Teaching Case

Macrocephaly, mild developmental delay.

The patient presented with macrocephaly (over 98 percentile), and mild retardation of psychomotor development. A 9-year-old male sibling was normal. An MRI examination was performed at 1.5T. Echo-planar diffusion-weighted imaging (TR=4000,TE=110 msec), and proton MR spectroscopy (TR=2000,TE=40) were added to the examination protocol.

van der Knaap syndrome is a new entity associated with diffuse leukoencephalopathy, and cystic degeneration of the white matter of the brain. The clinical course is mild, and slowly progressive. The distinguishing feature of van der Knaap syndrome from other leukoencephalopathies associated with either large or normal heads appears to be the presence of temporal, and frontal white matter cysts (cystic degeneration of the brain parenchyma) in combination with diffuse white matter abnormality on imaging studies. A recent report dealt with diffusion MRI, and proton MR spectroscopy in van der Knaap syndrome. It was noted that ADC values ranged from 3.0 X10-3 mm2/sec to 2.7 X10-3 mm2/sec in the temporal cysts, similar to that of CSF. ADC values within the abnormal parenchyma ranged between 2.0 X 10-3 mm2/sec to 2.1 X10-3 mm2/sec. It was cited that those values fell between normal parenchyma and CSF, compared to a control group of three healthy subjects. In that control group ADC values of the white matter ranged from 1.0 X10-3 mm2/sec to 1.07 X10-3 mm2/sec, and that of CSF ranged from 2.8 X10-3 mm2/sec to 3.4 X10-3 mm2/sec. In the previously reported cases of van der Knaap syndrome MR spectroscopy revealed decreased NAA/Cr ratios, and increased Cho/Cr ratios compared to normal individuals. These were relatively mild to moderate changes in conformity with the slowly progressive nature of van der Knaap syndrome.