Clinical manifestations

Presentation and course

Patients with infarction in the anterior cerebral artery territory may display any or all of the following.

Weakness. Classically, anterior cerebral artery stroke causes leg weakness involving both distal and proximal muscles equally, with milder predominantly distal arm weakness and relative sparing of the face (16; 17). A contralateral hemiparesis with a lower limb predominance (more pronounced distally) and early spasticity may also occur in complete or partial infarcts in the territory of pericallosal artery (04). However, a minority of patients may have monoparesis with isolated involvement of the leg, hemiparesis with predominantly arm weakness, and, rarely, complete sparing of the lower extremity (09; 11). These differences likely reflect involvement of different portions of the anterior cerebral artery distribution. Predominant leg weakness indicates involvement of the more posterior anterior cerebral artery territory, which affects the precentral gyrus (09) whereas involvement of the supplementary motor area has been proposed to explain the predominance of distal leg weakness in pericallosal territory infarction (04). Major arm weakness suggests infarction in the genu and posterior limb of the internal capsule supplied by the more anterior portion of the anterior cerebral artery, in particular, perforating vessels off the proximal anterior cerebral artery (21). Pure motor hemiparesis and ataxia-hemiparesis, typically regarded as lacunar syndromes, have also been reported in anterior cerebral artery infarction (09). Pure motor monoparesis of the leg and, rarely, the arm has also been reported with infarcts in this distribution (48). There are uncommon cases in which an isolated distal leg paresis presenting with peroneal- or tibial-like distribution results from small cortical infarcts involving the medial and superior margin of the precentral gyrus (“the foot motor area”) (03). Acute weakness in both lower limbs along with sphincter disturbance and frontal release signs following simultaneous bilateral anterior cerebral infarction is an even rarer occurrence and is often associated with developmental anomalies of the anterior part of the Willis circle (40). A hypoplastic A1 segment on the left was found on CT angiography in a young man who had an anterior cerebral infarction on both sides secondary to bilateral internal carotid artery occlusions. In this unusual case, the underlying mechanism of the bilateral anterior cerebral infarction was not determined (40). Though uncommon, unilateral axial weakness may be an isolated clinical manifestation of small acute infarction involving the posterolateral border of the anterior cerebral artery territory (31). In this setting, patients experienced unilateral truncal deviation even while seated, found it impossible to bend forward or backward, and displayed a body tilt contralateral to the weakness.

An acute transient spasticity (lasting a few hours up to 2 days) along with hemiparesis mainly in the lower limb has been described in two patients with acute infarcts involving the pericallosal artery on the right side. A transient loss of cortical inhibitory projections toward the lower motor control centers due to acute ischemia of the anterior cingulate cortex is the proposed pathophysiological substrate (05).

In addition to weakness associated with completed strokes, limb-shaking transient ischemic attacks involving the legs have been described related to poor anterior cerebral artery perfusion (29). Bilateral anterior cerebral artery infarction causes paraplegia, which may mimic acute spinal cord injury and, more rarely, flaccid tetraplegia. These bilateral insults usually occur in the setting of vasospasm following anterior communicating artery aneurysmal rupture or in the setting of a vascular anomaly, such as an azygous anterior cerebral artery or a hypoplastic A1 segment (73; 76). Although very uncommon, pure acute paraplegia due to bilateral anterior cerebral artery infarction may also occur after coronary artery bypass graft surgery (26).

In a review of 100 consecutive anterior cerebral artery infarcts, 70 had hemiparesis, 18 with leg monoparesis, and three with paraparesis (35). Although 64% had predominant leg weakness, 32% had similar involvement of arm and leg, and only 4% had greater arm than leg weakness. In cases of arm weakness, the shoulder tended to be more involved than the hand.

Motor deficit was present at stroke onset in 96% of 47 patients with isolated anterior cerebral artery territory infarction; the most common pattern of motor deficit (44% of patients) was brachiocrural weakness; a third of the patients exhibited classic crural monoplegia due to an anterior cerebral artery territory infarct, and 20% had contralateral hemiplegia with crural predominance (72).

