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We studied the EMG potentials evoked in the bilateral first dorsal interosseus muscle by electromagnetic stimulation of the corticomotoneuronal descending system in 10 Parkinson's disease patients and in 10 age- and sex-matched normal controls. We selected patients who did not have tremor but had predominant rigidity with asymmetric body involvement. On the rigid side of the PD patients, the threshold to cortical stimulation was lower than on the contralateral side or than normal values. On average, patients had normal central conduction times, but their motor evoked potentials (MEPs) on the rigid side were larger than those of controls when the cortical stimulus was at rest or during slight tonic contraction of the target muscle. In the latter condition, a silent period shorter than that of controls followed MEPs, whereas the peripheral silent period following ulnar nerve stimulation at the wrist was prolonged. Alpha motor neuron excitability, tested by the F-wave method, was enhanced on the rigid side at rest. In rigidity, spinal motor nuclei may be more responsive than normal to descending inputs from motor cortex, or the entire corticomotoneuron system may prove hyperexcitable under given conditions.

Summary:Purpose: To assess the effectiveness of slow repetitive transcranial magnetic stimulation (rTMS) as an adjunctive treatment for drug-resistant epilepsy.Methods: Forty-three patients with drug-resistant epilepsy from eight Italian Centers underwent a randomized, doubleblind, sham-controlled, crossover study on the clinical and EEG effects of slow rTMS. The stimulus frequency was 0.3 Hz. One thousand stimuli per day were given at the resting motor threshold intensity for 5 consecutive days, with a round coil at the vertex.Results: "Active" rTMS was no better than placebo for seizure reduction. However, it decreased interictal EEG epileptiform abnormalities significantly (p < 0.05) in one-third of the patients, which supports a detectable biologic effect. No correlation linked the rTMS effects on seizure frequency to syndrome or anatomic classification, seizure type, EEG changes, or resting motor threshold (an index of motor cortex excitability).Conclusions: Although the antiepileptic action was not significant (p > 0.05), the individual EEG reactivity to "active" rTMS may be encouraging for the development of more-powerful, noninvasive neuromodulatory strategies.

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Summary:Purpose: To assess whether single-and pairedpulse transcranial magnetic stimulation (TMS) can measure the interictal brain excitability of medicated patients with cryptogenic localization related epilepsy (CLE). Changes in the balance between excitation and inhibition are the core phenomena in focal epileptogenesis. TMS can assess this balance in the primary motor cortex.Methods: We selected 18 patients with CLE and similar clinical features in whom we located the epileptogenic area reliably, with 11 age-and sex-matched healthy controls. For both motor cortices, we determined the threshold to TMS, the duration of the cortical silent period, and the corticocortical inhibition and facilitation curve.Results: TMS was safe. The more antiepileptic drugs (AEDs) taken by the patients, the higher their threshold to TMS. The silent period duration failed to show significant changes. On paired TMS, a cluster analysis identified a homogeneous subgroup of patients (n = 7) who showed a significantly defective corticocortical inhibition and excess facilitation. With respect to the epileptogenic area, the phenomenon was bilateral in four of these patients, ipsilateral in two, and contralateral in one. The phenomenon was independent of AEDs and many other clinical variables. However, this patient group had a higher seizure frequency and a higher proportion of electroencephalograms (EEGs) showing interictal generalized epileptic discharges than the rest of the patients.Conclusion: Paired TMS provided a valuable pathophysiologic insight into the interictal excitatory state of the cortex in CLE. This method can potentially supply useful prognostic clinical information.