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White matter attenuation and megalencephaly
  1. R O ROBINSON,
  2. T COX
  1. Newcomen Centre
  2. Guy’s Hospital, St Thomas’ Street
  3. London SE1 9RT

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    Editor,—In 1985 one of us (ROR) published a case of unusual self resolving leukodystrophy.1 We now describe a second case. As with the first, neuroimaging was prompted by a large head size. At 14 months, she had an occipitofrontal circumference of 53.5 cm some 4 SDs above the mean. Her father’s head circumference was similarly increased being 63 cm. His father’s head was also said to have been large. Unfortunately the patient’s head circumference at birth was not available. Apart from a slight delay in acquisition of head control and sitting attributable to the mechanical disadvantage of her large head, her development up to that time was age appropriate. Computed tomography showed pronounced low attenuation throughout the cerebral white matter (see fig 1A). Investigations for progressive leukodystrophy including relevant lysosomal enzyme studies, very long chain fatty acids, peripheral neurophysiology, and urine forN-acetyl aspartate were all normal. A second computed tomogram at 2.2 years showed partial resolution of the white matter changes in all areas, but to a lesser extent in the frontal lobes (see fig 1B).

    Figure 1

    Computed tomograms showing (A) pronounced low attenuation throughout the cerebral white matter and (B) partial resolution of white matter changes but to a lesser extent in the frontal lobes.

    Her head growth continued parallel with the normal growth trajectory at 3.5 to 4 SDs above the mean. When seen aged 8.6 years, her occipitofrontal circumference was 57 cm. She was otherwise normal neurologically and academically functioning around the mean. Magnetic resonance imaging of her brain at this stage showed slight increase in signal in the terminal myelination areas and a small discreet high signal area in the anterior frontal lobe of uncertain aetiology and unlikely to be of clinical significance.

    This second case confirms that occasionally children with familial macrocephaly initially have pronounced white matter changes which appear alarming but are nevertheless benign.

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