Causes of Acute Stroke: A Patterned Approach

Abstract

Acute stroke is a leading cause of morbidity and mortality in the United States. Acute ischemic strokes have been classified according to The Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification system, and this system aids in proper management. Nearly every patient who presents to a hospital with acute stroke symptoms has some form of emergent imaging. As such, imaging plays an important role in early diagnosis and management. This article reviews the imaging patterns of acute strokes, and how the infarct pattern and imaging characteristics can suggest an underlying cause.

Keywords: Cause; Hemorrhagic; Imaging; Infarct; Ischemic; Stroke.

Fig. 1.

A 54-year-old man presenting with altered mental status. (A) Axial CT images show an acute left MCA territory infarction involving the left insular cortex, basal ganglia, posterior frontal, and anterior parietal lobes. (B) Axial images from CT angiography (computed tomography) of the head and neck show moderate to severe stenosis of the proximal left ICA (red arrow) and left MCA thrombus involving the distal M1 and proximal M2 segments (yellow arrow).

Fig. 2.

Anterior circulation infarctions. (A) A 96-year-old woman with history of aortic valve repair on Coumadin presenting with acute-onset left hemiparesis. Axial diffusion-weighted magnetic resonance (MR) shows infarctions involving both deep gray matter and cortex, typical of an MCA territory infarction. (B) Axial MR angiography (magnetic resonance) time of flight (TOF) shows stenosis of the right intracranial ICA (red arrow). (C) Three-dimensional (3D) maximum intensity projection (MIP) image shows occlusion of the M1 segment of the right MCA (yellow arrow), with infarction probably secondary to a combination of hemodynamic impairment and artery-to-artery emboli. (D) A 73-year-old woman with hypertension and hyperlipidemia presenting with acute right MCA syndrome. Axial diffusion-weighted image shows infarct involving the right frontal lobe and basal ganglia in an MCA distribution. (E) 3D MIP from MRA head shows luminal narrowing of the right M1/M2 junction of the MCA (white arrow).

Fig. 3.

Basilar occlusion. (A) Axial diffusion-weighted images show bilateral cerebellar, right and left pontine, and right thalamic infarcts. (B) 3D MIP image from MRA shows severe stenosis of the V1/V2 segment of the right vertebral artery (red arrow). (C) Sagittal MIP image from CTA head shows near-complete occlusion of the distal basilar artery (yellow arrow), which extended into the proximal PCAs.

Fig. 4.

A 72-year-old man with history of transient ischemic attacks, hypertension, and diabetes, presenting with right arm numbness. (A) Axial diffusion-weighted image shows acute infarction in an internal border zone distribution in the left frontoparietal lobes. (B) 3D MIP from MRA of the neck shows severe stenosis of the proximal cervical ICA.

Fig. 5.

A 75-year-old man with history of type 2 diabetes mellitus, hypercholesterolemia, hypertension, presenting with word-finding difficulty and right facial droop. (A) Axial diffusion-weighted images show acute infarctions involving MCA/PCA border-zone territories. (B) 3D MIP from MRA head shows complete lack of flow in the left V4 vertebral artery, as well as multifocal stenoses of the left PCA, both of which likely contributed to the border zone infarction.

Fig. 6.

(A) A 33-year-old woman presenting with confusion and aphasia, found to have a left MCA territory infarction and nonocclusive left M2 thrombus. Axial T2 FLAIR shows increased signal within multiple left MCA branches (yellow arrows) secondary to slow flow from the proximal partial occlusion. (B) A 94-year-old woman presenting with speech difficulties and left facial droop, found to have right MCA territory infarction. Susceptibility-weighted sequences show a tubular area of blooming in the anterior sylvian fissure, consistent with thromboembolus (white arrow). (C) A 90-year-old woman with history of congestive heart failure, hypertension, hyperlipidemia, presenting with left hemiparesis and dysarthria. Initial axial noncontrast head CT shows a dense right MCA (red arrow).

Fig. 7.

Multiple bilateral infarctions from cardioembolic source. (A) Axial diffusion-weighted MR images in a 36-year-old woman with systemic lupus erythematous and Libman-Sacks endocarditis. (B) Axial T2 FLAIR images in a 38-year-old male intravenous drug abuser with bacterial endocarditis. (C) Axial diffusion-weighted MR images in a 79-year-old man with atrial fibrillation.

