RESPIRATORY AND CARDIOVASCULAR CHANGES DURING RAPID SPONTANEOUS VARIATIONS OF VENTRICULAR FLUID PRESSURE IN PATIENTS WITH INTRACRANIAL HYPERTENSION

Intracranial pressure: current perspectives on physiology and monitoring

Intracranial pressure (ICP) monitoring is now viewed as integral to the clinical care of many life-threatening brain insults, such as severe traumatic brain injury, subarachnoid hemorrhage, and malignant stroke. It serves to warn of expanding intracranial mass lesions, to prevent or treat herniation events as well as pressure elevation which impedes nutrient delivery to the brain. It facilitates the calculation of cerebral perfusion pressure (CPP) and the estimation of cerebrovascular autoregulatory status. Despite advancements in our knowledge emanating from a half century of experience with this technology, important controversies remain related even to fundamental aspects of ICP measurements, including indications for monitoring, ICP treatment thresholds, and management of intracranial hypertension. Here, we review the history of ICP monitoring, the underlying pathophysiology as well as current perspectives on why, when and how ICP monitoring is best used. ICP is typically assessed invasively but a number of emerging, non-invasive technologies with inherently lower risk are showing promise. In selected cases, additional neuromonitoring can be used to assist in the interpretation of ICP monitoring information and adapt directed treatment accordingly. Additional efforts to expand the evidence base relevant to ICP monitoring, related technologies and management remain a high priority in neurosurgery and neurocritical care.

Current understanding of the effects of inspiratory resistance on the interactions between systemic blood pressure, cerebral perfusion, intracranial pressure, and cerebrospinal fluid dynamics

Negative intrathoracic pressure (nITP) is generated by the respiratory muscles during inspiration to overcome inspiratory resistance, thus enabling lung ventilation. Recently developed noninvasive techniques have made it possible to assess the effects of nITP in real time in several physiological aspects such as systemic blood pressure (BP), intracranial pressure (ICP), and cerebral blood flow (CBF). It has been shown that nITP from 0 to −20 cmH2O elevates BP and diminishes ICP, which facilitates brain perfusion. The effects of nITP from −20 to −40 cmH2O on BP, ICP, and CBF remain largely unrecognized, yet even nITP at −40 cmH2O may facilitate CBF by diminishing ICP. Importantly, nITP from −20 to −40 cmH2O has been documented in adults in commonly encountered obstructive sleep apnea, which justifies research in this area. Recent revelations about interactions between ICP and BP have opened up new fields of research in physiological regulation and the pathophysiology of common diseases, such as hypertension, brain injury, and respiratory disorders. A better understanding of these interactions may translate directly into new therapies in various fields of clinical medicine.

Human subarachnoid space width oscillations in the resting state

Abnormal cerebrospinal fluid (CSF) pulsatility has been implicated in patients suffering from various diseases, including multiple sclerosis and hypertension. CSF pulsatility results in subarachnoid space (SAS) width changes, which can be measured with near-infrared transillumination backscattering sounding (NIR-T/BSS). The aim of this study was to combine NIR-T/BSS and wavelet analysis methods to characterise the dynamics of the SAS width within a wide range of frequencies from 0.005 to 2 Hz, with low frequencies studied in detail for the first time. From recordings in the resting state, we also demonstrate the relationships between SAS width in both hemispheres of the brain, and investigate how the SAS width dynamics is related to the blood pressure (BP). These investigations also revealed influences of age and SAS correlation on the dynamics of SAS width and its similarity with the BP. Combination of NIR-T/BSS and time-frequency analysis may open up new frontiers in the understanding and diagnosis of various neurodegenerative and ageing related diseases to improve diagnostic procedures and patient prognosis.

Role of chiropractic and sacro-occipital technique in asthma treatment

Asthma is a multifactorial dysfunction of the respiratory system. Nutritional, environmental, genetic, and emotional factors all play animportant part in the etiology of this condition. One form of chiropractic, Sacro Occipital Technique (SOT), offers some conservative alternatives to the treatment of asthma. SOT expands the chiropractic armamentarium of techniques available, allowing methods putatively affecting the viscera, vertebra, post and preganglionic reflexes, as well as cranial and sacral influences on the primary respiratory mechanism. Though more research is needed to evaluate the efficacy of chiropractic care of asthma, the conservative nature of chiropractic care with its minimal side effects, warrants patient and a health practitioner's consideration prior to embarking on any course of treatment that might have serious side effects.

Normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) is a reversible disorder characterized by gait impairment, subcortical dementia, and urinary urgency and incontinence associated with impaired cerebrospinal fluid circulation and ventriculomegaly. Treatment with shunt surgery is most likely to increase mobility, and may also improve dementia and urinary symptoms. An international, independent study group recently published guidelines for the diagnosis and management of idiopathic NPH. This article helps geriatricians identify patients who might have NPH, and care for these patients after shunt placement.

The intracranial B-waves' amplitude as prognostication criterion of neurological complications in neuroendovascular interventions

The purpose of this study was to evaluate dynamics of B-waves' amplitudes (BWA) of blood flow velocity (BFV) in patients with cerebrovascular diseases during endovascular operations. We examined 12 patients with neurovascular pathology during neuroendovascular interventions. Patients were divided into two groups: 1st group (6 cases)--without intraoperative neurological complications, 2nd group (6 cases)--with complications. Bilateral monitoring of BFV in middle cerebral arteries was carried out applying Multi Dop X. To estimate BWA Fourier analysis was used. In the 1st group preoperative BWA on the affected side was 3.9 +/- 0.6 cm/s. Intraoperative (during an access to pathologic formation and its embolisation) BWA increased up to 7.7 +/- 1.1 cm/s (p < 0.05). Postoperative BWA decreased to 4.2 +/- 0.8 cm/s. In the 2nd group the preoperative BWA on the affected side was 9.6 +/- 1.1 cm/s (p < 0.05), thus higher than in the 1st group. Intraoperatively we observed further increase of BWA up to 12.1 +/- 2.6 cm/s, accompanied by occurrence or increase of neurological symptoms. Postoperative BWA decreased to 10.4 +/- 2.9 cm/s, whereas we didn't observe regression of neurological symptoms.

Slow rhythmic oscillations in intracranial CSF and blood flow: registered by MRI

Since Lundberg first described slow oscillations as so called B-waves during ICP-monitoring, similar oscillations have been found in various physiological systems. Thus, the detection of slow waves in intracranial CSF- and blood-flow with MR-techniques seemed very likely. We examined the interventricular CSF-flow and cerebral blood flow of 11 healthy volunteers with dynamic echo-planar imaging by simultaneous registration of respiration and peripheral pulse. The spectral analysis was restricted to slow waves, which were divided into B-waves (0.008-0.05 Hz), Mayer- or C-waves (0.05-0.15 Hz) and respiration-related waves (0.15-0.6 Hz). In the CSF, the integrated amplitude of B-waves accounted for 18.2%, Mayer- or C-waves for 26.9% and respiration-related waves for 55.0%. Proportional values were recorded in the artery and peripheral pulse. In the venous sinus, a higher percentage of B- and Mayer-/C-waves and a lower percentage of respiration related waves were found. In conclusion, with MR-EPI technique, slow rhythmic oscillations in the cerebral blood- and CSF-flow can be analysed non-invasively and independently from the cardiac cycle. The comparable distribution of slow waves in the pulse, arteries and CSF may reflect an origin in autoregulation, whereas divergent patterns like in the incompressible venous sinus may be of a passive origin.

Dural port therapy

INTRODUCTION

Dural port therapy (DPT) is a chiropractic procedure which can be used effectively with Sacro-Occipital Technique (SOT) procedures and which uses the sacrum as a lever to influence and balance the spine and cranium by way of the meningeal system.

DISCUSSION

Rationale and research is presented to explain the basis behind DPT's method of affecting the craniospinal system and its relationship to the meninges. Though the procedure can be used with most conditions, DPT appears to be safe to use with osteoporotic conditions, fractured vertebrae, and other conditions where a "thrust" to the spine may be contraindicated. Basic methods of using DPT are presented along with alternative methods which can be applied when the basic methods are not sufficient.

CONCLUSION

DPT reduces sacral, spinal, and cranial dura meningeal tension, lesions, torque and stress, as well as dural sleeve vasomotor interference. The possibility that the doctor can influence the nervous system directly in such a powerful manner warrants further investigation.

Intracranial oscillations of cerebrospinal fluid and blood flows: analysis with magnetic resonance imaging

PURPOSE

To detect oscillations of the cerebrospinal fluid (CSF) flow related to the heartbeat and frequencies lower than 0.6 Hz and to compare these oscillations of CSF and blood flow in cerebral vessels by using echo planar imaging in real time mode. The existence of such waves has been well known but has not yet been shown by MRI.

