Changes in nuclear 3,5,3'-triiodothyronine receptor expression in rat dorsal root ganglia and sciatic nerve during development: comparison with regeneration.

The action of the thyroid hormones on responsive cells in the peripheral nervous system requires the presence of nuclear triiodothyronine receptors (NT3R). These nuclear receptors, including both the alpha and beta subtypes of NT3R, were visualized by immunocytochemistry with the specific 2B3 monoclonal antibody. In the dorsal root ganglia (DRG) of rat embryos, NT3R immunoreactivity was first discretely revealed in a few neurons at embryonic day 14 (E14), then strongly expressed by all neurons at E17 and during the first postnatal week; all DRG neurons continued to possess clear NT3R immunostaining, which faded slightly with age. The peripheral glial cells in the DRG displayed a short-lived NT3R immunoreaction, starting at E17 and disappearing from the satellite and Schwann cells by postnatal days 3 and 7 respectively. In the developing sciatic nerve, Schwann cells also exhibited transient NT3R immunoreactivity restricted to a short period ranging from E17 to postnatal day 10; the NT3R immunostaining of the Schwann cells vanished proximodistally along the sciatic nerve, so that the Schwann cells rapidly became free of detectable NT3R immunostaining. However, after the transection or crushing of an adult sciatic nerve, the NT3R immunoreactivity reappeared in the Schwann cells adjacent to the lesion by 2 days, then along the distal segment in which the axons were degenerating, and finally disappeared by 45 days, when the regenerating axons were allowed to re-occupy the distal segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Horizontal vestibulo-ocular reflex dynamics in acute vestibular neuritis and viral labyrinthitis: evidence of otolith-canal interaction.

OBJECTIVE: To evaluate the dynamic properties of the horizontal vestibulo-ocular reflex (h-VOR) in the acute stage of two common labyrinthine diseases that provoke severe attacks of vertigo with spontaneous nystagmus: vestibular neuritis (vestibular loss alone) and viral labyrinthitis (cochleovestibular loss). MATERIAL AND METHODS: Sixty-three patients were investigated: 42 were diagnosed with vestibular neuritis and 21 with viral labyrinthitis. The h-VOR function was evaluated by conventional caloric and impulsive testing. A simplified model of vestibular function was used to analyze the vestibulo-ocular response to rotational stimulation. RESULTS: The results showed a significant difference in h-VOR characteristics between the two pathologies. Patients with vestibular neuritis exhibited a strong horizontal semicircular canal deficit, but no h-VOR asymmetry between the two rotational directions. In contrast, patients with viral labyrinthitis demonstrated moderate canal paresis and a marked h-VOR deficit in rotation toward the affected ear. CONCLUSION: These findings support the hypothesis that the h-VOR dynamic asymmetry that occurs after an acute unilateral inner ear lesion is not due to canal dysfunction alone, but involves complex adaptive changes in the central VOR that may implicate the otolith system. Based on histopathologic and clinical differences in the two pathologies reported in the literature, we postulate that this otolith-canal interaction is mainly linked to the loss of saccular function.

Activation of electrical triggers of atrial fibrillation in hyperthyroidism.

