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Asymmetric cortico-cortical inhibition in patients with progressive limb-kinetic apraxia
Y Okuma1, T Urabe, H Mochizuki
1Department of Neurology, Juntendo University School of Medicine, Tokyo, Japan.
Objectives:
To evaluate the activity of cortico-cortical (intracortical) inhibitory circuits within the motor cortex in patients with progressive asymmetric limb-kinetic apraxia.
Materials And Methods:
We studied 4 patients with progressive limb-kinetic apraxia whose clinical diagnosis was corticobasal degeneration (CBD) and 7 control subjects. Cortico-cortical inhibition was measured using the technique of double pulse transcranial magnetic stimulation over the motor cortex. The effects of conditioning stimuli on the test responses were examined.
Results:
In the normal control subjects, the conditioning magnetic stimulus suppressed motor evoked responses to the test stimulus at interstimulus intervals of 1 to 5 ms. This inhibition was significantly diminished on the affected side of the patients, but it was normal on the less affected side.
Conclusion:
Disruption of intracortical inhibitory circuits in the motor cortex may, at least in part, be related to severe limb clumsiness in the patients with progressive limb-kinetic apraxia.