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The split apparent diffusion coefficient sign: A novel magnetic resonance imaging biomarker for cortical pathology
Riccardo Ludovichetti1, Nathalie Nierobisch1, Ngwe Rawlings Achangwa1
1Department of Neuroradiology, Clinical Neuroscience Center, University Hospital Zurich, University of Zurich, Switzerland.
Introduction:
MRI is the imaging modality of choice for assessing patients with encephalopathy. In this context, we discuss a novel biomarker, the "split ADC sign," where the cerebral cortex demonstrates restricted diffusion (high DWI signal and low ADC) and the underlying white matter demonstrates facilitated diffusion (high or low DWI signal and high ADC). We hypothesize that this sign can be used as a biomarker to suggest either acute encephalitis onset or to raise the possibility of an autoimmune etiology.
Materials And Methods:
A full-text radiological information system search of radiological reports was performed for all entities known to produce restricted diffusion in the cortex excluding stroke between January 2012 and June 2022. Initial MRI studies performed upon onset of clinical symptoms were screened for the split ADC sign.
Results:
25 subjects were encountered with a positive split ADC sign (15 female; median age = 57 years, range 18-82). Diagnosis included six herpes simplex encephalitis, three peri-ictal MRI changes, eight PRES, two MELAS, and six autoimmune (3 anti-GABAAR, two seronegative, and one anti-Ma2/Ta). Subjects were imaged at a mean 1.8 days after the onset of symptoms (range 0-8).
Discussion:
We present a novel visual MRI biomarker, the split ADC sign, and highlight its potential usefulness in subjects with encephalopathy to suggest acute disease onset or to raise the possibility of an autoimmune etiology when location-based criteria are applied. When positive, the sign was present on the initial MRI and can therefore be used to help focus further clinical and laboratory workup.
Insights
A novel MRI biomarker, the "split ADC sign," shows restricted diffusion in the cerebral cortex and facilitated diffusion in white matter. This sign aids in identifying acute encephalitis and autoimmune conditions in encephalopathy patients.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Magnetic Resonance Imaging (MRI) is crucial for diagnosing encephalopathy.
- The
- split ADC sign
- is a novel diffusion-weighted imaging biomarker.
- This sign involves restricted diffusion in the cerebral cortex and facilitated diffusion in white matter.
Purpose of the Study:
- To introduce and validate the
- split ADC sign
- as a potential biomarker.
- To assess its utility in suggesting acute encephalitis or autoimmune etiology.
- To evaluate its presence on initial MRI scans for early diagnosis.
Main Methods:
- Retrospective analysis of radiological reports from January 2012 to June 2022.
- Screening of initial MRI studies for the
- split ADC sign
- in patients with encephalopathy (excluding stroke).
- Identification of 25 subjects with the positive sign.
Main Results:
- The
- split ADC sign
- was identified in 25 subjects (median age 57).
- Diagnoses included herpes simplex encephalitis, PRES, MELAS, and autoimmune conditions.
- The sign was present on average 1.8 days after symptom onset.
Conclusions:
- The
- split ADC sign
- is a novel visual MRI biomarker for encephalopathy.
- It aids in suggesting acute disease onset and identifying autoimmune etiologies.
- Its presence on initial MRI can guide further clinical and laboratory investigations.
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