Quantitative analysis of the activation strategies during freezing in parkinson's patients

Abstract

Freezing of Gait (FOG) is a symptom usually observed in the advanced stage of the Parkinson's Disease (PD). During it the subject suddenly becomes unable to start walking or to continue to move forward. Little is known about the gait of the subjects presenting FOG. In order to accurately analyse the alterations in the muscular activation strategies so as to evaluate hypotheses about the ON freezing generation in PD, in this paper we describe a system able to quantify the electromyographic activity of the distal and proximal muscles as well as of the basographic temporal patterns. Signals were recorded by using a portable commercial system that acquires surface electromyographic (sEMG) bilateral data coming from tibialis anterior (TA), gastrocnemius (GS), gluteus maximus (GX) and gluteus medius (GM) muscles together with basographic signals that was used for the identification of the four gait phases. The system presents the plot of all the signals during gaits just before freezing in order to easily analyse the characteristics of the activation patterns. To test the system, ten PD patients, presenting FOG in the ON phase of the medication cycle, were examined while performing normal walking or subject to freezing. Results showed that significantly abnormal timing occurred in the TA and GS muscles with overall preserved reciprocity. Before freezing, TA and GS swing activities already started prematurely during the pre-swing phase. Similar timing alterations were present in GX and GM activities with significant pattern inversions between omo- and contra-lateral muscles during swing phase. The analysis of these altered patterns, highlighted by the realized system, can contribute in the explanation of the muscular activation strategies that produce FOG. © 2008 Springer-Verlag.