Cortical hyperexcitability in post-traumatic stress disorder secondary to minor accidental head trauma: a neurophysiologic study.

OBJECTIVE We applied paired transcranial magnetic stimulation (pTMS) to patients with post-traumatic stress disorder (PTSD) secondary to minor accidental head trauma. Our purpose was to determine the potential abnormality of motor cortex excitability in this pathologic condition. METHODS pTMS stimulation, according to the conditioning-test paradigm employing interstimulus intervals (ISIs) of 1-6 ms, was used to investigate intracortical inhibition in control subjects and patients with PTSD. The study population consisted of 14 patients who had developed PTSD following minor head trauma, 12 healthy volunteers without a clinical history of head trauma and 11 healthy subjects who had reported accidental minor head trauma 1-4 months before the study. This clinical electrophysiologic study was performed at the Department of Neuroscience, University of Rome "Tor Vergata." RESULTS All patients with PTSD exhibited a significantly lower motor evoked potential (MEP) inhibition than controls at 2 ms, 3 ms and 4 ms ISI. The statistical analysis of the pTMS protocol showed a significant effect (F2,36 = 25.63, p < 0.001) of the factor "group," because patients with PTSD showed a mean conditioned MEP amplitude higher than that observed in both control groups for all 6 ISIs analyzed. The "ISI" factor was also significant (F5,180 = 89.85, Greenhouse-Geisser epsilon = 0.35; p < 0.001), with the mean conditioned MEP amplitude increasing from 22.5% to 127.8% as the ISI increased from 1 ms to 6 ms. Finally, the interaction of group with ISI was also significant (F10,180 = 8.97, p < 0.001), showing that the condition of PTSD secondary to head trauma was able to affect the MEP amplitude at different ISIs. CONCLUSIONS Our results demonstrate that PTSD can give rise to abnormalities in intracortical inhibition. Our results provide further evidence that alterations in cortical inhibitory circuits may underlie specific forms of neuroticism in humans.