Assessment of excitability at the brainstem and cortex in primary headaches with allodynia

PURPOSE The aims were to assess the excitability of motor cortex and trigeminal structures in patients with primary headaches experiencing allodynia and to investigate the alterations in interictal allodynia and blink reflex excitability after repetitive transcranial magnetic stimulation (rTMS). METHODS Patients with strictly lateralized primary headaches were included, and Allodynia Symptom Checklist was used to detect allodynia. Paired transcranial magnetic stimulation and blink reflex recovery studies were performed on both sides. Ten Hertz or sham rTMS was applied on the motor cortex in patients with interictal allodynia. Allodynic symptoms were registered quantitatively, and blink reflex study was repeated after these trials. RESULTS Seventeen of 34 patients with headache described allodynia. Our findings showed bilateral hyperexcitability of cortical and trigeminal structures in the allodynic group. Interictal allodynia, detected in 13 allodynic patients, improved after rTMS as compared with sham stimulation, and this effect appeared to be more evident in the late period. CONCLUSIONS Bilateral increases in the cortical and trigeminal excitability were shown in patients with allodynia, and rTMS was effective for reducing clinical allodynia. The authors suggest that allodynic condition of the patients should be taken into account in the planning and evaluation of electrophysiological studies, and rTMS may be considered as a treatment alternative for troublesome allodynia.