Localization is the cornerstone of clinical neurology. It is even more important in vascular neurology, because the anatomy of arteries is fixed and different arterial segments or systems are preferentially affected in different types of vascular disease. The young practitioner faced with the challenge of localization must already be able to do a full neurological history and examination, and tailor it to find details that distinguishing different parts of the brain. The final step requires identifying the syndrome and ascribing it to a particular arterial territory; the cognitive skill necessary to achieve this part of neurological practice is "pattern recognition".

Here are some of the basic vascular syndromes you will encounter in daily practice. Keep in mind that syndromes may be partial or atypical, and that the manifestations of many of them overlap. Some of the reasons for the variability of findings include collateralization of flow, partial spontaneous reperfusion, or anatomic variants. Also remember that the patient will not always be fully awake or aware of the symptoms, and that you may need to gather the information from observers, or deal without a history. A depressed level of consciousness, speech problems or poor cooperation of the patient may also limit the history and physical examination. One last challenge is the lacunar syndrome…one lacune can give the same clinical presentation in several different locations.

In general, the more detailed your exam and history, the closer to the diagnosis you will be. Besides, remember you now have technology to confirm your thoughts! I always wonder what Charcot and other famous neurologists would have given for a head CT, or better yet, a MRI machine!

More than 50% of patients with ICA stroke have a preceding TIA. Some investigators have argued that the incidence of infarction after a TIA in the ICA territory is only 5%. Embolism occurs in more than 30% of the patients with ICA strokes. About 60% will have recurrent TIAs and then a sudden onset of the stroke. Other patients have a stuttering presentation (5%) sometimes over a period of weeks. Some patients experience headaches in the homolateral side. Occasionally, pain over the ICA in the neck (carotidynia) accompanies the episode.

Previously thought to signal critical carotid disease, we know now that bruits are only good indicators of coronary artery disease! If the stenosis is too severe, there may not be a bruit. Sometimes the bruit is heard on a widely patent carotid artery contralateral to the diseased ICA, just because the patent one carries high-speed flow. Thus, relying on bruits alone may lead to miss the diagnosis of a severe carotid stenosis. On the side of the diseased artery, there may be a Horner's syndrome, owing to damage to the delicate sympathetic fibers normally surrounding the carotid artery.

The distinguishing feature of carotid artery territory ischemia is amaurosis fugax (transient monocular blindness = TMB). It consists of transient, painless loss of vision in one eye, described by the patient as seen a "shade" or "curtain" being pulled from top to bottom of one visual field. During the attack, the pupil is amaurotic and the retinal vessels are collapsed. The clinician may be able to see the embolus or a Hollenhorst plaque (cholesterol crystals) in the vessels of the optic fundus. TMB may occur in isolation as a TIA (transient ischemic attack) or as a premonitory sign to acute ischemic optic neuropathy (AION), ischemic oculopathy, or as part of a major arterial territory syndrome.

The patient with infarction of the entire ICA territory will have a hemiparesis, hemisensory defect, and hemianopia. If the left side is affected there will be aphasia. With right-sided infarcts there is be apraxia, anosognosia and inattention.

"Limb-shaking TIAs" occur with severe carotid stenoses. These TIAs manifest with brief, coarse, irregular or rhythmic movements of one or both contralateral extremities. They are precipitated by standing, neck extension or walking and, therefore, indicate a hemodynamic compromise of the ICA.

Infarction of the entire ICA territory carries a high mortality of 75-100%. The territory includes the eye (ophthalmic artery), and the territories of the middle cerebral artery (MCA) and anterior cerebral artery (ACA)...so all of the ipsilateral hemisphere, except for the narrow strip of occipital lobe supplied by the PCA will be infarcted. When edema ensues, peaking at about 2-3 days after the onset, death is very likely to occur. In such large infarcts, early edema (within 12-24h) may be enough to lead to herniation, especially among the young. This greater mortality among the young is due to the fact that age-related brain atrophy leaves less space available for edematous brain to accommodate in.

In a portion of the population (approximately 18%) the PCA arises from the ICA (this is called persistent fetal circulation); in this setting, ICA occlusion will lead to infarction of the ENTIRE hemisphere!

The ICA is not necessarily occluded, but may be severely stenotic or may harbor fractured complex atherosclerotic plaques with a superimposed friable thrombus. The thrombus may embolize or its tail may grow cranially and occlude the ostia of the branches of the ICA.

