Simultaneous cerebral and spinal fluid pressure recordings

Summary Cerebrospinal fluid pulsation is likely to be responsible for the progression of some diseases, and it is differences in pressure which are significant in causing the imposition of energy upon tissues. The normal range of such differences has not been extensively documented. A technique for measuring intracranial and intraspinal pressures simultaneously in erect conscious patients is described. Normally the pressures are in a continual state of pulsation in response to changes in pressure in the arteries and veins. The measurements of CSF pressure fluctuations in response to normal cardiac pulsation, respiratory changes, coughing, Queckenstedt's test, and a variation of Valsalva's manoeuvre have been recorded, and the physiology has been discussed.     

Intracranial pressure and cerebral blood flow

Intracranial pressure (ICP) is determined by the volumes of brain, blood and cerebrospinal fluid within the skull, which is of course of fixed volume. The Monro–Kellie hypothesis states that an increase in volume of one of these components must be compensated for by a reduction in volume of one or both of the others. If this compensation is insufficient, then potentially fatal increases in ICP can occur. Maintenance of relatively constant ICP is essential for normal perfusion of the brain. Cerebral blood flow is regulated both globally, in order to prevent hypo- or hyper-perfusion resulting from changes in systemic arterial blood pressure, and locally, to meet the dynamic oxygen and substrate demands of different brain regions. Monitoring of ICP and the cerebral blood supply is possible through a variety of invasive and non-invasive techniques, and these techniques are already established in anaesthesia and intensive care medicine.     

Reappraisal of the intracranial pressure and cerebrospinal fluid dynamics in patients with the so-called “Normal pressure hydrocephalus” syndrome

Summary Fifty-four shunt-responsive patients were selected from a prospective protocol directed to study patients with suspected normal pressure hydrocephalus (NPH). Patients with gait disturbances, dementia, non-responsive L-Dopa Parkinsonism, urinary or faecal incontinence and an Evans ratio greater or equal to 0.30 on the CT scan were included in the study.As a part of their work-up all patients underwent intracranial pressure monitoring and hydrodynamic studies using Marmarou's bolus test. According to mean intracranial pressure (ICP) and the percentage of high amplitude B-waves, patients were subdivided in the following categories: 1) Active hydrocephalus (mean ICP above 15 mmHg), which is in fact no tone normal pressure hydrocephalus; 2) Compensated unstable hydrocephalus, when mean ICP was below 15 mmHg and B-waves were present in more than 25% of the total recording time and 3) Compensated stable hydrocephalus when ICP was lower or equal to 15 mmHg and beta waves were present in less than 25% of the total recording time.The majority of the patients in this study (70%) presented continuous high or intermittently raised ICP (active or unstable compensated hydrocephalus group). Mean resistance to outflow of CSF (Rout) was 38.8 mm Hg/ml/min in active hydrocephalus and 23.5 mm Hg/ml/min in the compensated group (Students t-test, p < 0.05). Higher resistance to outflow was found in patients with obliterated cortical sulci and obliterated Sylvian cisterns in the CT scan.No statistically significant correlation was found when plotting the percentage of beta waves against pressure volume index (PVI), compliance or Rout. An exponential correlation was found when plotting beta waves against the sum of conductance to outflow and compliance calculated by PVI method (r=0.79).Patients with the so-called normal pressure hydrocephalus syndrome have different ICP and CSF dynamic profiles. Additional studies taking into consideration these differences are necessary before defining the sensitivity, specificity and predictive value of ICP monitoring and CSF studies in selecting appropriate candidates for shunting.     

Normal pressure hydrocephalus. Influences on cerebral hemodynamic and cerebrospinal fluid pressure--chemical autoregulation

Blood flow in the cerebral gray matter was measured in normal pressure hydrocephalus and Alzheimer disease by 133Xe inhalation. Flow values in the frontal and temporal gray matter increased after lowering cerebrospinal fluid (CSF) pressure by lumbar puncture in normal pressure hydrocephalus (p less than 0.05) and also after shunting. One case with cerebral complications did not improve clinically. In Alzheimer disease the reverse (decreases in flow in the gray matter) occurred after removal of CSF. Normal pressure hydrocephalus was associated with impaired cerebral vasomotor responsiveness during 100% oxygen and 5% carbon dioxide inhalation. This complication was restored toward normal after CSF removal and/or shunting. Cerebral blood flow measurements appear to be useful for confirming the diagnosis of normal pressure hydrocephalus and predicting the clinical benefit from shunting.     

