Sir Peter Mansfield Imaging Centre

Clinical populations

Carpal Tunnel Syndrome (CTS)

CTS is characterised by tingling, numbness, pain and parasthesia in the hands and fingers; it is caused by median nerve compression. These symptoms can lead to alterations in the tactile somatosensory system, evidenced by a reduced nerve conduction velocity, delayed cortical response to stimulation, altered cortical rhythms, and altered digit somatotopy (as measured by MEG)1.

Reduced interdigit separation in contralateral S1 and increased digit overlap (receptive fields) have been correlated with symptom severity and reduced ability to pinch and release2. There is also evidence of amplified representations for affected digits in contralateral S1, with one group suggesting that this is the cause for the patient's pain and parasthesia3.

ctsFig1. Carpal Tunnel Syndrome
 

Focal Hand Dystonia (FHD)

FHD is characterised by involuntary movements, cramps and tremors in the hand and arms, is often known as 'Writer's Cramp', and can be task-specific. Traditionally a motor disorder, recent research has shown an association with impaired temporal and spatial tactile discrimination, reduced interdigit separation in S1, and under activation in S2 to stimuli4,5.

FHD can be caused by over-use of the hand, and/or repeated movements, such as those that occur during the playing of music.

fhdFig2. A graphic depiction of a cramp caused by FHD
 

Hypothesis

  • In comparison to healthy participants, we hypothesise that patients will present with altered somatotopic maps, enlarged sensory fields, increased digit overlap, increased interhemispheric connectivity and impaired temporal discrimination.
  • We will perform longitudinal intervention studies in dystonia patients to determine whether cortical reorganisation is induced by botulinum toxin (BoNT-A); we will also quantify cortical maps pre- and post- median nerve decompression in CTS.

References

  1. Dhond, R. P. et al. Spatio-temporal mapping cortical neuroplasticity in carpal tunnel syndrome. Brain 135, 3062–3073 (2012).

  2. Maeda, Y. et al. Functional deficits in carpal tunnel syndrome reflect reorganization of primary somatosensory cortex. Brain 137, 1741–1752 (2014).

  3. Napadow, V. et al. Somatosensory cortical plasticity in carpal tunnel syndrome-a cross-sectional fMRI evaluation. Neuroimage 31, 520–530 (2006).

  4. Butterworth, S. et al. Abnormal cortical sensory activation in dystonia: An fMRI study. Mov. Disord. 18, 673–682 (2003).

  5. Nelson, A. J., Blake, D. T. & Chen, R. Digit-specific aberrations in the primary somatosensory cortex in Writer’s cramp. Ann. Neurol. 66, 146–54 (2009).