Orbital rule 15: Orbital fat lesions

1- You can define that the lesion is arising from orbital fat by exclusion.

     As if it is not arising from the globe, optic nerve, extra ocular muscles, lacrymal glands or orbital bony cage, it will remain only the orbital fat by exclusion, the origin of this lesion.

2-Lesions in the orbital fat can be classified into:

    -Ill defined lesions

     Orbital pseudo tumor.

    -Well defined lesions which can be further subdivided according to behavior of enhancement into

          

    Homogenous enhancement as cavernous hemangioma or neurofibroma or lymphoma.

    No enhancement as dermoid or epidermoid cysts.

3-Radiological findings of orbital pseudo tumor:

-Dirty fat.

-Thickening and enhancement of the posterior sclera.

-Affection of the lacrymal gland, eye led or muscle.

-MRI=Fat appears hypo intense in T1 due to exudative fluid.

            Fat appears more intense in T2.

 

Cavernous hemangioma

•          -Common neoplasm in adult.

•          -Rounded or oval homogeneously enhanced mass.

•          -Calcified phlebuli can be seen.

•          -MRI= T1---hyper intense

•                       T2---hyper intense

Could be hypo intense in T1 which make a problem in differentiation between it and Neurofibroma.(hemangioma is far common than Neurofibroma).(enhancement of Neurofibroma is less than that of hemangioma)(MRI can differentiate if hemangioma is hyper intense in T1 , but if it is hypo intense in T1 , it will not be able to differentiate.

Lymphoma

-Multiple enhancing lesions(multiplicity is diagnostic).

•          -It has tendency to coat the globe.

•          -When lymphoma is possible:

•          1-History of lymphoma.

•          2-Middleage with multiple masses.

•          3-Lesions encasing globe(well defined , homogenous). 

      4-Muscle affection (superior levator complex muscle).