Pain appears to be more intense in people with neuromyelitis optica spectrum disorder (NMOSD) than those with multiple sclerosis (MS), while fatigue levels are comparable between the two disorders, a study reports.
Its researchers also link certain types of central nervous system lesions to pain and fatigue in each condition.
The study, “Difference in fatigue and pain between neuromyelitis optica spectrum disorder and multiple sclerosis,” was published in the journal PLOS One.
NMOSD and MS are both caused by damaging nervous system attacks by the body’s immune system. While the two are distinct diseases, some symptoms — including pain and fatigue — are common to people with either disorder. How the severity of these symptoms compares between the two, however, is not clear. (Immune system attacks in NMOSD are mainly against optic nerves and the spinal cord.)
Researchers compared pain and fatigue levels, using standardized questionnaires, in people with NMOSD or MS being treated at Chiba University Hospital in Japan.
Data were analyzed for a total of 51 people with NMOSD (90.2% female, median age 52) and 85 people with MS (77.6% female, median age 42). Relative to the MS group, the NMOSD group was and had significantly shorter disease duration (median 8.0 vs. 11.0 years)
Fatigue was measured using the Modified Fatigue Impact Scale (MFIS) and the Multidimensional Fatigue Inventory (MFI). Pain was assessed using the Pain Effects Scale (PES). In all three scales, higher scores indicate a greater severity of the respective symptom.
Results showed the three scores were significantly correlated with each other, both among MS and NMOSD patients. That is, people who reported greater fatigue also tended to report more pain, and vice versa.
Neither MFIS nor MFI, or their associated subscores, were significantly different between the MS and NMOSD groups, indicating similar levels of fatigue. However, PES scores were significantly higher for NMOSD (median 14.0) than MS patients (median 12.0), indicating more severe pain experienced by those with NMOSD.
Researchers then looked for associations between nervous system lesions — that is, areas of active inflammation visible via MRI scans — and the symptoms’ scores.
In the NMOSD patient group, PES scores were significantly higher among those with extended spinal cord lesions, defined as lesions in more than three vertebrae. A similar trend was seen in the MS group, but this did not reach statistical significance.
“These results suggested that extended spinal cord lesions may have some role in the pathogenesis of pain,” the researchers wrote, adding that “further investigation is needed to investigate these relations.”
Fatigue scores did not differ significantly based on the presence of extended spinal cord lesions in either disease.
In NMOSD, brain abnormalities visible on MRI were not significantly associated with fatigue.
In MS patients, however, MFI and MFIS scores correlated significantly with total lesion volume (TLV) in the brain. In other words, people with more brain lesions were more likely to report greater fatigue.
“These results suggest that fatigue in MS patients may be associated with TLV,” the researchers wrote, adding “to the best of our knowledge, ours is the first report to show a positive correlation between TLV and fatigue score.”
Because differences were seen in fatigue-associated clinical features of the two diseases, the researchers speculated that “the cause of fatigue may be different in NMOSD and MS patients.” Specifically, “the origin of fatigue may be associated with spinal cord lesions causing pain in NMOSD patients, but with brain lesions in MS patients.”
Overall, results showed that “fatigue was not different between NMOSD and MS patients,” but “patients with NMOSD suffered from more severe pain compared with patients with MS,” the researchers wrote.
They suggest this finding might help “to develop more appropriate treatment strategies” for each patient group.
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