Objective: The aim of this study is to map the brain functional network alterations by estimating functional connectivity of brain structures in spinocerebellar ataxia type 2.

Background: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant and progressive neuro degenerative disorder.  it’s associated with the repetition of CAG trinucleotide of ATXN2 gene and characterized the atrophy of the cerebellum, gait ataxia, tremors and cognition dysfunctions.

Resting-state functional magnetic resonance imaging (rsfMRI) can reveal brain functional network alterations and may be associated with structural abnormalities of brain structures ^1-3. Atrophy and alterations in the rsfMRI connectivity suggest deficits in motor and cognition in SCA2 patients^5-7.

Method: Symptomatic and genetically confirmed 25 SCA2 patients (M/F:16/9, mean age 35.60±14.67 years) and healthy controls (HC, M/F:12/13, mean age 36.04±7.16 years) were recruited after institutional ethical clearance. All SCA patients were assessed with International Cooperative Ataxia Rating Scale (ICARS).

MR data was acquired on a 3T MR scanner (Ingenia 3.0 T, M/s. Philips Healthcare, The Netherlands) using 32-channel head coil. Tl weighted 3D Turbo Field Echo (TFE) sequence was used (TR/TE: 8.1 /3.7 ms; flip angle:8°; FOV-240*240; Slices -360 with no gap) and Resting state fMRI (rs-fMRI) data (220 dynamics, 35 contiguous axial slices, TR=2000 ms; TE= 40 ms). Resting-state fMRI was analyzed using “CONN connectivity toolbox, Version 22.a”, using default parameters⁴. Inter-group analyses were performed using T-test between the SCA2-HC with Holm-Bonferroni correction (p-FWE corrected value < 0.05 considered as significant).

Results: SCA2 patients exhibited reduced functional connectivity (FC) in bilateral Dorsal Attention network (FC network 21 and 22), left side fronto-parietal, LPFC network (FC network 23) and fronto-parietal-PPC network (FC network 24) with cerebellar-anterior network (FC network 31) and cerebellar-posterior network (FC network 32) in SCA2, in ROI to ROI rsfMRI analysis with respect to healthy controls. Atrophy and alterations in the connectivity suggest deficits in motor and cognition in SCA2 patients.

Conclusion: The decreased functional connectivity of attention and executive networks in SCA2 patients is associated with atrophy of the cerebellum and attributed to the motor and cognitive dysfunctions.

References: 1. Cocozza S, Saccà F, Cervo A, et al. Modifications of resting state networks in spinocerebellar ataxia type 2. Movement Disorders. 2015, 30:1382-90.
2. Olivito G, Cercignani M, Lupo M, et al. Neural substrates of motor and cognitive dysfunctions in SCA2 patients: a network-based statistics analysis. NeuroImage: Clinical. 2017;14:719-25.
3. Giocondo F, Curcio G. Spinocerebellar ataxia: a critical review of cognitive and socio-cognitive deficits. International Journal of Neuroscience. 2018;128:182-91.
4. Whitfield-Gabrieli S, Nieto-Castanon A. Conn: a functional connectivity toolbox for correlated and anticorrelated brain networks. Brain connectivity. 2012;2:125-41.
5. Olivito G, Lupo M, Iacobacci C, et al. Microstructural MRI basis of the cognitive functions in patients with spinocerebellar ataxia type 2. Neuroscience. 2017;366:44-53.
6. Reetz K, Rodríguez‐Labrada R, Dogan I, et al. Brain atrophy measures in preclinical and manifest spinocerebellar ataxia type 2. Annals of Clinical and Translational Neurology. 2018;5:128-37.
7. Olivito G, Lupo M, Iacobacci C, et al. Structural cerebellar correlates of cognitive functions in spinocerebellar ataxia type 2. Journal of neurology. 2018;265:597-606.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/brain-functional-state-mapping-in-resting-state-and-network-alteration-in-spinocerebellar-ataxia-type-2-in-comparison-with-healthy-controls/