The effect of isoflurane on cerebrospinal fluid pressure in patients undergoing neurosurgery

Ten patients with intracerebral tumours (TC) and 13 patients with subarachnoid haemorrhage (SAH) from a ruptured cerebral arterial aneurysm were studied before intracranial surgery, and during a 3-h postoperative period. Cerebrospinal fluid pressure (CSFP) determined by an intraventricular (TC group) or intraspinal (SAH group) catheter, and mean arterial blood pressure (MABP) were recorded under neurolept anaesthesia (control) followed by isoflurane inhalation. These two measurements were performed during normocapnia. A third measurement was made during hypocapnia, with unchanged isoflurane concentration. After the experimental period, isoflurane remained the main anaesthetic agent throughout the surgical procedure. After recovery from anaesthesia, the patients were monitored with CSFP and blood pressure during the first postoperative hours, and the quality of breathing was assessed by hourly blood-gas analyses. The results show that isoflurane causes a 10-14% reduction of MABP with no further changes during hyperventilation. Mean CSFP increased 27% in the TC group, and 12% in the SAH group after isoflurane induction and decreased from these levels by 29% during hyperventilation in both groups. Consequently, the impact on cerebral perfusion pressure (CPP) by isoflurane was a 19% and 21% mean decrease in the TC and SAH group, respectively. Controlled hyperventilation reduced this effect by partially restoring control CPP values, with 8% and 14% increase, respectively. In the postoperative follow-up, all patients had normal breathing and blood pressure with low values of CSFP. It is concluded that isoflurane can be used in intracranial surgery with adequate safety if combined with controlled hyperventilation.     

Intracranial pressure and cerebral haemodynamics

Intracranial pressure (ICP) refers to the pressure within the skull, which is determined by the volumes of the intracranial contents; blood, brain and cerebrospinal fluid. Monro–Kellie homeostasis stipulates that a change in the total intracranial volume is accompanied by a change in the ICP, which is more precisely described by the intracranial pressure–volume relationship. Maintenance of a relatively constant ICP is essential for maintenance of the cerebral perfusion pressure, which in turn determines global cerebral blood flow. Although the physiological process of autoregulation ensures that cerebral blood flow is tightly maintained over a range of cerebral perfusion pressures, large increases in the ICP can result in severely impaired autoregulation, meaning that cerebral blood flow may be compromised. In this review article we provide an overview of the physiological determinants of the ICP and cerebral blood flow. We go on to illustrate how pathological states can compromise physiological compensatory mechanisms in order to potentially dangerous disturbances of the ICP and cerebral blood flow.     

Intracranial pressure and cerebral haemodynamics

Intracranial pressure (ICP) refers to the pressure within the skull, which is determined by the volumes of the intracranial contents; blood, brain and cerebrospinal fluid. Monro–Kellie homeostasis stipulates that a change in the total intracranial volume is accompanied by a change in the ICP, which is more precisely described by the ICP–volume relationship. Maintenance of a relatively constant ICP is essential for maintenance of the cerebral perfusion pressure (CPP), which in turn determines global cerebral blood flow (CBF). Although the physiological process of autoregulation ensures that CBF is tightly maintained over a range of CPPs, large increases in the ICP can result in severely impaired autoregulation, meaning that CBF may be compromised. In this review article we provide an overview of the physiological determinants of the ICP and CBF. We go on to illustrate how pathological states can compromise physiological compensatory mechanisms in order to potentially dangerous disturbances of the ICP and CBF.     

Intracranial pressure and cerebral haemodynamics

Intracranial pressure (ICP) refers to the pressure within the skull, which is determined by the volumes of the intracranial contents; blood, brain and cerebrospinal fluid. Monro–Kellie homeostasis stipulates that a change in the total intracranial volume is accompanied by a change in the ICP, which is more precisely described by the intracranial pressure–volume relationship. Maintenance of a relatively constant ICP is essential for maintenance of the cerebral perfusion pressure, which in turn determines global cerebral blood flow. Although the physiological process of autoregulation ensures that cerebral blood flow is tightly maintained over a range of cerebral perfusion pressures, large increases in the ICP can result in severely impaired autoregulation, meaning that cerebral blood flow may be compromised. In this review article we provide an overview of the physiological determinants of the ICP and cerebral blood flow. We go on to illustrate how pathological states can compromise physiological compensatory mechanisms in order to potentially dangerous disturbances of the ICP and cerebral blood flow.     

The effect of increasing degrees of spinal flexion on cerebrospinal fluid pressure

The effects of increasing degrees of flexion on cerebrospinal fluid pressure were investigated in 12 neurosurgical patients requiring lumbar subarachnoid drains. Cerebrospinal fluid pressure and central venous pressure were measured in three positions: fully flexed ('chin on chest'), flexed at ninety degrees and straight. There was a significant increase in cerebrospinal fluid pressure on moving from the fully flexed to the flexed position (p < 0.0001), but not from the flexed to the straight position. These results were mirrored by smaller changes in central venous pressure. In patients without intracranial pathology these increases in cerebrospinal fluid pressure are probably unimportant. However, intracranial pathology may result in low cerebral perfusion pressures and any increase in cerebrospinal fluid pressure in this group may be harmful. The fully flexed position should be avoided when inserting lumbar drains in at risk patients.     

