Acute Stroke: Slideshow

Stroke is a clinical term for the acute loss of perfusion to the vascular territories of the brain from hemorrhagic or ischemic insults, resulting in ischemia and loss of neurologic function in the affected areas. Prompt recognition and treatment are necessary to return blood flow to deprived areas in order to restore neurologic function. The image shown is a brain specimen from a patient who suffered cardioembolic stroke.

Strokes are responsible for the deaths of many famous historical figures, including 10 US Presidents. The most famous of these cases is that of Woodrow Wilson. In September 1919, a stroke left him paralyzed in his left arm and leg, and another one the following month left him nearly incapacitated. Despite being unable to carry out the duties of his presidency, Wilson did not step down until his term expired in March 1921. He ultimately suffered a fatal stroke in 1924. It has been postulated that his disease contributed to the defeat of US support for the League of Nations.

The National Institutes of Health (NIH) notes that strokes are the leading cause of serious long-term disability and the third leading cause of death in the United States. Annually, there are approximately 795,000 cases of stroke, with nearly three quarters occurring in people older than 65 years. For each decade over age 55 years, the risk of having a stroke is more than doubled. The image shows age-adjusted prevalence of stroke among noninstitutionalized adults aged 18 years and older, by state during 2010, based on data from the Behavioral Risk Factor Surveillance System. Regions with higher stroke prevalence were generally states in the southeastern United States and Nevada.

Image courtesy of the CDC.

The total number of deaths due to stroke is declining across all races in the United States, due in part to better recognition and treatment. However, racial disparities remain: The dramatically high death rate among black individuals compared with other racial groups persists. Native Americans, Hispanics, and Alaska Natives continue to have the lowest death rates. The Centers for Disease Control and Prevention (CDC) provides an online mapping tool—the Interactive Atlas of Heart Disease and Stroke (http://nccd.cdc.gov/DHDSPAtlas/)—that allows users to view maps of stroke and heart disease on a county-, state- and country-wide level. This tool may help public health professionals, researchers, community leaders, and others to monitor trends in stroke and heart disease, set research priorities, and plan patient services. The image shown here was created using the Interactive Atlas; it maps the 2008-2010 US stroke death rate among people of all ages and races and both sexes.

Image courtesy of the CDC.

The NIH developed a stroke scale that not only allows quantification of neurologic impairment, but it also provides insights into the location of vascular lesions, is correlated with outcomes for ischemic strokes, and identifies candidates for thrombolytic therapy. Points are assigned based on the patient's performance in 6 major areas: level of consciousness, visual function, motor function, sensory function, cerebellar function, and language. The scale is used at the patient's first presentation and can be repeated over the hospital course to assess stroke evolution over time. The NIH Stroke Scale is available in text, .pdf, and portable graphic (shown here) versions at: http://stroke.nih.gov/resources/index.htm.

Strokes are grossly classified as ischemic (about 80%) and hemorrhagic (about 20%). Ischemic strokes occur from thromboembolic occlusion of cerebral arteries. Blood flow occlusion begins an ischemic cascade that, if unchecked, will result in irreversible infarction. Hypoxia-induced cell death causes inflammatory swelling, which may alter the brain architecture, producing a midline shift as shown here. Hemorrhagic strokes occur when bleeding occurs directly into or around the brain parenchyma; these types of stroke will be discussed later in this slideshow.

Image licensed under the Creative Commons Attribution ShareAlike 3.0 License.

Noncontrast computed tomography (CT) scanning of the head is the imaging modality of choice for assessing strokes, differentiating ischemic from hemorrhagic strokes, and ruling out other intracranial pathologies. In ischemic strokes, an early head CT scan may be grossly normal, because edema and infarction have not yet developed enough to be identified. However, other subtle findings—such as a loss of the gray-white matter differentiation (red arrow), obscuration of the lentiform nucleus (white asterisk), sulcal asymmetry (yellow arrow), an insular ribbon sign, or a hyperdense middle cerebral artery sign—may be apparent. The head CT scan shown was taken on day 1 in a patient who suffered a middle cerebral artery (MCA) stroke.

As the ischemic cascade progresses, more signs are visible on head CT scans. Over time, effacement of the third ventricle (white arrow), a midline shift (white line), hypodense areas in a vascular watershed pattern, and sulcal effacement (red arrow) develop. A midline shift may be subtle and is best determined by drawing a line from the anterior to posterior attachments of the falx cerebri and then looking for any deviation. The head CT scan shown was taken on day 3 after a patient suffered an acute ischemic stroke.

Magnetic resonance imaging (MRI) allows for earlier detection of brain injury than CT scanning. Many different protocols are used in addition to T1- and T2-weighted sequences, such as diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) to yield improved sensitivity. DWI can detect brain injury in 15-30 minutes as well as smaller areas of ischemia, and it is better at visualizing the brainstem and cerebellum. The image shown is a DWI MRI that demonstrates hypointensity in the distribution of the right MCA, with hyperintensities just anterior and posterior. The findings indicate an older MCA stroke with new flanking extensions of ischemia.

