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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.

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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.

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FIG. 14. (After Charcot, from Gray's Anatomy.) 1. LONG OR MEDULLARY ARTERIES. 2. SHORT OR CORTICAL ARTERIES.

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.

The manner in which the nervous tissues are affected is variable. Narrowing of the lumen of a vessel resulting from obliterative endarteritis brings about atrophy of the nervous elements, due to reduction of the blood supply, there being at the same time hypertrophy of the neuroglia tissue ("perivascular gliosis" of Alzheimer); thickening of the walls of the smallest arterioles and of the capillaries ("arterio-capillary fibrosis") results in atrophy through interference with osmotic processes; roughening of the intimal lining of the vessels results in the formation of thrombi or emboli with consequent infarction and softening; the brittle and weakened condition of the vessel walls and aneurismal dilatations combined with general rise of blood pressure result in rupture and hemorrhage with compression and destruction of nerve tissue to an extent depending upon the amount of extravasated blood.

The symptoms of arteriosclerotic brain disease may perhaps be most conveniently classified as follows: (1) systemic symptoms; (2) symptoms common to all forms of arteriosclerotic brain disease; (3) symptoms of occlusion of large vessels or their branches; (4) symptoms of affection of the medullary system of terminal arterioles; (5) symptoms of affection of the cortical system of terminal arterioles.

(1) Systemic symptoms. These will not be dwelt upon in detail here as they are more properly a subject of text-books of general medicine. As being among the most important may be mentioned: rigid and tortuous peripheral arteries, increased blood pressure, pulse high in tension but small in volume,

increased area of cardiac dullness, accentuation of the aortic sound, often evidences of chronic interstitial nephritis.

(2) Symptoms common to all forms of arteriosclerotic brain disease. (a) Physical symptoms: headaches, insomnia, muscular weakness, imperfect muscular control, attacks of faintness or dizziness, epileptiform or apoplectiform seizures. (b) Mental symptoms: diminished capacity for work, undue fatigability, emotional instability, states of depression or anxiety, drowsiness; later forgetfulness, disorientation, and general mental deterioration; a characteristic feature is the persistence of insight for a long time.

(3) Symptoms of occlusion of large vessels or their branches. The symptoms usually come on suddenly in the form of a stroke, often, but by no means always, accompanied by loss of consciousness lasting from a few minutes to several hours or even longer; this may be followed by a dazed, confused, or de-, lirious period from which the patient recovers with permanent symptoms the character of which depends upon the location and extent of the lesion.

(a) Occlusion of the anterior cerebral artery is uncommon; the symptoms depend upon the point of occlusion and upon whether the main vessel or one of its branches is occluded; there may be no special symptoms, or there may be loss of the sense of smell on one side or crural monoplegia.

(b) Occlusion of the middle cerebral artery or of its branches is very common; the characteristic symptoms for the four branches respectively are: (a) motor aphasia; (3) facial or brachial paralysis, or

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