Chronic inflammatory demyelinating polyradiculoneuropathy‐associated tremor: Phenotype and pathogenesis

Abstract

Background and purpose Tremor in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is underrecognized, and the pathophysiology remains incompletely understood. This study evaluated tremor in CIDP and tested the hypothesis, established in other demyelinating neuropathies, that tremor occurs due to mistimed peripheral inputs affecting central motor processing. Additionally, the tremor stability index (TSI) was calculated with the hypothesis that CIDP‐related tremor is more variable than other tremor disorders. Methods Consecutive patients with typical CIDP were prospectively recruited from neuromuscular clinics. Alternative causes of neuropathy and tremor were excluded. Cross‐sectional clinical assessment and extensive tremor study recordings were undertaken. Pearson correlation coefficient was used to compare nerve conduction studies and tremor characteristics, and t‐test was used for comparisons between groups. Results Twenty‐four patients with CIDP were included. Upper limb postural and action tremor was present in 66% and was mild according to the Essential Tremor Rating Assessment Scale. Tremor did not significantly impact disability. Surface electromyography (EMG) found high‐frequency spectral peaks in deltoid (13.73 ± 0.66 Hz), biceps brachii (11.82 ± 0.91 Hz), and extensor carpi radialis (11.87 ± 0.91 Hz) muscles, with lower peaks in abductor pollicis brevis EMG (6.07 ± 0.45 Hz) and index finger accelerometry (6.53 ± 0.42 Hz). Tremor was unchanged by weight loading but correlated with ulnar nerve F‐wave latency and median nerve sensory amplitude. TSI (2.3 ± 0.1) was significantly higher than essential tremor. Conclusions Postural tremor is a common feature in CIDP. Tremor was unaffected by weight loading, typical of centrally generated tremors, although there was a correlation with peripheral nerve abnormalities. The high beat‐to‐beat variability on TSI and gradation of peak frequencies further suggest a complex pathophysiology. These findings may assist clinicians with the diagnosis of neuropathic tremor.

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

“…Sway parameters in our study disclosed much poorer balance in the "eyes closed" conditions. 2 We have conducted a reanalysis of our data to measure the Romberg Quotient (RQ) of the sway path. The RQ is a parameter used to determine the degree to which the visual system plays a role in balance and is calculated by dividing "eyes closed" parameters by "eyes open" parameters.…”

Imbalance and lower limb tremor in chronic inflammatory demyelinating polyradiculoneuropathy

“…Upper limb tremor has been reported in 60%–80% of patients with inflammatory neuropathy, including CIDP, 2,3,27 and is termed neuropathic tremor. While upper limb neuropathic tremor was previously reported in the current CIDP cohort, 2 lower limb tremor has not been previously assessed in CIDP. The present study reports the novel finding of lower limb tremor evident in 32% of CIDP patients, being either postural or slow orthostatic (<12 Hz), with a small proportion (12%) exhibiting both types of tremor.…”

“…Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) is an acquired auto‐immune neuropathy characterized by progressive or recurrent symmetric proximal and distal weakness and sensory dysfunction developing over at least 8 weeks 1 . Imbalance, ataxia, and upper limb tremor are common clinical features of CIDP, contributing to disability 2–4 . Atypical CIDP subtypes, related to presence of nodal/paranodal or myelin‐associated glycoprotein antibodies also exhibit prominent tremor, ataxia, and imbalance 5 .…”

Peripherally-induced Movement Disorders: An Update

“…In a recent study of 24 patients with CIDP, 66% had an ET-like postural tremor [79]. Contrary to the presumption that tremor in neuropathy is primarily peripherally generated, the authors provide evidence for a co-existing role of a central component by demonstrating that tremor in CIDP was unaffected by weight loading [79]. Specific subtypes of CIDP, such as those associated with neurofascin155 (nfasc155) IgG4 antibodies, are particularly likely to be associated with disabling low-frequency, high-amplitude action tremor of the upper extremities [80,81].…”

“…Although the mechanisms are not well understood and probably vary from case to case, the prevalence of tremor in inflammatory neuropathies may range from 40-70% [76,78]. In a recent study of 24 patients with CIDP, 66% had an ET-like postural tremor [79]. Contrary to the presumption that tremor in neuropathy is primarily peripherally generated, the authors provide evidence for a co-existing role of a central component by demonstrating that tremor in CIDP was unaffected by weight loading [79].…”