Inhibitory motor dysfunction in parkinson's disease subtypes

Background: Parkinson's disease (PD) is divided into postural instability gait difficulty (PIGD) and tremor-dominant (TD) subtypes. Increasing evidence has suggested that the GABAergic neurotransmitter system is involved in the pathogenesis of PD.

Purpose: To evaluate the differences of GABA levels between PD motor subtypes using MEscher-GArwood Point Resolved Spectroscopy (MEGA-PRESS).

Study type: COHORT.: SUBJECTS: PD patients were classified into PIGD (n = 13) and TD groups (n = 9); 16 age- and sex-matched healthy controls were also recruited. All subjects were right-handed.

Sequence: All subjects underwent an magnetic resonance spectroscopy scan including MEGA-PRESS at 3.0T.

Assessment: The detected GABA signal also contains signal from macromolecules (MM) and homocarnosine, so it is referred to as GABA+. GABA + levels and Creatine (Cr) levels were quantified in the left basal ganglia (BG) using Gannet 2.0 by Tao Gong.

Statistical tests: Differences in GABA + levels between the three groups were analyzed using analysis of covariance. The relationship between GABA levels and a unified PD rating scale (UPDRS) was also analyzed.

Results: GABA + levels were significantly lower in left BG regions of PD patients compared with healthy controls (P < 0.001). In PD patients, the GABA concentration was lower in the TD group than the PIGD group (P = 0.019). Cr levels in PIGD and TD were lower than controls (P = 0.020; P = 0.002). A significant negative correlation was found in PIGD between GABA levels and UPDRS (r = -0.572, P = 0.041), while no correlation was found in TD (r = -0.339, P = 0.372).

Data conclusion: Low BG GABA levels in PD patients, and differences between PIGD/TD patients, suggest that GABAergic dysfunction may play an important role in the pathogenesis of Parkinson's disease.

Level of evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1610-1615.