Occasionally, though infrequently, an infarct in the cerebral anterior artery territory may be misdiagnosed as a functional disorder. A patient showed a strength of 0 out of 5 in both right limbs but had a positive Hoover sign and was able to bear weight. A CT scan disclosed an acute infarct confined to the supplementary motor area supplied by a distal branch of the left callosomarginal artery (49). An anatomofunctional organization of the supplementary motor area may explain the findings in this patient; a pre-supplementary motor area is involved primarily in planning movements, whereas the supplementary motor area itself is often involved in executing movements (49).

Extrapyramidal symptoms. Movement disorders are uncommon following anterior cerebral artery stroke. In one case series of nine patients with unilateral anterior cerebral artery strokes associated with involuntary movements, four had asterixis acutely, all resolving within several days. The other five, plus one who previously had asterixis, developed hemiparkinsonism in the contralateral limb. For the most part, these parkinsonian symptoms occurred several weeks after stroke onset when upper extremity strength improved, suggesting that pyramidal symptoms were masking extrapyramidal ones. Asterixis was associated with small, anterior frontal lesions, whereas hemiparkinsonism was found after stroke to the supplementary motor area or cingulate gyrus. The latter group improved over time (37). Infarction rarely involves the territory of both recurrent arteries of Heubner, but when it does, acute rigidity; bradykinesia, mainly in the upper limbs; weakness in the lower extremities; and abulia may occur (24). In addition to the above, micrographia has been observed following anterior cerebral artery infarcts, in some instances associated with contralateral motor neglect to cerebral infarct after complete recuperation from motor deficit (47).

Sensory symptoms. Sensory disturbances often occur in the same distribution as motor weakness, with leg symptoms most prominent and frequent sparing of arm and face (73). In one series, sensory disturbances always occurred in the setting of hemiparesis (09). Tactile, pain, and position sensory modalities are usually involved. A pure sensory deficit restricted to the distal contralateral leg and involving all sensitive modalities may, in very rare instances, result from a small cortical infarct in the paracentral lobule (58).

Gait apraxia. Gait apraxia is formally defined as loss of ability to properly use the lower extremities in the act of walking in the absence of weakness, extrapyramidal symptoms, or cerebellar ataxia. Often there is an association with other truncal movement abnormalities, such as rolling over in bed or rising from a seated position. The gait difficulty usually consists of impaired initiation of movement and shuffling of feet. Of note, oral and ideomotor apraxia of the upper limbs is not associated with gait apraxia. Further, the absence of gait apraxia in the setting of ideomotor apraxia argues that there are different neural systems subserving gait versus skilled hand and oral movements (27; 02). The usual location of anterior cerebral artery infarction resulting in apraxic gait includes the supplementary motor or cingulate cortices. These lesions are often bilateral, but can be unilateral and are often associated with utilization behavior syndromes described below (19).

Isolated astasia may occur, though very rarely, in unilateral infarcts involving the anterior corpus callosum and the cingulate gyrus, and this will probably impede integration of bilateral frontal executive function required for walking (77).

Incontinence. Urinary incontinence is often described as a component of anterior cerebral artery stroke. In one series of 27 patients with anterior cerebral artery stroke, 20% had urinary incontinence, although this was typically transient in patients with unilateral infarction. In the two patients with bilateral anterior cerebral artery lesions, both had persistent urinary incontinence and one also had fecal incontinence (09). A similar frequency of urinary incontinence was observed in a cohort of 36 patients with partial or complete pericallosal infarction (04). Damage to the anterior portion of the cingulate gyrus, medial superior frontal gyrus, or the midportion of the superolateral frontal gyrus is thought to result in this sphincter dysfunction. However, Kang and Kim did not find a clear relationship between stroke distribution and incontinence (35).

Neglect. Neglect syndromes are occasionally associated with anterior cerebral artery stroke. It has been reported that dominant hemisphere infarcts are associated with motor neglect of the contralateral side and nondominant infarcts are associated with sensory neglect (09). However, motor neglect, and even anosognosia, has been reported with unilateral right anterior cerebral artery lesions (41). Neglect can also be seen as part of callosal disconnection syndromes discussed below. In addition to attentional impairment manifested by neglect, patients with rupture of the anterior communicating artery have been found to exhibit impaired ability to perform dual tasks suggesting a deficit in divided attention (42).

