Background and Purpose: The neurophysiological
characteristics of motor cortex have been well characterized
in patients with Huntington’s disease. We present
the first data on cortical excitability in patients with
Sydenham’s chorea.
Methods: Motor cortex excitability was examined
using transcranial magnetic stimulation in 16 patients
in the early clinical stages of Sydenham’s chorea and
in 17 age- and sex-matched control subjects. Investigations
included resting and active motor threshold,
motor evoked potential, input–output curves, contralateral
silent period, and transcallosal inhibition.
Results: Resting and active motor threshold were significantly
higher and motor evoked potentials were significantly
smaller in patients in comparison with
controls. The input–output curves were shallower in
both hemispheres of patients with chorea compared
with controls. No significant differences were seen in
silent period or transcallosal inhibition duration.
Conclusion: Sydenham’s chorea is characterized by
reduced excitability of corticospinal output similar to
that observed in Huntington’s disease. VC 2014 International
Parkinson and Movement Disorder Society