Identifying brain regions for integrative sensorimotor processing with ankle movements

A musculoskeletal model of low grade connective tissue inflammation in patients with thyroid associated ophthalmopathy (TAO): the WOMED concept of lateral tension and its general implications in disease

Background

Low level connective tissue inflammation has been proposed to play a role in thyroid associated ophthalmopathy (TAO). The aim of this study was to investigate this postulate by a musculoskeletal approach together with biochemical parameters.

Methods

13 patients with TAO and 16 controls were examined. Erythrocyte levels of Zn, Cu, Ca²⁺, Mg, and Fe were determined. The musculoskeletal evaluation included observational data on body posture with emphasis on the orbit-head region. The angular foot position in the frontal plane was quantified following gait observation. The axial orientation of the legs and feet was evaluated in an unloaded supine position. Functional propioceptive tests based on stretch stimuli were done by using foot inversion and foot rotation.

Results

Alterations in the control group included neck tilt in 3 cases, asymmetrical foot angle during gait in 2, and a reaction to foot inversion in 5 cases. TAO patients presented facial asymmetry with displaced eye fissure inclination (mean 9.1°) as well as tilted head-on-neck position (mean 5.7°). A further asymmetry feature was external rotation of the legs and feet (mean 27°). Both foot inversion as well as foot rotation induced a condition of neuromuscular deficit. This condition could be regulated by gentle acupressure either on the lateral abdomen or the lateral ankle at the acupuncture points gall bladder 26 or bladder 62, respectively. In 5 patients, foot rotation produced a phenomenon of moving toes in the contra lateral foot. In addition foot rotation was accompanied by an audible tendon snapping. Lower erythrocyte Zn levels and altered correlations between Ca²⁺, Mg, and Fe were found in TAO.

Conclusion

This whole body observational study has revealed axial deviations and body asymmetry as well as the phenomenon of moving toes in TAO. The most common finding was an arch-like displacement of the body, i.e. eccentric position, with foot inversion and head tilt to the contra lateral side and tendon snapping. We propose that eccentric muscle action over time can be the basis for a low grade inflammatory condition. The general implications of this model and its relations to Zn and Se will be discussed.

How does the brain respond to unimodal and bimodal sensory demand in movement of the lower extremity?

Numerous electroencephalography (EEG) studies have shown that neurophysiological signals change in response to visual and sensory adaptations in upper extremity tasks. However, this has not been clearly studied in the lower extremity. In this study, we evaluated how sensory loading affects brain activations related to knee movement. Thirty-two channel EEG was recorded while ten subjects performed knee extension in four different conditions: no weight and no visual target (NWNT), weight affixed to the ankle and no visual target (WNT), no weight and a visual target (NWT), and both weight and target (WT). Surface electromyography (EMG) was recorded from the vastus medialis and vastus lateralis muscles to determine onset of the movement. EEG was epoched from -4.5 s before to 1 s after EMG onset. Epochs were averaged to acquire movement-related cortical potentials (MRCPs) of each task condition. MRCP amplitude during the pre-movement period from -2 s to EMG onset was evaluated at electrodes over motor, sensory, frontal, and parietal areas. The amplitude of the pre-movement potentials for the conditions was different across areas of interest. Over the motor area, NWNT had lower amplitude than any other condition and WT had higher amplitude than any other condition. There was no difference between unimodal NWT and WNT conditions. Mesial frontal and parietal areas showed larger MRCP to the bimodal condition than either unimodal or NWNT conditions. The parietal cortex was the only region that showed a difference between unimodal conditions with greater amplitude for NWT condition. Information concerning added sensory demand is processed by the motor cortex in a way that may be indifferent to the type of modality, but is influenced by the quantity of modalities at the level of the knee. Other brain structures such as parietal and premotor cortices respond based on the modality type to help plan appropriate strategies for motor control in response to sensory manipulations. This suggests that additional task demands in motor training may create a rich sensory environment that may be beneficial in promoting optimal neuromotor recovery.