Akinetic mutism and abulia. Alterations of consciousness and coma may occur after anterior cerebral artery infarction (46), but lack of responsiveness is more often associated with an akinetic or abulic state. Abulia is defined as a decrease in spontaneous speech and activity with increased response latency and decreased persistence with a task. Akinetic mutism is a more severe form of abulia and may be difficult to differentiate from a stuporous or locked-in state. In fact, EEG may further obfuscate the issue, as it may show slowing or even periodic lateralized epileptiform discharges (57). It can occur with either bilateral or unilateral anterior cerebral artery infarction, although symptoms may be more persistent with bilateral infarction. Akinetic mutism can be an early and transient finding, as observed in a patient with bilateral pericallosal infarction (04). Indeed, unilateral lesions tend to evolve into unilateral motor neglect over days. In one series, eight of 16 patients with left-sided and two of nine patients with right-sided anterior cerebral artery infarction presented with mutism (09). Another series found the rate of abulia and akinetic mutism to be 44% after either unilateral or bilateral anterior cerebral artery distribution infarcts (41). A similar proportion was found in a larger series with these symptoms being most frequent after bilateral lesions (67%), but was not uncommon after left- or right-sided strokes (51% and 25%, respectively) (35). Lesions causing abulia and akinetic mutism often involve the cingulate cortex, frontal pole/gyrus rectus, supplementary motor area, or the caudate (35; 11).

Mood disturbance. Depression after stroke is common and appears to increase in prevalence with more anterior cortical damage (50), a region partially supplied by the anterior cerebral artery. Depressive symptoms occurred in 10% of patients with complete or partial pericallosal territory infarction (04). A more specific lesion to the left caudate is highly associated with depression (64; 56). Alternatively, hyperactivity, agitation, and talkativeness have been associated with unilateral caudate lesions (12). Poststroke emotional incontinence, marked by excessive or inappropriate crying or laughing, is also associated with anterior cortical region stroke, and Kim and Choi-Kwon found it present in all four patients with anterior cerebral artery stroke in their series (38). Euphoria, emotional lability, and witzelsucht (a condition marked by the making of poor jokes and puns and the telling of pointless stories, at which the patient is intensely amused) are associated with mesial frontal infarction (10; 41). Finally, an acute confusional state has been reported following both right and left anterior cerebral artery infarction (09; 41). A left-side predominance was found in all cases of pericallosal infarction and acute confusional state (04).

Aphasia. It remains controversial whether anterior cerebral artery stroke can cause aphasia. It is clear that patients with such infarcts often suffer deficits in verbal expression in the form of reduced speech or muteness. These symptoms are usually in association with general psychomotor slowing and may be a manifestation of abulia (04; 11). Others have argued that these patients can have a transcortical motor aphasia, where spontaneous speech is reduced and naming is poor, but comprehension and repetition are normal (41). The "excellent, well-articulated repetition" is in striking contrast to the hesitant or absent spontaneous speech. Regardless of whether or not one considers these syndromes true aphasia, they often occur after damage to the supplementary motor area. Global aphasia has also been reported in one series with equivalent frequency to that of transcortical motor aphasia, occurring most frequently after superior frontal gyrus involvement (35). The lesions are most often on the left but can occur after bilateral infarcts and rarely on the right. Other language disturbances include reports of transcortical mixed aphasia, acquired stuttering, mirror writing, and echolalia (41; 11). Crossed aphasia may very rarely occur in anterior cerebral territory infarcts. An elderly woman with an acute infarct involving the right corpus callosum showed crossed aphasia characterized by nonfluent speech, paraphasias (literal and phonological), paragrammatism, and agrammatism in addition to diminished cerebral blood flow in the right corpus callosum and in the left frontotemporal lobe, suggesting a diaschisis phenomenon (32).

Callosal disconnection syndromes. Given its rich supply of the corpus callosum, one of the most striking cognitive deficits subsequent to stroke in the anterior cerebral artery distribution is that of callosal disconnection. These patients can have some combination of ideomotor apraxia, agraphia, and tactile anomia restricted to the left hand (28). The ideomotor apraxia is manifested by inability to perform skilled movements of the left hand (ie, using a scissors or brushing one's teeth) in the absence of weakness or ataxia. The patient may be able to imitate gestures with their left hand, but this too is often impaired. Left-hand writing is often unrecognizable with incorrectly formed letters and words. Perseverations and substitutions are seen in both dictated and spontaneous writing. The naming of objects through left-handed tactile cues is significantly impaired although the patient can match the object when given multiple choices. Strikingly, there is no evidence of a gesturing, writing, or naming deficit with use of the right hand. Apraxia for left eye-lid closure was also described in a patient with a right anterior cerebral artery stroke to the anterior corpus callosum (39).