CONTEXT: A shortening of the atrial refractory period has been considered as the main mechanism for the increased risk of atrial fibrillation in hyperthyroidism. However, other important factors may be involved. OBJECTIVE: Our objective was to determine the activity of abnormal supraventricular electrical depolarizations in response to elevated thyroid hormones in patients without structural heart disease. PATIENTS AND DESIGN: Twenty-eight patients (25 females, three males, mean age 43+/-11 yr) with newly diagnosed and untreated hyperthyroidism were enrolled in a prospective trial after exclusion of heart disease. Patients were followed up for 16 +/- 6 months and studied at baseline and 6 months after normalization of serum TSH levels. MAIN OUTCOME MEASURES: The incidence of abnormal premature supraventricular depolarizations (SVPD) and the number of episodes of supraventricular tachycardia was defined as primary outcome measurements before the start of the study. In addition, heart rate oscillations (turbulence) after premature depolarizations and heart rate variability were compared at baseline and follow-up. RESULTS: SVPDs decreased from 59 +/- 29 to 21 +/- 8 per 24 h (P = 0.003), very early SVPDs (so called P on T) decreased from 36 +/- 24 to 3 +/- 1 per 24 h (P < 0.0001), respectively, and nonsustained supraventricular tachycardias decreased from 22 +/- 11 to 0.5 +/- 0.2 per 24 h (P = 0.01) after normalization of serum thyrotropin levels. The hyperthyroid phase was characterized by an increased heart rate (93 +/- 14 vs. 79 +/- 8 beats/min, P < 0.0001) and a decreased turbulence slope (3.6 vs. 9.2, P = 0.003), consistent with decreased vagal tone. This was confirmed by a significant decrease of heart rate variability. CONCLUSION: Hyperthyroidism is associated with an increased supraventricular ectopic activity in patients with normal hearts. The activation of these arrhythmogenic foci by elevated thyroid hormones may be an important causal link between hyperthyroidism and atrial fibrillation.

Pulse oximetry and transcutaneous oxygen tension for detection of hypoxemia in critically ill infants and children.

We tested the performance of transcutaneous oxygen monitoring (TcPO2) and pulse oximetry (tcSaO2) in detecting hypoxia in critically ill neonatal and pediatric patients. In 54 patients (178 data sets) with a mean age of 2.4 years (range 1 to 19 years), arterial saturation (SaO2) ranged from 9.5 to 100%, and arterial oxygen tension (PaO2) from 16.4 to 128 mmHg. Linear correlation analysis of pulse oximetry vs measured SaO2 revealed an r value of 0.95 (p less than 0.001) with an equation of y = 21.1 + 0.749x, while PaO2 vs tcPO2 showed a correlation coefficient of r = 0.95 (p less than 0.001) with an equation of y = -1.04 + 0.876x. The mean difference between measured SaO2 and tcSaO2 was -2.74 +/- 7.69% (range +14 to - 29%) and the mean difference between PaO2 and tcPO2 was +7.43 +/- 8.57 mmHg (range -14 to +49 mmHg). Pulse oximetry was reliable at values above 65%, but was inaccurate and overestimated the arterial SaO2 at lower values. TcPO2 tended to underestimate the arterial value with increasing PaO2. Pulse oximetry had the best sensitivity to specificity ratio for hypoxia between 65 and 90% SaO2; for tcPO2 the best results were obtained between 35 and 55 mmHg PaO2.

Outcomes of optic nerve sheath decompression for nonarteritic ischemic optic neuropathy.

Efficacy of optic nerve sheath decompression (ONSD) in treating non-arteritic ischemic optic neuropathy (NAION) is not clear. We retrospectively analyzed the records of 91 patients with NAION, who were examined during a two-year period, and compared the final Snellen visual acuities of eyes treated with ONSD with those of eyes that did not have surgery. Seven of 18 eyes with ONSD (39%) demonstrated increased visual acuity of two or more lines; whereas 23 of 71 eyes without surgery (32%) had increased acuity. The ONSD group and no surgery group were further subdivided into eyes with progressive visual loss and nonprogressive visual loss. No statistically significant differences in visual outcome between groups were found. We did not find the high frequency of visual improvement that has been reported in some studies of ONSD for NAION.

Cross validation of experts versus registration methods for target localization in deep brain stimulation.

In the last five years, Deep Brain Stimulation (DBS) has become the most popular and effective surgical technique for the treatent of Parkinson's disease (PD). The Subthalamic Nucleus (STN) is the usual target involved when applying DBS. Unfortunately, the STN is in general not visible in common medical imaging modalities. Therefore, atlas-based segmentation is commonly considered to locate it in the images. In this paper, we propose a scheme that allows both, to perform a comparison between different registration algorithms and to evaluate their ability to locate the STN automatically. Using this scheme we can evaluate the expert variability against the error of the algorithms and we demonstrate that automatic STN location is possible and as accurate as the methods currently used.

