These findings, which are consistent with those reported in a previous natural history study called NARCOMS, suggest an ascending order of motor function deterioration in MS patients, and may help in understanding the underlying mechanisms of MS progression.
The study, “Ten-year disease progression in multiple sclerosis: walking declines more rapidly than arm and hand function,” was published in the journal Multiple Sclerosis and Related Disorders.
Over the course of MS, people typically experience a decline in motor function. This can lead to impaired mobility, affecting walking and daily activities, and arm and hand dysfunction that could hamper the use of utensils and walking aids.
Data from NARCOMS, a natural history study following more than 35,000 MS patients in North America, showed that problems in mobility were more frequently reported (59%) than were those with hand function (40%) at 10 years following a diagnosis.
“The foregoing suggests that walking declines more rapidly than arm and hand function in [MS patients] in the years after diagnosis,” the researchers wrote.
Previous studies also suggest that MS-associated neurodegenerative processes start earlier in people with progressive forms of the disease than in those with relapsing MS.
“However, to date, no longitudinal cohort studies have directly compared the decline in leg function with arm function,” the researchers wrote, noting that whether these declines are more pronounced in a specific MS type also remains unclear.
Researchers at the MS Center Amsterdam of the Amsterdam University Medical Centers, in the Netherlands, evaluated the decline in leg and arm function in MS patients over the first 10 years post-diagnosis.
This was part of the Functional Prognosis Multiple Sclerosis study, which followed 156 people newly diagnosed with MS (less than six months), who were recruited at five neurology clinics in that country between 1998 and 2000.
Participants were systematically examined seven times: at the study’s beginning (baseline), at six months, and at one, two, three, six and 10 years.
Leg function was assessed using the 10-meter timed walking test, in which patients were asked to walk as fast and safe as possible for a delineated 10 meters (about 3.3 feet). Arm and hand function were evaluated with the Action Research Arm test (ARAT), while hand dexterity was assessed through the Nine-hole peg test.
Participants’ median age was 37.1 years, more than half (64.7%) were women, and most (82.1%) were diagnosed with a relapsing form of MS. Eighteen (11.5%) patients used a walking aid at baseline.
After 10 years, 107 patients were still in the study and 96 of them had completed all seven predefined, periodic assessments.
Results showed that progressive MS patients had an earlier and faster decline in both leg function and hand dexterity, compared with those with relapsing MS forms.
Arm and hand functioning changed only slightly over time in both MS types, which may reflect ARAT’s poor sensitivity to functional impairment in the first 10 years of this disease, the researchers noted.
Fine motor hand skills, measured through the nine-hole peg test, changed significantly over time, with a faster rate of change in the progressive group than in the relapsing group.
Leg function also declined earlier and faster over these 10 years than arm and hand function in MS patients, particularly in those with progressive MS.
Leg function started to deteriorate faster than upper body function beginning at three years post-diagnosis in progressive MS patients, and beginning at six years in relapsing MS patients. At 10 years, the difference between leg and hand function was statistically significant in both patient groups.
“It seems that progressive motor dysfunction occurs in ascending order; leg function is impacted first, with arm function affected at a later stage,” the researchers wrote, noting that there is still no clear explanation for this progression.
This functional difference may be due to greater damage among the longest nerve connections, those between the brain and the lower limbs in MS patients, they hypothesized.
Overall, “this is the first longitudinal study that shows that walking declines earlier and more rapidly than arm and hand function in patients with MS,” the team concluded.
The researchers emphasized that future studies are needed to confirm these findings and to assess the role of neurodegeneration on long nerve connections, and its influence on this potentially ascending functional deterioration in MS patients.
This type of information may help clinicians make a better prognosis of the expected level of functioning in this patient population, they added.
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