Asymmetric ideomotor leg apraxia, a quite uncommon behavioral abnormality, may be observed following an infarct in the anterior cerebral artery territory. In a report, no intentional leg movement either by verbal command or by imitation, despite normal spontaneous gait and no motor or sensory deficit, was observed in the contralateral lower limb of a patient evaluated in the rehabilitation setting 30 days after stroke onset. A hypoperfusion in the cingulated gyrus, the anterior corpus callosum, and in both frontal lobes, especially on the side of infarct, was found by single-photon emission computed tomography (SPECT). These findings were explained by collateral vascular supply redistribution after anterior cerebral artery occlusion (33).

A patient with an isolated infarct in the left corpus callosum body exhibited a callosal disconnection syndrome comprising left-hand agraphia and apraxia, left-hand tactile anomia, and intermanual conflict (36). Interestingly, the patient had motor impersistence in the upper and lower right limbs (the dominant extremities), which resolved within three months.

Another interesting dissociation described with these strokes is in body representation. A case of a patient with left finger agnosia and inability to point to named body parts with his left hand has been described and is likely the result of left hemisphere dominance for body representation (55). Evidence of left neglect in the right hand as well as right neglect in the left hand after anterior cerebral artery infarct also offers a window into the hemispheric specialization for attention (75). A nondemented 69-year-old patient with an acute cerebral infarct mainly involving the left anterior cingulate cortex and the trunk of corpus callosum was reported to exhibit acquired hyperlexia (a tendency to read all words appearing in front of the patient) as a main behavioral trait, associated with “ambient” echolalia (a tendency to repeat words from unrelated conversations around the patient), compulsive manipulation of tools, visual groping, and callosal disconnection syndrome (70).

Although not a callosal disconnection syndrome, an amnestic syndrome characterized by anterograde amnesia, confabulation, tendency to laugh, and lack of inhibition has been described associated with a bilateral infarct involving the anterior columns of the fornix and genu of the corpus callosum due to occlusion of the anterior recurrent artery of Heubner arising at the level of the anterior communicating artery (60). An impairment of the hippocampal-diencephalic system or its pathways has been proposed to explain the alteration of episodic declarative memory.

Pathological grasp phenomena and alien hand. Infarction of the frontal lobe or basal ganglia can result in the grasp reflex seen in patients with anterior cerebral artery infarcts. In one series, hypobulia was strongly associated with the presence of the grasp reflex (35). Alternatively, the instinctive grasp reaction is usually the result of medial frontal lobe damage with or without callosal involvement. This reflex is manifested by the so-called magnet reaction, trap reaction, and instinctive groping, which are under incomplete volitional control (10).

Originally, alien hand was defined narrowly as the patient's inability to recognize his hand as his own when palpated behind his back and was felt to be a callosal disconnection sign. Alien hand phenomenon has evolved to incorporate a continuum of different dissociative movements between the right and left hand that can be roughly divided into two general categories: (1) simple unwilled, unskilled, quasi-reflex actions; and (2) complex, unwilled motor acts (22). In the former category many have included the grasp phenomena mentioned above. Also included in this first group is repetitive motor activity, such as patting or smoothing bedclothes. The patient will often try to restrain these movements with their other hand. These motor perseverations are usually associated with unilateral medial frontal lobe injury. Another behavior included in the first category is the compulsive manipulation of tools in which the patient is unable to resist using familiar tools placed in front of him. Again, the patient will often attempt to restrain the hand. Lesions in this case may be localized to the left mesial frontal area, involving the supplementary motor area, cingulate gyrus, and genu of the corpus callosum, but without a disconnection syndrome (52). Utilization behavior is yet another quasi-reflexive action where the patient will have a decreased threshold to use objects placed in front of him or her (44); unlike the above disorders, though, the patient's will is not different from the actual behavior (51).

