Peripheral Nerve Involvement In Type 3 Spinocerebellar Ataxia

Objective:To explore the characteristics of peripheral nerve involvement in Type 3 Spinocerebellar Ataxia (SCA3), and provide additional diagnostic basis for clinical diagnosis.Methods:According to the criteria of inclusion and exclusion for SCA 3 group and a control group, the SCA 3 patients group consists of 26 SCA3 cases with genetic diagnosis in the Neurology Department of the first Affiliated Hospital of Kunming Medical University from 2014 to 2016, and the control group contains 26 healthy persons matching the patients’group in age and gender. Nerve conduction velocities (NCVs) were measured for the SCA 3 patients group and control group, followed by comparison of these between the two groups, to determine whether there are any significant differences. The correlation between NCVs and durations, action potential amplitudes and durations, NCVs and CAG repeats, and action potential amplitudes and CAG repeats have been analyzed. This is to find the correlation factors for SCA3 peripheral nerve involvement. Electromyography studies were conducted on the SCA3 patients group, to determine whether muscular impairment occurs in SCA3. Does abnormal electrophysiology occur before symptoms? Statistical analysis of this data was provided in SPSS 17.0.Results:(1) Motor NCV of median nerves, ulnar nerves, tibial nerves and peroneal nerves in SCA3 patients were slower than control group (p<0.0001,p=0.002, p=0.0001,p=0.006).(2) Distal motor latencies of median nerves, ulnar nerves, tibial nerves, and peroneal nerves in SCA3 patients were higher than control group (p<0.0001, p<0.0001, p= 0.01,p= .0001).(3) CMAPs of median nerves, ulnar nerves, tibial nerves in SCA3 patients were lower than control group (p<0.0001, p=0.003, p=0.0001); the differences between peroneal nerves CMAPs in SCA3 patients and control group had no statistical significance (p=0.443).(4) Sensory NCVs of median nerves, ulnar nerves, tibial nerves and sural nerves in SCA3 patients were slower than control group (p<0.0001, p<0.0001, p=0.002, p=0.0001).(5) Distal sensory latencies of median nerves, ulnar nerves, tibial nerves and sural nerves in SCA3 patients were higher than control group (p<0.0001, p<0.0001, p=0.004,p=0.0001).(6) Sensory action potential amplitudes (SNAPs) of median nerves, ulnar nerves, tibial nerves and sural nerves in SCA3 patients were lower than control group (p<0.0001,p=0.001,p<0.0001,p=0.001).(7) Motor NCVs of median nerves, ulnar nerves, tibial nerves and peroneal nerves had no linear correlation with the durations of SCA3 patients, (r=0.071,p=0.729; r=0.020,p=0.922; r=0.108,p=0.599; r=0.01,p=0.959).(8) CMAPs of median nerves, ulnar nerves, tibial nerves and peroneal nerves had no linear correlation with the durations of SCA3 patients(r=0.113, p= 0.583 r=0.085, p=0.681; r=0.045,p=0.827; r=0.114,p=0.581).(9) Sensory NCVs of median nerves, ulnar nerves, tibial nerves and sural nerves had no linear correlation with the durations of SCA3 patients (r=0.089, p=0.666; r=0.151, p=0.460; r=0.028, p=0.892; r=0.02, p=0.924).(10) SNAPs of median nerves, ulnar nerves, tibial nerves and sural nerves had no linear correlation with the durations of SCA3 patients (r=0.117,p=0.570; r=0.007, p=0.971; r=0.137,p=0.504; r=0.223,p= 0.273).(11) Motor NCVs of median nerves, ulnar nerves, tibial nerves and peroneal nerves had no linear correlation with the CAG repeats of SCA3 patients (r= 0.376, p=0.058; r= 0.216,p= 0.290; r= 0.148,p= 0.472; r= 0.281, p= 0.165).(12) CMAPs of median nerves, ulnar nerves, tibial nerves and peroneal nerves had no linear correlation with the CAG repeats of SCA3 patients (r= 0.109,p= 0.596; r= 0.054, p= 0.792; r= 0.240, p= 0.237; r= 0.154,p= 0.450).(13) Sensory NCVs of median nerves, ulnar nerves had negative correlation with the CAG repeats of SCA3 patients (r= 0.546,p= 0.004; r= 0.464, p= 0.017); sensory NCVs of tibial nerves, sural nerves had no linear correlation with the CAG repeats of SCA3 patients (r= 0.279,p= 0.168; r= 0.288,p= 0.154).(14) SNAPs of median nerves, ulnar nerves, tibial nerves and sural nerves had no linear correlation with the CAG repeats of SCA3 patients (r= 0.09,p= 0.622; r= 0.372,p= 0.061; r= 0.175,p= 0.394; r= 0.240,p= 0.238).(15) Electrophysiological results had no correlation with the durations and CAG repeats of SCA3 patients (r=0.137, p=0.504; r=0.059, p=0.776);(16) There were 81% of patients with abnormal results for nerve conduction examinations, motor nerves and sensory nerves both showed abnormal results in 58% of patients. There were 11%of patients who only showed abnormalities in sensory nerves and 12% of patients who only showed abnormalities in motor nerves.(17) Abnormal NCVs and action potential amplitudes showed in 65% of patients. There were 12% of patients with abnormal action potential amplitudes and normal NCVs,4% of patients with abnormal NCVs and normal action potential amplitudes.(18) There were 57.69% of patients with abnormal motor NCVs or CMAPs without muscle wasting and weakness,38.46% patients with abnormal sensory NCVs or SNAPs without sensory symptoms and signs. There were 69.23% of patients with abnormal motor NCVs or CMAPs, only 38.46% of patients showed abnormal EMG.Conclusions:SCA3 shows obvious peripheral nerves impairment, the most common is mixed sensorimotor neuropathy, pure motor neuropathy and pure sensory neuropathy is also found in SCA3. Sensory NCVs of median nerves and ulnar nerves have a negative correlation with the CAG repeats of SCA3 patients. Electrophysiological evidence of neuropathy is high in SCA3, coexisting axonal neuropathy and demyelinating is common. Nerve conduction studies show higher sensitivity than EMG for motor nerves impairment in SCA3. Electrophysiological evaluations can detect the subclinical peripheral nerves impairment.