Effects of laserneedle stimulation in the external auditory meatus on brainstem and very early auditory evoked potentials in humans.

OBJECTIVES: For the first time, brainstem auditory evoked potentials (BAEP) and very early auditory evoked potentials (EAEP) were investigated in 23 volunteers (mean age: 26.5 +/- 3.6 years) under resting conditions and during continuous and frequency modulated (2 Hz) laser stimulation in the external auditory meatus. METHODS: Using a new ear adapter, the outer region of the auditory canal was stimulated with laser light (685 nm, 4 x 30-40 mW, duration: 10 minutes). RESULTS: The EAEPs were significantly changed during continuous (p=0.019), as well as frequency modulated (p=0.014) laser stimulation compared with control measurements. DISCUSSION: Physiologic alterations of inner ear mechanism such as extra-cerebral changes in conductance or stimulation-dependent depolarization processes in extra-cerebral regions of the auditory system could be possible explanations for the significant difference in measurement parameters.

Brain death: timing of apnea testing in primary brain stem lesion.

In a 73-year-old patient complete areflexia of the cerebral and peripheral nerves following the rupture of an aneurysm of the basilar artery was diagnosed. During apnea testing the spectral analysis of electroencephalography (EEG) revealed an irreversible shift of peak from 6 to 3 Hz within the low-frequency bands. These findings suggest that apnea testing in patients with primary lesion of the brain stem should be carried out only after an isoelectric EEG.

Continuous multivariable monitoring in neurological intensive care patients--preliminary reports on four cases.

Evoked potential monitoring is a standard examination method in neurological intensive therapy units. Previously, multimodality observation was only possible in follow-up examinations. First experience with a new bed-side system continuously monitoring 12 neurophysiological and clinical parameters is reported. It consists of a personal computer and various stimulation units. EEG activity, median nerve somatosensory evoked potentials (SEPs) and brainstem auditory evoked potential (BAEPs) are recorded. Additionally, EEG spectral band power, heart rate, heart rate variability, intracranial pressure, body temperature, expiratory PCO2, blood pressure and transcutaneously measured oxygenation can be monitored. This paper reports on 4 exemplary cases of the 33 patients we have monitored to date, illustrating the principles and main advantages of the system. The system was developed to support the observation of ICU patients as well as to aid therapeutic decisions. It supports the clinical determination of brain death by specifying the deterioration of various neurological systems.

Continuous and simultaneous monitoring of EEG spectra and brainstem auditory and somatosensory evoked potentials in the intensive care unit and the operating room.

Individual monitoring of EEG and evoked potentials is gradually becoming standard in neurosurgery: compressed power spectra during carotid endarterectomy, brainstem auditory evoked potentials (BAEP) during posterior fossa surgery, and somatosensory evoked potentials (SEP) mainly during spinal cord surgery. In this paper, a new technique is described in which EEG, BAEP, and SEP are recorded and evaluated simultaneously and continuously. This allows a better survey of different neuronal structures and systems in the brain and brainstem. First results from intraoperative and intensive care patient monitoring are reported.

Effects of popliteal illumination on cerebral near-infrared spectroscopy.

The endogenous clock of humans can be influenced by light application to the popliteal region. Previously, it had been assumed that light must fall directly into the eye in order to influence the inner circadian clock. This study, published in 1998, has not been reproduced. We investigated the effects of laser light illumination (785 nm for 5 min) on cerebral near infrared spectroscopy (NIRS) in 33 volunteers. There were significant (p < 0.001) delayed (2 min) alterations in NIRS parameters during popliteal light illumination. This could be further evidence for extraocular phototransduction in humans.

Effects of QiGong on brain function.

QiGong is an ancient and widely practiced Chinese meditation exercise. We studied the effects of QiGong on brain function with modern neuromonitoring tools in two subjects. In a male QiGong master (extremely trained practitioner), the technique induced reproducible changes in transcranial Doppler sonography, EEG, stimulus-induced 40 Hz oscillations, and near-infrared spectroscopy findings. Similar effects were seen after the application of multimodal stimuli and when the master concentrated on intense imagined stimuli (e.g. 22.2% increase in mean blood flow velocity (vm) in the posterior cerebral artery, and a simultaneous 23.1% decrease of vm in the middle cerebral artery). Similar effects were seen in the female subject. Neuromonitoring during QiGong appears able to objectify accompanied cerebral modulations surrounding this old Chinese meditation exercise.

