Myelin in SIDS: assessment of development and damage using MRI

Abnormalities of myelin that have been reported in Sudden Infant Death Syndrome (SIDS) include a delay in development and focal lesions presumed to be secondary to hypoxia. Magnetic resonance imaging (MRI) gives excellent images of white matter and can be used to map the progress of myelination and to demonstrate focal lesions. It was the aim of this study to determine whether any MRI abnormality of myelin could be detected in the brains of SIDS compared to control infants.

The brains of 28 SIDS and 14 control infants were fixed in formalin and scanned with MRI. The proton density, T2-weighted, and inversion recovery scans were assessed for the presence of focal white matter lesions. The amount of myelin in 26 sites was measured in the proton density scans, using a densitometer. The amount of myelin present could be assessed in 21 of 26 sites.

In 15 of 21 sites the amount of myelin for age was the same in SIDS and controls. In three sites the rate of myelination was greater in SIDS than control and in another three sites the amount of myelin for age was greater in SIDS than control infants, but these differences were not seen in infants aged less than 8 months. No focal abnormalities of white matter were seen in either SIDS or control infants.

The development of white matter in brains of SIDS infants less than 8 months old is the same as in controls, and in older SIDS infants white matter development may be slightly advanced compared to controls. No hypoxic changes can be seen in SIDS white matter on MRI.