Think of a young 26 yo female patient with a bit of optic neuritis in her past and now a rapidly progressing aphasic and encephalopathic picture. MRI reveals a huge left sided frontal demyelinating lesion with open-ring enhancement. What is the differential? How do you separate abscess from lymphoma and astrocytoma and proper demyelinating lesions, such as in tumefactive MS, ADEM/Hurst? What is the role of CSF and MR spectroscopy?
Given, then, a real (but huge) demyelinating lesion, how do you proceed? You apply the neurologic step ladder:
- Plasma exchange
- Cyclophosphamide or Rituximab
But before you give cytotoxic agents, I would require a proper biopsy. There are plenty of reasons for this – choice of the right agent, making sure you aren’t treating lymphoma or astrocytoma. There are also many case reports that justify this approach, such as this one.
There is a wonderful book called “Tough Calls in Acute Neurology”, which covers this topic better than any review article (in fact, ther are no proper reviews on this subject).