Computer-controlled acupuncture. Quantification and separation of specific effects.

The effects of acupuncture have been described and handed down empirically for centuries but there are few reports based on objective data. The aim of this study was to provide selective evidence of a specific effect of acupuncture on the brain and the eye using a Doppler ultrasound technique. A transcranial Doppler sonography arrangement was developed to monitor blood flow profiles in the supratrochlear and middle cerebral arteries simultaneously and continuously. Two acupuncture schemas were tested in a randomized cross-over study with 13 patients with ophthalmologic diseases. Applying acupuncture needles to special eye points increased the blood flow velocity in the supratrochlear artery significantly (p < 0.001) compared to the reference interval before acupuncture. In the middle cerebral artery only a minimal, non-significant increase in blood flow velocity was seen. In contrast, acupuncture of points that are held to increase cerebral blood flow velocity increased blood flow velocity in the middle cerebral artery significantly (p < 0.001) while leaving that in the supratrochlear artery unchanged. Specific acupuncture produce specific, reproducible quantifiable effects on blood flow velocity in arteries to the brain and eye.

Ultrasound-monitored effects of acupuncture on brain and eye.

A new transcranial Doppler sonography arrangement was used to monitor blood flow profiles in the supratrochlear and middle cerebral arteries simultaneously and continuously. The technique selectively demonstrated the specific effect of acupuncture on the cranial arteries, in a 25-year-old female with pigmentary retinopathy. Stimulation of points Zanzhu and Yuyao led to a marked increase of blood flow velocity in the supratrochlear artery and to a decrease of flow velocity, in the middle cerebral artery. These acupuncture-induced effects were reproducible even though both arteries originate from the same major vessel.

Effects of acupuncture on the oxygenation of cerebral tissue.

Monitoring of regional cerebral oxygen saturation (r. cereb. O2 satn.) was carried out continuously in 12 healthy subjects (mean age 35.2 +/- 4.4 years; range 26-41 years; 4 women, 8 men), prior to, during and following acupuncture. Measurements were obtained with the INVOS 3100 cerebral oximeter (Somanetics Corp., Troy, USA). In addition new robotic transcranial Doppler sonography (TCD) probes enabling three-dimensional imaging of the middle cerebral artery by the use of multi-scan techniques were used simultaneously. The results showed small increases in r. cereb. O2 satn. mean values (69.9% before, 70.3% during and 70.2% after acupuncture) and a significant (p < 0.01; ANOVA, Tukey test) increase in mean bloodflow velocity during acupuncture measured simultaneously at different depths within the right middle cerebral artery. There are reports in the literature about the effects of acupuncture on the oxygenation of cerebral tissue in a study with animals. An increase in the cerebral oxygen saturation could be registered with the help of microelectrodes in the cortex. This is parallel evidence to the present results with near infrared spectroscopy and transcranial Doppler sonography. Quantifiable changes in the physiological effects of acupuncture may contribute to improved acceptance of this unconventional complementary medical procedure.

A multifunctional helmet for noninvasive neuromonitoring.

Simultaneous and continuous recording and processing of different noninvasive neuromonitoring parameters were carried out, including spontaneous and evoked bioelectrical brain activities obtained by new "active electrodes," transcranial Doppler sonographic measurements using robotic probes, a multiscan principle for three-dimensional transcranial Doppler imaging, and recording of near-infrared spectroscopic data. The recording and processing were carried out over periods of some hours with a new recording technique integrated in a helmet construction.

Is there paradoxical arousal reaction in the EEG subdelta range in patients during anesthesia?

