Reaching movements in childhood dystonia contain signal-dependent noise

When reaching, children with dystonia exhibit movements that are slower and more variable than normal children. We hypothesize that in dystonia there is an increase in signal-dependent noise so that there is increased variability with increasing speed. This hypothesis predicts that slower movement in children with dystonia is at least partly due to a compensatory strategy to reduce variability by decreasing speed. To test this hypothesis, we measured the speed of arm movement while children attempted to contact buttons of different sizes. We tested 23 control children and 15 children between the ages of 4 and 16 years with dystonia owing to either cerebral palsy, idiopathic dystonia not due to the DYT1 (torsin A) mutation, or other identified causes. A consistent inverse relationship between movement time and button size was seen for both the control children and the children with dystonia. The variance of movement speed increased with the average speed for all subjects. Children with dystonia moved significantly more slowly at all button sizes, and their movement speed was more sensitive to changes in button size. Therefore, part of the reduction in speed in dystonia is due to relatively greater difficulty in contacting small targets. This finding is consistent with the hypothesis of increased signal-dependent noise in children with dystonia, and we present a simple computational model that provides a possible explanation for the origin of this noise.

Three year’s experience with the Stretta procedure: did it really make a difference?

BACKGROUND

Endoscopic treatment is merging as a new option for GERD treatment. Many modalities have been used with modest short-term success, but no long-term follow-ups have been published. We present our 3-yr experience at Vanderbilt University using endoscopic radiofrequency energy (Stretta procedure) for GERD treatment.

METHODS

Patients with follow-up >6 months were prospectively studied under IRB protocol. All were mailed SF-12 health status questionnaire and GERD specific quality-of-life (QOLRAD) questionnaires, queries about satisfaction with Stretta, and medication use. All were invited for 24-hour pH study.

RESULTS

Eighty-six Stretta procedures were performed between 8/2000 and 7/2003 on 85 patients; all were outpatients, 89% under conscious sedation. Seventy-seven patients qualified for the study; 61 completed the survey, 24 returned for pH study. Follow-up was 26.2 +/- 7.5 months (6-36). All were on daily PPIs, with proven GERD by pH study or endoscopy. Mean preoperative acid exposure time was 7.8+/-2.6%, mean DeMeester score was 40.2+/-17.6. Postoperative mean acid exposure time was 5.1+/-3.3 (p=0.001), DeMeester score was 29.5+/-20.5 (p=0.041). Normal postoperative acid exposure time (pH<4 in <4.2%) was achieved in 42% of patients tested. Patients were then divided according to medication use at the end of f/u in 2 groups: Responders (off or >50% decrease in PPI dose), and nonresponders (on >50% of original PPI dose, or had fundoplication). Response rate was 60% (39 patients), 8 nonresponders underwent fundoplication (12%). Satisfaction rate was 73%. Statistically significant difference was found between the 2 groups in all measurements; SF-12 physical and mental score for responders were 45.5+/-10.2, and 52.6+/-7.8; and for nonresponders were 37.8+/-11.2 and 40.9+/-11.3 (p=0.012, p=0.0001), respectively. Statistically significant difference was also found between responders and nonresponders in postoperative acid exposure (4.5+/-3.34 vs 7.2+/-2.3, p=0.034), and DeMeester score (26.3+/-20.4 vs 39.7+/-20.2, p=0.05). Paired T test was used to compare pre- and postoperative acid exposure in each group; statistically significant difference was found only among responders: total reflux time was 7.50+/-2.3 preop and 4.5+/-3.34 postop (p=0.0001), whereas for nonresponders it was 8.6+/-3.7 and 7.2+/-2.3 (p=0.8), DeMeester scores pre- and postop among responders were 40.0+/-19.7 and 26.3+/-20.4, respectively (p=0.016), whereas for nonresponders it was 40.5+/-14.3 and 39.7+/-20.2 (p=0.79).

CONCLUSIONS

Stretta is a safe modestly effective, totally endoscopic treatment for GERD. Symptomatic improvement when achieved is often associated with correlating improvement in distal acid exposure. This exposure normalizes in nearly half the treated patients.

