MRI is useful to assess the size, nature and extent of the cystic lesion as well as the mass effect on the cord and associated signs of meningeal inflammation. Increased CSF signal intensity on T1 weighted images leading to loss of CSF–cord interface is strongly suggestive of the arachnoiditis
Differential diagnosis on imaging includes other intradural cystic lesions like dermoids, epidermoids, hydatidosis and cysticercosis. In a rare case reported by Ciftci et al, multiple intradural cysticercosis were found in the basal cistern, cisterna magna, and cervical subarachnoid space which were isointense with cerebrospinal fluid both on T2 and T1 weighted images Dermoid can be diagnosed by presence of fat and midline in location, epidermoid are bright on spinal difusion where available. Hydatids are better diagnosed by exclusion. Inflammatory etiology with TB can be suggested by sepate, flow signal aberrations and leptomeningeal enhancement apart from brain findings.
Case by Dr MGK Murthy, Sr Consultant Radiologist