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Wallerian Degeneration of the Corticofugal Tracts in Chronic Stroke: A Pilot Study Relating Diffusion Tensor Imaging, Transcranial Magnetic Stimulation, and Hand Function

Department of Neuroscience, Uppsala University Hospital, Uppsala, Sweden, Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden, Department of Rehabilitation Medicine, Danderyd Hospital, Stockholm, Sweden, Pavel.Lindberg{at}rehab.uu.se

Pernille H. B. Skejø, MD

Department of Neuroradiology, Odense Hospital, Odense, Denmark

Elisabeth Rounis, PhD

Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK

Zoltan Nagy, MSc

Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden

Christina Schmitz, PhD

Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden

Helena Wernegren, MSc

Department of Rehabilitation Medicine, Danderyd Hospital, Stockholm, Sweden

Annika Bring, MSc

Department of Physical Therapy, Uppsala University Hospital, Uppsala, Sweden

Margareta Engardt, PhD

Department of Rehabilitation Medicine, Danderyd Hospital, Stockholm, Sweden

Hans Forssberg, PhD

Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden

Jörgen Borg, PhD

Department of Neuroscience, Uppsala University Hospital, Uppsala, Sweden

Objective. This study tested the hypothesis that degeneration of the corticofugal tracts (CFTs) is related to poor functional outcome in the upper limb after stroke. Methods. The authors used diffusion tensor imaging to determine the degree of white matter integrity of the CFT (FA_AH/UH) in chronic stroke patients and controls. The functional integrity of the corticospinal pathway was examined using transcranial magnetic stimulation. Recruitment curves and silent period duration were measured. The relationship between FA _AH/UH and functional outcome of the upper limb was also assessed using a battery of upper limb function tests. Results. In patients, FA _AH/UH correlated positively with the slope of recruitment curves (RC _AH/UH) and grip strength. FA_AH/UH also correlated negatively with the silent period duration (SP_AH/UH). According to the FA _AH/UH, patients were also classified into groups with minimal or extensive Wallerian degeneration (WD). Patients with more extensive WD had poorer grip strength, dexterity, and range of movement. Conclusions. The authors' results suggest that structural and functional integrity of the CFT is essential to maintain function of the upper limb after stroke.

Key Words: Stroke • Diffusion tensor imaging • Transcranial magnetic stimulation • Corticofugal tracts • Wallerian degeneration • Upper limb • Outcome

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