Glutamate excitotoxity mediated by the AMPA/kainate receptors damages not only neurons but also oligodendrocytes, myelin sheaths and axons ⁽²⁶⁾. Glutamate and aspartate in CSF is increased in patients with acute MS ⁽²⁷⁾. In an immunohistochemical study, active MS lesions showed high glutamate production in macrophages and microglia in close proximity to axonal damage ⁽²⁸⁾. Excitotoxicity in oligodendrocytes, myelin sheaths and axons seems to be an important mechanism in multiple sclerosis. Imaging findings in children with MS are not significantly different from those in adults, although tumefactive plaques are seen more frequently. DWI occasionally shows cytotoxic plaques as hyperintense with decreased ADC in acute MS (Figure 11).

Figure 11. A 13-year-old female with acute multiple sclerosis.

A. T2WI shows multiple hyperintense lesions in the periventricular white matter. The lesion in left fronto-parietal region is a tumefactive plaque (arrow).

B,C. DWI shows these lesions as hyperintense with decreased ADC that represents cytotoxic edema presumably related to excitotoxic injury of oligodendrocytes, myelin sheaths and axons.