The largest of these deep branches is the artery of Heubner (“recurrent artery of Heubner”; Fig. 33-8). This artery, which may, in fact, be up to four small vessels, shares its territory of supply with anteriorly placed lenticulostriate arteries that emanate from the middle cerebral artery. Strokes in this territory cause infarction of the head of the caudate and adjacent white matter. In the past, this was a common stroke syndrome from meningovascular syphilis.
The clinical picture of anterior cerebral artery stroke will depend on the location and size of the infarct, which, in turn, relates to the site of the occlusion (proximal or distal to the anterior communicating artery), the pattern of the circle of Willis, and the other ischemia-modifying factors mentioned earlier. Well-studied cases of infarction in the territory of the anterior cerebral artery are not numerous; hence the syndromes have not been completely elucidated (see Brust for a review of the literature and a description of developmental abnormalities of the artery).
Occlusion of the stem of the anterior cerebral artery, proximal to its connection with the anterior communicating artery (the A1 segment in neuroradiologic parlance) is usually well tolerated, because adequate collateral flow is provided by the anterior or cerebral artery of the opposite side. Maximal disturbance occurs when both arteries arise from one anterior cerebral stem, in which case there is infarction of the anterior and medial parts of both cerebral hemispheres resulting in paraplegia, incontinence, abulia and nonfluent aphasic symptoms, and frontal lobe personality changes (see Chap. 21).
Complete infarction as a result of occlusion of one anterior cerebral artery distal to the anterior communicating artery (A2 segment) results in a sensorimotor deficit of the opposite foot and leg and, to a lesser degree, of the shoulder and arm, with sparing of the hand and face (the distribution of which is shown in the MRI of Fig. 33-7). This is the complement of the superior division middle cerebral artery pattern. The motor disorder is more pronounced in the foot and leg than in the hip and thigh. Sensory loss, when it occurs, is mainly of the discriminative modalities but it may be mild or absent. The head and eyes may deviate to the side of the lesion. Urinary incontinence, a contralateral grasp reflex, and paratonic rigidity (gegenhalten) of the opposite limbs may be evident. With a left-sided occlusion, there may be a “sympathetic apraxia” of the left arm and leg or involuntary misdirected movements of the left arm (alien arm or hand), as described in Chaps. 3 and 21.
Language disturbances, particularly transcortical motor aphasia (see Chap. 22), may occur with anterior cerebral artery territory stroke. Disorders of behavior that may be overlooked in cases of anterior cerebral artery occlusion; they are abulia, or a slowness and lack of spontaneity in all reactions, muteness or a tendency to speak in whispers, and distractibility. Branch occlusions of the anterior cerebral artery produce only fragments of the total syndrome, usually a spastic weakness or associative sensory loss in the opposite foot and leg.