Colloid osmotic and hydrostatic pressures in chronic subdural haematomas

Summary Intracranial pressure (ICP) has been measured in eight patients with chronic subdural haematomas (CSH) for 24 hours prior to and for 24 hours following evacuation of the haematomas. In all patients ICP was increased prior to surgery (mean: 23 mm Hg), and it rose again to the preoperative level following evacuation of the haematomas in spite of disappearance of most symptoms and signs. In two of these patients and in another eight patients with CSH, colloid osmotic pressures were measured in samples obtained simultaneously from haematoma fluid and venous blood during surgery. The colloid osmotic pressure in haematoma fluid varied considerably between patients (lowest: 11.8 mm Hg, highest: 60 mm Hg), and thus the difference between colloid osmotic pressures in haematoma fluid and plasma also varied considerably. We suggest that the increased ICP in patients with CSH is the consequence of an increased resistance to absorption of cerebrospinal fluid due to compression of the underlying subarachnoid space. The findings with regard to colloid osmotic pressures suggest that osmotic gradients may be maintained across the boundaries of a chronic subdural haematoma.     

Monitoring of cerebrospinal dynamics using continuous analysis of intracranial pressure and cerebral perfusion pressure in head injury

Summary Cerebrospinal dynamics has been investigated by statistical analysis of results of computerised monitoring of 80 head injured patients admitted to the Intensive Care Unit at Pinderfields General Hospital. One minute average values of intracranial pressure (ICP), systemic arterial pressure (ABP), cerebral perfusion pressure (CPP), amplitude of the fundamental component of the intracranial pressure pulse wave and the short-term moving correlation coefficient between that amplitude and mean ICP (RAP) were recorded. It was found that reduction of CPP down to 40mmHg was more often caused by decrease in ABP than increase in ICP. Further falls in CPP below 40mmHg were caused by substantial increases in ICP above 25 mmHg. The relationship between the ICP pulse wave amplitude and CPP showed a significant gradual increase in amplitude with CPP decreasing from 75 to 30 mmHg. For CPP below 30 mmHg there is a sharp decrease in amplitude followed by a change in the coefficient RAP from positive to negative values. This was interpreted as a sign of critical disturbance in cerebral circulation.     

Cerebrospinal fluid and plasma vasopressin during short-time induced intracranial hypertension

Summary The response of plasma and ventricular cerebrospinal fluid vasopressin concentration to short-time induced intracranial hypertension was studied in 8 patients with hydrocephalus, defined as ventricular enlargement on computerized tomography. In connection with measurement of conductance to cerebrospinal fluid outflow, the concentration of vasopressin in plasma and cerebrospinal fluid was measured during perfusion at a low (20 mmHg) intraventricular pressure level. Mean plasma vasopressin concentration was increased from 2.4±0.4pg/ml (SEM) during perfusion at the low pressure level to 4.2±0.8 pg/ml (p<0.01) at the high pressure level. The cerebrospinal fluid concentrations of vasopressin at the low and high intraventricular pressure were 1.2 ±0.1pg/ml and 1.7±0.2 pg/ml (p<0.05), respectively. However, only half of the patients responded to the increase in intraventricular pressure with an increase in cerebrospinal fluid vasopressin concentration exceeding 50%. The results of the present study suggest that an increase in the intracranial pressure might be a stimulus for vasopressin release in both the blood and the cerebrospinal fluid.     

The prognostic value of clinical characteristics and parameters of cerebrospinal fluid hydrodynamics in shunting for idiopathic normal pressure hydrocephalus

Summary Background. It is difficult to predict which patients with symptoms and radiological signs of normal pressure hydrocephalus (NPH) will benefit from a shunting procedure and which patients will not. Risk of this procedure is also higher in patients with NPH than in the overall population of hydrocephalic patients. The aim of this study is to investigate which clinical characteristics, CT parameters and parameters of cerebrospinal fluid dynamics could predict improvement after shunting. Methods. Eighty-three consecutive patients with symptoms and radiological signs of NPH were included in a prospective study. Parameters of the cerebrospinal fluid dynamics were measured by calculation of computerised data obtained by a constant-flow lumbar infusion test. Sixty-six patients considered candidates for surgery were treated with a medium-pressure Spitz-Holter valve; in seventeen patients a shunting procedure was not considered indicated. Clinical and radiological follow-up was performed for at least one year postoperatively. Findings. The odds ratio, the sensitivity and specificity as well as the positive and negative predictive value of individual and combinations of measured parameters did not show a statistically significant relation to clinical improvement after shunting. Conclusions. We conclude that neither individual parameters nor combinations of measured parameters show any statistically significant relation to clinical improvement following shunting procedures in patients suspected of NPH. We suggest restricting the term normal pressure hydrocephalus to cases that improve after shunting and using the term normal pressure hydrocephalus syndrome for patients suspected of NPH and for patients not improving after implantation of a proven well-functioning shunt. An erratum to this article is available at .     

