Article

In children with Friedreich ataxia (FRDA), ataxia is assessed using the
surrogate marker the International Cooperative Ataxia Rating Scale (ICARS). We
aimed to determine whether ICARS scores in children with FRDA are confounded by
muscle weakness. Method In 12 children with FRDA (10 males, two females; mean age
13y 6mo, SD 2y 6mo) and 12 age-matched children without FRDA (nine males; three
females), we determined the association between muscle and ataxia parameters
(i.e. muscle ultrasound density (MUD), muscle force, sensory evoked potentials,
and ICARS scores). Children with FRDA were included on the basis of FXN gene
analysis. Children in the comparison group were included on basis of uneventful
pregnancy and normal cognitive and neurological development. Results In children
with FRDA, muscle ultrasound density was homogeneously increased in the biceps,
quadriceps, and tibialis anterior muscles (median 4SD). FRDA muscle weakness was
significantly more pronounced in proximal than in distal muscles (-2SD vs -0.5SD
respectively; p=0.004), with a stronger impairment of leg muscles than of arm
muscles (-2SD vs -0. SD respectively; p=0.001). Comparing MUD between children
with FRDA and an age-matched comparison group revealed a relatively strong
increase in MUD in the proximal leg muscles in the FRDA group. Under the
condition of persistently absent sensory evoked potentials, leg ICARS subscores
in the FRDA group appeared to be positively associated with leg muscle force
until a maximal plateau level of ICARS subscores was reached. Interpretation In
children with FRDA, ataxia scales based on ICARS are confounded by muscle
weakness. Longitudinal ICARS evaluations in children with FRDA do not necessarily
indicate altered ataxia.
CI - (c) The Authors. Developmental Medicine & Child Neurology (c) 2011 Mac Keith
Press.

Langue : ANGLAIS