Some spherical hyperplasia of myelin were toward neuron.Demyelination and vaculization of myelin sheath were observed in serious cases.

• 严重者则髓鞘呈空泡化、空网状及形成髓球状，并挤压及占据整个轴浆，部分轴索变性坏死及葱头样肥大神经改变。