PWI allows for the detection of at-risk brain tissue by directly measuring tissue perfusion. The DWI on the left shows a discrete area of ischemia, but the concomitant PWI on the right shows a much larger area that is at risk for subsequent ischemia and infarction.

Magnetic resonance angiography (MRA) is an MRI modality that uses gadolinium-based contrast medium for better visualization of the cerebral blood vessels. The vascular anatomy can be reconstructed in 3 dimensions for evaluation of the entire vascular tree in an attempt to identify vascular lesions at an earlier stage.

Hemorrhagic strokes are responsible for roughly 20% of all strokes, usually from intracerebral rather than subarachnoid etiologies. Affected individuals present with focal neurologic deficits similar to those with ischemic stroke, except patients with hemorrhagic stroke tend to appear more ill and show signs of increased intracranial pressure. Common etiologies include head trauma, leakage from small intracerebral arteries secondary to chronic hypertension, rupture of aneurysms or arteriovenous malformations, iatrogenic anticoagulation, cocaine abuse, and cerebral amyloidosis.

Noncontrast CT scanning is also the imaging modality of choice used to evaluate hemorrhagic strokes. It is very sensitive at detecting intracerebral and subarachnoid hemorrhages, as well as subdural hematomas. On noncontrast CT images, hemorrhage appears as a readily identifiable hyperdense area within the brain, as shown here.

MRI may also be used to recognize blood, localize the hemorrhage, and date the age of the hemorrhage. Depending on the MR protocols used, blood has a different appearance in an acute hemorrhage (<24 h). On T1-weighted imaging (left image), blood appears isointense, whereas on T2-weighted imaging (right image), blood appears hyperintense. MRI is also excellent at detecting reactive edema.

In chronic or subacute hemorrhages, MRI is able to carefully discriminate between new and old bleeds. The chronic component (>14 d) of a bleed is hypointense on both T1-weighted (left image) and T2-weighted (right image) sequences. The subacute component (>3 d) is hyperintense on T1 and mildly hypointense on T2 images. The change in appearance over time results from an evolution in the hemoglobin structure, the development of oxidation products, and the presence of unpaired electrons.

If a ruptured cerebral aneurysm is thought to be responsible for the hemorrhage, then angiography may be used. A catheter is threaded into the cerebral circulation, and digital subtraction angiography is performed with direct contrast injection. This technique allows for very accurate anatomic localization of a lesion as well as the ability to provide subsequent intervention.

Stroke treatment is a continuum that begins with prehospital care and ends with discharge. Therapies for ischemic stroke depend on the location of the lesion, the time since onset, and concomitant medical conditions. For patients who present within 3 to 4.5 hours of symptom onset without recent surgery or bleeding issues, thrombolysis with intravenous (IV) recombinant tissue plasminogen activator (rt-PA) is a proven measure. Use of t-PA versus placebo reduces patients' disability, based on the Rankin Scale of Global Disability (shown).

There is growing evidence that intra-arterial (IA) t-PA may be effective when given within 6 hours of stroke symptoms. In a case-control study presented at the 2014 International Stroke Conference, Paciaroni and the ICARO Investigators reported no significant difference in the rate of favorable outcomes following an acute cervical internal carotid artery occlusion between patients who received standard therapy with IV thrombolysis up to 4.5 hours after symptom onset and those who underwent endovascular therapy up to 6 hours after symptom onset.

Although t-PA is the major medical therapy for the treatment of acute ischemic stroke, numerous other modalities are under investigation to provide mechanical thrombectomy. Many of these investigations focus on the use of catheter-based therapies to disrupt or extract the clot. The devices under investigation use suction jets, laser energy, ultrasonography, and corkscrew extractors (shown). The technique of angioplasty and stent placement is well established in coronary vascular occlusion; this procedure is also being investigated for use in stroke treatment.

For patients with hemorrhagic primary or conversion strokes or those with life-threatening elevation in their intracranial pressure, urgent neurosurgical consultation is required. Surgical decompression may be necessary to evacuate a hematoma if herniation is a concern. The T2-weighted MRI shown demonstrates hemorrhagic conversion of an ischemic stroke, making the patient ineligible for t-PA and at risk for elevated intracranial pressure.

The advent of telemedicine stroke (telestroke) centers allows clinicians and patients in less accessible or underserved areas to connect with neurologists at major stroke centers via electronic communication, such as video conferencing. Experts in stroke care remotely assess a patient's stroke risk and determine whether an immediate transfer to a major hospital is warranted. The goal is to get at-risk patients to centers where they can be treated with antifibrinolytics as soon as possible after stroke onset.