Atherothrombotic infarction usually occurs during repose or sleep, and often in the morning hours. Some researchers think that physiological hypotension, hypoxemia (as in sleep apnea), or mechanical compression as well as a greater physiologic stress level (high levels of cortisol) may explain this circadian variation. Embolic infarction can occur at any time but especially when the patient is awake and active. Emboli can originate from the pulmonary veins, cardiac valves or chambers, or ulcerated plaques in the aortic arch or the arteries arising from it. A stroke resulting from en embolus arising from an atherosclerotic plaque in an artery is called atherothromboembolic; one resulting from an embolus arising in the heart is called cardioembolic. Telling these two apart clinically may at times be difficult, unless there is a clear history of cardiac disease (e.g. palpitations, atrial fibrillation, congestive heart failure). Some statistical data suggests that cardiac emboli are more likely to lodge in certain cerebral arterial branches like for example, the posterior division of the MCA.

These clinical characteristics and temporal relationships are not always reliable in clinically defining the pathophysiology or etiology. Also, they are not exclusive of the carotid artery territory strokes but they are discussed under ICA syndromes for convenience.

There are a variety of causes of ICA obstruction:

• congenital absence or atresia
• periarterial inflammation with thrombosis
• emboli
• mechanical (e.g. large thyroid tumor, head and neck cancer)
• radiation-induced fibrosis
• arteriopathies (Takayasus's arteritis, Moyamoya disease, fibromuscular dysplasia)
• dissection
• atherosclerosis (the most common)

This is the "syndrome of the three H's":

• hemiparesis (internal capsule)
• hemisensory defect (posterolateral nucleus of the thalamus) and
• hemianopia (lateral geniculate body or geniculocalcarine tract)

In a small proportion of cases, the left-sided lesions will produce aphasia and the right sided lesion may produce left hemi-inattention.

The syndrome consists of abulia, paratonia (gegenhalten), and a hemiparesis and a hemisensory deficit that mainly affect the lower extremity. If the corpus callosum is affected, there is left hand apraxia (anterior disconnection syndrome). There may be impaired planning, emotional disturbances and urinary incontinence.

Guess what? The MCA syndrome also includes hemiparesis, hemisensory deficit and a hemianopia. Now, the first two affect mainly the arm rather than the leg. You knew that!

There is also a gaze deviation toward the lesion (area 8 of Broadman on the contralateral side has no adversary!).

With left-sided lesions there is aphasia (motor, sensory, conduction or global...in order from frontal to posterior parietotemporal areas). With right-sided (non-dominant) lesions there will be inattention, apraxia, impaired prosody, anosognosia and confusional states.

Gerstmann syndrome is seen most frequently with left angular gyrus (posterior parietal area) lesions. It has four components: finger agnosia, right-left confusion, acalculia and agraphia. The posterior disconnection syndrome of alexia without agraphia occurs with left posterior lesions as well. Gerstmann syndrome may be associated with it or with a hemianopic defect, achromatopsia and other occipital symptoms.

The hemianopic defect of MCA infarction may be a complete homonymous hemianopia, a superior quadrantanopia (with temporal lesions) or an inferior quadrantanopia (with parietal lesions).

The bi-opercular syndrome of bilateral MCA territory infarctions includes paralysis of volitional tongue, jaw, pharynx, and facial musculature with preservation of the non-volitional, emotional movements. It could be mistaken for involvement of the lower motor neurons of the brainstem and is therefore called the pseudobulbar syndrome. However, the jaw jerk, facial, and gag reflexes are characteristically brisk. Limb movements are often normal. The syndrome may at times include bibrachial spastic paralysis and emotional incontinence.

MCA occlusions/stenoses are more likely to result in complete infarction than ICA occlusion because the MCA has no direct collaterals similar to the ACoA. Most infarctions in the MCA distribution are caused by embolism from the heart. Some are secondary to embolism from the distal stump of an occluded ICA or from a plaque in the ICA. Atherothrombosis of the MCA occurs only 1/10 as frequently as ICA atherothrombotic occlusion and is more frequent in women than in men. In Oriental and African-American populations, intracranial stenosis and occlusion (of the MCA or any other artery) is more common as a cause of stroke than is an extracranial stenosis. Diabetes, hypertension and smoking also increase the likelihood of intracranial stenoses.

Not everybody loses a visual hemifield or becomes blind with PCA occlusions. There are partial syndromes such as formed (people, objects) or unformed (flashes of lights, spots) hallucinations, visual or color agnosias, prosopagnosia (being unable to recognize familiar faces) or achromatopsia (color blindness).

Ocular ataxia, psychic paralysis of fixation and disturbances of visual attention (Balint syndrome) occurs with bilateral lesions of the occipital or parietooccipital lesions.

Infarction of the medial-inferior temporal lobe (dominant hemisphere or bilateral) will produces agitated delirium or acute amnestic syndromes.

Occlusion of the callosal branches of the PCA on the left side will result in infarction of the splenium of the corpus callosum and lead to alexia without agraphia, which is frequently associated with color anomia and prosopagnosia.

