title: A Meta-analysis of the Cortical Silent Period in Epilepsies.
abstract: OBJECTIVE
  The cortical silent period (CSP) following transcranial magnetic stimulation reflects GABAB-mediated inhibition in the primary motor cortex (M1) and could contribute to understand the pathophysiological substrates of epileptic conditions. Increased CSP duration has been reported in idiopathic generalized epilepsy (IGE) and in partial epilepsy (PE) involving the M1, although other studies yielded discordant findings. We used meta-analysis to systematically assess the consistency of CSP changes in untreated patients with epilepsies.
  
  
  METHODS
  Databases were searched for controlled studies evaluating the CSP in drug-naïve or drug-free patients with IGE or PE. For each study, the mean difference with 95% confidence intervals (CIs) between CSP duration obtained in patients and controls was calculated. The effect of motor threshold (MT) on the CSP duration has also been explored by meta-analysis and meta-regression.
  
  
  RESULTS
  Fourteen studies (267 patients and 234 controls) were included. A significant mean difference (14.16 ms, 95% CI, 1.20, 27.11 ms) was found, with longer CSP in patients than in controls. The mean difference was still greater (18.05 ms) if only the 202 IGE patients were analyzed. No MT difference emerged between patients and controls. Meta-regression showed no relationship between MT and CSP duration.
  
  
  CONCLUSIONS
  Meta-analysis confirms CSP modifications in epilepsies, with enhancement of this cortical inhibitory measure at least in most IGE patients. This provides rationale for further investigations aiming to verify the hypotheses that increased CSP reflects compensatory neural phenomena counteracting transition from the interictal to ictal state and that CSP variability reflects the pathophysiological heterogeneity of epileptic syndromes.
authors.affiliation: Unit of Neurology, Azienda Sanitaria di Firenze, Florence, Italy. Electronic address: cincotta@unifi.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cincotta
authors.affiliation: Unit of Neurology, Azienda Sanitaria di Firenze, Florence, Italy; Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Giovannelli
authors.affiliation: Unit of Neurology, Azienda Sanitaria di Firenze, Florence, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Borgheresi
authors.affiliation: Unit of Neurology, Azienda Sanitaria di Firenze, Florence, Italy.
authors.forename: Luciana
authors.initials: L
authors.lastname: Tramacere
authors.affiliation: Department of Neurosciences, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Viggiano
authors.affiliation: Unit of Neurology, Azienda Sanitaria di Firenze, Florence, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Zaccara
mesh_terms: D016022:Case-Control Studies; D004828:Epilepsies, Partial / Q000503:physiopathology*; D004829:Epilepsy, Generalized / Q000503:physiopathology*; D006801:Humans; D009044:Motor Cortex / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation
keywords: Epilepsy; Meta-analysis; Silent period; Transcranial magnetic stimulation