What is the cause of brain lesions ? what are the symptoms?

Non-specific term: Brain lesions is a non-specific term referring to abnormalites seen either on ct scan or MRI scan. These are varied and some can have severe clinical implications such as brain tumors or multiple sclerosis lesions. Other times lesions refer to small areas of infarct or stroke. These can also occur after head injury. Brain lesions are different in appearance compared to the normal surrounding brain.

Many causes.: Question is too general. Brain lesions is a generic term that encompasses all manner of things that could occur in the brain. Anything from stroke to infection to bleeding to scar or inflammation. The symptoms would depend upon both the location of the lesion and the type of lesion.