Imbalance and lower limb tremor in chronic inflammatory demyelinating polyradiculoneuropathy: Reply to Letter to the Editor

Upper and lower limb tremor in Charcot–Marie–Tooth neuropathy type 1A and the implications for standing balance

“…The presence of lower limb tremor was independently associated with imbalance in the present cohort, in keeping with a recent cohort with CIDP [ 18 ]. Notably, ankle power and lower limb vibration sensation, which can independently cause imbalance [ 43 ], were not significantly different between those with and without tremor, further highlighting the independent association of lower limb tremor and imbalance.…”

“…Of further relevance, a high frequency spectral peak in the vertical direction was recorded with posturography and associated with ‘good’ balance. The high frequency peak was similar to findings in acquired demyelinating neuropathy [ 18 ] and primary orthostatic tremor [ 46 ], and could represent an adaptive response to imbalance. A high frequency cortical drive to lower limb muscles coupled with increased cortical activity in the beta band (15–30 Hz) has been reported after balance perturbation in healthy controls [ 47 , 48 ], and is postulated to be an adaptive response leading to joint stiffening, thereby increasing stability.…”

“…The mean peak frequency of sway was 0.85 ± 0.1 Hz, similar to previously reported healthy controls [ 33 ], and did not differ between patients with and without lower limb tremor (Supplementary Table 1) nor in those with ‘good’ and ‘poor’ balance. The force exerted in the vertical plane was 4.3 ± 0.3 Hz across all conditions, similar to acquired demyelinating neuropathies [ 18 ]. Interestingly, a high frequency peak was observed in the vertical plane in 35% of patients, with median frequency of 17.1 Hz (15.8–17.4) (Fig.…”

“…Of further relevance, lower limb tremor in inherited neuropathies has not been previously assessed. A recent analysis of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) reported a lower limb tremor affected ~ 30% of patients and correlated with imbalance [ 18 ]. Given that imbalance is a prominent symptom in inherited neuropathies, it is of clinical importance to determine whether lower limb tremor is a contributing feature in CMT.…”