Investigating the combined effects of whole body vibration and vestibular stimulation on spasticity and dystonia in cerebral palsy

Author

Peter A. Michael, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

8-31-2020

Degree Name

Doctor of Philosophy in Biomedical Engineering - (Ph.D.)

Department

Biomedical Engineering

First Advisor

Sergei Adamovich

Second Advisor

Bryan J. Pfister

Third Advisor

Moshe Kam

Fourth Advisor

Catherine Mazzola

Fifth Advisor

Guang Yue

Abstract

This study identifies and addresses three voids and potential shortcomings associated with the classification, assessment and management of Cerebral Palsy (CP). These concerns should not undermine the significant advancement that has been made in this specific branch of rehabilitation, but addressing them is necessary. Cerebral Palsy is a group of motor impairments due to hypoxic-ischemic brain damage around the time of birth and very commonly manifests as excessive muscle tone and poor motor control. There are classifications within CP including spasticity and dystonia.

First, a level of discrepancy is present in the classification of CP between the clinical and research communities. Prior studies identify CP individuals as exhibiting varying degrees of spasticity, when in fact they often exhibit dystonia as well. Inconsistent clinical study results occur when mixed populations are unknowingly recruited. Proper classification of the type of movement disorder within CP is crucial. This study proposes the use of the Involuntary Muscle Tone (IMT) index, which is a novel measure to be computed from the pendulum knee drop (PKD) test and used to aid in proper classification. The PKD is a test of passive shank swing where the amplitudes of swing are used to observe tone present in the lower extremities, but data in this study suggests that this novel index of distance traveled can also be used as an indicator of classification.

This index also addressed the second issue, namely a lack of objective assessment that can be applied to all classifications of CP. Since it is sensitive to changes in tone, it can serve to complement the coarse five point Modified Ashworth Scale that is commonly used. Alternate methods of analyzing the PKD include the relaxation index, which does not provide a comprehensive outcome, and an optimization model which cannot be used if the shank trajectory deviates from an ideal scenario. The IMT index is unaffected by these challenges.

Lastly, this study utilizes these tools and knowledge to investigate the reduction in tone as a result of a novel approach that incorporates Whole Body Vibration (WBV) and Vestibular Stimulation (VS) into a single session of stimulation. While they have been assessed separately as potential therapies for movement disorders, their effects on the specific classifications of CP was not well defined. Additionally, there is a lack of a controlled study that investigates the effect of a combined stimulation.

Passive parameters of knee stiffness are extracted from the PKD trajectory and include the relaxation index and the Involuntary Muscle Tone Index. Pilot data in this study supports their use, in conjunction, to describe changes in amplitude of the first swing and amount of oscillation of the leg, respectively. Active motor function was assessed via self-regulated gait and voluntary leg movements following a target. Age-matched control data showed negligible change and was used to calculate a 95% confidence interval for comparison of changes in CP data.

Analysis shows that upon receiving a single session of combined stimulation, all individuals with spastic-dystonic CP experienced a reduction in co-contraction and stiffness. Relaxation index and Involuntary Muscle Tone Index improved by as much as 53% and 89% respectively, while stride length and walk speed improved by as much as 37% and 27% respectively. Lastly, the pilot subject for the voluntary shank movement task exhibited a 15-degree increase in tracking accuracy and range of motion as well as a 170 ms improvement in reaction time. All improvements in CP data were outside of the 95% control margin of error.

These findings may indicate that the proposed stimulation can be used as both a standalone therapeutic modality or combined with physical, occupational or robotic therapies that these subjects would have otherwise been too rigid to participate in safely. While these results are promising, a larger study with more participants is necessary.

Recommended Citation

Michael, Peter A., "Investigating the combined effects of whole body vibration and vestibular stimulation on spasticity and dystonia in cerebral palsy" (2020). Dissertations. 1745.
https://digitalcommons.njit.edu/dissertations/1745