August 2017

Dyslexia affects ability to adjust to impaired sensory feedback

French investigators used this platform to measure postural stability in kids with dyslexia under several sensory-perturbing conditions. (Photo courtesy of Nathalie Goulème, PhD.)

Kids struggle to maintain balance

By Katie Bell

Children with dyslexia are unable to compensate with other available inputs when sensory feedback to the soles of their feet, their vision, or both is less informative, resulting in poor postural stability, according to research from Paris, France, which may have implications in training to help these children improve their use of sensory inputs.

The study set out to test the influence of foot soles and visual information on the postural control of 24 children with dyslexia (mean age 9.3 years) and compare their data with those of 24 gender- and aged-matched children without dyslexia. The participants were not receiving any drug treatment and did not have an orthopedic anomaly or a personal history of vestibular or visual deficit or neurological or psychiatric disorders.

Investigators used a platform with two dynamometric clogs to measure postural stability with and without 4-mm foam placed under the participants’ feet and with their eyes open and closed. Specifically, the researchers measured the surface area, length, and mean velocity of the center of pressure (CoP), while the Romberg Quotient (RQ), which is the ratio between the surface area of the CoP with eyes closed and eyes open, was calculated with and without foam.

The results showed the surface area, length, and mean velocity of the CoP were greater in the children with dyslexia compared to those without dyslexia, predominantly during the foam and eyes-closed conditions.

Lead author Nathalie Goulème, PhD, a researcher at the Université Paris Diderot Robert Debré Hôpital, remarked, “To improve postural control, in clinic we can suggest exercises on a platform where children have to maintain their stability depending on environmental condition [eyes closed, support unstable, with optokinetic stimulation]. Thus, children with disorders could improve their integration weighting sensorial input and using the better sensory strategy.”

Goulème further noted that visual feedback placed in front of a child, on a screen, while they maintain their stability could improve their ability to know their oscillations and control them. She added that, “More usually, I need to suggest to a child and his family to try sport/games/ leisure activities [requiring] hand-eye coordination and involving equilibrium.”

Additionally, the results showed the RQ was smaller in the children with dyslexia than in participants without dyslexia, indicating children with dyslexia have more trouble with balance than children without dyslexia under both eyes-open and eyes-closed conditions. The RQ was also greater without foam than with foam in both groups, but more so in children with dyslexia, and the authors noted the cutaneous inputs of the foot soles can involve a change in the integration of visual inputs.

Kids with dyslexia are more unstable than controls under both eyes-open and eyes-closed conditions.

The authors suggested the impairment of the cerebellar integration of all the sensorial inputs is responsible for the postural deficits evident in children with dyslexia, and that the use of visual inputs by these children could be disturbed by an alteration in somatosensory input integration.

Goulème said that, along with training by stimulation, “most of the time, children can have prismatic treatment, proprioceptive features on orthoses for the foot sole, advice for daily life [eg, training to improve attention, exercises for posture].” She added that dyslexia is a heterogeneous disorder and that adapting treatment to the individual child is paramount.

She noted that everyone has to maintain their stability during a simultaneous task, such as reading. “Consequently, if only maintaining postural control is difficult and involves a high level of energy, attention will be shared and unfortunately learning can be decreased or slower,” she said.

The authors, who published their findings in July in Gait & Posture, recommend further research to explore the children’s ability to weigh sensory inputs by cerebellum adaptation.

Lisa Selby-Silverstein, PT, PhD, NCS, physical therapist at Rainbow Rehab in Marlton and Mount Holly, NJ, and professor of physical therapy at Neumann University, in Ashton, PA, said, “Most of these children are not getting PT for balance difficulties as access to that care depends on awareness and advocacy by the adults around these children. It also will depend on an understanding by the therapists receiving that referral of the issues at hand.”

Selby-Silverstein, who is also a member of the American Physical Therapy Association’s Foot and Ankle Special Interest Group, further noted she likes to encourage physical therapy aimed at optimizing the child’s tolerance and total body alignment in custom-casted foot orthoses to improve their foot alignment and decrease foot deformity, both of which are likely to contribute to improved balance.

“In light of this research, however, it would be important to see if firm contoured inserts would improve balance rather than impair balance as the four-millimeter flat foam did,” Selby-Silverstein added.

Katie Bell is a freelance writer based in New York City.

Source:

Goulème N, Villeneuve P, Gérard CL, et al. Influence of both cutaneous input from the foot soles and visual information on the control of postural stability in dyslexic children. Gait Posture 2017;56:141-146.

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