Population-Based Measurement of Quality of Diabetes Care Using HbA1c Values in the State of Thuringia/Germany

INTRODUCTION/HYPOTHESIS

There remains insufficient knowledge about the quality of diabetes therapy regarding structure, process and outcome given by primary care in Thuringia, and elsewhere in Germany. The project assesses a means of determining the quality of diabetes therapy in primary care by analysis of HbA1c values within a broad territory.

METHODS

HbA1c tests of Thuringian patients were analysed by 20 participating medical laboratories between January 1 and March 31, 2002; each HbA1c test was identified by the postal code of the Thuringian General Practitioner (GP) who ordered the test and adjusted by a standardisation procedure (mean normal of healthy subjects 5 %). The German state of Thuringia (population of 2,421,871) consists of 23 urban and rural districts. This format was also used in the present study.

RESULTS

Twenty participating laboratories contributed 59,702 HbA1c tests from diabetic patients in Thuringia. Adjusted mean HbA1c of entire Thuringia: 6.75 %, 36.4 % of all HbA1c tests were above 7.0 % and 3,0 % of all HbA1c values above 10.0 %. Regional percentage of HbA1c tests above 7.0 % ranged between 28.2 % and 47.3 %. Regional percentage of HbA1c tests above 10.0 % ranged between 1.8 % and 4.8 %. Subgroup analyses comparing urban vs. rural districts showed significantly lower mean HbA1c (6.72 % vs. 6.75 %, CI 0.01 - 0.06, p < 0.01) and percentage of HbA1c tests above 7 % (8.19 % vs. 8.24 %, CI 0.01 - 0.08, p < 0.01) in urban areas.

CONCLUSIONS

Mean HbA1c as an indicator of glycaemic control of diabetes patients in primary care in Thuringia was good. The percentage of patients who need immediate medical intervention to prevent acute complications varied between districts, which is indicative for differences in quality of diabetes care in Thuringia. However, the proposed method is still experimental and has not yet been evaluated. Consequently, considerable bias might influence the results.

Long-term follow-up study of the Stretta procedure for the treatment of gastroesophageal reflux disease

BACKGROUND

The endoscopic delivery of temperature-controlled radiofrequency energy to the gastroesophageal junction (Stretta procedure) recently has been shown effective for patients with gastroesophageal reflux disease (GERD). However, its effectiveness has been assessed mainly over short periods (6-12 months). This study aimed to evaluate long-term results of the Stretta procedure.

METHODS

All patients undergoing the Stretta procedure since August 2000 were prospectively evaluated under an institutional review board-approved protocol. All patients with a follow-up period longer than 18 months were recruited for a 24-h pH study and mailed a follow-up survey, which included the following: Short Form 12 (SF-12) health status questionnaire, GERD-specific quality-of-life questionnaire (QOLRAD), and queries regarding long-term satisfaction and medication use.

RESULTS

The Stretta procedure was performed on 82 patients, and 41 patients with a follow-up period longer than 18 months qualified for the study. Follow-up surveys were completed by 36 patients (88%) during a mean follow-up period of 27.1 +/- 3.7 months. Of these 36 patients, 30 (83%) were highly satisfied with the procedure and would have it performed again. More than half of the Fifty Stretta patients (56%) had completely discontinued their use of proton pump inhibitors (PPIs), and an additional 31% had reduced their dose significantly. The mean PPI equivalent doses were 37.8 +/- 22.2 mg/day before the Stretta procedure and 11.6 +/- 14.6 mg/day at 27-month follow-up assessment (p = 0.001). According to the patient outcomes for daily PPI use (yes/no), the patients were divided into two groups: responders (n = 20) and nonresponders (n = 16). The responder group scored higher in QOLRAD score (p = 0.0001), SF-12 physical score (p = 0.038), and SF-12 mental score (p = 0.003). In the 24-hour pH study, the responder group demonstrated a significant decrease in distal esophageal acid exposure time (6.4% +/- 1.5% to 3.1% +/- 1.4%; p = 0.0001).

CONCLUSION

The Stretta procedure results in a statistical significant long-term decrease in GERD symptoms and PPI use. The treatment effect is durable beyond 2 years, and 56% of patients had discontinued their user of all antisecretory drugs.