More dramatic forms of alien limb phenomena are in the second group, including mirror movements by the "alien" limb, the pushing aside of one limb by the other, the interference caused by the "alien" limb joining an act performed unimanually by the other hand, and inter-manual conflict (22). The last is marked by the actions of one hand at cross-purpose to the other. This is almost always associated with callosal damage, often with involvement of the supplementary motor area and cingulate cortex. An example of inter-manual conflict is a patient using one hand to open a door while the other attempts to close it (13). The actions of the alien limb can reach truly bizarre and complicated proportions such as attempting to choke the patient against his will (22) or excessive masturbation with that limb (61). Alien limb was observed in 10 out of 100 patients reported in a series and possibly associated with lesions of the corpus callosum/cingulate gyrus (35). The neurophysiological abnormality underlying alien hand syndrome remains unknown. In a report, two patients who developed, respectively, intermanual conflict and a grasping reflex after acute anterior cerebral infarction both showed reduced amplitude by single pulse on motor-evoked potential and a lack of intracortical inhibition by paired pulse on transcranial magnetic stimulation (63). Somatosensory-evoked potentials showed no abnormalities.

The extent of damage of interhemispheric corpus callosum fibers secondary to acute frontal ischemia was evaluated by means of diffusion tensor tractography and compared with normal subjects. The patient was a woman evaluated in a rehabilitation setting after an infarct on the left anterior cerebral artery restricted to the corpus callosum and the anterior portion of the cingulate gyrus. She exhibited a frontal alien hand syndrome, left agraphia, motor and somatosensory deficits on the right side, and impaired visual recognition. Diffusion tensor tractography, performed 16 days after the stroke onset, disclosed extensive callosal damage, excluding the fibers of the anterior genu and posterior splenium (34).

Interestingly, alien hand syndrome was observed upon admission in 0.8% out of 127 Asian patients with acute corpus callosum infarct, whereas decline in cognitive function, psychiatric symptoms, and aphasia were observed in 26%, 21%, and 17% of patients, respectively (69). These clinical findings caused a median delay of 24 hours in appropriate evaluation and management of acute stroke. The most common clinical manifestation, observed in nearly 75% of patients, was limb paralysis. Corpus callosum infarcts accounted for 2.3% of 5584 acute ischemic strokes; the corpus callosum splenium was most commonly affected, and 20% of patients showed genu involvement. Anterior cerebral artery stenosis was found on MR or CT angiography in 30% of patients. Large artery atherosclerotic occlusive disease was the most common etiology among the 127 patients, followed by small vessel disease in 14% of patients, based on TOAST criteria. Corpus callosum infarcts often coexisted with basal ganglia infarcts. Isolated callosal infarction, either in the genu or splenium, occurred in 21 patients and showed longer admission delay, more vascular risk factors, more cognitive and mental symptoms, and higher 1-year recurrence and mortality rates than patients with complex callosal infarcts (69). An infarction of the genu, rostrum, and splenium of the corpus callosum manifesting with both anterior and posterior types of the foreign limb phenomenon has been described in a young patient. The underlying mechanism of this extensive corpus callosum ischemia was an occlusive atherosclerotic disease of the anterior cerebral circulation combined with a possible steal phenomenon of the posterior circulation (66).

Prognosis and complications

Few data have been systematically reported on outcome after anterior cerebral artery stroke. One study found that at the time of discharge (the median length of hospital stay was 12 days), only 10% of 51 patients were independent; 40% and 43% of patients had moderate and severe disability, respectively; and 10% died from either brain herniation or infectious complications (06). By contrast, a good outcome at hospital discharge was observed in patients with a nontraumatic dissection of the anterior cerebral artery (mean age of 55 years) versus patients with isolated anterior cerebral artery infarct not due to arterial dissection (mean age of 77 years) (67). As mentioned above, bilateral infarction tends to be more severe with prolonged akinesia, urinary symptoms, and gait difficulty. Indeed, in the series of Kumral and colleagues, only the two patients with bilateral anterior cerebral artery infarcts were considered “dependent” at three months from stroke onset (41). Motor deficit usually has a favorable prognosis. Out of the 47 patients with isolated anterior cerebral artery territory infarction, 83% were able to walk without assistance at 90 days after stroke onset. Favorable prognosis is thought to be due to the compensatory capacity of leptomeningeal anastomoses because they may preserve the posterior corticofugal fibers from the primary motor cortex in the late phase of ischemic stroke (72). The temporal and spatial evolution of anterior cerebral artery territory infarct topography was assessed by CT perfusion and brain MRI in these 47 patients. At stroke onset, the perfusion deficit extended from the superior frontal gyrus and anterior cingulate gyrus posteriorly; superomedially to the paracentral lobule, precuneus, and superior parietal lobule; and inferomedially as far as the posterior cingulate gyrus. After seven days of stroke onset, the anterior cingulate gyrus and the superior frontal gyrus were the most commonly infarcted regions, whereas the paracentral lobule was rarely infarcted (72).

