Precipitating and relieving factors of migraine versus tension type headache

Background

The correlation between intracranial pressure (ICP) and intraocular pressure (IOP) is still controversial in literature and hence whether IOP can be used as a non-invasive surrogate of ICP remains unknown. The aim of the current study was to further clarify the potential correlation between ICP and IOP.

Methods

The IOP measured with Goldmann applanation tonometer was carried out on 130 patients whose ICP was determined via lumber puncture. The Pearson correlation coefficient between ICP and IOP was calculated, the fisher line discriminated analysis to evaluate the effectivity of using IOP to predict the ICP level.

Results

A significant correlation between ICP and IOP was found. ICP was correlated significantly with IOP of the right eyes (p?<?0.001) and IOP of the left eyes (p?=?0.001) and mean IOP of both eyes (p?<?0.001), respectively. However, using IOP as a measurement to predict ICP, the accuracy rate was found to be 65.4%.

Conclusion

Our data suggested that although a significant correlation exists between ICP and IOP, caution needs to be taken when using IOP readings by Goldmann applanation tonometer as a surrogate for direct cerebrospinal fluid pressure measurement of ICP.     

Robust Peak Recognition in Intracranial Pressure Signals

Background  

The waveform morphology of intracranial pressure pulses (ICP) is an essential indicator for monitoring, and forecasting critical intracranial and cerebrovascular pathophysiological variations. While current ICP pulse analysis frameworks offer satisfying results on most of the pulses, we observed that the performance of several of them deteriorates significantly on abnormal, or simply more challenging pulses.     

Continuous Multimodality Monitoring in Children after Traumatic Brain Injury—Preliminary Experience

Introduction

Multimodality monitoring is regularly employed in adult traumatic brain injury (TBI) patients where it provides physiologic and therapeutic insight into this heterogeneous condition. Pediatric studies are less frequent.

Methods

An analysis of data collected prospectively from 12 pediatric TBI patients admitted to Addenbrooke’s Hospital, Pediatric Intensive Care Unit (PICU) between August 2012 and December 2014 was performed. Patients’ intracranial pressure (ICP), mean arterial pressure (MAP), and cerebral perfusion pressure (CPP) were monitored continuously using brain monitoring software ICM+^®,) Pressure reactivity index (PRx) and ‘Optimal CPP’ (CPPopt) were calculated. Patient outcome was dichotomized into survivors and non-survivors.

Results

At 6 months 8/12 (66%) of the cohort survived the TBI. The median (±IQR) ICP was significantly lower in survivors 13.1±3.2 mm Hg compared to non-survivors 21.6±42.9 mm Hg (p = 0.003). The median time spent with ICP over 20 mm Hg was lower in survivors (9.7+9.8% vs 60.5+67.4% in non-survivors; p = 0.003). Although there was no evidence that CPP was different between survival groups, the time spent with a CPP close (within 10 mm Hg) to the optimal CPP was significantly longer in survivors (90.7±12.6%) compared with non-survivors (70.6±21.8%; p = 0.02). PRx provided significant outcome separation with median PRx in survivors being 0.02±0.19 compared to 0.39±0.62 in non-survivors (p = 0.02).

Conclusion

Our observations provide evidence that multi-modality monitoring may be useful in pediatric TBI with ICP, deviation of CPP from CPPopt, and PRx correlating with patient outcome.     

MRI Evidence for Altered Venous Drainage and Intracranial Compliance in Mild Traumatic Brain Injury

Purpose

To compare venous drainage patterns and associated intracranial hydrodynamics between subjects who experienced mild traumatic brain injury (mTBI) and age- and gender-matched controls.

Methods

Thirty adult subjects (15 with mTBI and 15 age- and gender-matched controls) were investigated using a 3T MR scanner. Time since trauma was 0.5 to 29 years (mean 11.4 years). A 2D-time-of-flight MR-venography of the upper neck was performed to visualize the cervical venous vasculature. Cerebral venous drainage through primary and secondary channels, and intracranial compliance index and pressure were derived using cine-phase contrast imaging of the cerebral arterial inflow, venous outflow, and the craniospinal CSF flow. The intracranial compliance index is the defined as the ratio of maximal intracranial volume and pressure changes during the cardiac cycle. MR estimated ICP was then obtained through the inverse relationship between compliance and ICP.

