Precisely timed oculomotor and parietal EEG activity in perceptual switching

Blinks and saccades cause transient interruptions of visual input. To investigate how such effects influence our perceptual state, we analyzed the time courses of blink and saccade rates in relation to perceptual switching in the Necker cube. Both time courses of blink and saccade rates showed peaks at different moments along the switching process. A peak in blinking rate appeared 1,000 ms prior to the switching responses. Blinks occurring around this peak were associated with subsequent switching to the preferred interpretation of the Necker cube. Saccade rates showed a peak 150 ms prior to the switching response. The direction of saccades around this peak was predictive of the perceived orientation of the Necker cube afterwards. Peak blinks were followed and peak saccades were preceded by transient parietal theta band activity indicating the changing of the perceptual interpretation. Precisely-timed blinks, therefore, can initiate perceptual switching, and precisely-timed saccades can facilitate an ongoing change of interpretation

Trigeminal Neuralgia

Trigeminal Neuralgia (TN) is the most common cranio-facial pain syndrome, with an incidence of up to 5 in 100,000. Long-term medical treatment is commonly required, with up to 10% of cases suffering adverse drug-related events. In 1951, Lars Leksell pioneered the application of stereotactic irradiation for the treatment of TN, which may now achieve up to 90% pain control at 1 year and 60% at 3-5 years. Radiosurgical treatment targets either the nerve\u2019s emergence (the root entry zone) or the retrogasserian portion of the nerve (pars triangularis). Targeting the latter may reduce the risk of complications, but requires a higher maximum dose to obtain optimal results. Generally speaking, radiosurgical treatment achieves optimal results in patients receiving high doses of radiations ranging from 70 to 90 Gy. Hypoesthesia and facial numbness are frequently observed after high-dose trigeminal irradiation. Mild hypoesthesia is acceptable and is considered by many an efficacy endpoint of the procedure. Bothersome facial numbness is relatively rare. Sensitive trigeminal disturbances and paresthesia after treatment have been reported to range respectively 6%\u201354% and 0%\u201317%. The prescribed dose and brainstem-delivered dose are correlated with the subsequent rate of sensitive trigeminal disturbances. CyberKnife frameless non-isocentric radiosurgery is an emerging and non-invasive treatment for TN. Because of the non-isocentric geometry of radiation beams delivery, CyberKnife technique offers the possibility of homogeneous irradiation of an extended segment of the trigeminal nerve, so introducing some new concepts for the radiosurgical treatment of TN. Clinical results of CyberKnife radiosurgery seems to be satisfactory. We here review the basics of radiosurgery for TN and present a detailed analysis of the technique using the CyberKnife frameless system