体位变化对脑室引流术患者颅内压和平均动脉压及脑灌注压的影响

目的 探讨脑室引流患者的体位变化对平均动脉压、颅内压和脑灌注压的影响.方法 对60例接受过脑室穿刺术并留置脑室引流管患者,监测其抬高床头0°、15°、30°、45°时的颅内压(ICP)和平均动脉压(MAP),再计算出脑灌注压(CPP),比较不同体位状态下患者的MAP、ICP和CPP.结果 ICP随着床头的抬高而显著降低...     

Significance of the ventricular fluid pressure wave form in the diagnosis of cerebral circulatory arrest and brain death

Summary The fluctuations in the absolute value of the ventricular fluid pressure (VFP) with simultaneous changes in the amplitude and frequency of the oscillations of the ventricular fluid wave form are described in seven patients who developed brain death following either a head injury or a cerebrovascular accident, and are compared with those observed in nineteen patients who survived similar brain pathology. The findings in the two groups were significantly different. It is suggested that VFP monitoring does provide reliable evidence of brain death even while the patient is on artificial respiration.     

Safety and accuracy in the clinical recording of cerebrospinal fluid pressure

Summary A pressure transducer with a disposable, presterilized fluid chamber was developed to increase the safety margin when recording cerebrospinal fluid (CSF) pressure. With this system the fluid compartment is completely separated from the transducer proper, reducing electrical hazard and the risk of infection. The operational range is form — 20 mm Hg to 300 mm Hg with good static accuracy. The transducer with stopcocks has a flat frequency response of up to 75 Hz, showing that the two-part principle is compatible with good dynamic performance.The transducer system was easy to handle and well suited to the recording of ventricular fluid pressure, detection of spinal subarachnoid block, the investigation of CSF absorptive capacity, as well as blood pressure recording. When the transducer was connected to standard disposable stopcocks, needles, and tubing as for these recordings, the dynamic accuracy of the whole apparatus was satisfactory for analysis of the pulsatile wave-form. A total of 185 CSF pressure recordings was performed without complication.     

地氟醚对颅脑手术病人脑脊液压力及大脑中动脉血流速度的影响

目的 观察地氟醚以不同ＭＡＣ值维持麻醉期间对脑脊液压力（ＣＳＦＰ）和大脑中动脉血流速率（ＶｍＭＣＡ）的影响。方法 ６０名颅内肿瘤病人,随机分为２组,Ａ组选用地氟醚维持麻醉,Ｂ组选用异氟醚维持麻醉。每组病人又按维持麻醉的不同ＭＡＣ值分为三小组：分组ＭＡＣ值为０．５、０．８和１．１。通过蛛网膜下腔导管监测ＣＳＦＰ的变化,分别于麻醉前、诱导插管时观察记录,并于ＭＡＣ值稳定于预定值开始,每５分钟测量一次直     

Computerized tomography-guided epidural blood patch in the treatment of spontaneous low cerebrospinal fluid pressure headache

A 54-year-old woman suffering from migraine for 35 years was referred to the pain clinic with a changed pattern of headache that had developed over the last 6 weeks. The pain was located in the central forehead region; aggravation in the prone and immediate relief in the supine position led to the hypothesis of a spontaneous low cerebrospinal fluid (CSF) pressure headache. Cisternography revealed a cyst-like formation in the cervico-thoracic region, indicating cerebrospinal fluid leakage. Magnetic resonance imaging (MRI) myelography confirmed ventral leakage but failed to locate the exact site. Computerized tomography (CT)-guided epidural blood patching between T1 and T2 completely relieved the headache.     

Diagnosis of genuine stress incontinence—a comparison of the fluid bridge (flow) test and a pressure test

Two urodynamic investigations designed to make a diagnosis of genuine stress incontinence were compared in 103 women complaining of stress incontinence and 19 continent women. A fluid bridge (flow) test and a stress urethral pressure profile (using a microtip catheter system) were performed. Both tests gave similar results, confirming the diagnosis in 90% of the incontinent group.