Results

Compared to the controls, subjects with mTBI demonstrated a significantly smaller percentage of venous outflow through internal jugular veins (60.9±21% vs. controls: 76.8±10%; p = 0.01) compensated by an increased drainage through secondary veins (12.3±10.9% vs. 5.5±3.3%; p<0.03). Mean intracranial compliance index was significantly lower in the mTBI cohort (5.8±1.4 vs. controls 8.4±1.9; p<0.0007). Consequently, MR estimate of intracranial pressure was significantly higher in the mTBI cohort (12.5±2.9 mmHg vs. 8.8±2.0 mmHg; p<0.0007).

Conclusions

mTBI is associated with increased venous drainage through secondary pathways. This reflects higher outflow impedance, which may explain the finding of reduced intracranial compliance. These results suggest that hemodynamic and hydrodynamic changes following mTBI persist even in the absence of clinical symptoms and abnormal findings in conventional MR imaging.     

Osmolality of Cerebrospinal Fluid from Patients with Idiopathic Intracranial Hypertension (IIH)

Introduction

Idiopathic intracranial hypertension (IIH) is a disorder of increased intracranial fluid pressure (ICP) of unknown etiology. This study aims to investigate osmolality of cerebrospinal fluid (CSF) from patients with IIH.

Methods

We prospectively collected CSF from individuals referred on suspicion of IIH from 2011–2013. Subjects included as patients fulfilled Friedman and Jacobson’s diagnostic criteria for IIH. Individuals in whom intracranial hypertension was refuted were included as controls. Lumbar puncture with ICP measurement was performed at inclusion and repeated for patients after three months of treatment. Osmolality was measured with a Vapor Pressure Osmometer.

Results

We collected 90 CSF samples from 38 newly diagnosed patients and 28 controls. At baseline 27 IIH-samples and at 3 months follow-up 35 IIH-samples were collected from patients. We found no significant differences in osmolality between 1) patients at baseline and controls (p = 0. 86), 2) patients at baseline and after 3 months treatment (p = 0.97), and 3) patients with normalized pressure after 3 months and their baseline values (p = 0.79). Osmolality in individuals with normal ICP from 6–25 cmH₂O (n = 41) did not differ significantly from patients with moderately elevated ICP from 26–45 cmH₂O (n = 21) (p = 0.86) and patients with high ICP from 46–70 cmH₂O (n = 4) (p = 0.32), respectively. There was no correlation between osmolality and ICP, BMI, age and body height, respectively. Mean CSF osmolality was 270 mmol/kg (± 1 SE, 95% confidence interval 267–272) for both patients and controls.

Conclusions

CSF osmolality was normal in patients with IIH, and there was no relation to treatment, ICP, BMI, age and body height. Mean CSF osmolality was 270 mmol/kg and constitutes a reference for future studies. Changes in CSF osmolality are not responsible for development of IIH. Other underlying pathophysiological mechanisms must be searched.     

Elevated Intracranial Pressure and Cerebral Edema following Permanent MCA Occlusion in an Ovine Model

Introduction

Malignant middle cerebral artery (MCA) stroke has a disproportionately high mortality due to the rapid development of refractory space-occupying cerebral edema. Animal models are essential in developing successful anti-edema therapies; however to date poor clinical translation has been associated with the predominately used rodent models. As such, large animal gyrencephalic models of stroke are urgently needed. The aim of the study was to characterize the intracranial pressure (ICP) response to MCA occlusion in our recently developed ovine stroke model.

Materials and Methods

30 adult female Merino sheep (n = 8–12/gp) were randomized to sham surgery, temporary or permanent proximal MCA occlusion. ICP and brain tissue oxygen were monitored for 24 hours under general anesthesia. MRI, infarct volume with triphenyltetrazolium chloride (TTC) staining and histology were performed.

Results

No increase in ICP, radiological evidence of ischemia within the MCA territory but without space-occupying edema, and TTC infarct volumes of 7.9+/-5.1% were seen with temporary MCAO. Permanent MCAO resulted in significantly elevated ICP, accompanied by 30% mortality, radiological evidence of space-occupying cerebral edema and TTC infarct volumes of 27.4+/-6.4%.

Conclusions

Permanent proximal MCAO in the sheep results in space-occupying cerebral edema, raised ICP and mortality similar to human malignant MCA stroke. This animal model may prove useful for pre-clinical testing of anti-edema therapies that have shown promise in rodent studies.     

