the lesions arising from adjacent structures was revealed on MRI in 93 (79.5%) cases. Of which superior displacement of the optic chiasms was found in 51 patients, anterior displacement in 2 cases, inferior displacement in 10 cases, and posterior displacement in 1 patient. Only one aspect of the optic chiasms was compressed by the lesions in 13 cases, and the optic chiasms were poorly defined in 16 patients. Conclusion: MRI could accurately show the optic chiasmal lesions, which could contribute to clinical diagnosis and treatment