Transcranial sonography and functional imaging in glucocerebrosidase mutation Parkinson disease

Background: Heterozygous glucocerebrosidase (GBA) mutations are the leading genetic risk factor for Parkinson disease, yet imaging correlates, particularly transcranial sonography, have not been extensively described. Methods: To determine whether GBA mutation heterozygotes with Parkinson disease demonstrate hyperechogenicity of the substantia nigra, transcranial sonography was performed in Ashkenazi Jewish Parkinson disease subjects, tested for the eight most common Gaucher disease mutations and the LRRK2 G2019S mutation, and in controls. [¹⁸F]-fluorodeoxyglucose or [¹⁸F]-fluorodopa positron emission tomography is also reported from a subset of Parkinson disease subjects with heterozygous GBA mutations. Results: Parkinson disease subjects with heterozygous GBA mutations (n = 23) had a greater median maximal area of substantia nigral echogenicity compared to controls (n = 34, aSNmax = 0.30 vs. 0.18, p = 0.007). There was no difference in median maximal area of nigral echogenicity between Parkinson disease groups defined by GBA and LRRK2 genotype: GBA heterozygotes; GBA homozygotes/compound heterozygotes (n = 4, aSNmax = 0.27); subjects without LRRK2 or GBA mutations (n = 32, aSNmax = 0.27); LRRK2 heterozygotes/homozygotes without GBA mutations (n = 27, aSNmax = 0.28); and GBA heterozygotes/LRRK2 heterozygotes (n = 4, aSNmax = 0.32, overall p = 0.63). In secondary analyses among Parkinson disease subjects with GBA mutations, maximal area of nigral echogenicity did not differ based on GBA mutation severity or mutation number. [¹⁸F]-fluorodeoxyglucose (n = 3) and [¹⁸F]-fluorodopa (n = 2) positron emission tomography in Parkinson disease subjects with heterozygous GBA mutations was consistent with findings in idiopathic Parkinson disease. Conclusions: Both transcranial sonography and positron emission tomography are abnormal in GBA mutation associated Parkinson disease, similar to other Parkinson disease subjects.