Optic Nerve Sheath Diameter Remains Constant during Robot Assisted Laparoscopic Radical Prostatectomy

Background

During robot assisted laparoscopic radical prostatectomy (RALRP), a CO₂ pneumoperitoneum (CO₂PP) is applied and the patient is placed in a head-down position. Intracranial pressure (ICP) is expected to acutely increase under these conditions. A non-invasive method, the optic nerve sheath diameter (ONSD) measurement, may warn us that the mechanism of protective cerebrospinal fluid (CSF) shifts becomes exhausted.

Methods

After obtaining IRB approval and written informed consent, ONSD was measured by ocular ultrasound in 20 ASA I–II patients at various stages of the RALRP procedure: baseline awake, after induction, after applying the CO₂PP, during head-down position, after resuming the supine position, in the postoperative anaesthesia care unit, and on day one postoperatively. Cerebral perfusion pressure (CPP) was calculated as the mean arterial (MAP) minus central venous pressure (CVP).

Results

The ONSD did not change during head-down position, although the CVP increased from 4.2(2.5) mm Hg to 27.6(3.8) mm Hg. The CPP was decreased 70 min after assuming the head-down position until 15 min after resuming the supine position, but remained above 60 mm Hg at all times.

Conclusion

Even though ICP has been documented to increase during CO₂PP and head-down positioning, we did not find any changes in ONSD during head-down position. These results indicate that intracranial blood volume does not increase up to a point that CSF migration as a compensation mechanism becomes exhausted, suggesting any increases in ICP are likely to be small.     

A simple mathematical model of the interaction between intracranial pressure and cerebral hemodynamics

Ursino, Mauro, and Carlo Alberto Lodi. A simplemathematical model of the interaction between intracranial pressure andcerebral hemodynamics. J. Appl.Physiol. 82(4): 1256-1269, 1997.A simplemathematical model of intracranial pressure (ICP) dynamics oriented toclinical practice is presented. It includes the hemodynamics of thearterial-arteriolar cerebrovascular bed, cerebrospinal fluid (CSF)production and reabsorption processes, the nonlinear pressure-volumerelationship of the craniospinal compartment, and a Starling resistormechanism for the cerebral veins. Moreover, arterioles are controlledby cerebral autoregulation mechanisms, which are simulated by means ofa time constant and a sigmoidal static characteristic. The model isused to simulate interactions between ICP, cerebral blood volume, andautoregulation. Three different related phenomena are analyzed: thegeneration of plateau waves, the effect of acute arterial hypotensionon ICP, and the role of cerebral hemodynamics during pressure-volume index (PVI) tests. Simulation results suggest the following:1) ICP dynamics may become unstablein patients with elevated CSF outflow resistance and decreasedintracranial compliance, provided cerebral autoregulation is efficient.Instability manifests itself with the occurrence of self-sustainedplateau waves. 2) Moderate acutearterial hypotension may have completely different effects on ICP,depending on the value of model parameters. If physiological compensatory mechanisms (CSF circulation and intracranial storage capacity) are efficient, acute hypotension has only negligible effectson ICP and cerebral blood flow (CBF). If these compensatory mechanismsare poor, even modest hypotension may induce a large transient increasein ICP and a significant transient reduction in CBF, with risks ofsecondary brain damage. 3) The ICPresponse to a bolus injection (PVI test) is sharply affected, viacerebral blood volume changes, by cerebral hemodynamics andautoregulation. We suggest that PVI tests may be used to extractinformation not only on intracranial compliance and CSF circulation,but also on the status of mechanisms controlling CBF.

     

Growth rate and rupture rate of unruptured intracranial aneurysms: a population approach

Background  

Understanding aneurysm growth rate allows us to predict not only the current rupture risk, but also accumulated rupture risk in the future. However, determining growth rate of unruptured intracranial aneurysms often requires follow-up of patients for a long period of time so that significant growth can be observed and measured. We investigate a relationship between growth rate and rupture rate and develop a theoretical model that can predict average behavior of unruptured intracranial aneurysms based on existing clinical data.     

Hypertonic Saline for Brain Relaxation and Intracranial Pressure in Patients Undergoing Neurosurgical Procedures: A Meta-Analysis of Randomized Controlled Trials

Background

A wealth of evidence from randomized controlled trials (RCTs) has indicated that hypertonic saline (HS) is at least as effective as, if not better than, mannitol in the treatment of increased intracranial pressure(ICP). However, there is little known about the effects of HS in patients during neurosurgery. Thus, this meta-analysis was performed to compare the intraoperative effects of HS with mannitol in patients undergoing craniotomy.

