A child presented with clinical features of demyelination. The chances of progression to MS is least with which of the following:

A i.e. Absent olgoclonal band Multiple sclerosis is a demyelination disorder characterized by selective destruction of CNS myelin predominantly of white matter long tractQ. Diagnosis suggestive MRI findings include >1 hyperintense T2 lesion in at least 2 out of & MS typical regions of CNS (i.e. periventricular, juxta coical, infratentorial or spinal cord) and Gd-enhancement. Lesions >6mm located in corpus callosum (juxtacoical), periventricular white matter, brainstem & cerebellum (infratentorial) and spinal cord are paicularly helpful diagnostically. (Harrison 18/e p 3399). However when the Q was asked Harrison 16/e p 2461 mentioned - confirmatory MRI must have either 4 lesions involving the white matter or 3 lesion if periventricular in locations. Acceptable lesion must be > 3 mm in diameter. CT findings of MS include focal decreased attenuation in periventricular white matter (most characteristic), contrast enhancing plaques (enhancement may be decreased or abolished by coicosteroid administration) and cerebral atrophy. MRI is imaging modality of choice and most characteristic diagnostic feature of MS plaque is not their high signal intensity (on T2WI) but their anatomical distribution. There is a predilection for periventricular distribution & ependymal surface (especially along occipital horns >frontal horns). If not pathognomic, corpus callosum lesions are so characteristic of MS to be almost specific. Other MS sites are corona radiata, internal capsule, centrum semiovale; and surface of pons esp near 5th CN entery zone, middle cerebral paduncle (brachium pontis), floor of 4th ventricle and colliculi in posterior cranial fossa. T1WI are less sensitive but chronic plaques of MS (esp in corpus callosum are often well shown as black holes (low signal lesions) surrounded by a very thin halo of mildly increased signal intensity. Progression to MS is more likely with presence of oligoclonal bandQ (not absent), bilateral optic neuritis, poor recovery & complete cord transection.