MATERIALS AND METHODS

In a slice perpendicular to the aqueduct, CSF flow as well as CBF, could be determined in sagittal sinus, basilar artery, and capillary vessels. After Fourier analysis, four frequency bands were assigned.

RESULTS

In the very high-frequency (heart rate) range, the integrals under the CSF curves were more closely related to arterial CBF than to changes in the sinus. Also, in the high-frequency (respiration rate), low-frequency (0.05-0.15 Hz), and very-low-frequency (0.008-0.05 Hz) ranges, the integrals under the CSF curves corresponded with arterial and capillary CBF.

CONCLUSION

Slow and fast oscillations in CSF flow are detectable in healthy persons with a proportional allotment to arterial and capillary CBF.

[Intracranial hypertension in the infant: from its physiopathology to its therapeutic management]

The pathophysiology of elevated intracranial pressure (ICP) is assessed from a three cerebral compartment model and from brain compliance. The mechanisms leading to elevated ICP (expanding process, cerebral edema, brain swelling, hydrocephalus) and their consequences (brain herniation, ischemia-anoxia phenomenon, Cushing reaction and neurogenic pulmonary edema) are overviewed. The causes of elevated ICP in children are reported with emphasis on traumatology. Diagnostic procedures include clinical assessment, fundoscopy, cerebral computerized tomography scan and specific problems of cerebrospinal fluid investigation. Methods and results of intracranial pressure monitoring are reported. The treatment of elevated ICP is based upon clinical follow-up and monitoring of ICP. General therapeutic rules consist of adequate position, suppression of any neck, skull and abdominal compression, stimuli limitation and fluid restriction. Specific treatments include mechanical ventilation, sedation and analgesia, barbiturates, anticonvulsant drugs, mannitol, corticosteroids, hypothermia, enteral nutrition, and antibiotics.

Nocturnal sleep study in multiple sclerosis: correlations with clinical and brain magnetic resonance imaging findings

It has been suggested that sleep disturbances in multiple sclerosis (MS) may be related to periodic leg movements (PLM) during sleep, but to date polysomnographic studies were conducted only on small and unselected patient groups. Aim of this study was to evaluate 8-hour polysomnography in MS patients and to correlate sleep results with clinical and brain magnetic resonance imaging (MRI) data. Twenty-five clinically definite MS patients, without mood disorders and drug-free, entered the study. The patients were compared to 25 age- and sex-matched subjects. MS patients had significantly reduced sleep efficiency and experienced more awakenings during sleep. No difference was found in sleep architecture parameters between MS patients and controls. PLM was found in 9 patients (36%) and 2 controls (8%; p = 0.02). Of the six patients who complained of insomnia two had PLM and 2 others presented with PLM and central sleep apnea. In patients with PLM greater MRI lesion loads were detected in the infratentorial regions, particularly in cerebellum and brainstem. Larger studies in neurological diseases that produce focal lesions in these brain areas could provide useful information on the PLM pathogenesis.

Periodic activity in cerebral arousal mechanisms--the relationship to sleep and brain damage

Periodic activity during light sleep is well recognised in many physiological systems, particularly respiration. In damaged brains this activity can become exaggerated. It involves the autonomic nervous system, the muscles, the cerebrospinal fluid (CSF) pressure, the cerebral blood flow and the electroencephalogram (EEG). It is related to the level of arousal. The EEGs of 52 subjects were studied. In stage 0-1 sleep, periods of alpha activity alternated with periods of theta activity related to the level of arousal. The intervals between the alpha onsets were measured and the data pooled. There was a dominant interval of about 16 sec. It is suggested that this is a physiological cerebral rhythm involving the cortex and the brain-stem activating mechanisms, responsive to outside stimuli but essentially endogenous. It is related to the controls of the autonomic, motor, and some cerebral auto-regulatory mechanisms. It may be severely disturbed in brain damage.

Quantification of abnormal intracranial pressure waves and isotope cisternography for diagnosis of occult communicating hydrocephalus

Nineteen consecutive patients with suspected occult communicating hydrocephalus were investigated by means of clinical evaluation, neuropsychological testing, isotope cisternography, computed tomography scanning, and continuous intracranial pressure monitoring. Semi-quantitative grading systems were used in the evaluation of the clinical, neuropsychological, and cisternographic assessments. Clinical examination, neuropsychological testing, and computed tomography scanning were repeated 3 months after ventriculoperitoneal shunting. All patients showed abnormal intracranial pressure waves and all improved after shunting. There was close correlation between number, peak, and pulse pressures of B waves and the mean intracranial pressure. However, quantification of B waves by means of number, frequency, and amplitude did not help in predicting the degree of clinical improvement postshunting. The most sensitive predictor of favorable response to shunting was enlargement of the temporal horns on computed tomography scan. Furthermore, the size of temporal horns correlated with mean intracranial pressure. There was no correlation between abnormalities on isotope cisternography and clinical improvement.