Methods

According to the research strategy, we searched PUBMED, EMBASE and Cochrane Central Register of Controlled Trials. Other sources such as the internet-based clinical trial registries and conference proceedings were also searched. After literature searching, two investigators independently performed literature screening, quality assessment of the included trials and data extraction. The outcomes included intraoperative brain relaxation, intraoperative ICP, total volume of fluid required, diuresis, hemodynamic parameters, electrolyte level, mortality or dependence and adverse events.

Results

Seven RCTs with 468 participants were included. The quality of the included trials was acceptable. HS could significantly increase the odds of satisfactory intraoperative brain relaxation (OR: 2.25, 95% CI: 1.32–3.81; P = 0.003) and decrease the mean difference (MD) of maximal ICP (MD: −2.51mmHg, 95% CI: −3.39—1.93mmHg; P<0.00001) in comparison with mannitol with no significant heterogeneity among the study results. Compared with HS, mannitol had a more prominent diuretic effect. And patients treated with HS had significantly higher serum sodium than mannitol-treated patients.

Conclusions

Considering that robust outcome measures are absent because brain relaxation and ICP can be influenced by several factors except for the hyperosmotic agents, the results of present meta-analysis should be interpreted with cautions. Well-designed RCTs in the future are needed to further test the present results, identify the impact of HS on the clinically relevant outcomes and explore the potential mechanisms of HS.     

Neuron-Specific Enolase Is Correlated to Compromised Cerebral Metabolism in Patients Suffering from Acute Bacterial Meningitis; An Observational Cohort Study

Introduction

Patients suffering from acute bacterial meningitis (ABM) with a decreased level of consciousness have been shown to have an improved clinical outcome if treated with an intracranial pressure (ICP) guided therapy. By using intracranial microdialysis (MD) to monitor cerebral metabolism in combination with serum samples of biomarkers indicating brain tissue injury, S100B and Neuron Specific Enolase (NSE), additional information might be provided. The aim of this study was to evaluate biomarkers in serum and MD parameters in patients with ABM.

Methods

From a prior study on patients (n = 52) with a confirmed ABM and impaired consciousness (GCS ≤ 9, or GCS = 10 combined with lumbar spinal opening pressure > 400 mmH₂O), a subgroup of patients (n = 21) monitored with intracerebral MD and biomarkers was included in the present study. All patients were treated in the NICU with intracranial pressure (ICP) guided therapy. Serum biomarkers were obtained at admission and every 12 hours. The MD parameters glucose, lactate, pyruvate and glycerol were analyzed. Outcome was assessed at 12–55 months after discharge from hospital. Mann-Whitney U-Test and Wilcoxon matched-pairs signed rank test were applied.

Results

The included patients had a mean GCS of 8 (range, 3–10) on admission and increased ICP (>20 mmHg) was observed in 62% (n = 13/21) of the patients. Patients with a lactate:pyruvate ratio (LPR) >40 (n = 9/21, 43%) had significantly higher peak levels of serum NSE (p = 0.03), with similar, although non-significant observations made in patients with high levels of glycerol (>500 μmol/L, p = 0.11) and those with a metabolic crisis (Glucose <0.8 mmol/L, LPR >25, p = 0.09). No associations between serum S100B and MD parameters were found. Furthermore, median MD glucose levels decreased significantly between day 1 (0–24h) and day 3 (48–72h) after admission to the NICU (p = 0.0001). No correlation between MD parameters or biomarkers and outcome was found.

Conclusion

In this observational cohort study, we were able to show that cerebral metabolism is frequently affected in patients with ABM. Furthermore, patients with high LPR (LPR>40) had significantly higher levels of NSE, suggesting ongoing deterioration in compromised cerebral tissue. However, the potential clinical impact of MD and biomarker monitoring in ABM patients will need to be further elaborated in larger clinical trials.     

