Study of the Week: Spinal Muscular Atrophy Type 3 Linked to Cognitive Impairments

Welcome to Study of the Week from Patient Worthy. In this segment, we select a study we posted about from the previous week that we think is of particular interest or importance and go more in-depth. In this story we will talk about the details of the study and explain why it’s important, who will be impacted, and more.

If you read our short form research stories and find yourself wanting to learn more, you’ve come to the right place.


This week’s study is…

Cognitive profiles and clinical factors in type III Spinal Muscular Atrophy: a preliminary study

We previously published about this research in a story titled “SMA Type 3 Linked to Poorer Cognitive Ability” which can be found here. The study was originally published in the science research journal Neuromuscular Disorders. You can view the abstract of this study here.

The research team was affiliated with the University of Padova.

What Happened?

In progressive neurodegenerative disease, cognitive abilities of the patient can sometimes be affected. In the case of spinal muscular atrophy, there hasn’t been a lot of research on this subject. In this study, a team of scientists sought to evaluate the cognitive abilities of 22 patients living with type 3 spinal muscular atrophy and compare them to a group of healthy controls.

In order to do this, the control group and the patient group completed a series of neuropsychological evaluations, or batteries. These evaluations looked at various aspects of cognitive processing and ability, such as visuospatial processing, language, memory, global cognition, and executive function. The goal was not only to determine whether patients were experiencing cognitive deficits, but also to find out if they were associated with other clinical factors of the disorder.

With this in mind, each patient’s clinical severity was also measured. Tools used for this purpose included the Six Minute Walk Test, the Hammersmith Functional Motor Scale, and the Revised Upper Limb Module. In comparison to healthy controls, the patients had worse performance in language, executive functions, and visuospatial abilities. The scientists found that patients with worse motor ability had worse attention performance but greater memory, language, and verbal fluency. In male patients, cognitive test performance followed closely with motor function; however, this was not the case in females.

The researchers concluded that these findings demonstrate a possible brain pathology and cognitive adaptive mechanisms as a result of motor dysfunction, with sex appearing to be a possible mediating factor.

About Spinal Muscular Atrophy Type 3

Spinal muscular atrophy is a type of neuromuscular disorder in which the motor neurons are destroyed, leading to muscle wasting. Without prompt treatment, the disease is lethal in many cases. This disorder is linked to genetic defects of the SMN1 gene. This gene encodes a protein called SMN, and when not present in certain amounts, neurons are unable to function. There are different kinds of spinal muscular atrophy that are categorized by when symptoms first appear. In type 3, symptons appear after a year or more. These symptoms may include loss of reflexes, muscle weakness and poor muscle tone, problems with feeding and swallowing, developmental delays, respiratory muscle weakness, tongue twitching, and a bell shaped torso. In type 3, progression is slow and respiratory involvement does not occur. Most patients lose the ability to walk at some point in their lives, but life expectancy is normal or close to normal. The most effective treatment currently available for the disease is called Zolgensma. To learn more about spinal muscular atrophy, click here.

Why Does it Matter?

These findings confirm that patients with type 3 spinal muscular atrophy experience some degree of cognitive impairment, which has important implications for both the management of the disorder and the understanding of the disease overall:

“It is important to note that these preliminary findings show cognitive changes in SMA type III are associated to motor functioning…however, they are not sufficient to establish to what extent cognitive test performance represents the clinical profile of SMA type 3 patients. Studies with larger sample are needed to understand the frequency of cognitive ‘impairments’ and what factors can mediate cognitive functions trajectories.” – Sabrina Lezoni, MSc, University of Padova, First Author

The possibility of brain pathology in these patients, which is affecting their cognition, is a possibility that must be studied more comprehensively in order to improve outcomes for people living with this disorder.

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