If the occlusion affects the penetrator branches there will be aphasia, akinetic mutism or the Dejérine-Roussy syndrome (contralateral hypoesthesia with pain, vasomotor disturbances, transient or persisting hemiparesis and choreoathetoid or ballistic movements).

Infarctions in the distribution of the penetrating branches of the PCA to the midbrain will produce the Benedikt syndrome: ipsilateral oculomotor paresis with contralateral ataxia and choreoathetosis.

The Nothangel syndrome (ipsilateral oculomotor paresis with contralateral ataxia) or the Weber syndrome (ipsilateral oculomotor paresis with contralateral hemiparesis) may also result. Other probabilities are internuclear ophthalmoplegia (which may be bilateral), WEBINO syndrome, or the Parinaud syndrome, locked-in state, decerebrate rigidity and altered consciousness.

Infarctions in the BA distribution range from small lacunes with contralateral hemiparesis and ataxia to the devastating locked-in-state or top-of-the basilar syndromes.

Basilar atherosclerotic disease leads to occlusion of the ostia of small penetrator branches. The lipohyalinosis of hypertension and diabetes can also cause occlusion of these small vessels. This leads to lacunar infarctions. These tiny strokes lead to pure motor hemiparesis, dysarthria-clumsy hand syndrome, ataxic hemiparesis, etc. Although the localizing value of these syndromes is not perfect, they are most frequently described as being pontine infarcts.

Atherosclerosis of the basilar artery can also lead to its occlusion and, thus, occlusion of many of its branches leading to ischemia of the entire anterior pontine area and the locked in state. "Locked-in" patients are quadriparetic, the face is weak bilaterally and their bulbar functions are all affected bilaterally. The only motor function left is vertical gaze (midbrain function), a devastating state.

The Millard-Gubler pontine syndrome consists of ipsilateral weakness of the facial and abducens muscles and contralateral hemiparesis. It occurs when a small lesion affects the ventrocaudally located fascicles of CNVII, CNVI and the corticospinal fibers.

Other pontine syndromes:

Foville syndrome: consists of contralateral hemiplegia sparing the face (corticospinal tracts) ipsilateral nuclear facial paresis (facial nucleus or fascicles), and ipsilateral gaze palsy (PPRF).

Raynaud-Cestan syndrome occurs with rostral anterior pontine lesions and produces ipsilateral ataxia and rubral tremor, contralateral sensory loss (all modalities), and contralateral hemiparesis and/or ipsilateral gaze palsy.

Syndrome of Marie-Foix : this syndrome consists of ipsilateral cerebellar ataxia, contralateral hemiparesis and hemihypoesthesia (variable); it occurs with lateral pontine infarcts, usually affecting the brachium pontis.

The most popular syndrome of ischemia in the vertebral artery territory is the Wallenberg syndrome, also called lateral medullary syndrome; it may also be seen with occlusion of the PICA (posterior inferior cerebellar artery). The typical features are ipsilateral facial hypalgesia and thermoanesthesia with contralateral body sensory loss (also temperature and soft touch) due to damage to the trigeminal spinal nucleus and the spinothalamic tracts. There is also paresis of the palate, vocal cord and pharynx (due to ischemia of the nucleus ambiguus) and vertigo, nausea and vomiting (with involvement of the vestibular nuclei). An ipsilateral Horner syndrome also occurs because there is ischemia of descending sympathetic fibers. Ipsilateral cerebellar symptoms (appendicular) also occur due to ischemia of the posterior-inferior cerebellum. Hiccups and diplopia may occur as well. Because there is ischemia of the cerebellar tonsils, these patients run the risk of tonsilar herniation, which rarely gives any warning except...respiratory arrest and pulmonary edema followed rapidly by death. Keep an eye on these patients.

With slightly more medial lesions, an otherwise-pure Wallenberg syndrome may occur with contralateral facial and body hemisensory deficits; this happens when the trigeminothalamic (rather than the spinal trigeminal nucleus) is affected.

The medial medullary syndrome of Dejérine occurs with occlusion of the anterior spinal artery or the vertebral artery. It consists of ipsilateral tongue paresis and contralateral hemiparesis (pyramidal ischemia) and loss of position and vibratory sense (medial lemniscus damage) The face is not weak, because the infarct is lower in the medulla.

Now this is one of my favorites: hemiplegia cruciata occurs with high anterior spinal artery occlusions and trauma. It consists of contralateral arm weakness and ipsilateral leg weakness. This happens because the pyramidal fibers innervating the arm cross before those of the leg do. The syndrome is rarely isolated, though, as you can imagine. Go to the spinal cord page if you want to know more.

. Whenever there is cerebellar ischemia, the situation becomes especially dangerous. Progressive edema may lead to ventricular obstruction and brainstem compression. The patient may need surgical management.

Send your questions or comments to: