Nervous and mental diseases . aplegic —The causes of combined sclerosis are numerous. It mustbe at once recognized that this extensive symptom group is frequentlya secondary cord-process: (1) In a certain small number of cases,primarily tabetic, a diffuse myelitis also invades the lateral tracts; (2) it is found more frequently ingeneral paresis than are lesionsentirely confined to the pos-terior columns; (3) a diffusemyelitis gives rise to ascendingand descending degenerationsthat furnish a posterolateralsclerosis; (4) leptomeningitismay entail a marginal myelitisthat i
Nervous and mental diseases . aplegic —The causes of combined sclerosis are numerous. It mustbe at once recognized that this extensive symptom group is frequentlya secondary cord-process: (1) In a certain small number of cases,primarily tabetic, a diffuse myelitis also invades the lateral tracts; (2) it is found more frequently ingeneral paresis than are lesionsentirely confined to the pos-terior columns; (3) a diffusemyelitis gives rise to ascendingand descending degenerationsthat furnish a posterolateralsclerosis; (4) leptomeningitismay entail a marginal myelitisthat invades the periphery ofthe cord and principally affectsits posterior half; (5) vascularlesions, affecting principallythe posterior field, induce asclerosis in the posterior andlateral tracts; (6) pellagra some-times causes a combined pos-terolateral sclerosis; (7) toxicconditions, as in the pernicious anemias, may cause it; (8) the postero-lateral sclerosis may be evidence of an embryonic deficiency as inFriedreichs Fig. 196.—Combined posterolateral sclerosis. Schemeshowing usual area of cord-change limited to the pos-terior arterial field of the cord (Brissaud). DISEASES OF THE WHITE MATTER OF THE CORD. 465 There is frequently a history of antecedent syphilis or one of expo-sure to cold, traumatism, concussion, or muscular strains. Sometimesacute infections lead to it. It is much more common in males than infemales, and usually appears between twenty-five and forty years of age. Morbid Anatomy.—The sclerosis implicates both the lateral andposterior columns, but sometimes one, sometimes the other with greaterintensity. The columns of Goll, usually commencing above the lumbarenlargement, are degenerated to the medulla. The columns of Burdachare also affected mainly above the lumbar enlargement, but less in-tensely, and the root-zone usually escapes. The crossed pyramidal tractis, as a rule, partially affected, its inner portion being customarilyspared. Its lesion
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