Motor cortical excitability assessed by transcranial magnetic stimulation in psychiatric disorders: a systematic review.
BACKGROUND
Transcranial magnetic stimulation (TMS) is a popular neurostimulation technique suitable for the investigation of inhibitory and facilitatory networks in the human motor system. In the last 20 years, several studies have used TMS to investigate cortical excitability in various psychiatric disorders, leading to a consequent improvement in pathophysiological understanding. However, little is known about the overlap and specificity of these findings across these conditions.


OBJECTIVE
To provide a systematic review of TMS studies (1985-2013) focusing on motor cortical excitability in dementia, schizophrenia, affective disorders (major depression and bipolar), attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder (OCD), Tourette Syndrome (TS), substance abuse (alcohol, cocaine, cannabis, nicotine) and other disorders (borderline personality disorder, posttraumatic stress disorder (PTSD)).


METHODS
Systematic literature-based review.


RESULTS
Across disorders, patients displayed a general pattern of cortical disinhibition, while the most consistent results of reduced short-interval intracortical inhibition could be found in schizophrenia, OCD and Tourette Syndrome. In dementia, the most frequently reported finding was reduced short-latency afferent inhibition as a marker of cholinergic dysfunction.


CONCLUSIONS
The results of this systematic review indicate a general alteration in motor cortical inhibition in mental illness, rather than disease-specific changes. Changes in motor cortical excitability provide insight that can advance understanding of the pathophysiology underlying various psychiatric disorders. Further investigations are needed to improve the diagnostic application of these parameters.
Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Nussbaumstr. 7, D-80336 Munich, Germany.
Tilmann
T
Bunse
Centre of Mental Health, County Hospital Darmstadt-Dieburg, Groß-Umstadt, Germany; Department of Psychiatry and Psychotherapy, Georg-August-University, Göttingen, Germany.
Thomas
T
Wobrock
Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Nussbaumstr. 7, D-80336 Munich, Germany.
Wolfgang
W
Strube
Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Nussbaumstr. 7, D-80336 Munich, Germany.
Frank
F
Padberg
Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Nussbaumstr. 7, D-80336 Munich, Germany.
Ullrich
U
Palm
Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Nussbaumstr. 7, D-80336 Munich, Germany.
Peter
P
Falkai
Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University, Nussbaumstr. 7, D-80336 Munich, Germany. Electronic address: Alkomiet.Hasan@med.uni-muenchen.de.
Alkomiet
A
Hasan
D019054:Evoked Potentials, Motor / Q000502:physiology*; D006801:Humans; D001523:Mental Disorders / Q000175:diagnosis / Q000503:physiopathology*; D009044:Motor Cortex / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
Cortical excitability; Cortical inhibition; Psychiatric disorder; Systematic review; Transcranial magnetic stimulation