Ans. is 'c' i.e. Krabbe's disease Deep white matter lesion along with the involvement of thalamus suggests Krabbe's disease.Krabbe's disease is a leukodystrophy.LeukodystrophyIt is a term commonly used to refer to demyelination disorders.They are mainly due to genetic defects in the formation and maintenance of myelin.They usually present in infants and children with increasing development delay, progressive dementia and neurological deficit.These disorders are inherited as autosomal recessive trait and are associated with lysosomal enzyme deficiencies.They include the following disorders:-Metachromatic leukodystrophyGloboid leukodystrophy (Krabbe's disease)Spongiform degeneration (Canavan's disease)T. scan of leukodystrophies:-C. T. scan of the leukodystrophies shows low density areas in the white matter which are bilateral but not necessary symmetric and becomes more extensive as the disease process progresses.Krabbe's diseaseIt occurs due to deficiency of the enzyme P-galactocerebroside.It presents in infancy with retardation and spasticity.CT scan appearance of Krabbe's diseaseB/L symmetrical hypodensities in both frontoparietal and occipital regions in the white matter zone.Both thalamus and basai ganglia are hyperdenseCerebellum unaffected, ventricles normal, septum midlineMetachromatic leukodystrophyIt is a common leukodystrophy which commences in infancy.It occurs due to deficiency of the enzyme Arylsulphatase A.C. T. shows diffuse symmetric attenuation of the cerebellar and cerebral white matter.Alexander's diseaseIt is one of the few leukodystrophies that occurs sporadically and is characterized histopathologically by the abundant presence of Rosenthal fibres in the affected brain.Definitive diagnosis thus depends on brain biopsy.It occurs due to mutation in glial fibrillary acidic protein (GFAP).C. T. scan demonstrates degeneration of the white matter most prominent in the frontal lobes.Canavan's diseaseIt occurs due to deficiency of the enzyme aspart acylase leading to accumulation of N-Acetyl aspartic acid in the brain.C. T. scan shows diffuse white matter degeneration primarily in the cerebral hemispheres with less involvement in the cerebellum and brainstem.