Asymmetric atrophy of the multifidus in persons with hemiplegic presentation post-stroke.

: To identify the asymmetry of fatty infiltration and cross-sectional areas (CSAs) of individual paravertebral muscles in persons with hemiplegic presentation post-stroke.: We retrospectively reviewed 26 patients with unilateral hemiplegia who underwent lumbar magnetic resonance imaging post-stroke. CSAs and functional CSAs (FCSAs) of individual paraspinal muscles (multifidus, erector spinae, quadratus lumborum, and psoas major) at the mid-disc level were bilaterally measured from L1-L2 to L5-S1 on T2-weighted lumbar axial images. The FCSA-to-total CSA ratio of each paraspinal muscle was also calculated. These parameters were compared between the more-affected and less-affected sides, and between the less chronic and chronic phases.: FCSA ( = .049) and FCSA-to-total CSA ratio ( = .044) were significantly smaller at the L5-S1 multifidus on the more-affected side than on the less-affected side in the chronic phase. Other muscles showed no meaningful changes. The erector spinae on the more-affected side and the multifidus on the less-affected side significantly increased in size in the chronic phase compared with the less chronic phase.: Persons with hemiplegic presentation may have unilateral atrophy and fatty infiltration of the multifidus on the more-affected side during the chronic phase. The comparison between the less chronic and chronic phases suggested that the recovery pattern of the trunk muscles could differ between sides in unilateral hemiplegia: increased size of the multifidus, a tonic stabilizer, on the less-affected side and of the erector spinae, a phasic muscle, on the more-affected side. This finding could be applied to trunk rehabilitation strategies for persons post-stroke.