MRI Evaluation of Stroke: Does Contrast Imaging of the Brain Add Diagnostic Value? Michael Lanfranchi, MD 1, Neel Madan, MD 2, Sirishma Kalli, MD 2, William A Mehan, MD, MBA 2 Departments of Radiology 1 Massachusetts General Hospital 2 Tufts Medical Center

Disclosures The authors have no relevant financial disclosures

Background Diffusion MR imaging has vastly improved our ability to detect acute ischemia 1 Leptomeningeal and intravascular enhancement are two patterns of contrast enhancement observed during the acute stage of ischemic infarction 2 Parenchymal pattern of enhancement can help estimate the age of an infarct 3 1 Beaulieu C, et.al. Ann Neurol Elster AD, et.al. Radiology Karonen JO, et.al. AJNR.2001

Background Gadolinum-enhanced MRI of the brain may also be included to evaluate for stroke mimics, increase diagnostic certainty, and to maximize the diagnostic potential of the study (i.e. utilize gadolinium administered for neck MRA) The yield is not clearly defined in the acute setting, and may contribute to prolonged scan times and decreased interpretation efficiency

Hypothesis Conventional-sequences (including DWI) without gadolinium would be sufficient for identifying significant abnormalities and contrast-enhanced sequences would not provide additional diagnostic value

Methods We reviewed the reports of 250 consecutive patients with gadolinium-enhanced MRIs of the brain at Tufts Medical Center for suspected acute stroke from March 2011 to May 2012 Presence or absence of parenchymal, meningeal, vascular, and extra-cranial enhancement on the contrast-enhanced T1-weighted sequence was recorded

Methods Two-independent, blinded neuroradiologists interpreted only the non-contrast sequences randomly on a subgroup comprised of 62 of these patients ( 11 with abnormal enhancement) Intracranial and incidental extra-cranial abnormalities were documented and statistical analysis was performed to assess the accuracy of the non-contrast sequences for detecting the enhancing abnormalities

Results Demographics of the Study Population Number of Patients250 Age20-90 (median 63) Females119 Males131

Results Distribution- Patterns of Enhancement on Post-gadolinium T1-weighted Sequences Number of Patients with Abnormal Enhancement 16/250 (6%) Gyriform Parenchymal Enhancement Pattern due to Subacute Infarction 4/16 (25%) Vascular Enhancement Related to Acute Infarction or Developmental Venous Anomalies/Capillary Telangiectasia 5/16 (31%) Intracranial Mass Lesions1/16 (6%) Meningeal Enhancement1/16 (6%) Extra-cranial lesions *5/16 (31%) * Of the 5 extra-cranial lesions, 1 nasopharyngeal carcinoma, 3 calvarial lesions (presumed intraosseous hemangiomas in patients without oncologic histories), and one scalp lesion were identified

Results Blinded Neuroradiolgists Performance for Detection of Abnormality on Convention-Sequences Without Gadolinium (excluding 1 DVA) Combined Sensitivity94% Combined Specificity96% Combined Positive Predictive Value79% Combined Negative Predictive Value99% Inter-observer Agreement (kappa)0.88

Case Examples

Case 1 AB C D 70 year-old male presenting to the ED with new onset left hand weakness. Axial DWI (A) and ADC map (B) images show an area of diminished diffusion in the right precentral gyrus with associated FLAIR hyperintensity (C) and gyiform enhancement (D), consistent with subacute infarction. A chronic infarction is also evident in the right middle frontal gyrus. Both blinded neuroradiologists correctly characterized the subacute and chronic infarctions using the unenhanced sequences only.

B Case 2 72 year-old male presenting to the ED with acute neurologic deficit. A mass in the right fossa of Rosenmuller showing mild T2 hyperintensity (A) relative to muscle and avid enhancement (B) was incidentally discovered and subsequently found to represent a nasopharyngeal carcinoma. Both blinded neuroradiologists correctly identified the lesion on the unenhanced sequences. A

Case 3 64 year-old female presenting to the ED with headache, fevers, and neurologic deficits. Sulcal FLAIR hyperintensity (C) with corresponding abnormal leptomeningeal enhancement (D) is evident, most pronounced in the left parietal lobe. No diminished diffusion is identified to indicate acute infarction. She was subsequently found to have a pyogenic meningitis. Based upon the sulcal FLAIR signal abnormalities, both blinded neuroradiologists raised the possibility of meningitis.

Conclusion A small proportion of suspected acute stroke patients have abnormal enhancement The majority of the enhancing lesions may be clinically insignificant or are detectable on conventional, unenhanced sequences Contrast-enhanced sequences may not add additional diagnostic value for routine stroke evaluation

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