Case 119. 
Measles encephalitis (subacute sclerosing panencephalitis) (8 y-o M)
    Brain lesion featured by progressive mental retardation and myoclonus (history of measles in infancy)    
Key words : subacute sclerosing panencephalitis, measles virus
The disease SSPE is featured by inflammatory demyelination and gliosis in the white matter of the brain. Astrocytic gliosis and vacuolar degeneration of neuropil are observed (HE). Neuronophagia is mildly seen in the gray matter.   Nuclear inclusions are formed in oligodendroglial cells (HE, high power). Inclusions are also infrequently seen in neurons, but never in astroglia.
NP antigen of measles virus is demonstrated in the nuclear inclusions in oligodendroglia (immunostaining).   Electron micrograph of the nuclear inclusion in an oligodendrocyte. Elongated, spiral or rod-like tubules, 15 nm in diameter and 5 nm in the inner space, occupy the nuclear matrix. Measles virus causing SSPE is defective of M (matrix) protein.