Different anesthetic drugs can produce different electroencephalographic (EEG) patterns. Nondrug induced influences, such as surgical stimulation, may also alter the EEG in anesthetized patients. Increases of delta activity are interpreted as signs of deepening of anesthesia. These EEG patterns are sometimes also found in frontal leads after surgical stimulation during isoflurane anesthesia. However, to avoid incorrect anesthetic management under EEG monitoring, this phenomenon of "paradoxical arousal" must be taken into consideration. This study demonstrates that, after surgical stimulation, frontal activity was enhanced in the 2-3 Hz and 3-4 Hz frequency bands. On the other hand, in the subdelta range (the 0.05-1 Hz and 1-2 Hz frequency bands), there was an opposite reaction. This significant (p<0.001, according to ANOVA and Dunn's method) reduction of EEG power as a result of the surgical stimuli was found in 25 patients (mean age, 49.1+/-16.3 years) scheduled for elective neurosurgical intervention in the lumbosacral region. This report shows some of the problems arising from the common practice of arbitrarily subdividing a power spectrum in frequency bands.

Cerebral oximetry in dead subjects.

Near-infrared spectroscopy is a technique used to monitor cerebral oxygenation. To validate the method, we measured regional oxygen saturation (rSo2) in the brains of 18 dead subjects (mean age, 74.4 +/- 14.6 years) 19.8 +/- 18.2 h (range, 1-73) after cessation of systemic circulation, and in 15 healthy probands (mean age, 34.2 +/- 8.7 years) with an INVOS 3100 cerebral oximeter. The mean (+/-SD) rSo2 in the dead subjects was 51.0 +/- 26.8% [range, 6-88%; left, 48.4 +/- 28.0% (n = 21); right, 54.4 +/- 25.7% (n = 16)]. The mean rSo2 in the control group was 68.4 +/- 5.2% (range, 60-76%; left, 68.1 +/- 5.0%; right, 68.7 +/- 5.6%). After removal of the brain at autopsy in five of the dead subjects, the rSo2 was 73.4 +/- 13.3% (15 measurements). Six of 18 of the dead subjects had values above the lowest values found in the healthy adults (> or = 60%). These findings raise concerns about the validity of cerebral rSo2 data in adults obtained by the INVOS 3100 system.

The influence of positioning on spectroscopic measurements of brain oxygenation.

This study was designed to evaluate the influence of body position during neurosurgical and cerebrovascular operations on regional cerebral oxygen saturation (rSO2). Awake volunteers (group I; n = 14), anesthetized patients (group II; n = 48) undergoing lumbar discectomy, and 12 patients undergoing carotid endarterectomy (group III) with internal carotid artery (ICA) stenosis were studied. Anesthesia in the patient groups was performed with sevoflurane (1.1 Vol% insp.) in N2O2/O2 mixture (FiO2 0.4) rSO2 was monitored with a INVOS 4100 cerebral oxymeter (Somanetics Corporation, Troy, MI). Measurements were done in all groups in supine position with head turned to the right and left side. Furthermore, in groups I and II, rSO2 was measured in right lateral, left lateral, prone, or sitting position. In each position the parameters were registered at three times (1, 3, and 5 min after taking up the position). In the healthy volunteers, the mean rSO2 values of both hemispheres were 71.3 +/- 5.0%. No significant changes of rSO2 were found interhemispherical and upon turning the head to both sides or positioning to the prone and both lateral positions. After assuming the sitting position, the decrease of rSO2 was not significant. In group II, rSO2 decreased significantly in the sitting position. In group III, baseline readings for rSO2 obtained from the side of ICA stenosis were significantly lower, compared to the contralateral side. After turning the head to the ipsilateral side, this difference diminished. In contrast, turning the head toward the contralateral side, the rSO2 difference remained nearly constant, both values decreasing constantly throughout the observation period. In conclusion, after different positioning maneuvers awake and under anesthesia, alterations of rSO2 can be registrated by near-infrared spectroscopy (NIRS).

Inflammatory reactions of the skin caused by adhesive EEG electrodes.

