ABSTRACT
In a typical case of multiple sclerosis (MS) the lesions, which are confined to the CNS, are so obvious that a confident diagnosis can be made by naked eye alone. In some cases they are apparent as soon as the brain is taken out, in the form of irregular gray patches on the normally whitish surface of the pons (Fig. 10.1), or on the cut surfaces of the upper cervical cord and optic nerves. If the brain is incised fresh (a step which we do not recommend except when fresh plaque tissue is required, e.g. for chemical or histochemical examination or for preparing cryostat blocks), sharply demarcated gray or pinkish-gray patches may be met with (Fig. 10.2). These so-called plaques, are firmer to the touch than the surrounding brain tissue. In the fixed state, the difference in texture is hardly appreciable. In the spinal cord, for reasons given below, the plaques, though generally obvious, are sometimes less clearly demarcated. Since they are gray in color, the plaques are less eye-catching in gray matter than in white; but gray matter is not spared. The grayness of the plaques is of course due to destruction of myelin.
