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

2. No disclosures

3. 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

4. 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

5. 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

6. 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

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

8. TCS Tutorial Case Axial T2 Axial FLAIR Axial DWI
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
Cor FLAIR

9. UCS Tutorial Case
Sag FLAIR
Axial FLAIR
Axial DWI
Cor FLAIR

10. UCS Tutorial Case
Sag FLAIR
Axial FLAIR
Axial DWI
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)
Cor FLAIR

11. Results
TCS correctly identified
Patient
Age
Gender
Indication for exam
Reader 1
Reader 2
Reader 3
TCS 1 29 F
FHxA. Rule out aneurysm Y
TCS 2 46
TCS 3 55
TCS 4 56 M
TCS 5 26
TCS 6 52
TCS 7 13
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
UCS correctly identified
Patient
Age
Gender
Indication for exam
Reader 1
Reader 2
Reader 3
UCS 1 12 F
HIE due to hanging Y
UCS 2 16 M
Viral encephalitis N
UCS 3 55
HIE due to cardiac arrest
UCS 4 75
UCS 5 14
UCS 6 49
UCS 7 18
TCA overdose
HIE, hypoxiemic ischemic injury; FHxA, family history of intracranial aneurysms; TCA, tricyclic antidepressants

12. Results – TCS Patients – Axial T2

13. Results – UCS Patients – Axial T2

14. 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
Mild
Moderate
Severe
UCS2
UCS4
UCS7

15. 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

16. Results
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%)
Sequence
Reader 1
Reader 2
Reader 3
Average
Axial DWI
89% (25/28)
100% (28/28)
96%
Axial T2
100%
Axial FLAIR
100% (24/24)
92% (22/24)
97%
Sagittal FLAIR
100% (7/7)
Coronal FLAIR

17. 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

18. 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:
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;
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;
Wagner M, Jurcoane M, Hattingen E. The U sign: Tenth landmark to the central region on brain surface reformatted MR imaging. AJNR 2013:34;