Threshold of cerebral perfusion pressure as a prognostic factor in hydrocephalus during infancy

An analysis of the intracranial pressure (ICP) was done on 30 hydrocephalic infants using a newly devised computerized analyzing system. As a cerebrovascularly compromised index of the ICP, the transmission ratio of systemic arterial pulse pressure (SABP) to ICP as defined by Ikeyama [eta HB (PP of ICP/PP of SABP)] was used. Cerebral perfusion pressure (CPP) versus eta HB showed significant bilinear relationship. From this correlation the threshold of CPP in relation to ICP level was calculated. A reduction of CPP below this level abruptly reduced the correlation with ICP. Thus, the CPP threshold showed an increase related to age (from 20 mm Hg in preterm babies at birth to 80 mm Hg at 12 months of age) and is correlated with the psychomotor development evaluated 6-36 months after shunting. The abnormal waves that appear when there is a high level of eta HB and that also appear below the threshold level of CPP can be defined as pressure waves, based on the physiological findings. It was shown that in hydrocephalus during infancy, a prolonged ICP below the threshold of CPP is one of the cerebrohemodynamic factors that can adversely affect the outcome of psychomotor development.

Role of the medulla oblongata in plateau-wave development in dogs

Plateau waves reflect both dilatation of the cerebral vessels and an increase in the cerebral blood volume under increased intracranial pressure (ICP). They are often associated with changes in arterial blood pressure (BP) and respiration, suggesting a role of the brain stem in their development. In experiments conducted on dogs in which intracranial hypertension was induced by occluding the neck veins, the authors stimulated the brain-stem reticular formation in the medulla oblongata and caudal pons to identify the brain sites that produce plateau-like responses. A rise in ICP was observed following stimulation of most areas of the brain stem and was associated with changes in arterial BP, cerebral perfusion pressure (CPP), cerebral blood flow (CBF), respiration, and pulse rate. The stimuli delivered to the medial reticular formation of the caudal medulla caused an arterial depressor response, a decrease in CPP and CBF, suppressed ventilation, and bradycardia; these responses were similar in many respects to plateau waves observed in clinical practice and almost corresponded to the depressor region of the vasomotor center. It is hypothesized that the medullary depressor area may play a role in eliciting cerebral vasomotor reaction concerned with the development of plateau waves in a state of increased ICP.

Effect of baclofen on sleep-related periodic leg movements

Five patients with nocturnal myoclonus (periodic leg movements during sleep), mean age 59.6 years, were monitored polygraphically for fifteen successive nights. Using a double-blind drug study design with placebo at baseline, we investigated the effect of baclofen on these patients. All patients had the repetitive sleep-related abnormal movements during both the baseline nights and those on which baclofen had been administered. The number of movements varied during the four baseline nights, but the movements induced sleep fragmentation, i.e., very short electroencephalographic changes. Baclofen increased the number of movements but decreased their amplitude during non-rapid eye movement (REM) sleep and shortened the interval between movements. Its effect on sleep was dose related: as dosages increased, delta sleep progressively increased and REM sleep decreased. Sleep fragmentation resulting from muscle twitches decreased, as indicated by the diminution in alpha electroencephalographic arousals and K complexes. Baclofen dosages of 20 mg and 40 mg were the most efficacious.

Origin and evolution of plateau waves. Experimental observations and a theoretical model

Laboratory observations made in cats with fluid-percussion head injuries have suggested that plateau waves or Lundberg "A-waves" are not independent of systemic circulatory events. Four distinct phases in the evolution of the plateau wave have been identified, and each related to a circulatory change in a causal manner. The first phase is the premonitory drift phase where intracranial pressure (ICP) gradually increases prior to the plateau proper. This phase is caused by a slow gradual decline in systemic arterial blood pressure (SABP) which increases ICP by autoregulatory vasodilation and reduces cerebral perfusion pressure (CPP) to a range of 70 to 80 mm Hg. The second phase is the plateau phase initiated at a CPP of about 70 to 80 mm Hg, and is characterized by a rapid increase in ICP as CPP falls further to 40 to 50 mm Hg. The plateau lasts as long as the CPP remains stable and above ischemic levels. The third phase is the ischemic response, characterized by CPP being returned toward normal by increases in SABP in response to very low CPP's. The fourth phase is the resolution, characterized by a rapid decline in the ICP to baseline levels with stabilization of the SABP and CPP, and is best explained by autoregulatory vasoconstriction. Plateau waves appear to occur as the result of intact or mostly intact autoregulation responding to changes in CPP. The series of events that follow are best explained by what is known of normal autoregulation; the various properties of plateau waves are viewed and explained as the expected and logical consequences of an unstable CPP acting upon a generally intact cerebrovascular bed in the face of elevated ICP and decreased compliance.

