Motor and respiratory functions are main challenges to patients with multiple sclerosis

Abstract Introduction People with multiple sclerosis (MS) present wide and varied symptoms. Objective To investigate the impact of MS on subjects’ motor and respiratory functions. Methods One hundred one participants were enrolled in this study. The subjects had previous diagnosis of relapsing-remittent MS (n = 48) or presented no neurologic diseases (n = 53, control group). Assess-ments involved mobility (Timed Get Up and Go) and balance (Berg Balance Scale) tests. A force platform was used to evaluate postural stabilometry. Respiratory functions were assessed with a portable spirometer and a digital manovacuometer. Data analyses were carried out with Student´s t-tests, chi-square, and Pearson correlation index. Significance was set at 5%. Results Compared to control peers, participants with MS showed higher motor dysfunctions affecting mobility, balance, and postural stability. Spirometry indicated normal parameters for pulmonary flows and lung capacities in both groups. The manovacuometer, differently, pointed to a respiratory muscle weakness in 48% of participants with MS. Correlation analyses highlighted that respiratory functions are more associated to dynamic than to static motor tests. Conclusion Pathological changes in MS lead to motor dysfunction on mobility, balance and postural stability. Respiratory tests showed normal pulmonary flows and lung capacities in patients with MS, but with commitment of respiratory muscle strength. Respiratory functions were more impacted by dynamic tasks rather than static motor tasks.


Introduction
Multiple sclerosis (MS) is a chronic, autoimmune and demyelinating disease that affects the white matter of the central nervous system.The disease is characterized by lesions in the myelin sheath of neurons, resulting in a slow nerve conduction.1,2 Depending on the location of lesions, a wide range of neurological symptoms arises and affects patients' everyday life.
Among all symptoms seen in MS, motor signs stand out because of its impact on subjects' independence.3 Balance disturbance, mobility problems and postural instability are some of the symptoms seem in MS. [4][5][6] The physiological mechanism related to motor dysfunctions is associated to an inaccurate stimulus on patients' cortex that end up delaying motor actions and reactions.7 As consequence, patients are subject to a greater risk of falls and many of them start using assistive devices (such as bracing, walking sticks, and wheelchairs) for safety.8 Another factor associated to disability in MS is the commitment of the respiratory system.Previous studies reported respiratory dysfunctions in MS and its association to perceived fatigue, physical endurance and quality of life.9-12 The commitment of the respiratory system is consequence of the presence of demyelinating plaques on patients' brainstem, and it usually occurs in the later stage of the disease.
In spite of previous studies showing commitment of motor and respiratory functions in MS, the large number of confounding variables and the lack of standardization makes the understanding of the clinical condition challenging.Furthermore, until the present moment no study has provided complementary analyses associating motor and respiratory functions in MS.
In this scenario, we performed an in-depth analysis aiming to investigate the impact of MS on motor and respiratory functions, and to verify how motor and respiratory variables affect each other.A control group was included to compare results of subjects with and without MS.
We believe the finding of this study may guide physical therapists and other health care professionals during patient's treatment as it brings news information about the impact of pathological changes in MS.

Results
One hundred one participants completed the trial.
Patients with MS needed more time and steps to perform the Timed Get Up and Go test than subjects of the control group.In addition, scores of the BBS and stabilometric measures (support base area and imbalance speed) confirmed worse motor function of subjects with MS.

Discussion
This study investigated the impact of MS on subject's motor and respiratory functions.There is an important connection between cognition, respiratory and motor functions, which, if not controlled, could biased the results.

Figure 1 Figure 1 -
Figure 1 -Flow diagram of the study.
= peak expiratory flow; FVC = forced vital capacity; FEV1 = forced expiratory volume in the first second; MIP = maximum inspiratory pressure.R values of the Pearson correlation index.*p < 0.05.
Results showed motor decline and respiratory muscle weakness in subjects with MS.Pulmonary flows and lung capacities presented normal parameters.Respiratory functions were more impacted by dynamic than static tasks.The understanding of these factors is important to analyze the impact of MS in subjects' everyday life.

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In this sense, we included two questionnaires to assess the cognitive functions of participants.Data indicated normal cognitive values in both groups, allowing the conclusion that such factor did not affect the results.This study has two important limitations.First, the sample was formed by subjects in the mild and moderate stages of the disease.Further studies should be performed with patients in the advanced stage of MS.Second, this study concentrated analyses in inspiratory muscle strength.New studies should explore both inspiratory and expiratory muscle strength of subjects with MS.Conclusion Patients with MS present motor dysfunctions affecting mobility, balance and postural stability.Furthermore, subjects with MS showed an important commitment of respiratory muscle strength.Associations between motor and respiratory variables indicate that respiratory functions are more impacted by dynamic than static tasks.The findings of this study should help physical therapists in the understanding of the clinical profile of patients with MS, which may guide new therapies seeking the improvement of patients' health status and quality of life.

Table 1 -
Socio-demographic profile of participants of multiple sclerosis (MS) and control groups Note: Data are presented in number of events and percentage for categorical variables, and mean ± standard deviation for continuous variables; p-value of the chi-square test for the categorical variables and p-value of the Student´s t-test for the continuous variables.Fisioter Mov.2023;36:e36101 5

Table 2
Manovacuometric scores, differently, pointed to a respiratory muscle weakness in almost half of the participants of the MS group.Table3details respiratory functions of the MS and control groups.Table4shows correlation analyses between motor and respiratory functions in MS.Respiratory functions were more associated with dynamic than static tasks.Negative values in correlation analyses indicate that lower scores in pulmonary parameters are related to a worse result on the Timed Get Up and Go test (increasing time and number of steps) and to a higher risk of imbalance (larger support base area).Positive correlations with the BBS shows that as lower the respiratory variable were, the lower was the score of the BBS.

Table 2 -
Motor evaluation of the participants Note: Data are presented in mean ± standard deviation; p-value of Student´s t-test.Charro PD et al.Fisioter Mov.2023;36:e36101 6

Table 3 -
Respiratory functions in participants of multiple sclerosis and control groups Note: FEV = forced expiratory volume; FVC = forced vital capacity.Data are presented in mean ± standard deviation and percentage; p-value of Student´s test for continuous variables and chi-square for categorical variables.
37,38orrelation indexes indicate that lower values in pulmonary parameters are related to a worse result on the TUG test and on the BBS.This may indicate a higher difficulty of subjects with MS in performing complex motor tasks that end up affecting other systems, like the respiratory.Authors encourage new studies aiming to confirm this premise.The literature already confirmed the presence of cognitive decline in early and moderate stages of MS.37,38