Motor Cortex Excitability In Linear Headache Patients: Atranscranial Magnetic Stimulation Study

BackgroundLinear headache(LH) was discovered and reported as a special pattern of headache in recent years. These patients presented with a recurrent fixed distending or pulsating head pain, which was circumscribed in a line-shaped area distributing from occipital or occipitocervical region to ipsilateral nose, forehead or parietal region, but was not confined to the territory of one particular nerve.Despite of the unique clinical features in LH patients, there were lots of similarities between LH and migraine without aura(MO), which indicated that LH might be a new variant of MO. With the development of transcranial magnetic stimulation(TMS), TMS was widely applied in evaluating the cortex excitability of nervous and mental diseases safely and noninvasively.ObjectiveEvaluating the cortex excitability of LH patients by TMS, and making a comparison between LH patients and the patients with MO.Material and MethodsEight LH patients, fourteen MO patients and fourteen healthy right-handed, age and sex matched volunteers were included in the study. Each subject underwent transcranial magnetic stimulation and was submitted to the following: determination of resting motor threshold(RMT), cortical silent period(CSP), input–output curves(I-OC).Results1 Resting motor thresholdComparing RMT on the left motor cortex with it on the right cortex of the LH group and MO group respectively, the difference was not statistically significant(P>0.05). No significant differences were observed among the three groups with respect to RMT(P>0.05).2 Cortical silent periodThere were no significant differences between the left motor cortex compared to the right cortex in LH group, MO group and control group, respectively. No significant differences were observed among the three groups with respect to CSP(P>0.05).3 Input- output curveWith the increase of stimulus intensity, the amplitude of motor-evoked potential(MEP) was increased dramatically in each group(left: P<0.05; right: P<0.05). Comparing I-OC on the left motor cortex with it on right cortex of the LH group and MO group respectively, the difference was not statistically significant. Results showed a greater motor-evoked potential amplitude in response to increasing intensity of stimuli on the right motor cortex in patients with LH and WO compared to controls(P<0.05). However, there was no significant difference between LH patients and control in input output curve on the left motor cortex, despite the rapid increase in amplitude of MEP with increased intensity of stimulation in LH patients compared with control group. In addition, there was no significant difference between LH and MO in input-output curve.ConclusionThe excitability of motor cortex in patients with LH in interictal period was hyperexcitability, which suggested that the increased excitability of the motor cortex might be one of the underlying mechanisms. No significant differences were observed between the LH group and MO group with respect to excitability and inhibition,meanwhile, combined with plenty of similarities in clinical characteristics, we speculated that LH might be a new variant of MO or a novel headache syndrome which overlapped the pathogenesis of MO.