Fig. 8.

(A) A 77-year-old woman with history of hypertension and advanced congestive heart failure with new-onset right hemiparesis. Axial diffusion-weighted MR image shows acute left ACA territory infarction likely secondary to cardioembolic source from advanced heart failure, because no vascular abnormality of the ACA was seen. (B) An 80-year-old man with history of prior stroke, atrial fibrillation, coronary artery disease, and hypertension presenting with new-onset left-sided weakness after collapse. Axial diffusion-weighted MR images reveal acute infarction in the right frontal cortex and right caudate head in a combined ACA/MCA distribution, likely cardioembolic in cause from known atrial fibrillation.

Fig. 9.

Infarctions measuring less than 20 mm in the typical locations for small vessel infarctions, consistent with lacunar infarcts. (A) Axial diffusion-weighted MR shows acute infarct in the left thalamus in a hyperlipidemic smoker. (B) Axial diffusion-weighted MR shows acute infarct in the right internal capsule in a patient with multiple vascular risk factors. (C) Axial diffusion-weighted MR shows acute infarct in the right pons in a patient with hyperlipidemia and hypertension.

Fig. 10.

A 49-year-old man with no known past medical history presented with acute-onset right-sided hemiparesis and confusion. (A) Axial noncontrast CT of the head shows a large left thalamic hematoma (arrow) with intraventricular extension. (B) Axial and MIP images from follow-up CTA show stenosis of the left cavernous ICA (arrow) as well as multiple collateral vessels, consistent with moyamoya.

Fig. 11.

A 55-year-old man with nasopharyngeal carcinoma presenting with altered mental status and fever, found to have Streptococcus intermedius meningitis. (A) Axial diffusion-weighted MR images show left basal ganglia and internal capsule infarction (star). On further inspection, the patient is noted to have mild ventriculomegaly and layering foci of restricted diffusion in the atria of the lateral ventricles, consistent with ventriculitis (yellow arrows). Restricted diffusion is also present in the basilar cisterns, consistent with basilar meningitis (red arrows). (B) Axial TOF image from MRA head at initial presentation and CTA head 8 days later. At 8-day follow-up, there is increased narrowing in the supraclinoid ICA (yellow arrows) and basilar artery (red arrows) secondary to vasospasm from basilar meningitis.

Fig. 12.

A 27-year-old woman presenting with fever and acute visual loss after abscess drainage for lower extremity necrotizing fasciitis. (A) Axial diffusion-weighted MR image shows a small infarct in the right middle cerebellar peduncle (circle). (B) Secondary findings of sulcal restricted diffusion (red arrow) and leptomeningeal enhancement on axial T1 postcontrast MR (yellow arrows) suggest meningitis as the cause of infarction.

Fig. 13.

Herpes zoster vasculitis. A 65-year-old woman initially presented with sudden-onset left hand weakness and facial droop. (A) Axial diffusion-weighted MR shows a right parietal infarct (star). (B) The patient was also noted to have failure of suppression of sulcal cerebrospinal fluid on T2 FLAIR, which corresponded to right convexity subarachnoid hemorrhage on noncontrast CT (yellow arrows). Vascular imaging was normal on initial presentation. (C) The patient returned 8 months later with right hand clumsiness and was found to have a new left insular infarct on axial diffusion-weighted MR (red arrow). (D) Axial T1-weighted image shows intrinsic T1 hyperintensity, consistent with hemorrhage (circle). (E) 3D MIP from MRA at that time reveals focal high-grade stenosis of an M2 branch of the left MCA (yellow arrow). Lumbar puncture revealed herpes zoster infection.

Fig. 14.

SLE. A 36-year-old woman with history of SLE presents with change in mental status and palate numbness. (A) Axial diffusion-weighted MR image shows punctate acute right frontal cortical infarct (red arrow). (B) Secondary findings of chronic right frontal subcortical infarct (yellow arrow) and white matter lesions paralleling the ventricles (oval) on axial T2 FLAIR images are characteristic of lupus. (C) Additional chronic infarcts were seen in this young patient, including a chronic right cerebellar infarct on axial T2-weighted MR image (red arrow) and left caudate infarct on axial T2 FLAIR-weighted MR image (yellow arrow). (D) There is a normal appearance of the vessels on 3D MIP image from MRA, which is typical of SLE.