无创颅内压监测在创伤性急性弥漫性脑肿胀治疗中的临床应用研究

目的:探讨无创颅内压监测(Intracranial pressure,ICP)监测对救治创伤性急性弥漫性脑肿胀(Posttraumatic acute diffuse brains welling,PADBS)患者的辅助作用,为无创ICP检测的临床应用提供参考依据。方法:收集2011年1月至2016年1月我院神经外科收治的114例PADBS患者的临床资料进行回顾性分析,依据纳入与排除标准共取得病例组53例,对照组61例,分别给予采用无创颅内压监测和有创颅内压监测,根据患者资料进行组间比较及生存分析。结果:病例组与对照组不同分型颅内压检测值比较无统计学差异(P0.05);患者48h内进行大骨瓣开颅手术时间的生存分析,病例组中位手术时间为35.6个月,对照组中位DFS为33.5个月,两组患者检测进行手术时间的生存曲线无统计学差异(P0.05);有创ICP检测患者继发性出血率为3.2%,脑脊液感染病况为7.9%;两组患者预后情况差异并无统计学意义(P0.05)。无创ICP检测患者住院天数短于有创ICP检测患者(P0.05)。结论:无创ICP应用于PADBS治疗的临床价值与有创ICP相当,但无创ICP更便捷、创伤小,有利于对患者进行持续性检测。     

Effect of Maximal Apnoea Easy-Going and Struggle Phases on Subarachnoid Width and Pial Artery Pulsation in Elite Breath-Hold Divers

Purpose

The aim of the study was to assess changes in subarachnoid space width (sas-TQ), the marker of intracranial pressure (ICP), pial artery pulsation (cc-TQ) and cardiac contribution to blood pressure (BP), cerebral blood flow velocity (CBFV) and cc-TQ oscillations throughout the maximal breath hold in elite apnoea divers. Non-invasive assessment of sas-TQ and cc-TQ became possible due to recently developed method based on infrared radiation, called near-infrared transillumination/backscattering sounding (NIR-T/BSS).

Methods

The experimental group consisted of seven breath-hold divers (six men). During testing, each participant performed a single maximal end-inspiratory breath hold. Apnoea consisted of the easy-going and struggle phases (characterised by involuntary breathing movements (IBMs)). Heart rate (HR) was determined using a standard ECG. BP was assessed using the photoplethysmography method. SaO₂ was monitored continuously with pulse oximetry. A pneumatic chest belt was used to register thoracic and abdominal movements. Cerebral blood flow velocity (CBFV) was estimated by a 2-MHz transcranial Doppler ultrasonic probe. sas-TQ and cc-TQ were measured using NIR-T/BSS. Wavelet transform analysis was performed to assess cardiac contribution to BP, CBFV and cc-TQ oscillations.

Results

Mean BP and CBFV increased compared to baseline at the end of the easy phase and were further augmented by IBMs. cc-TQ increased compared to baseline at the end of the easy phase and remained stable during the IBMs. HR did not change significantly throughout the apnoea, although a trend toward a decrease during the easy phase and recovery during the IBMs was visible. Amplitudes of BP, CBFV and cc-TQ were augmented. sas-TQ and SaO₂ decreased at the easy phase of apnoea and further decreased during the IBMs.

Conclusions

Apnoea increases intracranial pressure and pial artery pulsation. Pial artery pulsation seems to be stabilised by the IBMs. Cardiac contribution to BP, CBFV and cc-TQ oscillations does not change throughout the apnoea.     

A Non-Invasive Method to Assess Cerebral Perfusion Pressure in Geriatric Patients with Suspected Cerebrovascular Disease

Background

Cerebral perfusion pressure (CPP) can adversely impact cerebrovascular hemodynamics but cannot be practically measured in most clinical settings. Here, we aimed to establish a representative mathematical model for CPP in geriatric patients with suspected cerebrovascular disease.

Methods

A total of 100 patients (54 males and 46 females between 60–80 years of age) with suspected cerebrovascular disease and no obvious cerebrovascular stenosis were selected for invasive CPP monitoring via catheterization of the middle segment of the common carotid arteries and openings of the vertebral arteries bilaterally. Curves were function-fitted using MATLAB 7.0, and data was statistically processed by SPSS 20.0.

Results

MATLAB 7.0 constructed eighth-order Fourier functions that fit all recorded CPP curves. Since the coefficients of the 100 functions were significantly different, all functions were standardized to derive one representative function. By manipulating the heart rate and maximum/minimum CPP of the representative function, estimated CPP curves can be constructed for patients with differing heart rates, intracranial pressures (ICPs) and blood pressures.

