Daneault et al. Journal of Medical Case Reports 2011, 5:449 http://www.jmedicalcasereports.com/content/5/1/449 been effectively controlled with carbamazepine (current dose: 600 mg twice a day). Her last reported seizure occurred two years ago. Her usual pre-ictal symptoms include nausea, vomiting or headache. Ictal symptoms included numbness and involuntary contraction of the right hand and forearm that could propagate up to the neck and face. Rarely, she experienced convulsions. This indicates that the abnormal oscillations first emerged in the somatosensory cortex and propagated to motor areas as they intensify. PT was measured simultaneously on the index finger of both hands using laser displacement sensors (LDS 90/40, LMI Technologies, Heerlen, The Netherlands). Electromyography (EMG) of the extensor digitorum communis and flexor digitorum superficialis of both forearms was recorded using bipolar, pre-amplified sur- face electrodes. Her heart rate and respiration were also monitored. She was seated facing a computer screen. Four conditions were planned, the first one being bilat- eral tremor recording while she was asked to look at a horizontally moving line on the computer screen. Dur- ing that condition, the participant was asked to keep both index fingers in a horizontal position while her arms and hands were resting on a custom-designed sup- port. Because of the seizure, the three remaining condi- tions were not performed. The trials lasted 60 seconds and a rest period of 60 seconds was allotted between trials. For details on analysis, see Daneault et al. [8]. For the first two trials, there were no reports of any physical problems or symptoms by our patient. Only after the third trial did she mention she was not feeling well. She reported slight dizziness, sweating and men- tioned she was seeing spots. However, after a minute of rest she felt better and opted to continue. During the fourth trial, she identified having had a seizure. The experiment was then halted. Analysis revealed significant changes in PT character- istics throughout the experiment. First, to illustrate the changes in PT amplitude and spectral characteristics, an example of PT of both fingers and related power spec- trums in the second and fourth trials is shown (Figure 1). Note that the right hand exhibited a prominent peak at 2 Hz. However, the origin of this prominent peak, whether stemming from a change in mechanical proper- ties or from abnormal central oscillations, cannot be addressed by the current protocol. While PT of both fingers was within normal physiolo- gical parameters during the first trial, an increase in amplitude was then observed for the right index finger (Figure 2). Although this increase was not clinically sig- nificant during the first three trials, Figure 2 clearly illustrates that the PT amplitude began to change as early as the second trial; even before our patient was conscious of any predictors such as the ones Page 2 of 6 experienced after the third trial. Interestingly, PT ampli- tude for the left index finger remained relatively steady throughout the recordings. Changes observed in PT amplitude were accompanied with alteration of spectral characteristics. Median power frequency (MPF) and power dispersion (frequency band containing 68% of total power centered at the MPF) both decreased for the right index finger starting in the second trial (Figure 2). MPF decreased to approach Essential tremor properties [10] while power dispersion remained within the physiological range. As for PT amplitude, spectral characteristics of the left index finger remained relatively steady throughout the recordings. EMG results did not show any predictive signs of the imminent seizure. Although variability in EMG activity amplitude was observed between trials, no significant pattern emerged for either muscle or side. RMS values (arbitrary units) ranged from 2.27e-4 to 3.04e-4 for the right extensor, 4.06e-6 to 1.31e-4 for the right flexor, 8.63e-5 to 3.81e-4 for the left extensor and 2.37e-5 to 5.66e-5 for the left flexor. Our patient’s heart rate characteristics did not change significantly between trials; the mean RR interval was 847 ± 68.9 milliseconds, mean heart rate was 71.6 ± 6.1 beats/second, mean NN50 was 12.3 ± 4.1 spikes and mean pNN50 was 19.2 ± 5.5%. The characteristics of respiration also did not change significantly; the mean duration of every breath was 4.1 ± 0.7 seconds and the mean irregularity of the signal, that is, the standard deviation of the linear envelope of the respiration signal, was 0.7 ± 0.1. The seizure and its preceding signs did not affect the heart rate and breathing of our patient, hence they could not have been used to forecast the arrival of this epileptic seizure. The present case illustrates that unconscious, subtle changes in PT can be observed prior to conscious signs that a seizure may occur. This is interesting since the patient’s epileptiform activity originates in the somato- sensory cortex and propagates to the motor areas; thus, the structures of the central network implicated in PT, whether somatosensory or motor, could be hypersensi- tive to abnormal oscillations. The present findings demonstrate that contralateral to the localization of the epileptic activity, while PT amplitude increased, MPF and power dispersion showed a marked decrease. These characteristics are usually associated with the presence of a dominating central oscillation (or oscillations) within the power spectrum of PT. This can be the case even while no significant change in EMG was observed because of the inherent limitations of this technique. The altered characteristics never reached extreme values that would normally be found in pathological cases such as Parkinson’s or Essential tremors [9,10]. The striking feature in our patient’s case is the obvious difference in