Left MCA Infarct with Hyperdense MCA Sign

Sudden Onset Right Side Weakness • Xray of the Week

This 76 year old female presented with sudden onset of right side weakness. What is the diagnosis?

Figure 1. Non-contrast axial CT scan of the brain.

Figure 2. A. Non-contrast axial CT scan of the brain demonstrates high attenuation within the left middle cerebral artery (MCA), appearing as a high attenuation dot (red arrow) as the MCA is in the short axis.

Figure 2. B. The high attenuation MCA is visualized as a line (red arrow) as the artery is in the long axis.

Figure 2. C. There is also an old infarct in the left basal ganglia. (yellow arrow) Note that the gray and white matter differentiation is normal indicating that the high attenuation MCA is the only sign of infarct.

Figure 3. A. Axial T2-weighted image demonstrating the old lacunar infarct in the left basal ganglia (blue arrows). High signal intensity is present throughout the left MCA distribution due to the acute infarct.

Figure 3. B. The axial diffusion weighted image (DWI) demonstrates high signal intensity due to restricted diffusion in the left MCA distribution.

Figure 3. C. Axial apparent diffusion coefficient (ADC) map demonstrates the left MCA infarct with low signal, confirming this is an acute infarct rather than "T2 shine through".

Discussion:

The hyperdense artery sign (HAS) has a 90-100% specificity (1-5) for acute infarct and was first reported in 1983(6). Other causes of HAS include high hematocrit(5), viral infection(3), dissection(7), and retained contrast (4). However, sensitivity is only 30%. In order to have objective criteria for HAS, Koo et al (3) set a ratio of 1.2 when compared to the non-affected contralateral vessel or an absolute value of > 43 HU. In patients with the hyperdense artery sign, the outcome is often poor with a large infarct and significant neurological deficit. This is likely due to the high volume of thrombus required to produce the high attenuation within the artery.

References:

1. Unnikrishnan D, Yada S, Gilson N A case of large right MCA stroke with hyperdense MCA sign in CT imaging Case Reports 2017;2017:bcr-2017-222529. http://dx.doi.org/10.1136/bcr-2017-222529

2. Abd Elkhalek YI, Elia RZ. Qualitative and quantitative value of hyperdense MCA sign as a prognostic marker for infarction. The Egyptian Journal of Radiology and Nuclear Medicine (2016)47, 1043-1048. https://doi.org/10.1016/j.ejrnm.2016.06.005

3. Koo CK, Teasdale E, Muir KW. What constitutes a true hyperdense middle cerebral artery sign? Cerebrovasc Dis. 2000 Nov-Dec;10(6):419-23. https://doi.org/10.1159/000016101

4. Jensen-kondering U, Riedel C, Jansen O. Hyperdense artery sign on computed tomography in acute ischemic stroke. World J Radiol. 2010;2 (9): 354-7.

5. Rauch RA, Bazan C 3rd, Larsson EM, Jinkins JR. Hyperdense middle cerebral arteries identified on CT as a false sign of vascular occlusion. AJNR Am J Neuroradiol. 1993;14:669–673. https://www.ncbi.nlm.nih.gov/pubmed/8517357

6. Gács G, Fox AJ, Barnett HJ, Vinuela F. CT visualization of intracranial arterial thromboembolism. Stroke.1983;14:756–762.

7. Yakushiji Y, Haraguchi Y, Soejima S, Takase Y, Uchino A, Koizumi S, Kuroda Y. A hyperdense artery sign and middle cerebral artery dissection. Intern Med. 2006;45:1319–1322. https://www.ncbi.nlm.nih.gov/pubmed/17170508

Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice serves as the Chair of the Radiology Department of Valley Presbyterian Hospital in Los Angeles, California and is a radiologist with Renaissance Imaging Medical Associates. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015 Dr. Rice along with Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field.

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