The test of treatment is of value in many cases, improvement or recovery under salvarsan or mercury and iodides with reduction or disappearance of the lymphocytosis indicating cerebral syphilis and not general paresis.

In cerebral arteriosclerosis the findings in the cerebro-spinal fluid are negative, so that a difficulty in differentiation arises only in connection with those cases of the endarteritic type of cerebral syphilis in which the findings are likewise negative, and in such cases, as already stated, the differentiation cannot always be made with certainty even post mortem. A history of syphilitic infection will, naturally, turn the probability toward cerebral syphilis. The age of the patient may help in the differentiation; cases occurring in persons under 45 are almost surely syphilitic; in persons between 45 and 60 the probability is still strongly in favor of syphilis; after 60 this probability diminishes with advancing senility.

Prognosis. Cerebral syphilis is a grave affection; untreated cases progress more or less rapidly with tissue destruction and often a fatal termination. Treatment, however, if instituted early may result in a quick and perfect cure; the most favorable cases from this point of view are those of the diffuse meningitic type; cases of the gummatous type are often stubbornly resistant to treatment; in most cases of the endarteritic type recovery cannot be expected owing to the tissue destruction which occurs early in the course of the disease, but some relief may be secured through abatement or arrest of the syphilitic process.

Treatment. This is that of syphilis in general. The special points to be emphasized in connection with cerebral syphilis are: (1) the treatment must be intensive and instituted promptly upon the development of the symptoms in order to forestall, as far as possible, tissue destruction; (2) it should be controlled by repeated examinations of the blood and cerebro-spinal fluid, and it should be persisted in after clinical recovery until the findings in the blood and cerebro-spinal fluid become permanently negative; (3) intra-spinal medication may be of value in some cases which have resisted other methods of treatment; (4) every case in which the differentiation between general paresis and cerebral syphilis has not been made with certainty should be submitted to the test of a thorough course of treatment; (5) Horsley recommends that if improvement does not occur in a case of cerebral gumma after six weeks' medicinal treatment, the growth be removed by operation.

CHAPTER XIII.

CEREBRAL ARTERIOSCLEROSIS.1

CEREBRAL arteriosclerosis is not always of syphilitic origin, though probably much more frequently so than would be indicated by clinical statistics.

Disease of the arteries of the brain is often found at autopsies in cases which have shown during life no mental or nervous disturbances. The occurrence of such disturbances is probably determined by a certain extent or degree of arterial disease. Arteriosclerotic brain disease is but a part of general arteriosclerosis, though not infrequently the process is found to be much more marked in the brain than elsewhere.

The symptoms vary widely in different cases, depending chiefly upon the vessel or system of vessels affected.

Fig. 13 is a diagram of the arterial supply of the brain showing the circle of Willis, its branches and their distribution.

The terminal arterioles form two distinct systems: a system of short vessels supplying the cortex, and a

1 Binswanger. Berlin. kiln. Wochenschr., 1894. - Alzheimer. Allg. Zeitschr. f. Psychiatrie, 1902. - Gowers. Manual of Diseases of the Nervous System. — Lambert. N. Y. State Hosp. Bulletin, Vol. I; also in 20th Ann. Report N. Y. State Commission in Lunacy, pp. 91 et seq.

system of long vessels which penetrate deeper and supply the marrow; the ganglionic vessels at the base constitute a part of the medullary system. The manner of distribution of the terminal arterioles is shown in Fig. 14.

Arteriosclerotic disease may affect chiefly the large vessels given off from the circle of Willis or their principal branches; or it may affect chiefly the terminal arterioles, either the cortical or the medullary system, though the process is hardly ever sharply limited to any one system of vessels.