Impaired neck motor control in chronic whiplash and tension-type headache.

OBJECTIVES: The purpose of this study is twofold, first to present a new method based on head laser tracking designed to measure head or hand movements and second to further investigate if patients suffering from chronic whiplash or tension-type headache have impaired motor control of neck muscles. MATERIAL AND METHODS: A new laser tracking instrument was designed to measure the ability of a test person to track a reference point moving on the wall by a laser fixed to the forehead or held in the hand. The reference point to be tracked moves in runs of a circle or a square at three different speeds 10, 20, or 30 cm/s. We used a 1 × 1 ×1 m setup geometry to provide head movements well below pain release. Groups of 22 patients diagnosed with chronic whiplash-associated disorder grade 2, 19 patients diagnosed with chronic tension-type headache, and 37 control persons were compared. RESULTS: A small but highly significant dyscoordination of head movements was observed in both patient groups and in whiplash also of the hand. CONCLUSIONS: Our study presents a new method based on laser tracking for precision quantitative measurements of head or hand movements during standardized conditions. The results confirm that motor control of head movements is impaired in both chronic whiplash and tension-type headache, and in whiplash also of the hand. This suggests involvement of the central nervous system in the pathology of these diseases.

Customizable in situ TEM devices fabricated in freestanding membranes by focused ion beam milling.

Nano- and microelectromechanical structures for in situ operation in a transmission electron microscope (TEM) were fabricated with a turnaround time of 20 min and a resolution better than 100 nm. The structures are defined by focused ion beam (FIB) milling in 135 nm thin membranes of single crystalline silicon extending over the edge of a pre-fabricated silicon microchip. Four-terminal resistance measurements of FIB-defined nanowires showed at least two orders of magnitude increase in resistivity compared to bulk. We show that the initial high resistance is due to amorphization of silicon, and that current annealing recrystallizes the structure, causing the electrical properties to partly recover to the pristine bulk resistivity. In situ imaging of the annealing process revealed both continuous and abrupt changes in the crystal structure, accompanied by instant changes of the electrical conductivity. The membrane structures provide a simple way to design electron-transparent nanodevices with high local temperature gradients within the field of view of the TEM, allowing detailed studies of surface diffusion processes. We show two examples of heat-induced coarsening of gold on a narrow freestanding bridge, where local temperature gradients are controlled via the electrical current paths. The separation of device processing into a one-time batch-level fabrication of identical, generic membrane templates, and subsequent device-specific customization by FIB milling, provides unparalleled freedom in device layout combined with very short effective fabrication time. This approach significantly speeds up prototyping of nanodevices such as resonators, actuators, sensors and scanning probes with state-of-art resolution.