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The Uniform Cortex Sign: A Diagnostic Sign of Diffuse Cortical Injury at MR Imaging of the Brain Presentation #: EP-79 Authors: Apurva Patel, Basem Bahakeem, Andrew Leung

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No disclosures

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Background Identification of the central sulcus on MR imaging is important for accurate anatomic localization of motor and sensory cortices, especially in patients undergoing surgical treatment Several topographic features can be utilized on CT and MR imaging to localize the central sulcus One such feature is thin cortex sign (TCS), described as the greatest difference in cortical thickness between gyri banking a single sulcus which is found along the central sulcus

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Purpose The TCS has been described in earlier studies using T1 and T2 weighted sequences in normal patients and in patients with neoplasms who can have marked distortion of normal anatomy We propose that the TCS is lost in cases of diffuse cortical injury which results in the novel uniform cortex sign (UCS) We also investigate the utility of axial T2, DWI and FLAIR; sagittal FLAIR; and coronal FLAIR sequences in qualitatively identifying the TCS

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Materials and Methods From July 2014 to November 2014: The UCS group was formed from patients with diffuse cortical abnormality on MRI The TCS control group was formed from asymptomatic patients undergoing MR examination for aneurysm screening 9 patients with TCS and 8 patients with UCS were obtained

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Materials and Methods Radiologist training Using selected MR images from two control (TCS) and one UCS subject, three fellowship trained Neuroradiologists were given a tutorial on the TCS and UCS Two Ax T2, two Ax DWI, two Ax FLAIR, one Sag FLAIR and seven contiguous Cor FLAIR images were shown for all three tutorial patients The remaining seven control and seven UCS subjects were used to determine the utility of the UCS in identifying patients with diffuse cortical injury Each reader was given selected deidentified images (same as above) from the database of 14 patients in random order Each reader was asked to identify and mark the TCS on each image if present If readers felt that the TCS was absent, they were asked to say that a UCS was present

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TCS Tutorial Case Cor FLAIR Axial FLAIR Axial DWI Axial T2 Can you identify the TCS?

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TCS Tutorial Case Cor FLAIR Axial FLAIR Axial DWI Axial T2 Cortical thickness along anterior and posterior banks of the central sulcus is less than that of adjacent sulci Furthermore, the cortical thickness of the posterior bank is less than that of the anterior bank Generalized cortical thinning is qualitatively observed on coronal FLAIR imaging as the pre- and postcentral cortices travel obliquely through the coronal plane

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UCS Tutorial Case Axial FLAIR Cor FLAIR Axial DWI Sag FLAIR

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UCS Tutorial Case Axial FLAIR Cor FLAIR Axial DWI Sag FLAIR There is loss of the normal thin cortex banking the central sulcus All cortices appear uniform in thickness, giving rise to the UCS (Each red oval marks the region of the central sulcus which was identified using other anatomic landmarks in the absence of TCS)

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Results TCS correctly identified PatientAgeGenderIndication for exam Reader 1Reader 2 Reader 3 TCS 129FFHxA. Rule out aneurysm YY Y TCS 246FFHxA. Rule out aneurysm YY Y TCS 355FFHxA. Rule out aneurysm YY Y TCS 456MFHxA. Rule out aneurysm YY Y TCS 526FFHxA. Rule out aneurysm YY Y TCS 652MFHxA. Rule out aneurysm YY Y TCS 713MFHxA. Rule out aneurysm YY Y UCS correctly identified PatientAgeGenderIndication for examReader 1 Reader 2Reader 3 UCS 112FHIE due to hangingY YY UCS 216MViral encephalitisN NN UCS 355FHIE due to cardiac arrestY YY UCS 475MHIE due to cardiac arrestY NY UCS 514FHIE due to hangingY YY UCS 649FHIE due to cardiac arrestY YY UCS 718MTCA overdoseY YY TCS correctly identified in all 7 control cases by all three readers UCS correctly identified in 5/7 cases by all readers UCS2 All readers thought a TCS was present UCS4 Reader 2 thought a TCS was present HIE, hypoxiemic ischemic injury; FHxA, family history of intracranial aneurysms; TCA, tricyclic antidepressants

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Results TCS Patients Axial T2 TCS1 TCS4 TCS2 TCS3 TCS6 TCS5 TCS7

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Results UCS Patients Axial T2 UCS1 UCS4UCS3UCS2 UCS5UCS6 UCS7

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Results UCS and Severity of Cortical Injury Axial T2 images of patients with mild, moderate and severe cortical injury demonstrate that the UCS is more conspicuous in cases of severe injury UCS2 UCS4 UCS7 Mild Moderate Severe

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Results Follow-up exam of Patient UCS 2 All three readers failed to correctly identify the UCS in Patient UCS 2 who presented with mild diffuse cortical injury in the setting of viral encephalitis Comparison of the initial MR to the post-treatment MR confirms that the UCS was indeed present on the initial exam which is no longer evident on the post-treatment exam Initial Exam Post-treatment Exam

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Results SequenceReader 1Reader 2Reader 3Average Axial DWI89% (25/28)100% (28/28) 96% Axial T2100% (28/28) 100% Axial FLAIR100% (24/24)92% (22/24)100% (24/24)97% Sagittal FLAIR100% (7/7) 100% Coronal FLAIR100% (7/7) 100% The TCS was correctly identified by all 3 readers on all the axial T2, sagittal FLAIR and coronal FLAIR images Axial DWI TCS correctly identified 81/84 times (96%) Axial FLAIR TCS correctly identified 70/72 times (97%)

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Conclusion We confirm that the TCS can be used as a tool to identify the central sulcus in normal patients The UCS is a reliable indicator of diffuse cortical injury The extent of cortical swelling is variable depending on the severity of cortical injury The sensitivity of UCS may be lower in the setting of mild diffuse cortical injury

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References Biega TJ, Lonser RR, Butman JA. Differential cortical thickness across the central sulcus: A method for identifying the central sulcus in the presence of mass effect and vasogenic edema. AJNR 2006;27:1450-1453 Togao O, Yoshiura T, Mihara F, et al. Cortical thickness difference across the central sulcus visualized in the presence of vasogenic edema. EJR 2008:66;274- 281 Meyer JR, Sudipta R, Russell EJ, et al. Localization of the central sulcus via cortical thickness of the precentral and postcentral gyri on MRI. AJNR 1996:17;1699-1706 Wagner M, Jurcoane M, Hattingen E. The U sign: Tenth landmark to the central region on brain surface reformatted MR imaging. AJNR 2013:34;323-326