Anatomical variations of arteries in the anterior circulation may affect hemodynamics throughout the Circle of Willis and, consequently, influence outcome when infarcts occur in this arterial system. Absence of the A1 segment of the anterior cerebral artery on intracranial vascular imaging occurred in 6% of 1146 patients with acute ischemic stroke. This finding was associated with a large stroke volume, higher stroke severity, and worse outcome compared to stroke patients with the bilateral A1 segment present, although absence of the A1 segment was, interestingly, not associated with a higher risk of ipsilateral infarct in the anterior cerebral artery (68).

Prognosis data for nonmotor clinical manifestations of anterior cerebral artery infarct are scarce. Nowak and coworkers reported favorable outcomes in two patients who developed a disabling frontal alien hand syndrome (continuous involuntary groping and grasping of surrounding objects) and right-side hemiparesis with crural predominance in the setting of anterior cerebral infarct on the dominant side. After a period of rehabilitation therapy, the alien hand syndrome manifestations resolved completely in both patients, one at seven months and the other at nine months after stroke (59).

Clinical vignette

A 67-year-old woman with diabetes and hypertension presented with abrupt onset of left-sided weakness. Examination showed complete paralysis of her left leg, moderate left arm weakness proximally with mild left hand weakness, and a left facial droop. Left-sided extinction to double simultaneous stimuli was present. Two days later she reported that her left arm felt like it did not belong to her. She had spontaneous involuntary grasping movements with her left hand that she attempted to suppress by using her right hand to grasp her left fingers. She was fully aware of the involuntary nature of her left hand movements. MRI demonstrated acute infarction in the territory of the left anterior cerebral artery. Magnetic resonance angiography of the head and neck did not reveal large vessel atherosclerosis in the cerebral vessels. Transesophageal echocardiography revealed severe aortic arch atherosclerosis with a large, complex, and mobile plaque.

Biological basis

Etiology and pathogenesis

Anterior cerebral artery stroke occurs due to a similar variety of mechanisms as infarction in other vascular territories (09). Isolated anterior cerebral artery stroke is infrequent, accounting for only 0.6% to 3% of all strokes (25; 41; 35). In a series of 27 patients with anterior cerebral artery infarcts (09), stroke was attributed to carotid disease with artery-to-artery embolus in nine patients. Cardioembolism was believed the etiology in seven patients (4 with atrial fibrillation; one with a recent myocardial infarction and intracardiac thrombus on echocardiography; and two with mitral valve prolapse and distal occlusion seen on angiography). Six patients had no clear etiology, but the majority had risk factors for atherosclerotic disease. Strokes in the remaining patients were attributed to chronic disseminated intravascular coagulation in a patient with ovarian adenocarcinoma, internal carotid artery dissection, a lacune of the recurrent artery of Heubner, acute alcohol intoxication, and intracranial arterial thrombosis. Another published series of 48 patients with MRI-confirmed anterior cerebral artery infarcts revealed a similar distribution, with one fourth due to cardioembolism, one fourth due to large vessel disease, and one third without clear cause, but the majority with either hypertension, diabetes mellitus, or ipsilateral “non-significant” atherosclerotic disease (41). A study from East Asia found that intrinsic anterior cerebral artery disease accounted for at least 61% of the strokes in this territory whereas only 6% were clearly due to internal carotid artery disease (35). Causes of large vessel strokes were relatively evenly distributed among local branch occlusion, in situ thrombotic occlusion, and artery-to-artery embolism. Cardioembolism was a relatively infrequent cause (10%). This lower frequency of embolism than western cultures confirms reports from other East Asian populations. Nevertheless, in a cohort of 51 patients with a mean age of 74 years who were among a western hospital stroke registry of 3,808 patients, the most frequent etiology was cardioembolism (45%), followed by atherothrombotic infarction (29%) (06). Unfortunately, the study did not specify the frequency of the different potential cardiac sources of embolism, though it was reported that 23% of patients had atrial fibrillation as a stroke risk factor. Additionally, the cause of ischemic stroke could not be determined in nearly 12% of patients.

