Mehdi M. Mirbagheri

Differences in white matter microstructure between Parkinson's disease patients with and without REM sleep behavior disorder

REM sleep behavior disorder (RBD) is characterized by increased muscle tone and violent limb movements and usually occurs during the early stages of Parkinson disease (PD). PD patients with RBD represent faster motor progression and cognitive dysfunction. We used diffusion imaging to assess which regions are involved in this phenomenon. In the current study, we computed Quantitative Anisotropic (QA), which is based on spin distribution function (SDF) that quantifies the density of diffusing water and is more sensitive to psychological differences between groups and also diffusion MRI connectometry to conduct group analysis between age and gender matched PD patients with and without RBD. The major regions with significantly reduced QA in PD patients with RBD were left and right cingulum and left and left inferior occipital fasciculus.REM sleep behavior disorder (RBD) is characterized by increased muscle tone and violent limb movements and usually occurs during the early stages of Parkinson disease (PD). PD patients with RBD represent faster motor progression and cognitive dysfunction. We used diffusion imaging to assess which regions are involved in this phenomenon. In the current study, we computed Quantitative Anisotropic (QA), which is based on spin distribution function (SDF) that quantifies the density of diffusing water and is more sensitive to psychological differences between groups and also diffusion MRI connectometry to conduct group analysis between age and gender matched PD patients with and without RBD. The major regions with significantly reduced QA in PD patients with RBD were left and right cingulum and left and left inferior occipital fasciculus.

Contribution of reflex hyper-excitability to muscle stiffness in children with cerebral palsy

We aimed to investigate the contribution of reflex hyper-excitability to muscle stiffness in children suffering from cerebral palsy. To address this major controversial clinical issue, we studied the relation between the sonoelastography image and the Hoffman reflex (H-reflex) of lower limb muscles in fifteen children with spastic hemiplegic cerebral palsy. Muscle stiffness was quantified using the sonoelastography images of the affected ankle plantar-flexor muscles. The major parameters were autocorrelation, variance, difference entropy, energy, and histogram ratio. Hyper-excitability of stretch reflexes was evaluated using H-reflex responses of the ankle plantar-flexors. The important features were peak-peak amplitude of maximum H response, maximal M-wave, H/M ratio, latency of H, M, the time interval between H and M, and the stimulus intensity elicited max-H and max-M. The correlations between the major parameters quantifying sonoelastography images and H-reflex responses were calculated using Pearson-correlation analysis. The correlation analysis showed a relation between two features of sonoelastography images (i.e. autocorrelation and variance) and the maximal H/M ratio of the H-reflex response. These findings indicate that an abnormal increase in muscle stiffness, which typically occurs in CP patients, is at least partially due to hyper-excitability of reflexes. The clinical implication is that abnormal reflex responses may play a significant role in neuromuscular abnormalities, which are caused by spasticity in children with cerebral palsy.

The correlation between transcranial magnetic stimulation parameters and neuromuscular properties in children with cerebral palsy

We studied the correlation between corticospinal signaling and neuromuscular properties in children with Cerebral Palsy (CP). Corticospinal signaling was evaluated using Transcranial Magnetic Stimulation (TMS). Neuromuscular properties were quantified using Hoffmann reflex (H-reflex), sonoelastography, clinical measurements, and isokinetic measures. In particular, we determined the relationship between the TMS parameters of the ankle joint and the neuromuscular features of ankle extensors and flexors as well as popular clinical measures of gait speed, endurance, balance and mobility. Seventeen CP patients and twelve healthy control subjects were evaluated. Our findings showed that the motor evoked potential (MEP) latency of TMS was significantly longer in CP than in healthy subjects. The MEP-latency was significantly correlated with the H-reflex response (r=0.71, p-value=0.04) and isokinetic features; i.e. max acceleration extension time (r=0.5, p-value=0.005), and max flexion time in the cycle (r=0.5, p-value =0.002). No significant correlation was observed between MEP-latency and clinical measurements of gait and sonoelastography of ankle muscles. The results suggest that the changes in corticospinal signaling could contribute to muscle weakness and hyperexcitability of reflexes observed in children with CP.

