Involvement of the nigrostriatal system in Gerstman–Sträussler–Scheinker disease with the PRNP-P102L mutation

Introduction

Gerstmann–Sträussler–Scheinker disease (GSS) is an autosomal-dominant inherited prion disease most often associated with the human prion protein gene (PRNP)-P102L mutation. Although patients manifest considerable phenotypic heterogeneity, the involvement of the nigrostriatal system has not been well-studied.

Methods

We performed dopamine transporter single-photon emission computed tomography (DAT-SPECT) using ¹²³I-ioflupane to investigate the nigrostriatal system function in nine patients with the PRNP-P102L mutation. We also examined the pathological findings in another patient whose predominant feature was ataxia and who died 5 years after disease onset.

Results

Striatum uptake of ¹²³I-ioflupane indicated by specific binding ratio (SBR) values was significantly reduced in two patients. The DAT-SPECT examination was performed 6 months after disease onset in one of these patients who manifested rapidly developing cognitive decline mimicking Creutzfeldt–Jakob disease. DAT-SPECT was also performed 9 years after disease onset in another patient who manifested the conventional features of GSS involving ataxia and dementia in the initial phase but showed akinetic mutism at the examination time. Another patient examined 2 years after disease onset who predominantly manifested ataxia showed marginally abnormal SBR values. An autopsy case showed moderate neuronal loss in the substantia nigra, and the degree of neuronal loss was similar in most other parts of the brain.

Conclusion

Nigrostriatal system involvement may occur in patients with GSS associated with the PRNP-P102L mutation, even though parkinsonism is not the predominant feature.