Objective  To characterize changes in gait by age in patients with Dravet syndrome.

Design  Prospective, cross-sectional study.

Setting  Tertiary children's hospital.

Patients  Twenty-six subjects with Dravet syndrome, aged 2 to 34 years. Twenty-three patients had mutations of the sodium channel α1 subunit gene, SCN1A.

Interventions  Assessment via video gait analysis, physical examination of the lower limbs, use of the Functional Mobility Scale, and radiographs of the pelvis and feet.

Main Outcome Measures  Classification of the sagittal gait pattern and foot posture, assessment of muscle extensibility and joint range, and rating of functional mobility.

Results  Children aged 0 to 5 years had a normal or near-normal gait, whereas 5 of 10 children aged 6 to 12 years and 8 of 9 children aged 13 years or older had crouch gait. Physical examination showed that with increasing age, passive knee extension (P = .008) and hip extension (P = .003) decreased, external tibial torsion (P = .007) and pes planovalgus (P = .05) increased, and increased hip internal rotation did not show age-related change (P = .27). The Functional Mobility Scale showed universal independent walking over 5 and 50 m; however, adolescents showed wide variation in their ratings over 500 m, indicating mobility ranging from wheelchair use to independent walking (P = .02).

Conclusions  Children with Dravet syndrome show progressive gait deterioration in the second decade of life, with crouch gait and skeletal malalignment comprising increased femoral neck anteversion, external tibial torsion, and pes valgus. These age-related changes have a significant impact on mobility and independence in the community setting.