Andreas Hufschmidt

Some methods and parameters of body sway quantification and their neurological applications

SummaryMethods and parameters are described to quantify body sway as measured by a force-transducing platform. Analogue data representing the coordinates of the bodys center of force (COF) are fed into a digital computer. The following parameters are then calculated and tested for their diagnostic significance: sway path (SP), mean amplitude of sway (MA), mean sway frequency (MF), their lateral and sagittal components, and the quotients sagittal/lateral of these as well as the sway area (SA) circumscribed by the COF. Quotients of eyes open/eyes closed for all these parameters determine the visual stabilization of posture. Sway position and sway direction histograms allow for a more detailed analysis of MA and SP. Despite considerable inter and intraindividual variance of these parameters (in 28 normals), some of them seem of clinical significance not only for documentation and follow-up studies but also for differential diagnosis.In patients with cerebellar lesions (n=12), SP and MA were up to 10 times larger with a marked antero-posterior instability, MF being above normal. Patients with labyrinthine lesions (n=10) showed significant instability only with eyes closed, MF being slightly below normal.ZusammenfassungEs werden Methodik und Parameter für eine quantitative Auswertung der Standunruhe bei Kranken und Gesunden beschrieben. Aus den Analogsignalen einer Kraftmeßplattform werden die folgenden Daten über die Bewegungen des Körperkraftschwerpunktes digital errechnet: Schwingungsweg (SP), dessen mittlere Amplitude (MA), mittlere Frequenz (MF), die lateralen und sagittalen Komponenten, deren Quotienten und die von den Körperschwankungen umschlossene Fläche (SA). Quotienten der Werte bei offenen und geschlossenen Augen beschreiben die visuelle Standstabilisation. Positions- und Richtungshistogramme dokumentieren zusätzlich die Vorzugsrichtungen der Körperunruhe.Eine Analyse der Signifikanz dieser Parameter zeigte trotz großer Varianz bei Normalen deren klinische Brauchbarkeit. Patienten mit Kleinhirnerkrankungen (vorwiegend des Vorderlappens) zeigen bis zu 10mal höhere Werte, z. B. für MA und SP vorwiegend in sagittaler Richtung und eine erhöhte mittlere Frequenz (MF), während Patienten mit weitgehend kompensierten Vestibularisläsionen nur bei geschlossenen Augen vermehrt schwanken, wobei MF erniedrigt ist.

[Slow brain potentials in writing: the correlation between writing hand and speech dominance in right-handed humans].

