Summary Multiple‐imputation (MI) methods for imputing missing data in observational health studies with repeated measurements were evaluated with particular focus on incomplete time varying explanatory variables. Standard and random‐effects imputation by chained equations, multivariate normal imputation and Bayesian MI were compared regarding bias and efficiency of regression coefficient estimates by using simulation studies. Flexibility of the methods in handling different types of variables (binary, categorical, skewed and normally distributed) and correlations between the repeated measurements of the incomplete variables were also compared. Multivariate normal imputation produced the least bias in most situations, is theoretically well justified and allows flexible correlation for the repeated measurements. It can be recommended for imputing continuous variables. Bayesian MI is efficient and may be preferable in the presence of categorical and non‐normally distributed continuous variables. Imputation by chained equations approaches were sensitive to the correlation between the repeated measurements. The moving time window approach may be used for normally distributed continuous variables with auto‐regressive correlation.

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The purpose of this study was to evaluate the correlation between magnetic resonance imaging (MRI) findings and demographic and clinical characteristics, response to treatment times, and recurrence rates of Sydenham's chorea (SC), the most common of the acquired pediatric choreas. The clinical and radiological findings of 12 patients presenting to the pediatric neurology clinic in the previous 4 years and diagnosed with SC on the basis of the modified Jones criteria were investigated retrospectively from the hospital files. In addition, we measured the maximum prefrontal cortex and basal ganglia (globus pallidus, putamen, and caudate nucleus) thicknesses in the axial plane from patients' cerebral MRIs and compared these values with prefrontal cortex and basal ganglia thicknesses of a healthy control group measured using the same technique. Patient and control groups' cranial and basal ganglia MRIs were found to be normal. However, patients' globus pallidus thicknesses were significantly lower than those of the healthy control group. Additionally, the globus pallidus values of patients with recurrent SC and a prolonged healing time were lower than average. However, we determined no significant difference in terms of prefrontal motor cortex, caudate nucleus, or putamen thicknesses between the patient and control groups. Low globus pallidus thicknesses in patients with SC may indicate atrophy associated with globus pallidus involvement. Further experimental and prospective and long-term studies are needed for a better understanding of the factors affecting the pathophysiology, recurrence, and healing time of SC.