Estimation of gait parameter using sonoelastography in children with cerebral palsy

We aimed to study the relationship between neuromuscular abnormalities associated with spasticity and gait impairments in spastic children with hemiplegia cerebral palsy (CP). Neuromuscular abnormalities of the tibialis anterior and medial gastrocnemius muscles of the spastic ankle were quantified using sonoelastography with two major features; i.e. entropy and histogram ratio of sonoelastography images. Gait impairments were evaluated in the gait laboratory using motion capture system, and the spatial and temporal features were extracted. The correlation analysis showed a significant relation between both the entropy and histogram ratio of sonoelastography images with walking speed and step time. The findings demonstrate that the neuromuscular abnormalities associated with spasticity may contribute to gait impairments in children with CP.

Can an anti-gravity treadmill improve stability of children with cerebral palsy?

We aimed to study the effects of an anti-gravity treadmill (AlterG) training on balance and postural stability in children with cerebral palsy (CP). AlterG training was performed 3 days/week for 8 weeks, with up to 45 minutes of training per session. The subject was evaluated before and after the 8-week training. The effects of training on the balance and postural stability was evaluated based on the Romberg test that was performed by using a posturography device. The parameters quantifying Center-of-Pressure (CoP) were calculated using different analytical approaches including power spectral density and principal components analyses. All of the key parameters including the Stabilogram, the Fast Fourier Transform (FFT) Energy, the Eigenvectors, and the Eigenvalues of CoP were modified between 14%-84%. The results indicated that the balance features were improved substantially after training. The clinical implication is that the AlterG has the potential to effectively improve postural stability in children with cerebral palsy.

Pendulum test measure correlates with gait parameters in children with cerebral palsy

Individuals with cerebral palsy (CP) usually suffer from different impairments including gait impairment and spasticity. Spastic hypertonia is a defining feature of spasticity and manifests as a mechanical abnormality. The objective of this study was to determine the relationship between spastic hypertonia and gait impairments in spastic children with CP, addressing an important controversial issue. Spastic hypertonia was quantified using the pendulum test. The gait impairments were evaluated using the motion capture system in a gait laboratory. Our results showed significant correlations among gait parameters; i.e. walking speed, step length, and the pendulum test measures. This indicates that neuromuscular abnormalities are associated with spasticity and may contribute to gait impairments. The clinical implication is that the impaired gait in children with CP may be improved with the treatment of neuromuscular abnormalities.Individuals with cerebral palsy (CP) usually suffer from different impairments including gait impairment and spasticity. Spastic hypertonia is a defining feature of spasticity and manifests as a mechanical abnormality. The objective of this study was to determine the relationship between spastic hypertonia and gait impairments in spastic children with CP, addressing an important controversial issue. Spastic hypertonia was quantified using the pendulum test. The gait impairments were evaluated using the motion capture system in a gait laboratory. Our results showed significant correlations among gait parameters; i.e. walking speed, step length, and the pendulum test measures. This indicates that neuromuscular abnormalities are associated with spasticity and may contribute to gait impairments. The clinical implication is that the impaired gait in children with CP may be improved with the treatment of neuromuscular abnormalities.

Real-time tracking of laparoscopic instruments using kinect for training in virtual reality

Training of laparoscopic surgery in Virtual Reality (VR) environment has been proved as an effective step before clinical practice. Tracking the position of instruments in realtime is an essential part of developing a VR trainer. In this study, we used Microsoft Kinect and color markers instead of using similar traditional means such as mechanical sensors. The orientation and position of instruments were determined and compared with the results obtained using the SinaSim commercial laparoscopic surgery trainer, which measures these values using encoders. The final results indicated that even though the newly developed systems possess an inferior accuracy compared to the mechanical sensors, low cost and portability makes it capable of replacing traditional methods of tracking.Training of laparoscopic surgery in Virtual Reality (VR) environment has been proved as an effective step before clinical practice. Tracking the position of instruments in realtime is an essential part of developing a VR trainer. In this study, we used Microsoft Kinect and color markers instead of using similar traditional means such as mechanical sensors. The orientation and position of instruments were determined and compared with the results obtained using the SinaSim commercial laparoscopic surgery trainer, which measures these values using encoders. The final results indicated that even though the newly developed systems possess an inferior accuracy compared to the mechanical sensors, low cost and portability makes it capable of replacing traditional methods of tracking.