Older age, muscle stiffness linked to worse scoliosis in Rett syndrome

Older age and increased muscle stiffness are linked to more severe scoliosis, a lateral curvature of the spine, in girls and women with Rett syndrome, according to a small study.

Other factors associated with the severity of scoliosis included walking problems and difficulty climbing and descending stairs. No link with the type of mutation was observed in the MECP2 gene, the main cause of Rett.

The findings “confirm the great importance of monitoring spinal deformities from early childhood and throughout life,” the researchers wrote.

I study, “Clinical and genetic correlations of scoliosis in Rett syndrome”, Was published in European journal of the spine.

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Scoliosis is common among girls with Rett syndrome, with onset at the mean age of 11 years. By the time they reach 16, 85% have some degree of scoliosis. In addition to its impact on lung function, the curved spine can also impair daily activities, such as walking and sitting, and is often painful.

Previous studies have reported a link between scoliosis and specific mutations in the MECP2 gene. While some mutations were associated with the onset of scoliosis later in life, others were associated with an early and severely curved spine.

However, it is not known whether the severity of scoliosis is also linked to motor and neurological characteristics.

The study and its results

To fill this gap, researchers in Italy and Germany analyzed clinical data from 75 girls (mean age 11.1 years) with a clinical and genetically confirmed diagnosis of Rett. The girls, followed at the IRCCS Don Carlo Gnocchi Foundation, Milan, were enrolled for a three-year period, and all underwent a neurological examination. These included assessment of the limbs and spine as well as sitting posture.

The degree of scoliosis was assessed using a numerical scale – score between zero and three – where zero meant no scoliosis and three meant “severe scoliosis, pronounced curve that prevents standing without external support”.

Manifestations of Rett were measured by the Rett Assessment Rating Scale (RARS), which was completed by the parents, and the patient’s motor skills using the Rett Syndrome Motor Evaluation Scale (RESMES). In both cases, higher scores indicate more severe impairments. RESMES can also be used to assess motor function at home by healthcare professionals.

Spasticity (muscle stiffness or spasms) of the arms and legs was assessed using a modified Ashworth scale, with scores ranging from zero to five. Higher scores indicated more severe stiffness. Two additional scales measured pain and targeted hand function. On the PainAD scale, with total scores ranging from zero to 19, a score greater than three indicated moderate to severe pain. Scores on the hand function scale ranged from one (no hand function) to eight, meaning the ability to use the hand in different situations.

About half of the patients (62.7%) had scoliosis. Overall, it was mild (17 patients, 22.6%) or moderate (25 patients, 33.3%). Five participants (6%) had severe scoliosis.

Patients with scoliosis were older than those without, mean age 14.5 vs. 11.1 years. Severe scoliosis was found in 16% of girls between the ages of 10 and 18 and in 15% of those over the age of 18. No serious cases were found in younger girls (under 10).

The worsening of spasticity and motor function is related to the increase in the severity of scoliosis.

Statistical analyzes revealed that the severity of scoliosis was related to age, excessive muscle tone (hypertonicity), difficulty in standing, walking (walking on the flat and on stairs) and postural transitions. No link was observed with the general severity of Rett’s disease as assessed by RARS, nor with sitting and running.

Contrary to previous studies, no consistent association was found between specific mutations and scoliosis severity. This, however, “could be attributed to the fact that the sample size was relatively small for genetic investigations,” the researchers wrote.

Overall, “we found that age, reduced standing, postural transitions and walking, as well as hypertonia, were associated with the severity of scoliosis,” they added.

The results support a careful and regular monitoring of scoliosis within the first signs of postural abnormalities, with the help of tools such as RESMES.

“The RESMES scale can be performed by caregivers in a home setting, allowing careful monitoring of (loco-) motor disorders of girls with [Rett] and early rehabilitation, ”concluded the study.

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