The Movement Disorder Society

MDS Abstract of the 16th International Congress of Parkinson's Disease and Movement Disorders, Volume 27,
June 2012 Abstract Supplement

Movement Disorders 2012
Dublin, Ireland June 17-21, 2012.


Modulation of orthostatic tremor during gait

Blahak,  C., Wolf,  M.E., Bazner,  H., Capelle,  H.H., Krauss,  J.K., Hennerici,  M.G.

Objective:

To evaluate the modulation of orthostatic tremor (OT) in different leg muscles during gait.

Background:

OT is a rare form of tremor that occurs in legs upon standing upright with a typical tremor frequency of 13–18 Hz. The tremor syndrome is characterized clinically by increasing unsteadiness upon standing that disappears when walking or sitting down. So far no systematic electrophysiological study analysing the course of OT during gait has been published.

Methods:

We performed gait analysis in 6 OT patients (1 male, mean age 65.2±9.5 years) during walking on a treadmill with preferred gait velocity (range 0.5-0.8m/s). Basic step cycle parameters were determined using pressure-sensitive soles, and tremor was analysed in surface EMG recordings from vastus medialis (VM), biceps femoris (BF), tibialis anterior (TA) and soleus (SO) muscles using the Zebris CMS 70P gait analysis system (Isny; Germany). Tremor amplitude was calculated for each single tremor beat with respect to the relative percentage of step cycle using Microsoft Excel routines. Statistical analysis used non parametric testing for paired (Wilcoxon test) and multiple repeated (Friedman test) samples.

Results:

Mean tremor frequency was not different during gait compared to stance (16.6±0.9Hz vs. 16.2±1.0Hz; p=0.42). Mean OT amplitude was found to be modulated throughout the stepcycle in all muscles (p<0.01 in Friedmann test respectively, for a single case example see Fig.).

Fig. 1 (1233).

Considerable OT activity could be observed in all muscles around heel strike from the end of the swing phase into the first half of stand phase, in contrast OT markedly decreased at the end of the stand phase at toe off in TA, RF and SO. Maximum tremor activity was observed in RF and TA around heel-strike into the first one-third of the stand phase and in SO during mid-stance, whereas in BF OT activity was more variable with a maximum in two patients during the first half of the swing phase.

Conclusions:

The electromyographic amplitude of OT is modulated during gait without showing an exclusive association to either the EMG activation patterns or the load of the leg during the step cycle. Different spinal neural pathways like presynaptic or Ib inhibition, that are likely to be involved in the modulation of spinal reflexes when walking, might play a major role for the observed OT modulation during gait.

Keywords :

Gait disorders: Clinical features,Gait disorders: Pathophysiology,Orthostatic tremor (also see Tremors),Tremors: Clinical features

To cite this abstract, please use the following information:
Blahak, C., Wolf, M.E., Bazner, H., Capelle, H.H., Krauss, J.K., Hennerici, M.G.; Modulation of orthostatic tremor during gait [abstract]. Movement Disorders 2012;27 Suppl 1 :1233