Abstract
Objectives Neuropathy causes imbalance to a greater degree than expected based on clinical and neurophysiological findings alone. Our hypothesis was that inflammatory neuropathy patients might experience subclinical lower limb tremor that then causes imbalance, similar to primary orthostatic tremor.
Methods Patients with CIDP were consecutively recruited from neuromuscular clinics in Sydney. Tremor studies with surface electromyography (EMG) to rectus femoris, biceps femoris, tibialis anterior, and medial gastrocnemius were performed, as well as posturography using force platform analysis. Nerve conduction studies were performed to correlate tremor findings with neuropathy. Berg Balance Scale (BBS) was undertaken to quantify balance.
Results Twenty-six patients with CIDP were recruited, mean age 65±2.6 years. They were moderately impacted by imbalance, with mean BBS 43/56. A spectral peak on Fast Fourier Transform was found between 10–12 Hz in 11/26 (42%) patients when seated with legs held out in front. Posturography disclosed a high frequency peak from 12–18 Hz in the ‘z’ axis (up-down) in 9/26 (34%) patients while standing, similar to primary orthostatic tremor. Interestingly, however, a corresponding spectral peak on EMG was only present in 4/9 patients. Overall, tremor was detected in 58% of patients. There were no correlations between peripheral nerve conduction studies and these findings.
Conclusions Patients with CIDP suffer moderate imbalance. Lower limb tremor was detected in 58% of patients, and a subset had similar neurophysiological hallmarks to primary orthostatic tremor. This raises the question of whether orthostatic tremor is the cause of imbalance in CIDP, or a physiological compensatory mechanism in those with imbalance.
