Research Report
Population: Adult
Cecilia N Prudente, PT, PhD, Postdoc, University of Minnesota cecilianasciprud@gmail.com
Keywords: Plasticity, fMRI, Head Movements, Cervical Dystonia
Purpose/Hypothesis: The neuroanatomical substrates for head movements in humans are not well delineated, particularly regarding the side of cortical control for neck muscles. The lack of fundamental information regarding head motor control is relevant to cervical dystonia (CD), a disorder characterized by involuntary contractions of neck muscles. Current understanding of the neuroanatomical basis of CD is very limited. This study addressed the neuroanatomical substrates of head movements in normal individuals and in CD using functional magnetic resonance imaging (fMRI) and an isometric head rotation task. The experiments had two main goals: to delineate the neural basis for normal head movements and to identify abnormalities associated with CD. Based on prior fMRI studies of hand tasks in CD, we hypothesized that CD subjects would show increased activation of the precentral gyrus, basal ganglia and cerebellum in comparison to controls during isometric head rotation.
Subjects: Seventeen healthy volunteers and 16 individuals with CD participated in the study. All CD participants had predominantly rotational CD. Involuntary rotational movements were towards the right for 10 subjects and left for 6.
Materials/Methods: Scanning was conducted during isometric head or hand tasks in both groups. Head tasks consisted of submaximal isometric horizontal head rotation to the right or left. Isometric wrist extension was examined as a positive control and to establish the relative locations of head and hand regions in the motor cortex. Electromyography recordings of neck and hand muscles during scanning ensured compliance with tasks.
Results: Isometric head rotation in controls induced significant activation in the bilateral precentral gyrus, both medial and lateral to the hand area, as well as bilateral supplementary motor area, insula, putamen, and ipsilateral cerebellum. CD subjects had an overall broader activation of cortical and subcortical areas except in the medial precentral gyrus, which showed less prominent activation. However, statistical comparisons failed to reveal significant differences between groups. Analyses of CD data normalized to the side of torticollis indicated that isometric head rotation in the direction of abnormal movements is associated with more activation in the ipsilateral anterior cerebellum, whereas moving the head in the opposite direction is associated with more activity in sensory and motor cortical areas. These results imply significant asymmetries of brain activity associated with the torticollic and non-torticollic directions of head movements in CD.
Conclusions: The findings in healthy and CD participants begin to fill a critical gap in the understanding of normal and abnormal head movements in humans. Based on our task-based data, we plan to compare the functional connectivity of specific regions between controls and CD using resting-state fMRI data that have already been collected.
Clinical Relevance: The results may help guide future medical or surgical interventions for CD targeting relevant brain regions.
Citation:
Prudente, Cecilia N, PT, PhD. Functional imaging of isometric head rotation in cervical dystonia.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online. https://u.osu.edu/ivstep/poster/abstracts/051_prudente/