1. Slow cerebral potential shifts were recorded from the scalp over both cerebral hemispheres by retrograde summation while 23 right-handers were writing. Averaging included writing errors, but eliminated eye movements and other artifacts. Repeated writing of the same word or sentence was compared to writing different dictated words, to drawings, and to other control experiments. 2. Surface negative readiness potentials (Bereitschaftspotential) appeared about 1 s before writing, which was similar to those preceding other voluntary movements. 3. During writing, the writing potentials in different cortical regions began with a negative increase of the Bereitschaftspotential, usually followed by a plateau or positive waves. One or several biphasic potentials persisted for another 2 s after writing had ceased. 4. The writing potentials had rather constant forms in the same individual, but showed large interindividual variations of form and polarity. The largest initial negativity (with both ear lobes serving as reference) occurred at the vertex and the left motor region contralateral to the writing hand. 5. The left hemispheric preponderance of writing potentials, maximal at the precentral region contralateral to the writing hand, was less marked when writing with the left hand. An interaction of the writing hand and language dominance is assumed. 6. Writing the same word or short sentence repeatedly caused potentials of larger amplitude than the preceding readiness potentials. Writing dictated words or drawing figures after verbal stimuli that require language processing caused larger potentials in the left hemisphere than did repeated word writing. 7. The fact that negative potentials with larger left hemispheric amplitudes appear after verbal stimuli may indicate that language information is processed in the speech-dominant hemisphere before and during writing or drawing. 8. By variously combining bipolar leads, the lateral differences of the potential fields can be more clearly distinguished than by using only unipolar leads with ear reference.Summary1.Slow cerebral potential shifts were recorded from the scalp over both cerebral hemispheres by retrograde summation while 23 right-handers were writing. Averaging included writing errors, but eliminated eye movements and other artifacts. Repeated writing of the same word or sentence was compared to writing different dictated words, to drawings, and to other control experiments.2.Surface negative readiness potentials (Bereitschaftspotentiale) appeared about 1 s before writing, which was similar to those preceding other voluntary movements.3.During writing, the writing potentials in different cortical regions began with a negative increase of the Bereitschaftspotential, usually followed by a plateau or positive waves. One or several biphasic potentials persisted for another 2 s after writing had ceased.4.The writing potentials had rather constant forms in the same individual, but showed large interindividual variations of form and polarity. The largest initial negativity (with both ear lobes serving as reference) occurred at the vertex and the left motor region contralateral to the writing hand.5.The left hemispheric preponderance of writing potentials, maximal at the precentral region contralateral to the writing hand, was less marked when writing with the left hand. An interaction of the writing hand and language dominance is assumed.6.Writing the same word or short sentence repeatedly caused potentials of larger amplitude than the preceding readiness potentials. Writing dictated words or drawing figures after verbal stimuli that require language processing caused larger potentials in the left hemisphere than did repeated word writing.7.The fact that negative potentials with larger left hemispheric amplitudes appear after verbal stimuli may indicate that language information is processed in the speech-dominant hemisphere before and during writing or drawing.8.By variously combining bipolar leads, the lateral differences of the potential fields can be more clearly distinguished than by using only unipolar leads with ear reference.Zusammenfassung1.Langsame Hirnpotentiale über beiden Großhirnhemisphären beim Schreiben mit der rechten und linken Hand (Schreibpotentiale) wurden durch Rückwärtssummation und Mittelung bei 23 Rechtshändern mit EMG und Schreibdruck registriert. Bei Aufsummierung wurden Schreibfehler mitgezählt, aber Augen- oder Bewegungsartefakte durch Markierung ausgeschaltet. Das Schreiben gleicher Wörter und Sätze wurde mit dem Diktatschreiben verschiedener Wörter, mit Zeichnen und anderen Kontrollen verglichen.2.Vor dem Schreibakt entstehen die gleichen oberflächennegativen Bereitschaftspotentiale wie vor anderen Bewegungen.3.Während des Schreibens beginnt das Schreibpotential mit einem negativen Anstieg des Bereitschaftspotentials, dann folgen negative Plateaus oder positive Wellen. In der Regel überdauern eine oder mehrere biphasische Potentialverschiebungen den Schreibakt um etwa 2 s.4.Die Schreibpotentiale sind bei derselben Person formkonstant, zeigen aber große interindividuelle Variationen der Form und Polung. Die größte Negativität gegen beide Ohrelektroden erreichen sie in Scheitelmitte und links präzentral kontralateral zur Schreibhand.5.Die Amplituden der negativen Maxima der Schreibpotentiale sind größer als die Bereitschaftspotentiale, aber beim Schreiben der gleichen Wörter oder kurzer Sätze meist kleiner als die Schreibpotentiale beim Diktatschreiben.6.Die größten Seitendifferenzen der Schreibpotentiale links und rechts entstehen präzentral. Ein Linksüberwiegen über der motorischen Region kann beim Diktatschreiben des Rechtshänders sowohl kontra- wie ipsilateral zur schreibenden Hand auftreten. Eine cerebrale Wechselwirkung von Sprachdominanz und Schreibhand ist daher anzunehmen.7.Die größeren negativen Schreibpotentiale, die über dem linken Großhirn bei Diktatschreiben und bei verbaler Auslösung des Figurzeichnens auftreten, können einer stärkeren Tätigkeit der sprachdominanten Hemisphäre bei der Sprach- und Schreibtransformation entsprechen.8.Verschiedene bipolare Ableitungskombinationen können die Potentialquellen und Seitendifferenzen besser charakterisieren als unipolare Ableitungen gegen beide Ohren.

