New tool tracks hidden symptoms in people with Friedreich’s ataxia
Modified assessment captures non-movement problems often missed
An international team of scientists has modified a standardized neurological assessment so it can better measure the severity of non-movement symptoms in people with Friedreich’s ataxia (FA).
The researchers found that the updated assessment closely matches established measures of FA severity. They said the findings highlight how often overlooked symptoms can affect people with FA, while also offering a practical way to track those symptoms.
The study, “Analysis of a Modified Version of the Inventory of Non-Ataxia Signs Over 12 Years in Patients with Friedreich’s Ataxia in the EFACTS Study,” was published in Movement Disorders.
FA affects more than movement and balance
Ataxia, the symptom that gives FA its name, is marked by problems with coordination and balance. However, people with FA also commonly experience non-movement symptoms, ranging from difficulty swallowing to muscle wasting and urinary problems.
The Inventory of Non-Ataxia Signs (INAS) is a clinician-administered 30-item assessment developed to measure the severity of non-ataxia symptoms in people with different forms of ataxia. Each symptom is scored on a scale from zero (absent) to three (severe).
In this study, researchers created a modified version of the INAS specifically tailored for FA, mainly by removing items not relevant to FA. The revised tool assesses 16 non-ataxia symptoms. Two scores were calculated: INAS count, which reflects how many of the 16 symptoms are present (out of 16), and INAS sum, which adds together all severity ratings for a maximum score of 84.
The researchers calculated both modified INAS scores using data from more than 1,000 people with FA enrolled in the European Friedreich’s Ataxia Consortium for Translational Studies (EFACTS), a large European study. The mean modified INAS count was 4.6, while the mean modified INAS sum score was 15.1 — indicating many people with FA may have at least a few non-ataxia symptoms causing notable problems.
“Our results emphasize the high prevalence and progressive worsening of many neurological non-ataxia symptoms in patients with Friedreich’s ataxia,” the researchers wrote.
Compared with the linear progression of ataxia, non-ataxia signs and symptoms appear to progress at a more variable and slower rate.
Using long-term data, the researchers examined how well each score could detect changes over time. They found that INAS sum was good at identifying changes over five years or longer, but was much less responsive over shorter periods. INAS count showed markedly less responsiveness, showing little ability to detect changes with less than a decade of follow-up.
“The modified INAS sum showed high responsiveness in the medium and long term but not in the short term; in contrast, the modified INAS count exhibited poor responsiveness in the medium term and moderate responsiveness in the long term,” the researchers wrote.
Both scores tended to increase over time, reflecting how non-ataxia symptoms worsen as FA progresses. However, the researchers noted there was a lot of variability in non-ataxia symptoms, which contrasts with how ataxia tends to worsen over time.
“The relatively modest responsiveness of the modified INAS in the total cohort in the short term underscores the challenges of developing effective outcome measures for Friedreich’s ataxia, given its slow progression and substantial heterogeneity [variability],” the researchers wrote. “Compared with the linear progression of ataxia, non-ataxia signs and symptoms appear to progress at a more variable and slower rate.”
Non-movement symptoms worsen fastest in children
The fastest worsening in INAS scores was seen in children with FA. In contrast, adults with late-onset FA, whose symptoms began after age 25, showed the slowest rates of worsening.
“The non-ataxia symptoms with consistent worsening over time included muscle weakness, muscle atrophy [wasting], impaired vibration sensation, urinary dysfunction, dysphagia [difficulty swallowing], and spasticity [stiffness or tightness],” the researchers wrote.
The researchers also found that both modified INAS scores closely tracked with established measures of FA severity, including the Scale for the Assessment and Rating of Ataxia (SARA) and the Activities of Daily Living (ADL) scale. Overall, they concluded their modified INAS scores may be useful for assessing non-ataxia symptoms in people with FA.
“In particular, the modified INAS may provide a valuable assessment tool in non-ambulatory patients … and in children who typically progress faster,” the scientists wrote. “The added value of the continuous scoring of the modified INAS sum is its greater granularity, capturing both the onset of new symptoms and the progression of existing ones.”
As limitations, the researchers noted the smaller number of participants in later timepoints and that missing values were more frequent among patients with more severe impairment.
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