Objective: We report a case of familial Gerstmann-Straussler-Scheinker (GSS) disease, who presented with cerebellar ataxia, but did not show abnormalities in diffusion weighted image (DWI) or fluid attenuated inversion recovery (FLAIR) image. Systematic review was performed to find the characteristics of GSS with normal brain image.

Background: GSS is an autosomal dominant neurodegenerative disease, resulting in transmissible spongiform encephalopathy. Typical feature of GSS with P102L mutation is progressive cerebellar ataxia at younger onset followed by cognitive decline. Major findings of brain image include high signal intensities in DWI or FLAIR image.

Method: Case report. Literature search was conducted in PubMed using free terms and controlled vocabulary (MeSH).

Results: A 34-year-old male presented with gait disturbance, dysarthria and dysphagia for two years. Seven family members including his father had history of ataxia in their 30s and 40s. Neurological examination showed abnormal finger-to-nose, heel-to-shin test, and tandem gait, suggesting cerebellar ataxia. SARA score was 17. He scored 30 on the Mini-Mental State Examination. DWI and FLAIR performed 2 years from onset did not reveal abnormalities. Gene tests for spinocerebellar ataxia 1,2,3,6,7,8,17 were negative.
The father of the patient had gait disturbance and dementia for a year at the age of 58. High signal intensities in fronto-temporo-parietal cortex were found in DWI and FLAIR, as found in prion disease. Blood test for PRNP polymorphism showed P102L mutation, which is related to GSS. Identical mutation was found in his son.
We found 36 case series during systematic review. Twenty-seven out of 64 patients (42.2%) did not show high signal intensities in DWI or FLAIR, while 13 out of 64 patients (20.3%) showed abnormalities. The mean time from symptom onset to image was not significantly different between patients with high signal intensities than patients without those (28.8 vs 35.3 months, p=0.63).

Conclusion: GSS should be considered in the differential diagnosis for familial autosomal dominant cerebellar ataxia, regardless of the presence of the high signal intensities in DWI or FLAIR.

References: 1. Webb TE, Poulter M, Beck J, et al. Phenotypic heterogeneity and genetic modification
of P102L inherited prion disease in an international series. Brain 2008;131: 2632–2646.
2. Hsiao K, Baker HF, Crow TJ, et al. Linkage of a prion protein missense variant to Gerstmann-Sträussler syndrome. Nature. 1989;338(6213):342-345. doi:10.1038/338342a0 Kang MJ, Suh J, An SS, Kim S, Park YH. Pearls & Oy-sters: Challenging diagnosis of Gerstmann-Sträussler-Scheinker disease: Clinical and imaging findings. Neurology. 2019;92(2):101-103. doi:10.1212/WNL.0000000000006730
3. Kang MJ, Suh J, An SS, Kim S, Park YH. Pearls & Oy-sters: Challenging diagnosis of Gerstmann-Sträussler-Scheinker disease: Clinical and imaging findings. Neurology. 2019;92(2):101-103. doi:10.1212/WNL.0000000000006730

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MDS Abstracts - https://www.mdsabstracts.org/abstract/challenging-diagnosis-of-familial-gerstmann-straussler-scheinker-disease-with-normal-brain-image-a-case-report-and-systematic-review/