THE HISTOLOGY OF DISSEMINATED SCLEROSIS. .693 



transition zone between white and grey matter, and a few small areas are limited to the 

 grey matter. 



On the left side an even broader band of sclerosis extends along the margin of the lateral 

 ventricle from the caudate nucleus to the posterior horn. A few minute areas are found 

 on the ventricular surface and in the substance of the splenium, and from the posterior horn 

 irregular projections of sclerotic tissue pass into the adjoining white matter, again cutting 

 across the tapetum, the optic radiations, and the inferior longitudinal fasciculus. Along 

 the course of these bundles of fibres small round or oval areas are found in the substance 

 of the white matter of the occipital lobe : some of these reach to the medullary rays of the 

 convolutions of the calcarine fissure. The anterior horn shows a patch more or less tri- 

 angular, near its tip, and another area extends inwards just anterior to the caudate nucleus. 

 The genu of the corpus callosum at this level is normal. The optic thalamus is very ex- 

 tensively affected, the irregular surface zone extending inwards into its substance for about 

 one-third of its transverse diameter, leaving here and there a few bundles of less affected 

 fibres. Two isolated early areas are seen in the substance of the optic thalamus itself, one 

 circular, and the other, elongated, involves the internal capsule. Numerous minute elon- 

 gated areas are present in the claustrum and on either side of it, and one of these extends 

 for some distance into the putamen. From the claustrum the sclerosis extends into the 

 apices of several of the convolutions of the island of Reil. Several small areas are present 

 in the frontal and parietal and occipital white matter, and an extensive demyelination affects 

 the medullary rays, especially of the parietal convolutions. 



(2) Sections through the upper part of the basal ganglia (figs. 72-73) show a still greater 

 degree of peri-ventricular involvement : the lateral walls of the lateral ventricles throughout 

 their whole extent on both sides presenting broad, irregular bands of sclerosis which cut 

 into the substance of the optic thalamus and white matter. 



On the right side the posterior horn sclerosis forms a wide band, the apex of which 

 extends for a long distance into the occipital white matter, along the course of and involving 

 the tapetum, optic radiation, and inferior longitudinal fasciculus. The splenium along its 

 whole ventricular surface is also irregularly affected. The anterior horn presents a crescentic 

 zone of sclerosis, which again extends into the white matter of the frontal lobe along several 

 lines. The genu of the corpus callosum presents a narrow band of sclerosis along its ven- 

 tricular surface. From the ventricular surface of the caudate nucleus and the lateral part 

 of the optic thalamus, irregular areas of sclerosis project into their substance. Very numerous 

 small circular areas are found in the anterior portion of the optic thalamus, and larger areas 

 extend from it across the internal capsule into the lenticular nucleus. Two areas cut across 

 the anterior limb of the internal capsule, cutting across the fibres passing between the caudate 

 nucleus and the lenticular nucleus. A narrow band of sclerosis extends along the greater 

 part of the claustrum : this is continuous posteriorly with the lateral portion of the post- 

 erior horn sclerosis, and laterally it sends projections into the medullary rays and grey 

 matter of the island of Reil. Two well-defined areas are present in the frontal operculum, 

 one limited to the cortex, the other reaching from the white matter to the surface. The 

 parietal lobe shows numerous early and late areas in its white matter and an extensive and 

 continuous affection of the medullary rays and cortex. In the occipital lobe very numerous 

 small areas he posterior to the splenium, while the tissue from posterior horn to the base 

 of the calcarine fissure presents one long stretch of sclerosis, with smaller detached areas 

 in the adjoining medullary rays. 



On the left side the sclerosis resembles very closely that of the opposite side. The ex- 

 tensive involvement of the optic radiations ; the very numerous areas in the substance of 

 the optic thalamus, internal capsule, lenticular nucleus and claustrum ; the continuous 

 demyelination of numerous medullary rays and convolutions — especially of the parietal 

 lobe ; and the areas in the corpus callosum, are all present in an equally marked degree. 

 TRANS ROY. SOC. EDIN, VOL. L, PART III (NO. 18). 96 



