Muscle problems affect more than one-third of NMOSD patients
Review of nearly 100 articles IDs wide range of related movement disorders
More than one-third of people with neuromyelitis optica spectrum disorder (NMOSD) have involuntary muscle contractions or movements, while about one-quarter develop a lack of motor coordination.
That’s according to a systematic review of nearly 100 published studies, which found that individuals with NMOSD may experience a wide range of movement disorders, with distinct characteristics and frequency. The most common problems involved sudden muscle stiffness and spasms, which affected nearly 40% of patients.
Overall, the analysis covered more than 1,700 people with NMOSD, 487 of whom were found to have movement disorders.
“These findings might help further characterize the clinical manifestations of NMOSD and identify diagnostic clues that may aid in clinical practice,” the researchers wrote.
Their study, “Movement Disorders in Neuromyelitis Optica Spectrum Disorder: A Systematic Review,” was published in the journal Movement Disorders Clinical Practice.
A progressive autoimmune disorder, NMOSD mainly causes inflammation in the spinal cord and the optic nerve, which relays signals to and from the eye. The disease exhibits a relapsing pattern, characterized by sudden periods of symptom worsening that can cause cumulative neurological impairments.
Movement disorders associated with damage to and loss of myelin, the protective sheath around nerve fibers, comprise a number of neurological manifestations that are secondary to NMOSD and other inflammatory diseases affecting the brain and spinal cord.
Muscle spams, stiffness ID’d as most common problems for patients
These movement disorders can include tonic spasms, or sudden muscle stiffness, as well as tremors and poor movement coordination, known as ataxia. Involuntary movements called paroxysmal dyskinesias can also occur.
According to the team, NMOSD “presents a unique opportunity” to study spinal movement disorders, because most patients “have no or minimal brain lesions and no neurodegeneration.”
Meanwhile, this review also sheds new light on muscle problems seen in people with NMOSD, the researchers noted.
“Although there is also a substantial amount of literature reporting MD [movement disorders] in NMOSD, to the best of our knowledge, there is no single large study reviewing the current literature regarding the spectrum of MD in NMOSD,” the team wrote.
For their review, the researchers, from institutions in Brazil, systematically evaluated published studies through July 2024 to evaluate the prevalence and characteristics of movement disorders in people with NMOSD.
The analysis included 96 articles; most were case reports or small case series. The majority of patients (79.9%) had self-reactive antibodies against aquaporin-4 (AQP4), a protein found on the surface of nerve-supporting cells, which are commonly present in NMOSD patients.
The results showed that “several distinct MDs were observed,” according to the researchers.
More work needed to determine prevalence, pattern of each movement disorder
The most frequent movement disorders were tonic spasms or paroxysmal dystonia, and ataxia.
Tonic spasms or paroxysmal dystonia were reported in 31 studies, covering 241 patients, with a pooled frequency of spasms of 39% (range, 22.8%-55.2%). People with spasm events had an average age of 45.9 at symptom presentation.
Spasms could occur at any time in the disease course, although they were rarely present at NMOSD onset. Most commonly, they affected the legs, either alone (36.5%) or together with the arms (20.8%). In 15.7% of the patients, all four limbs were affected, while 14.6% had spasms just in the arms.
“These observations confirm spasms and paroxysmal dystonia as common MDs in NMOSD, occurring in almost half of the patients,” the researchers wrote.
Ataxia was reported in 56 studies with 152 patients, with a pooled prevalence of 26% (range, 9%-42%). People with ataxia had a mean age of 37.5, and this movement disorder was the first disease symptom in 80% of these patients. A large proportion of patients with ataxia had lesions in the spinal cord (42.3%), usually in its upper regions (cervical and thoracic).
The pooled frequency of restless leg syndrome, a condition marked by an irresistible urge to move the legs, was 32.2% (range, 0%-72%), while the prevalence of tremor was 3% (0%-6%).
These [findings] confirm spasms and paroxysmal dystonia [sudden muscle stiffness] as common [movement disorders] in NMOSD, occurring in almost half of the patients.
Other movement disorders characterized by involuntary, excessive movements or muscle contractions, such as dystonia, chorea, and myoclonus, were more rarely reported. Dystonia is marked by repetitive involuntary muscle contractions, while chorea is characterized by random, jerky movements, and myoclonus by brief, irregular twitching movements.
As limitations to their work, the researchers noted the lack of a standardized movement disorders classification across studies, writing that “inconsistent terminology across studies (eg, overlapping use of ‘spams,’ ‘dystonia,’ or ‘hyperkinetic movements’) complicates comparative analyses.”
Still, their systematic review of published studies showed the wide clinical spectrum of movement disorders in people with NMOSD, with tonic spasms and ataxia as the most common muscle-related problems.
“More studies are necessary with standardized [clinical] protocols and advanced neuroimaging correlations to better characterize the prevalence and pattern of each MD in NMOSD,” the researchers wrote. “This knowledge might help to identify patients with NMOSD, which presents MD as a clinical feature and improves outcomes.”
About the Author
