of infiltration into the surrounding brain. Good-quality CT (computed tomography) is less effective at delineating the extent of the tumor, and will completely miss some of the smaller tumors that are seen with MRI.
Low-grade gliomas in adults typically do not enhance. If a degree of enhancement is present, however, it is generally considered to mean that anaplastic change is present, that the grade of the tumor will be higher, and that the prognosis will be correspondingly worse than if there was no enhancement. There are some exceptions to this, such as pleomorphic xanthoastro-cytomas and pediatric astrocytomas, which occasionally present in young adults and where enhancement is not necessarily an ominous finding. It is important to recognize that CT and MRI scanning are not always a reliable way of determining the histological grade of a tumor . Interpretation of brain scans of patients who have undergone previous treatment can be particularly difficult, with post-operative changes causing enhancement that can mimic recurrent tumor, and radiotherapy producing white matter changes that are very similar to infiltrating tumor or cerebral edema caused by recurrent tumor.
The typical MRI findings for low-grade astro-cytomas are of low-signal intensity on T1 spinecho sequences, and of high-signal intensity on T2 and proton-density sequences, with varying degrees of white matter infiltration and edema around the central part of the tumor. On CT, the tumors appear as areas of low density, sometimes with patchy calcification, which is seen most commonly in oligodendrogliomas.
Was this article helpful?
The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.