In a prospective series of 2702 Asian patients with acute ischemic stroke identified by diffusion-weighted MR imaging who underwent a thorough etiological investigation, 49 patients (with a mean age of 68 and a median initial NIHSS score of 3) had an anterior cerebral artery territory infarct. Based on the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification system, the leading etiology among these 49 patients was large artery disease (65%) followed by cardioembolism (10%); multiple and other subtypes were identified in 4% and 2% of these patients, respectively, whereas etiology could not be determined in 18% of cases (15).

Large artery atherosclerosis was the main etiology in 66% of a cohort of 288 Korean patients (mean age 70.8 years, 50% female) with isolated anterior cerebral artery infarcts, followed by cardioembolism, which accounted for 20% thereof (14). Compared to patients who had infarcts in the middle cerebral, posterior cerebral, and vertebrobasilar artery territories, the proportion of large artery disease and previous ischemic stroke was significantly higher in patients with anterior cerebral artery territory infarcts.

A variety of less common causes of anterior cerebral artery stroke have been reported, including fibromuscular dysplasia, Wegener granulomatosis, isolated angiitis, radiation vasculitis, subarachnoid neurocysticercosis, and reversible segmental vasoconstriction and vasodilation (10). Arterial dissection has very rarely been reported as a cause of anterior cerebral infarct; nevertheless, an angiographically-proven anterior cerebral artery dissection was the main etiology in 42 (43%) of Asian patients with infarct restricted to this arterial territory (67). In line with Sato’s cohort, arterial dissection angiographically diagnosed by MRA, CTA, or both, was found in one third of 34 ethnic Asian patients. Cardioembolism and large atherosclerotic vasculopathy were found in the same proportion of patients (32%). Patients with arterial dissection were younger compared to those with anterior cerebral artery infarct without arterial dissection (54). More rarely, a cerebral infarct with a simultaneous subarachnoid hemorrhage localized in the interhemispheric fissure may result from an anterior cerebral artery dissection (71). In a meta-analysis of 80 cases of spontaneous anterior cerebral artery dissection reported between 2002 and 2015, sudden-onset headache occurred in around half of the patients, whose median age was 51 years (ranging from 35 to 82), and in 60% of whom were male (30). In this meta-analysis, the most common pattern of presentation of spontaneous anterior cerebral artery dissection was ischemia, affecting 73% of patients; 10% of patients had subarachnoid hemorrhage, and 17% had a combination of both patterns. A median National Institutes of Health Stroke Scale of 4.9 was found in patients with infarct. The string sign or pearl-and-string sign occurred in nearly 90% of cases, and one-third of patients showed a double lumen in different neuroimaging techniques. Clinical outcome was good in 77% of patients and unfavorable in only 6%. The novel SARS-CoV-2 infection has been associated with acute stroke, usually in patients with respiratory symptoms. A study reported an older man who had had a previous ischemic stroke and atrial fibrillation and subsequently developed a contralateral hemiparesis due to an acute infarct in the anterior cerebral artery (08). Endothelial injury, a hypercoagulable state, and a cardiac arrhythmia caused or aggravated by the coronavirus may act alone or in combination to produce an acute stroke (08).

Anterior cerebral artery stroke may occur in conjunction with middle cerebral artery infarction due to occlusion of the internal carotid artery, or due to trans-falcine herniation in the setting of poststroke cerebral edema. Anterior cerebral artery territory infarction may also occur in the setting of subarachnoid hemorrhage from a ruptured anterior communicating artery aneurysm, due either to focal vasospasm or complications of surgical aneurysm repair. Some data suggest that alcohol dependence may be associated with a greater likelihood of stroke in the superior anterior cerebral artery territory than other cerebrovascular territories, when compared to stroke features in social drinkers (43).

Several explanations for the low frequency of isolated anterior cerebral artery infarction have been put forth, usually invoking rheology. An analysis of the vascular anatomy suggested that anterior cerebral artery strokes are uncommon because the anterior cerebral artery origin is, in vivo, almost 180 degrees opposite the direction of flow from the terminal internal carotid artery and this configuration favors embolization to the middle cerebral artery rather than the anterior cerebral artery (45). Some have argued that when anterior cerebral artery stroke does occur, it is in the setting of vascular anomalies such as an azygous anterior cerebral artery, resulting in increased blood flow through the proximal anterior cerebral artery. Others have argued that there is an increased risk in the setting of tenuous perfusion due, in part, to anterior cerebral artery stenosis (65).

