Megalencephalic leukoencephalopathy: a further case of a new neurodegenerative white matter disease.

The case is presented of a 4.5-year-old boy with cystic megalencephalic leukoencephalopathy who met the diagnostic criteria of a recently described neurodegenerative white matter disorder, i.e. leukoencephalopathy with swelling and a discrepantly mild clinical course (van der Knaap 1995). He demonstrated an extremely mild and slowly progressive clinical course with near normal psychomotor development, particularly of mental functions, which contrasted with somewhat disturbed gross and fine motor skills. Repeated CT and MRI scanning showed extensive hemispheral cerebral white matter changes and demonstrated predominant frontal involvement of the periventricular and subcortical white matter. MRI was more sensitive in the detection of preserved structures, i.e. occipital subcortical and central white matter, as well as in the visualisation of swelling and cystic lesions in the tip of the temporal lobes, which represent the hallmark of this entity. Thus, MRI is an essential diagnostic tool for this entity.