Auditory stimulation does not induce implicit memory during anaesthesia

Background and aim of the study: Formation of implicit memory during general anaesthesia is still debated. Perceptual learning is the ability to learn to perceive. In this study, an auditory perceptual learning paradigm, using frequency discrimination, was performed to investigate the implicit memory. It was hypothesized that auditory stimulation would successfully induce perceptual learning. Thus, initial thresholds of the frequency discrimination postoperative task should be lower for the stimulated group (group S) compared to the control group (group C). Material and method: Eighty-seven patients ASA I-III undergoing visceral and orthopaedic surgery during general anaesthesia lasting more than 60 minutes were recruited. The anaesthesia procedure was standardized (BISR monitoring included). Group S received auditory stimulation (2000 pure tones applied for 45 minutes) during the surgery. Twenty-four hours after the operation, both groups performed ten blocks of the frequency discrimination task. Mean of the thresholds for the first three blocks (T1) were compared between groups. Results: Mean age and BIS value of group S and group C are respectively 40 } 11 vs 42 } 11 years (p = 0,49) and 42 } 6 vs 41 } 8 (p = 0.87). T1 is respectively 31 } 33 vs 28 } 34 (p = 0.72) in group S and C. Conclusion: In our study, no implicit memory during general anaesthesia was demonstrated. This may be explained by a modulation of the auditory evoked potentials caused by the anaesthesia, or by an insufficient longer time of repetitive stimulation to induce perceptual learning.

Ulnar Nerve Transposition at the Elbow under Local Anesthesia: A Patient Satisfaction Study.

Background Ulnar nerve decompression at the elbow traditionally requires regional or general anesthesia. We wished to assess the feasibility of performing ulnar nerve decompression and transposition at the elbow under local anesthesia. Methods We examined retrospectively the charts of 50 consecutive patients having undergone ulnar nerve entrapment surgery either under general or local anesthesia. Patients were asked to estimate pain on postoperative days 1 and 7 and satisfaction was assessed at 1 year. Results On day 1, pain was comparable among all groups. On day 7, pain scores were twice as high when transposition was performed under general anesthesia when compared with local anesthesia. Patient satisfaction was slightly increased in the local anesthesia group. These patients were significantly more willing to repeat the surgery. Conclusion Ulnar nerve decompression and transposition at the elbow can be performed under local anesthesia without added morbidity when compared with general anesthesia.

Transcutaneous carbon dioxide pressure for monitoring patients with severe croup.

In a prospective investigation of 17 children with severe croup, we analyzed the effect of epinephrine inhalations and mild sedation with chloral hydrate on transcutaneous carbon dioxide pressure (tcPCO2), pulse oximetry measurements, and croup scores. There was a highly significant reduction (p less than 0.001) in the tcPCO2 values and croup scores after inhalation of epinephrine. The changes in the tcPCO2 values correlated with the clinical findings. Mild sedation also significantly improved the croup scores but failed to influence the tcPCO2 values. There was not statistically significant difference in pulse oximetry saturation, fraction of administered oxygen, heart rate, or respiratory rate before and after inhalation of epinephrine or chloral hydrate administration. Monitoring tcPCO2 appears to be a reliable and objective tool for managing patients with upper airway obstruction, whereas croup scores may be misleading.

Closed loop electrical muscle stimulation in spinal cord injured rehabilitation

The effect of motor training using closed loop controlled Functional Electrical Stimulation (FES) on motor performance was studied in 5 spinal cord injured (SCI) volunteers. The subjects trained 2 to 3 times a week during 2 months on a newly developed rehabilitation robot (MotionMaker?). The FES induced muscle force could be adequately adjusted throughout the programmed exercises by the way of a closed loop control of the stimulation currents. The software of the MotionMaker? allowed spasms to be detected accurately and managed in a way to prevent any harm to the SCI persons. Subjects with incomplete SCI reported an increased proprioceptive awareness for motion and were able to achieve a better voluntary activation of their leg muscles during controlled FES. At the end of the training, the voluntary force of the 4 incomplete SCI patients was found increased by 388% on their most affected leg and by 193% on the other leg. Active mobilisation with controlled FES seems to be effective in improving motor function in SCI persons by increasing the sensory input to neuronal circuits involved in motor control as well as by increasing muscle strength.