Fig. 15.

Intravascular DLBCL. A 54-year-old man presenting with 3 weeks of ascending numbness and malaise, initially treated for Guillain-Barré syndrome. (A) Patient returned for ongoing symptoms, and axial diffusion-weighted MR image revealed multiple bilateral areas of acute infarction in a watershed distribution (red arrows). (B) After 2 months, axial diffusion-weighted and T2 FLAIR images show multiple additional infarcts and infarctlike lesions, with diffusion restriction and corresponding T2 hyperintensity (ovals). (C) Axial T1 postcontrast images revealed leptomeningeal enhancement (yellow arrows). (D) Axial T2 FLAIR shows central pontine T2 hyperintensity (white arrow).

Fig. 16.

CADASIL. A 38-year-old woman with known CADASIL presented with altered mental status. (A) Axial diffusion-weighted MR image shows a focus of diffusion restriction in the left temporal subcortical white matter consistent with acute infarct (star). (B) Axial T2 FLAIR images show confluent periventricular white matter hyperintensity involving the anterior temporal and frontal white matter, as well as the external capsule, in a pattern consistent with CADASIL (red arrows). (C) Axial susceptibility-weighted image shows nonspecific microhemorrhages (yellow arrows).

Fig. 17.

Cervical carotid dissection. A 40-year-old man with no past medical history presented with acute left facial droop and right jaw pain. (A) Axial diffusion-weighted image shows right-sided parietal and caudate head infarcts. (B) Axial T1-weighted sequence shows hyperintensity surrounding the right petrous ICA consistent with blood in the dissection flap (yellow arrow). (C) MRA neck performed for confirmation shows hyperintensity surrounding the proximal cervical ICA on T1 fat-saturated sequence (red arrow). (D) 3D MRA MIP image shows resultant long segment smooth stenosis extending from just distal to the bifurcation to the petrous ICA (yellow arrows).

Fig. 18.

A 61-year-old-woman with breast cancer and left upper extremity deep venous thrombosis. Axial diffusion-weighted images show multiple bilateral infarctions involving multiple vascular territories. Cause was presumed as secondary to undetected patent foramen ovale, because no large vessel or cardioembolic sources were identified.

Fig. 19.

Three different patients with systemic hypertension, presenting with hemorrhagic infarctions in characteristic locations. In all of these cases, vascular imaging revealed no abnormality. (A) Axial CT with hemorrhagic infarct in the pons. (B) Axial CT with hemorrhagic infarct in the right basal ganglia. (C) Axial T1-weighted MR image with hemorrhagic infarct in the left thalamus.

Fig. 20.

A 16-year-old boy with no significant past medical history presenting with acute-onset left-sided weakness, headache, and subsequent coma. (A) Axial noncontrast head CT revealed right basal ganglia and intraventricular hemorrhage causing a leftward midline shift. (B) Subsequent CT angiography of the head revealed an arteriovenous malformation with its nidus at the junction between the thalamus and posterior limb of the right internal capsule, supplied by a PCA branch with deep venous drainage.

Fig. 21.

A 53-year-old woman with history of breast cancer presented after being found down unresponsive. (A) Noncontrast head CT at time of presentation shows hemorrhagic infarctions of the bilateral basal ganglia and thalami. (B) Tubular hyperdensity is seen in the bilateral internal cerebral veins (red arrows), vein of Galen (yellow arrows), and straight sinus (white arrow), consistent with venous sinus thrombosis and venous infarction.

Fig. 22.

Cerebral amyloid angiopathy. A 65-year-old woman with recurrent transient neurologic symptoms of unclear cause and migraine with aura, presenting with acute-onset right face and right arm numbness and weakness. (A) Axial noncontrast head CT and axial T1-weighted MR image show a left high parietal intra-parenchymal hemorrhage. (B) Axial susceptibility-weighted images reveal multifocal subarachnoid and subcortical microhemorrhages. Brain biopsy was positive for β-amyloid plaques.