PT  - JOURNAL ARTICLE
AU  - Adra, N.
AU  - Goodheart, A.E.
AU  - Rapalino, O.
AU  - Caruso, P.
AU  - Mukerji, S.S.
AU  - González, R.G.
AU  - Venna, N.
AU  - Schmahmann, J.D.
TI  - MRI Shrimp Sign in Cerebellar Progressive Multifocal Leukoencephalopathy: Description and Validation of a Novel Observation
AID  - 10.3174/ajnr.A7145
DP  - 2021 Jun 01
TA  - American Journal of Neuroradiology
PG  - 1073--1079
VI  - 42
IP  - 6
4099  - http://www.ajnr.org/content/42/6/1073.short
4100  - http://www.ajnr.org/content/42/6/1073.full
SO  - Am. J. Neuroradiol.2021 Jun 01; 42
AB  - 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.JCVJC polyomavirusMSmultiple sclerosisNPVnegative predictive valuePMLprogressive multifocal leukoencephalopathyPPVpositive predictive valuePRESposterior reversible encephalopathy syndrome