Like stroke in other arterial distributions, the clinical syndromes associated with anterior cerebral artery infarction are related to its vascular anatomy. The artery can be divided into five segments. The A1 segment is from the bifurcation of the internal carotid to the anterior communicating artery. Penetrating vessels from this segment perfuse the genu, as well as portions of the anterior and posterior limbs of the internal capsule, the rostral thalamus, hypothalamus, and pallidum. Portions of the optic nerve, chiasm, and tract are also supplied by this segment. Perforators from the anterior communicating artery supply the anterior hypothalamus, mesial anterior commissure, fornix, corpus callosum, anterior cingulate gyrus and, importantly, the basal forebrain.

The A2 and A3 segments are the ascending portion of the anterior cerebral artery, whereas the A4 and A5 segments are its horizontal portion. A2 penetrating vessels supply the gyrus rectus, inferior frontal areas, anterior diencephalon, and rostrum of the corpus callosum. The recurrent artery of Heubner is an important penetrating vessel that supplies the head of the caudate, anterior limb of the internal capsule, and anterior hypothalamus, pallidum, and putamen (73). This artery originates most commonly from the A2 segment (58%) but can arise at the anterior cerebral artery/anterior communicating artery junction (12%), the distal A1 segment (30%), or, rarely, the anterior communicating artery (78). Eight cortical vessels arise from the pericallosal (A2-A5) and callosomarginal (which originates from the A3 segment) arteries. The paired pericallosal arteries travel just below the falx cerebri, whereas the callosomarginal artery courses along the cingulate sulcus. The eight cortical arteries include the orbitofrontal, frontopolar, anterior internal frontal, middle internal frontal, posterior internal frontal, paracentral, superior parietal, and inferior parietal arteries (10). The anterior cerebral artery supplies the corpus callosum except for its most posterior portion, which is supplied by the posterior carotid artery.

Considerable anatomic variation occurs. The anterior cerebral artery distribution may extend quite laterally on the dorsal surface of the brain or be restricted medially (74). The variable border zones amongst individuals between the anterior carotid artery-middle cerebral artery and anterior carotid artery-posterior carotid artery territories may account for the spectrum of clinical syndromes that can occur following anterior cerebral artery infarction. Vascular anomalies are common. A hypoplastic or absent A1 segment is found in 5% to 18% of people and is associated with a high rate of anterior communicating artery aneurysms (62; 10). An azygous anterior cerebral artery is less common; a dominant, or bihemispheric, anterior cerebral artery is more frequently present.

Epidemiology

As stated previously, isolated anterior cerebral artery infarcts are rare, comprising only 0.6% to 3% of all ischemic strokes (25; 06; 67; 54; 20; 14).

Prevention

Prevention of anterior cerebral artery strokes is similar to the prevention of strokes in other vascular territories; it is described in more depth elsewhere in MedLink Neurology.

Differential diagnosis

Confusing conditions

In general, the differential diagnosis for anterior cerebral artery infarction is the same as for stroke and includes other causes of acute, focal neurologic disease. Of note, anterior cerebral artery strokes may be clinically similar to middle cerebral artery infarction depending on the vascular anatomy. Additionally, bilateral anterior cerebral artery infarction can cause paraplegia that may mimic acute spinal cord injury.

Diagnostic workup

This is similar to the diagnosis of stroke in general, and is described elsewhere in MedLink Neurology.

Management

Acute management is the same as for stroke in general, and is described elsewhere in MedLink Neurology.

Physical and cognitive therapy may provide benefit after anterior cerebral artery stroke. Abulia and akinetic mutism has received attention as a symptom complex possibly amenable to pharmacologic intervention. Case reports have described improvement in such patients with use of the dopamine agonist bromocriptine (53) as well as return of symptoms following medication withdrawal (07). As akinetic mutism and abulia may be related to disruption of the mesolimbic system, this intervention appears biologically plausible (01). A functional interruption of the subcortical dopaminergic pathway may be related to akinetic mutism due to unilateral anterior cerebral artery territory infarction, a condition that may improve with low doses of levodopa (18). More research is necessary in this area.