Significance of coil orientation for motor evoked potentials from nasalis muscle elicited by transcranial magnetic stimulation

OBJECTIVE: In transcranial magnetic stimulation (TMS) of the motor cortex, the optimal orientation of the coil on the scalp is dependent on the muscle under investigation, but not yet known for facial muscles. METHODS: Using a figure-of-eight coil, we compared TMS induced motor evoked potentials (MEPs) from eight different coil orientations when recording from ipsi- and contralateral nasalis muscle. RESULTS: The MEPs from nasalis muscle revealed three components: The major ipsi- and contra-lateral middle latency responses of approximately 10 ms onset latency proved entirely dependent on voluntary pre-innervation. They were most easily obtained from a coil orientation with posterior inducing current direction, and in this respect resembled the intrinsic hand rather than the masseter muscles. Early short duration responses of around 6 ms onset latency were best elicited with an antero-lateral current direction and not pre-innervation dependent, and therefore most probably due to stimulation of the nerve roots. Late responses (>18 ms) could inconsistently be elicited with posterior coil orientations in pre-innervated condition. CONCLUSIONS: By using the appropriate coil orientation and both conditions relaxed and pre-innervated, cortically evoked MEP responses from nasalis muscle can reliably be separated from peripheral and reflex components and also from cross talk of masseter muscle activation.

Functional imaging of the parotid glands using blood oxygenation level dependent (BOLD)-MRI at 1.5T and 3T

PURPOSE: To evaluate the function of the parotid glands before and during gustatory stimulation, using an intrinsic susceptibility-weighted MRI method (blood oxygenation level dependent, BOLD-MRI) at 1.5T and 3T. MATERIALS AND METHODS: A total of 10 and 13 volunteers were investigated at 1.5T and 3T, respectively. Measurements were performed before and during gustatory stimulation using ascorbate. Circular regions of interest (ROIs) were delineated in the left and right parotid glands, and in the masseter muscle for comparison. The effects of stimulation were evaluated by calculating the difference between the relaxation rates, DeltaR(2)*. Baseline and stimulation were statistically compared (Student's t-tests), merging both parotid glands. RESULTS: The averaged DeltaR(2)* values prestimulation obtained in all parotid glands were stable (-0.61 to 0.38 x 10(-3) seconds(-1)). At 3T, these values were characterized by an initial drop (to -2.7 x 10(-3) seconds(-1)) followed by a progressive increase toward the baseline. No significant difference was observed between baseline and parotid gland stimulation at 1.5T, neither for the masseter muscle at both field strengths. A considerable interindividual variability (over 76%) was noticed at both magnetic fields. CONCLUSION: BOLD-MRI at 3T was able to detect DeltaR(2)* changes in the parotid glands during gustatory stimulation, consistent with an increase in oxygen consumption during saliva production.

Eingeschränkte Mundöffnung - was nun?: Diagnostik und Therapie bei progredientem Trismus: Ein Fallbericht.

Eine 28-jährige Patientin stellte sich mit einer seit Jahren bestehenden progredient eingeschränkten Mundöffnung vor. Die initial klinische Diagnostik zeigte keine pathologischen intraartikulären Befunde. Trotzdem blieb eine konservative Therapie fruchtlos. Erst die weitere bildgebende Diagnostik führte zur Diagnose gleich mehrerer struktureller Veränderungen: einer Hyperplasie der Processus coronoidei und einer hypertrophen Kaumuskulatur mit verdickten Aponeurosen. Zusätzlich fand sich auch eine typische quadratische Unterkieferform, bedingt durch eine Hypertrophie der Kieferwinkel. Beim hier illustrierten Fall zeigen sich alle typischen Zeichen dieser bis anhin noch wenig beschriebenen Kaumuskel-Aponeurosen-Hyperplasie. Eine chirurgische Behandlung mit Coronoidektomie und Aponeurektomie verhalf schliesslich zu einer deutlichen Verbesserung der Mundöffnung. Wenngleich die eingeschränkte Mundöffnung ein Symptom vieler Erkrankungen des stomatognathen Systems ist, kann eine über längere Zeit bestehende oder auch progrediente eingeschränkte Mundöffnung diagnostisch und therapeutisch eine Herausforderung darstellen. Bei adäquater Diagnostik und Therapie ist die Prognose des oben genannten Symptomenkomplexes günstig und führt zu einer Verbesserung der mundgesundheitsbezogenen Lebensqualität.