Periodic movements in sleep (nocturnal myoclonus): relation to sleep disorders

Periodic movements in sleep (PMS) are stereotyped, repetitive, nonepileptiform movements of the lower extremities. A total of 409 sleep disorder patients were studied with all-night polysomnogram recording, and 53 (13%) had PMS. Such movements occurred in a wide variety of sleep-wake disorders in addition to insomnia. The prevalence and magnitude of PMS were not statistically greater in patients with insomniac disorders than in those with syndromes of excessive daytime sleepiness or other sleep-wake disorders. The results suggest that although PMS is responsible for disturbed sleep in relatively few patients, chronic sleep-wake disturbance is associated with PMS and may lead to the development of these movements.

The definition of "Cheyne-Stokes rhythms"

The review of the literature on Cheyne-Stokes respiratory periods reveals enormous variation of the opinions expressed. The original description concerned periodicity characterized by rhythmic changes of respiratory phases and respiratory pauses in a relation of 60 : 15 seconds. In the respiratory phase there were 30 respirations of increasing depths and frequency at the beginning of the phase and decreasing depths and frequency at the end of the phase. Literature data about Cheyne-Stokes respiration comprise a multiplicity of all rhythymic forms. The duration of respiratory cycles varies between 12 and 130 seconds. The relation of the respiratory phase and respiratory pause between 6 : 4 or 75 : 70 seconds, and the number of breaths between 3 and 30 during one respiratory phase. Cheyne-Stokes periods were observed in health subjects as well as in patients with neurological, neurosurgical, cardiac, pulmonary and paediatric diseases. Cheyne-Stokes periods were explained as sequel of prolongation of circulation time between pulmonary alveoli and respiratory centre, through increased sensitivity of the respiratory centre to CO2, diminished sensitivity of the respiratory centre to CO2 and O2-deficit, local blood flow disturbances, section of pathways in the brain stem with disinhibition of basic rhythms, brain immaturity, alterations of consciousness, and respiratory obstructions. Rhythmic changes of the heart beat, of excitability of the heart muscle, of blood pressure, of EEG and of neurological and mental signs were observed. In spite of numerous observations detailed analysis of the respiratory cycle was performed in only a few cases. Major studies are lacking.

Intracranial hypertension in patients with ruptured intracranial aneurysm

Simultaneous continuous recording of intracranial pressure (ICP) and systemic blood pressure was carried out in 26 patients admitted within 1 week after subarachnoid hemorrhage (SAH) due to a ruptured intracranial aneurysm. The patients were graded as described by Hunt and Hess. Recordings were made for 1 to 5 days. The more impaired the consciousness, the higher the rate of ICP. In Grade III, IV, and V patients, the mean ICP level was in the range of 15 to 40 mm Hg, 30 to 75 mm Hg, and exceeded 75 mm Hg, respectively. A definite correlation between vasospasm shown by cerebral arteriogram and the clinical grade was not observed. In our series of ICP recordings, we never observed a typical plateau wave. The variations of ICP seen in Grade III and IV patients were the B- and C-waves (15 to 45 mm Hg in amplitude) described by Lundberg, and those in Grade V patients were the high amplitude monotonous waves synchronous with the arterial pulses (15 to 40 mm Hg in amplitude). These phenomena may indicate that Grade III and IV patients with SAH are in a condition of cerebral vasomotor instability, and Grade V patients have cerebral vasomotor paralysis.

Patterns of arousal in comatose patients

The EEG changes, with associated cardiorespiratory phenomena and, where possible, postmortem findings, are described in six patients in coma, with some reference to other similar cases. Spontaneously occurring periodic changes were observed at varying intervals between 20 s and 4 min but most commonly at 1/2-2 min. These involved simultaneous cardiorespiratory, EEG, and somatic motor phenomena related to changes in the level of arousal. It is suggested that a physiological periodicity of the arousal mechanisms exists which may be of importance in the understanding of the pathophysiology of comatose states.