Cystic metastasis versus brain abscess: role of MR imaging in accurate diagnosis and implications on treatment.

Intracranial cystic metastases are difficult to differentiate from non neoplastic lesions like a cystic abscess on routine magnetic resonance imaging (MRI) sequences in patients with a known primary cancer. Diffusion weighted MRI sequences can help in differentiating between the two. This carries significant implications on the intent and nature of treatment. We present a case of a forty five-year- old patient of squamous cell carcinoma of larynx who developed an intracranial cystic ring enhancing lesion following chemotherapy. Though routine MRI was equivocal, MR diffusion was highly suggestive of an abscess and this led to surgical excision which confirmed the diagnosis. We discuss this case and review the literature regarding the role of newer MRI sequences and the ramifications on patient treatment.