Automatic processing of self-regulation of slow cortical potentials: evidence from brain-computer communication in paralysed patients

OBJECTIVE

Direct brain-computer communication utilizes self-regulation of brain potentials to select letters, words or symbols from a computer menu. Selection of letters or words with brain potentials requires simultaneous processing of several tasks such as production of certain brain potentials at predefined time points simultaneously with processing of presented letter strings. This study addresses the question of whether the self-regulation of slow cortical potentials (SCP) automatizes with practice and can thus be considered as a skill comparable to motor or cognitive skills.

METHODS

Two nearly completely paralysed patients learned over several months to produce electrocortically negative and positive SCP by means of visual feedback. Improved performance and a reduction in performance variability were regarded as behavioural indicators for automaticity, while the topographic focalization of cortical activation was considered as a neurophysiological indicator for automaticity. Different indicators of automaticity were expected to covary along with practice.

RESULTS

In patient 1, performance measured as the percentage of correct SCP shifts increased simultaneously with the topographic focalization of cortical activation. His performance became more stable with practice. For this patient the criteria for automaticity were all met. In patient 2, performance also improved, but his cortical activity became topographically less focal. His performance was less stable than that of patient 1.

CONCLUSIONS

The present findings, albeit on only two subjects, provide preliminary evidence that SCP self-regulation may automatize with long-term practice and can therefore be considered a skill.

Infectious complications in pediatric acute myeloid leukemia: analysis of the prospective multi-institutional clinical trial AML-BFM 93

Infections still remain a major cause of therapy-associated morbidity and mortality in children with acute myeloid leukemia (AML). To improve supportive care measurements, detailed information on frequency and characteristic features of infectious complications is needed. We retrospectively analyzed the medical charts of 304 children, treated in 30 hospitals according to the multi-institutional clinical trial AML-BFM 93. Overall, 855 infectious complications occurred in 304 patients (fever without identifiable source (n=523; 61.2%), clinically (n=57; 6.7%) and microbiologically documented infections (n=275; 32.1%)). Neutropenia was present in 74.1% of the infectious episodes. In all, 20 patients died of infection-associated complications (15/276 (5.4%) patients without and 5/28 (17.9%) with Down syndrome), most of them during early induction therapy (n=11). Blood stream infections occurred in 228 episodes (Gram-positive (n=202) and Gram-negative (n=42) pathogens). Invasive fungal infection was probable or proven in 15 patients. In 113 out of the 855 infectious episodes (13.3%), pneumonia was radiologically diagnosed. Better strategies of supportive care might help to improve overall survival in children undergoing chemotherapy for AML. Therefore, children with AML should be treated in specialized pediatric centers, and there should be a very low threshold to readmit patients, in particular patients with pulmonary symptoms.

Synthesis of novel acetylene-containing amino acids

Novel synthetic procedures for the modification of non-proteinogenic acetylene-containing amino acids have been developed. The functionalization either proceeds via zinc/copper-mediated introduction of alkyl substituents, or via tungsten-catalyzed ring-closing alkyne metathesis reactions.

Desflurane compared with propofol for postoperative sedation in the intensive care unit

BACKGROUND

We hypothesized that emergence from sedation in postoperative patients in the intensive care unit would be faster and more predictable after sedation with desflurane than with propofol.

METHODS

Sixty patients after major operations were allocated randomly to receive either desflurane or propofol. The target level of sedation was defined by a bispectral index(TM) (BIS(TM)) of 60. All patients were receiving mechanical ventilation of the lungs for 10.6 (SD 5.5) h depending on their clinical state. The study drugs were stopped abruptly in a calm atmosphere with the fresh gas flow set to 6 litres min(-1), and the time until the BIS increased above 75 was measured (t(BIS75), the main objective measure). After extubation of the trachea, when the patients could state their birth date, they were asked to memorize five words.

RESULTS

Emergence times were shorter (P<0.001) after desflurane than after propofol (25th, 50th and 75th percentiles): t(BIS75), 3.0, 4.5 and 5.8 vs 5.2, 7.7 and 10.3 min; time to first response, 3.7, 5.0 and 5.7 vs 6.9, 8.6 and 10.7 min; time to eyes open, 4.7, 5.7 and 8.0 vs 7.3, 10.5 and 20.8 min; time to squeeze hand, 5.1, 6.5 and 10.2 vs 9.2, 11.1 and 21.1 min; time to tracheal extubation, 5.8, 7.7 and 10.0 vs 9.7, 13.5 and 18.9 min; time to saying their birth date, 7.7, 10.5 and 15.5 vs 13.0, 19.4 and 31.8 min. Patients who received desflurane recalled significantly more of the five words. We did not observe major side-effects and there were no haemodynamic or laboratory changes except for a more marked increase in systolic blood pressure after stopping desflurane. Using a low fresh gas flow (air/oxygen 1 litre min(-1)), pure drug costs were lower for desflurane than for propofol (95 vs 171 Euros day(-1)).