Definition and classification of negative motor signs in childhood

In this report we describe the outcome of a consensus meeting that occurred at the National Institutes of Health in Bethesda, Maryland, March 12 through 14, 2005. The meeting brought together 39 specialists from multiple clinical and research disciplines including developmental pediatrics, neurology, neurosurgery, orthopedic surgery, physical therapy, occupational therapy, physical medicine and rehabilitation, neurophysiology, muscle physiology, motor control, and biomechanics. The purpose of the meeting was to establish terminology and definitions for 4 aspects of motor disorders that occur in children: weakness, reduced selective motor control, ataxia, and deficits of praxis. The purpose of the definitions is to assist communication between clinicians, select homogeneous groups of children for clinical research trials, facilitate the development of rating scales to assess improvement or deterioration with time, and eventually to better match individual children with specific therapies. "Weakness" is defined as the inability to generate normal voluntary force in a muscle or normal voluntary torque about a joint. "Reduced selective motor control" is defined as the impaired ability to isolate the activation of muscles in a selected pattern in response to demands of a voluntary posture or movement. "Ataxia" is defined as an inability to generate a normal or expected voluntary movement trajectory that cannot be attributed to weakness or involuntary muscle activity about the affected joints. "Apraxia" is defined as an impairment in the ability to accomplish previously learned and performed complex motor actions that is not explained by ataxia, reduced selective motor control, weakness, or involuntary motor activity. "Developmental dyspraxia" is defined as a failure to have ever acquired the ability to perform age-appropriate complex motor actions that is not explained by the presence of inadequate demonstration or practice, ataxia, reduced selective motor control, weakness, or involuntary motor activity.

Watching Your Foot Move--An fMRI Study of Visuomotor Interactions during Foot Movement

The objective of this study was to investigate brain areas involved in distinguishing sensory events caused by self-generated movements from similar sensory events caused by externally generated movements using functional magnetic resonance imaging. Subjects performed 4 types of movements: 1) self-generated voluntary movement with visual feedback, 2) externally generated movement with visual feedback, 3) self-generated voluntary movement without visual feedback, and 4) externally generated movement without visual feedback, this design. This factorial design makes it possible to study which brain areas are activated during self-generated ankle movements guided by visual feedback as compared with externally generated movements under similar visual and proprioceptive conditions. We found a distinct network, comprising the posterior parietal cortex and lateral cerebellar hemispheres, which showed increased activation during visually guided self-generated ankle movements. Furthermore, we found differential activation in the cerebellum depending on the different main effects, that is, whether movements were self- or externally generated regardless of visual feedback, presence or absence of visual feedback, and activation related to proprioceptive input.

Functional response to active and passive ankle movements with clinical correlations in patients with primary progressive multiple sclerosis

Patients with multiple sclerosis (MS) activate a more diffuse cortical network than do healthy subjects when they perform motor tasks. This brain functional reorganisation might contribute to the limiting of disability, but it is unclear whether there is a loss of regional activation in more advanced disease. The aim of this study was to assess whether functional reorganisation diminishes in more disabled patients with primary progressive (PP) MS. The differences in the fMRI response to active and passive movements of the dominant ankle of 13 patients and 16 controls were assessed. The relationships between functional activation and disability and brain lesion load and atrophy were investigated.Patients showed greater fMRI activation than controls with passive movements in the superior temporal gyrus, rolandic operculum, and putamen. The fMRI response to active and passive movements in the ipsilateral inferior frontal gyrus was lower in patients with greater disability and greater brain T2 lesion load, respectively. Furthermore, the fMRI activation with active movements in the contralateral cerebellum was lower in patients with worse mobility. The increased activity with passive movements in regions that participate in sensori-motor integration, such as the putamen, reflects true functional reorganisation, since passive movements induce brain activation through sensory afferents only. The inverse correlation between the fMRI response in regions that are associated with motor control, and clinical or MRI measures of disease progression, suggests that there is a loss of distributed activation in more disabled patients. This may inform future treatment strategies.