Abstract
BackgroundSpinocerebellar ataxia type 31 (SCA31) is caused by non-coding pentanucleotide repeat expansions in the BEAN1 gene. Clinically, SCA31 is characterized by late adult-onset, pure cerebellar ataxia. To explore the association between parkinsonism and SCA31, five patients with SCA31 with concomitant nigrostriatal dopaminergic dysfunction (NSDD) development, including three cases of L-DOPA responsive parkinsonism, were analyzed.MethodsTo assess regional brain atrophy, cross-sectional and longitudinal imaging analyses were retrospectively performed using magnetic resonance imaging (MRI) planimetry. The midbrain-to-pons (M/P) area ratio and cerebellar area were measured on midsagittal T1-weighted MRI in five patients with SCA31 with concomitant NSDD (NSDD(+)), 14 patients with SCA31 without NSDD (NSDD(−)), 32 patients with Parkinson’s disease (PD), and 15 patients with progressive supranuclear palsy (PSP). Longitudinal changes in the M/P area ratio were assessed by serial MRI of NSDD(+) (n = 5) and NSDD(−) (n = 9).ResultsThe clinical characteristics assessed in the five patients with NSDD were as follows: the mean age at NSDD onset (72.0 ± 10.8 years), prominence of bradykinesia/akinesia (5/5), rigidity (4/5), tremor (2/5), dysautonomia (0/5), vertical gaze limitation (1/5), and abnormalities on 123I-ioflupane dopamine transporter scintigraphy (3/3) and 3-Tesla neuromelanin MRI (4/4). A clear reduction in the midbrain area and the M/P area ratio was observed in the NSDD(+) group (p < 0.05) while there was no significant difference in disease duration or in the pons area among the NSDD(+), NSDD(−), and PD groups. There was also a significant difference in the midbrain and pons area between NSDD(+) and PSP (p < 0.05). Thus, mild but significant midbrain atrophy was observed in NSDD(+). A faster rate of decline in the midbrain area and the M/P area ratio was evident in NSDD(+) (p < 0.05).ConclusionThe clinical characteristics of the five patients with SCA31 with concomitant NSDD, together with the topographical pattern of atrophy, were inconsistent with PD, PSP, and multiple system atrophy, suggesting that SCA31 may manifest NSDD in association with the pathomechanisms underlying SCA31.
Highlights
Spinocerebellar ataxia type 31 (SCA31) is an inherited neurodegenerative disorder characterized by slowly progressive, late adult-onset, pure cerebellar ataxia [1, 2]
Clinical characteristics of patients with SCA31 complicated with nigrostriatal dopaminergic dysfunction (NSDD) Of the 20 genetically confirmed cases of SCA31, NSDD developed in five patients, including four presenting with rigidity and bradykinesia/akinesia and one presenting with bradykinesia/akinesia with an abnormal dopamine transporter (DAT) scintigraphy finding
According to the presence or absence of NSDD, the patients with SCA31 were divided into two groups (NSDD(+): SCA31 with NSDD, n = 5, NSDD(−): SCA31 without NSDD, n = 14)
Summary
Spinocerebellar ataxia type 31 (SCA31) is an inherited neurodegenerative disorder characterized by slowly progressive, late adult-onset, pure cerebellar ataxia [1, 2]. A few cases of SCA31 presenting with extracerebellar signs, including parkinsonism, postural tremor, dystonia, and spastic paraparesis, have been reported [4,5,6]. In Japan, genetic testing for SCA31 is usually performed in patients with pure cerebellar ataxia but yields a bias against extracerebellar manifestations of SCA31. A few patients with SCA31 have undergone neuropathological assessment, and there are no reports of autopsy cases of SCA31 presenting with extracerebellar signs except two cases in which dementia developed at the terminal stage [7, 8]. Spinocerebellar ataxia type 31 (SCA31) is caused by non-coding pentanucleotide repeat expansions in the BEAN1 gene. SCA31 is characterized by late adult-onset, pure cerebellar ataxia. To explore the association between parkinsonism and SCA31, five patients with SCA31 with concomitant nigrostriatal dopaminergic dysfunction (NSDD) development, including three cases of L-DOPA responsive parkinsonism, were analyzed
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