CONCLUSIONS

We found shorter and more predictable emergence times and quicker mental recovery after short-term postoperative sedation with desflurane compared with propofol. Desflurane allows precise timing of extubation, shortening the time during which the patient needs very close attention.

Parietal gamma-band activity during auditory spatial precueing of motor responses

Magnetoencephalographic gamma-band activity (GBA) was used to investigate synchronization of cortical networks in putative auditory dorsal stream areas during the transformation of auditory spatial information into motor preparation. GBA was compared between lateralized vowels precueing either ipsi- or contralateral responses in two experiments with randomized versus blocked task presentation. In both studies, parietal GBA was higher for the contralateral than the ipsilateral precues. Spectral amplitudes at 54-64 Hz were maximal at 120 ms post precue onset during randomized presentations, while in the blocked task 62-72 Hz activity was present at precue onset and less peaked. These findings suggest a fast activation of parietal networks when auditory spatial precues are used to plan contralateral responses.

Location changes enhance hemispheric asymmetry of magnetic fields evoked by lateralized sounds in humans

Auditory mismatch negativity, the brain's change-detection response, has been shown to be more sensitive than other early auditory cortex responses to the hemispheric specialization of speech processing. The present study used magnetoencephalography to assess hemispheric differences in cortical evoked responses during auditory spatial processing. We compared N1m to lateralized vowels presented with equal probabilities with mismatch fields (MMNm) to rare lateralized noises interspersed in a sequence of frequent midline sounds. Both N1m and MMNm dipole amplitudes were higher in the hemisphere contralaterally to the side of sound lateralization, but this effect was about four times bigger in the mismatch paradigm. Moreover, only MMNm dipoles showed shorter latencies in the hemisphere contralaterally to stimulation. Apparently stimulus changes activate specialized auditory networks more strongly than non-deviant events.

Amplitude-squeezed emission from a transverse single-mode vertical-cavity surface-emitting laser with weakly anticorrelated polarization modes

We discuss the polarization-resolved intensity noise characteristics of a transverse single-mode vertical-cavity surface-emitting laser (VCSEL). Measurements by a sensitivity-enhanced lock-in amplifier detection scheme yield only an imperfect anticorrelation between the strong and the weak orthogonally polarized fundamental modes. Yet the total emission shows amplitude squeezing of 0.4 dB below the shot-noise level. Unlike for transverse two-mode emission, a perfect anticorrelation between the two polarization modes is not necessary for generation of amplitude-squeezed emission in a transverse single-mode VCSEL, in agreement with theoretical predictions.

Brain-computer communication: self-regulation of slow cortical potentials for verbal communication

OBJECTIVE

To test a training procedure designed to enable severely paralyzed patients to communicate by means of self-regulation of slow cortical potentials.

DESIGN

Application of the Thought Translation Device to evaluate the procedure in patients with late-stage amyotrophic lateral sclerosis (ALS).

SETTING

Training sessions in the patients' homes.

PARTICIPANTS

Two male patients with late-stage ALS.

INTERVENTIONS

Patients learned voluntary control of their slow cortical potentials by means of an interface between the brain and a computer. Training was based on visual feedback of slow cortical potentials shifts and operant learning principles. The learning process was divided into small steps of increasing difficulty.

MAIN OUTCOME MEASURES

Accuracy of self-control of slow cortical potentials (percentage of correct responses). Learning progress calculated as a function of training session.

RESULTS

Within 3 to 8 weeks, both patients learned to self-regulate their slow cortical potentials and to use this skill to select letters or words in the Language Support Program.

CONCLUSIONS

This training schedule is the first to enable severely paralyzed patients to communicate without any voluntary muscle control by using self-regulation of an electroencephalogram potential only. The protocol could be a model for training patients in other brain-computer interface techniques.