Conclusions

CPP can be well-modeled through an eighth-order Fourier function that can be constructed from a patient’s brachial artery blood pressure (BABP), ICP and heart rate. This function is representative of geriatric patients with cerebrovascular disease and can be used in the future study of cerebral hemodynamics.     

Structural olfactory nerve changes in patients suffering from idiopathic intracranial hypertension

Background

Complications of idiopathic intracranial hypertension (IIH) are usually caused by elevated intracranial pressure (ICP). In a similar way as in the optic nerve, elevated ICP could also compromise the olfactory nerve system. On the other side, there is growing evidence that an extensive lymphatic network system around the olfactory nerves could be disturbed in cerebrospinal fluid disorders like IIH. The hypothesis that patients with IIH suffer from hyposmia has been suggested in the past. However, this has not been proven in clinical studies yet. This pilot study investigates whether structural changes of the olfactory nerve system can be detected in patients with IIH.

Methodology/Principal Findings

Twenty-three patients with IIH and 23 matched controls were included. Olfactory bulb volume (OBV) and sulcus olfactorius (OS) depth were calculated by magnetic resonance techniques. While mean values of total OBV (128.7±38.4 vs. 130.0±32.6 mm³, p=0.90) and mean OS depth (8.5±1.2 vs. 8.6±1.1 mm, p=0.91) were similar in both groups, Pearson correlation showed that patients with a shorter medical history IIH revealed a smaller OBV (r=0.53, p<0.01). In untreated symptomatic patients (n=7), the effect was greater (r=0.76, p<0.05). Patients who suffered from IIH for less than one year (n=8), total OBV was significantly smaller than in matched controls (116.6±24.3 vs. 149.3±22.2 mm³, p=0.01). IIH patients with visual disturbances (n=21) revealed a lower OS depth than patients without (8.3±0.9 vs. 10.8±1.0 mm, p<0.01).

Conclusions/Significance

The results suggest that morphological changes of the olfactory nerve system could be present in IIH patients at an early stage of disease.     

等渗透剂量的7.5%高渗盐水和20%甘露醇治疗颅内高压疗效的对比研究

目的:比较等渗透剂量的7.5%高渗盐水(hypertonic saline,HTS)和20%甘露醇治疗颅高压的疗效。方法:当患者的颅内压(intracranial pressure,ICP)超过20 mm Hg时,一组患者接受了4 m L/kg 7.5%HTS(HTS组,n=27),另外一组患者接受了0.5 g/kg 20%甘露醇(甘露醇组,n=31)的降颅压治疗,两种药物均经深静脉在30 min内快速滴注完成。用药期间,连续监测患者ICP,平均动脉压(mean arterial pressure,MAP)、脑灌注压(cerebral perfusion pressure,CPP)及中心静脉压(central venous pressure,CVP)。记录有效降颅压持续时间、ICP最大降幅及其时间,用药前及用药后1 h、3 h、6 h抽血查电解质和血浆渗透压等。结果:静脉快速滴注7.5%HTS和20%甘露醇后,两者均可有效降低ICP(P0.05)。两组在控制颅高压的有效率、起效时间及ICP降幅无统计学差异(P0.05),但HTS组的作用持续时间要明显长于甘露醇组(P0.05)。两组渗透压较用药前相比均有显著上升(P0.05)。用药前后,两组MAP、CPP和CVP变化无统计学差异(P0.05)。结论:等渗透剂量的7.5%HTS与20%甘露醇均可有效降低患者的ICP,两者降颅压效果相当,均可作为治疗颅内高压的一线治疗药物。     

Pressure balance and imbalance in the optic nerve chamber: The Beijing Intracranial and Intraocular Pressure (iCOP) Study

To determine the interdependence of intracranial pressure (ICP) and intraocular pressure (IOP) and how it affects optic nerve pressures, eight normal dogs were examined using pressure-sensing probes implanted into the left ventricle, lumbar cistern, optic nerve subarachnoid space in the left eye, and anterior chamber in the left eye. This allowed ICP, lumbar cistern pressure (LCP), optic nerve subarachnoid space pressure (ONSP) and IOP to be simultaneously recorded. After establishing baseline pressure levels, pressure changes that resulted from lowering ICP (via shunting cerebrospinal fluid (CSF) from the ventricle) were recorded. At baseline, all examined pressures were different (ICP<LCP<ONSP), but correlated (P>0.001). As ICP was lowered during CSF shunting, IOP also dropped in a parallel time course so that the trans-lamina cribrosa gradient (TLPG) remained stable (ICP-IOP dependent zone). However, once ICP fell below a critical breakpoint, ICP and IOP became uncoupled and TLPG changed as ICP declined (ICP-IOP independent zone). The optic nerve pressure gradient (ONPG) and trans-optic nerve pressure gradient (TOPG) increased linearly as ICP decreased through both the ICP-IOP dependent and independent zones. We conclude that ICP and IOP are coupled in a specific pressure range, but when ICP drops below a critical point, IOP and ICP become uncoupled and TLPG increases. When ICP drops, a rise in the ONPG and TOPG creates more pressure and reduces CSF flow around the optic nerve. This change may play a role in the development and progression of various ophthalmic and neurological diseases, including glaucoma.     