The correct choice of electrodes for neurophysiologic monitoring is one of the unsolved problems in clinical practice and scientific research. In addition to the familiar electrodes, i.e., cup (silver-/silver-chloride, gold) and needle electrodes, adhesive electrodes (e.g., Zipprep electrodes) have been offered for rapid application and accurate signal recording. This case report indicates that adhesive electrodes can lead to superficial lesions of the skin or inflammatory infiltration.

Quantification of autonomic activity in the brainstem in normal, comatose and brain dead subjects using heart rate variability.

The heart rate variability is defined as variation in distance between sequential ventricular complexes in the electrocardiogram and can be given in percent by referring the standard deviation to the average values of heart rate. The bivariate distribution of heart rate variability and of heart rate shows a discrimination of the group of comatose patients from brain dead subjects and normals.

[Cerebral near infrared spectroscopy and acupuncture--results of a pilot study]. / Zerebrale Nahinfrarot-Spektroskopie und Akupunktur--Ergebnisse einer Pilotstudie.

For the first time, we have studied the effects of manual acupuncture and of laser puncture on cerebral oxygenation in three healthy male volunteers using transcranial near-infrared spectroscopy (NIRO 300, Hamamatsu Photonics, Japan). The results indicate that acupuncture of specific acupuncture points leads to an increase in oxygenated haemoglobin and in the tissue oxygenation index. However, needling and laser puncture at placebo points does not produce the same effect on cerebral oxygenation. This fact provides further proof of specific quantifiable effects of acupuncture on the brain.

Transcranial cerebral oximetry--is it clinically useless at this moment to interpret absolute values obtained by the INVOS 3100 cerebral oximeter?

Dynamic changes of regional cerebral oxygenation (rSO2) were measured simultaneously to laser Doppler flowmetry in a 35-year-old female during cerebral aneurysm surgery. In addition, to demonstrate the uselessness of the absolute values obtained by the INVOS 3100, cerebral oximeter readings from a pumpkin ("Styrian Cucurbita") are demonstrated. The results of the present study and of other reports discussed in this paper demonstrate that the INVOS 3100 cerebral oximeter should not be used at this moment as a measure reflecting absolute rSO2 values. However, it seems to be relevant that the INVOS 3100 system can monitor the dynamic changes in rSO2, although limitations have to be taken into consideration.

[Burst suppression detection in pEEG]. / Burst-Suppression-Erkennung beim pEEG.

In the present paper, experience with the detection of burst suppression in the pEEG is described. The possibilities and limitations of the method during monitoring of anaesthesia under real conditions are discussed.

[Cerebral monitoring in anesthesia and intensive care]. / Zerebrales Monitoring in Anästhesie und Intensivmedizin.

To ensure efficient computer-based cerebral monitoring in the ICU and during anaesthesia, sophisticated and sometimes expensive equipment is needed. It is thus all the more important that the clinician should have a good understanding and knowledge of the various methods involved, the origins of the different signals and their relationships, and of the possibilities of artefacts occurring, if the information that this equipment is capable of providing is to be fully and properly utilized. The present paper describes a number of new techniques of cerebral monitoring, and their successful application in the intensive care unit and the operating theatre.

[Thermographic visualization of changes in peripheral perfusion during acupuncture]. / Visualisierung von peripheren Durchblutungsänderungen während der Akupunktur mittels Thermographie.

Using infrared thermography, the present study evaluated the effects of changes in peripheral perfusion occurring during the initial phase of manual acupuncture (Nei Guan, Qu Chi) under standardised conditions. Thermographic recordings (AGEMA 570 PRO, Flir Systems Inc., Portland, USA) were used to assess superficial changes in temperature in the hands of 6 normal subjects (mean age 33.3 +/- 7.5 years, 3 females, 3 males). Baseline status, acupuncture needling and stimulation were analysed in a single session under controlled conditions (24 degrees C ambient temperature). In all subjects a significant (p = 0.015) short-term cooling effect on superficial hand temperature occurred following needle placement. Thereafter, acupuncture stimulation produced different generalised long-lasting effects. In three subjects a warming effect was seen (increase > 2 degrees C) while in the other three subjects the temperature decreased in all fingers and in the wrist.