Spasticity severity after stroke and relation to hand motor recovery and corticospinal tract integrity

Introduction/Background Spasticity of muscles controlling the hand is common after stroke, however, its impact on hand motor recovery and its neural correlates are poorly understood. This longitudinal observational study investigated hand spasticity after stroke in relation to motor recovery, secondary complications and lesion location. Material and method Sixty-one patients were assessed at three weeks (T1), three (T2) and six months (T3) after stroke. Neural (NC) and viscoelastic (EC and VC) stretch-resistance in wrist and finger flexors were quantified with the NeuroFlexor method. Clinical evaluation included Fugl–Meyer (FMA-HAND), Box and Block Test (BBT), passive range of movement (ROM) and pain (FMA-subscale). Magnetic Resonance Imaging data were analyzed for weighted corticospinal tract lesion load (wCST-LL) and voxel-based lesion symptom mapping (VLSM). Results Four spasticity subgroups were defined: early severe (SS, n = 10), early moderate (MS, n = 10), late developing (LS, n = 17) and no spasticity (NS, n = 24). All groups except SS improved in FMA-HAND to T3. SS and LS had no recovery in BBT. SS showed a larger loss of ROM and more frequent arm pain at T3. wCST-LL predicted NC at T3, also when including FMA-HAND and lesion volume as covariates. VLSM showed that lesioned white matter below the cortical hand knob correlated positively with spasticity. Conclusion Severe hand spasticity impairs motor recovery, ROM and may increase risk for development of arm pain. This study provides the first data showing that spasticity is related to lesion load of the CST. The significance of early quantification of spasticity for prediction of motor outcome and rehabilitation planning will be discussed.