The Effect of the Level of Hand Fatigability on Multiple Sclerosis on General Fatigue and Functionality

Introduction Multiple sclerosis (MS) is the most common neurological disease that causes disability in young adults. It usually progresses with exacerbations and remissions and causes various problems by affecting the central nervous system in different localizations.

Fatigue is one of the most common symptoms of MS and has the greatest impact on the patient's quality of life . Fatigability, which is defined as motor and muscle fatigue during motor tasks, is the exercise-induced decrease in the muscle's ability to produce power or force during sustainable tasks . In individuals with MS, fatigability levels are higher than in healthy individuals, as the nervous system cannot provide the necessary activation stimulus during maximum voluntary or continuous contractions . From the early stages of the disease, individuals with MS face problems such as decreased grip strength, and difficulty in holding small objects, which reduce dexterity and complicate daily living activities .

When fatigue studies in MS are examined; It was observed that the studies focused mostly on the lower extremity and walking, and the studies on the upper extremity were also quite limited . To the best of our knowledge, our study is the first in its field to evaluate rough and pinching hand fatigability, general fatigue, and functionality levels in Relapsing-Remitting MS (RRMS) patients and compare them with age- and sex-matched healthy individuals.

It is stated that the EDSS, which we use to evaluate the disability levels of RRMS patients, is not sensitive enough to evaluate functional parameters such as dexterity and cognition in MS . Therefore, other specific assessment methods such as the Ataxia Rating and Rating Scale (SARA), the Nine-Hole Peg Test (NHPT), and the Skill Questionnaire-24 (DextQ-24) were used to determine the level of functioning. SARA is an internationally accepted scale that is frequently used in the evaluation of ataxia. NHPT is the gold standard of performance-based assessment, which detects the patient's progress over time and is sensitive to changes in treatment . DextQ-24, which was developed to measure manual dexterity and consists of 24 questions, is divided into five subgroups washing/care, dressing, food and kitchen, daily activities, TV/CD/DVD. The lowest total score is 24, and the highest is 96. An increase in the score means a decrease in dexterity. Beck Depression Inventory (BDI) is a valid and reliable depression scale for neurological diseases .

The Fatigue Severity Scale (FSS) was used to determine the severity of the fatigue levels of individuals during the day, and the Fatigue Impact Scale (FIS) was used to determine the effects of fatigue on activities of daily living. The Turkish validity and reliability study of both scales was conducted by Armutlu et al. Static and dynamic fatigue levels in the coarse and pinch grip were assessed with a Jamar® digital hand dynamometer and pinch meter, respectively, in the standard measuring position recommended by the American Association of Hand Therapists . For the Dynamic Fatigue Index, a maximum of 15 voluntary contractions were requested from the participant. No rest was given between contractions and the number of remaining contractions was reported to the participant. The highest value of the first 3 contractions (MVC1) and the highest value of the last 3 contractions (MVC2) were recorded and the dynamic fatigue index was calculated with the formula 100*[1-(MVC2/MVC1)]. For the Static Fatigue Index, after a one-minute rest break, the participant was asked to maintain the maximum voluntary contraction for 30 seconds and the participant was not informed about the remaining time. Assuming that the participant can sustain the maximum voluntary contraction for 30 seconds, taking into account the area generated in the graph (Hypothetical Area Under the Force Curve [HAUC]) and the area calculated by the time the participant can walk (Actual Area Under the Power Curve [AUC]) Static Fatigue Index 100*[1- (AUC/HAUC)] formula.

The multi-dimensional evaluation of MS, which threatens all aspects of life and causes limitations in daily living activities, from the early period has an important place in the treatment and rehabilitation of individuals with MS. Determination of hand fatigability is essential to understand the decrease in performance in daily life in individuals with MS and to understand its reflection on upper extremity functionality and to plan targeted rehabilitation. Our study draws attention to the fact that hand fatigability may increase in activities that require repetitive and continuous contraction in individuals with RRMS from the early period and its relationship with upper extremity functionality. For a clearer distinction of fatigability, studies with different and more objective assessments of fatigue index and more studies with different types and different EDSS levels in individuals with RRMS are needed.