Transorbital Sonographic Evaluation of Normal Optic Nerve Sheath Diameter in Healthy Volunteers in Bangladesh

Introduction

Measurement of optic nerve sheath diameter (ONSD) by ultrasound is increasingly used as a marker to detect raised intracranial pressure (ICP). ONSD varies with age and there is no clear consensus between studies for an upper limit of normal. Knowledge of normal ONSD in a healthy population is essential to interpret this measurement.

Methods

In a prospective observational study, ONSD was measured using a 15 MHz ultrasound probe in healthy volunteers in Chittagong, Bangladesh. The aims were to determine the normal range of ONSD in healthy Bangladeshi adults and children, compare measurements in males and females, horizontal and vertical beam orientations and left and right eyes in the same individual and to determine whether ONSD varies with head circumference independent of age.

Results

136 subjects were enrolled, 12.5% of whom were age 16 or under. Median ONSD was 4.41 mm with 95% of subjects in the range 4.25–4.75 mm. ONSD was bimodally distributed. There was no relationship between ONSD and age (≥4 years), gender, head circumference, and no difference in left vs right eye or horizontal vs vertical beam.

Conclusions

Ultrasonographic ONSD in Bangladeshi healthy volunteers has a narrow bimodal distribution independent of age (≥4 years), gender and head circumference. ONSD >4.75 mm in this population should be considered abnormal.     

Endoscopic management of hypertensive intraventricular haemorrhage with obstructive hydrocephalus

Background  

Intracranial haemorrhage accounts for 30–60 % of all stroke admissions into a hospital, with hypertension being the main risk factor. Presence of intraventricular haematoma is considered a poor prognostic factor due to the resultant obstruction to CSF and the mass effect following the presence of blood resulting in raised intracranial pressure and hydrocephalus. We report the results following endoscopic decompression of obstructive hydrocephalus and evacuation of haematoma in patients with hypertensive intraventricular haemorrhage.     

Cerebral blood flow autoregulation in early experimental S. pneumoniae meningitis.

We studied cerebral blood flow (CBF) autoregulation and intracranial pressure (ICP) during normo- and hyperventilation in a rat model of Streptococcus pneumoniae meningitis. Meningitis was induced by intracisternal injection of S. pneumoniae. Mean arterial blood pressure (MAP), ICP, cerebral perfusion pressure (CPP, defined as MAP - ICP), and laser-Doppler CBF were measured in anesthetized infected rats (n = 30) and saline-inoculated controls (n = 30). CPP was either incrementally reduced by controlled hemorrhage or increased by intravenous norepinephrine infusion. Twelve hours postinoculation, rats were studied solely during normocapnia, whereas rats studied after 24 h were exposed to either normocapnia or to acute hypocapnia. In infected rats compared with control rats, ICP was unchanged at 12 h but increased at 24 h postinoculation (not significant and P < 0.01, respectively); hypocapnia did not lower ICP compared with normocapnia. Twelve hours postinoculation, CBF autoregulation was lost in all infected rats but preserved in all control rats (P < 0.01). Twenty-four hours after inoculation, 10% of infected rats had preserved CBF autoregulation during normocapnia compared with 80% of control rats (P < 0.01). In contrast, 60% of the infected rats and 100% of the control rats showed an intact CBF autoregulation during hypocapnia (P < 0.05 for the comparison of infected rats at normocapnia vs. hypocapnia). In conclusion, CBF autoregulation is lost both at 12 and at 24 h after intracisternal inoculation of S. pneumoniae in rats. Impairment of CBF autoregulation precedes the increase in ICP, and acute hypocapnia may restore autoregulation without changing the ICP.