MRI Shrimp Sign in Cerebellar Progressive Multifocal Leukoencephalopathy: Description and Validation of a Novel
N Adra1,2,3, A E Goodheart1,2, O Rapalino4
1From the Department of Neurology (N.A., A.E.G., S.S.M., N.V., J.D.S.).
Background And Purpose:
There are no validated imaging criteria for the diagnosis of progressive multifocal leukoencephalopathy in the cerebellum. Here we introduce the MR imaging shrimp sign, a cerebellar white matter lesion identifiable in patients with cerebellar progressive multifocal leukoencephalopathy, and we evaluate its sensitivity and specificity.
Materials And Methods:
We first identified patients with progressive multifocal leukoencephalopathy seen at Massachusetts General Hospital between 1998 and 2019 whose radiology reports included the term "cerebellum." Drawing on a priori knowledge, 2 investigators developed preliminary diagnostic criteria for the shrimp sign. These criteria were revised and validated in 2 successive stages by 4 additional blinded investigators. After defining the MR imaging shrimp sign, we assessed its sensitivity, specificity, positive predictive value, and negative predictive value.
Results:
We identified 20 patients with cerebellar progressive multifocal leukoencephalopathy: 16 with definite progressive multifocal leukoencephalopathy (mean, 46.4 [SD, 9.2] years of age; 5 women), and 4 with possible progressive multifocal leukoencephalopathy (mean, 45.8 [SD, 8.5] years of age; 1 woman). We studied 40 disease controls (mean, 43.6 [SD, 21.0] years of age; 16 women) with conditions known to affect the cerebellar white matter. We defined the MR imaging shrimp sign as a T2- and FLAIR-hyperintense, T1-hypointense, discrete cerebellar white matter lesion abutting-but-sparing the dentate nucleus. MR imaging shrimp sign sensitivity was 0.85; specificity, 1; positive predictive value, 1; and negative predictive value, 0.93. The shrimp sign was also seen in fragile X-associated tremor ataxia syndrome, but radiographic and clinical features distinguished it from progressive multifocal leukoencephalopathy.
Conclusions:
In the right clinical context, the MR imaging shrimp sign has excellent sensitivity and specificity for cerebellar progressive multifocal leukoencephalopathy, providing a new radiologic marker of the disease.
Insights
A new MR imaging finding, the "shrimp sign," aids in diagnosing cerebellar progressive multifocal leukoencephalopathy (PML). This cerebellar white matter lesion shows high sensitivity and specificity, offering a valuable new radiologic marker for PML.
Area of Science:
- Neurology
- Radiology
- Infectious Diseases
Background:
- Progressive multifocal leukoencephalopathy (PML) diagnosis lacks validated cerebellar imaging criteria.
- Cerebellar involvement in PML presents diagnostic challenges.
- Novel imaging markers are needed for accurate PML detection in the cerebellum.
Purpose of the Study:
- Introduce the "MR imaging shrimp sign" for cerebellar white matter lesions.
- Evaluate the sensitivity and specificity of the shrimp sign in diagnosing cerebellar PML.
- Establish a new radiologic marker for progressive multifocal leukoencephalopathy.
Main Methods:
- Retrospective identification of patients with cerebellar PML (1998-2019).
- Development and validation of diagnostic criteria for the shrimp sign by multiple investigators.
- Assessment of sensitivity, specificity, and predictive values against disease controls.
Main Results:
- The MR imaging shrimp sign is a T2/FLAIR-hyperintense, T1-hypointense lesion near the dentate nucleus.
- Sensitivity was 0.85, specificity 1, positive predictive value 1, and negative predictive value 0.93 for cerebellar PML.
- The sign was observed in fragile X-associated tremor ataxia syndrome, distinguishable from PML.
Conclusions:
- The MR imaging shrimp sign demonstrates high accuracy for diagnosing cerebellar PML.
- This sign serves as a significant new radiologic marker for progressive multifocal leukoencephalopathy.
- Clinical context is crucial for interpreting the shrimp sign and differentiating from other conditions.
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