Fast corticospinal system and motor performance in children: conduction proceeds skill

Transcranial magnetic stimulation and motor performance tests were used to study the correlation between corticospinal maturation and actual motor performance in a group of young school children (n = 10, mean age = 7 years, age range = 6-9 years). The results were compared with normal adults (n = 10, mean age = 24 years, age range = 22-26 years). In children the central conduction time under the preinnervation condition of facilitation and the postexcitatory silent period was similar to that in adults. However, the central conduction time under relaxation, the latency jump (defined as the difference between the two preinnervation conditions), and the stimulus intensity were statistically different between children and adults (P < 0.01-0.001). Children did not reach the same level of performance as adults in any of the motor performance tasks (simple acoustic reaction time, tapping, ballistic movement, tracking, and diadochokinesis) (P < 0.05-0.01). The results indicate that at an early school age, children already possess mature fast corticospinal pathways able to access spinal motoneurons through the pyramidal tract. However, despite the partially adult-like level of neuronal maturation, young school children were not able to perform deliberate motor actions with the same proficiency as adults.

Anisotropy of callosal motor fibers in combination with transcranial magnetic stimulation in the course of motor development.

Objectives:The corpus callosum (CC) represents a key structure for hand motor development and is accessible to investigation by diffusion tensor magnetic resonance imaging (DTI) and transcranial magnetic stimulation (TMS). To identify quantifiable markers for motor development, we combined DTI with TMS. Materials and Methods:We examined groups of 11 healthy preschool-aged children, 10 healthy adolescents, and 10 healthy adults with both, DTI and TMS/ipsilateral silent period (iSP). DTI-values for fractional anisotropy (FA) were calculated for areas I to V of the CC. ISP-values for latency, duration, and extent of electromyography suppression were calculated. Results:FA was significantly lower in areas II to IV of the CC in children as compared with adults (P < 0.05). In area III, where callosal motor fibers cross the CC, FA differed significantly between children and adolescents (P < 0.05). TMS parameters demonstrated significant age-related differences in duration and extent of iSP (P < 0.05). No significant differences were detected regarding latency of iSP. Conclusions:The maturation of callosal motor fiber connectivity seems to reflect the degree of interhemispheric inhibition between the motor cortices with anisotropy of callosal motor fibers being a potential marker for motor development.

Canalicular magnetic stimulation lacks specificity to differentiate idiopathic facial palsy from borreliosis in children.

OBJECTIVE To investigate the role of transcranial magnetic stimulation (TMS) to differentiate between idiopathic facial nerve palsy (iFNP) and facial nerve palsy due to borreliosis (bFNP). PATIENTS AND METHODS Transcranial and intracanalicular magnetic and peripheral electrical stimulation of the facial nerve together with clinical grading according to the House and Brackmann scale were performed in 14 children and adolescents with facial palsy (median age 11.5 yr, range 4.6-16.5 yr). Serum and cerebrospinal fluid (CSF) were evaluated for antibodies against Borrelia burgdorferi and CSF cell count, glucose and protein content were screened with methods of routine laboratory testing. Data of patients were compared with normal values established in 10 healthy subjects (median age 10.2 yr, range 5.1-15.3 yr). RESULTS Patients with iFNP showed a significant decrease in MEP amplitude to canalicular magnetic stimulation compared with healthy controls (p=0.03). However, MEP amplitude did not discriminate sufficiently between the two groups, because the ranges of dispersion of MEP amplitudes overlapped. Patients with bFNP had normal MEP amplitudes to canalicular magnetic stimulation compared with normal subjects. CONCLUSION Diagnostic assessment by TMS failed to provide a reliable diagnostic criterion for distinguishing between iFNP and bFNP in children and adolescents.

Motor Habits in Visuo-manual Tracking: Manifestation of an Unconscious Short-term Motor Memory?

Normal subjects were tested in short, repetitive trials of a tracking task, with an identical shape of target movement being used throughout one session. Analysis of the net error curves (pursuit minus target movement) revealed that subjects regularly exhibit a remoteness effect: neighbouring trials were more similar than distant ones. The effect is demonstrated to be stronger in the absence of visual cues, and was found to be absent in a patient with complete loss of proprioception when he was performing without visual feedback as well.The results are discussed in terms of a short term memory store contributing to unconscious movement habits in tracking. This may represent part of the motor learning process working together with conscious visuo-motor control mechanisms. Its function is probably related to the acquisition of automatic movements.