A new perspective on cerebrospinal fluid dynamics after subarachnoid hemorrhage: From normal physiology to pathophysiological changes

Knowledge about the dynamic metabolism and function of cerebrospinal fluid (CSF) physiology has rapidly progressed in recent decades. It has traditionally been suggested that CSF is produced by the choroid plexus and drains to the arachnoid villi. However, recent findings have revealed that the brain parenchyma produces a large portion of CSF and drains through the perivascular glymphatic system and meningeal lymphatic vessels into the blood. The primary function of CSF is not limited to maintaining physiological CNS homeostasis but also participates in clearing waste products resulting from neurodegenerative diseases and acute brain injury. Aneurysmal subarachnoid hemorrhage (SAH), a disastrous subtype of acute brain injury, is associated with high mortality and morbidity. Post-SAH complications contribute to the poor outcomes associated with SAH. Recently, abnormal CSF flow was suggested to play an essential role in the post-SAH pathophysiological changes, such as increased intracerebral pressure, brain edema formation, hydrocephalus, and delayed blood clearance. An in-depth understanding of CSF dynamics in post-SAH events would shed light on potential development of SAH treatment options. This review summarizes and updates the latest physiological characteristics of CSF dynamics and discusses potential pathophysiological changes and therapeutic targets after SAH.

Real-Time Evaluation of Optic Nerve Sheath Diameter (ONSD) in Awake, Spontaneously Breathing Patients

(1) Background: Reliable ultrasonographic measurements of optic nerve sheath diameter (ONSD) to detect increased intracerebral pressure (ICP) has not been established in awake patients with continuous invasive ICP monitoring. Therefore, in this study, we included fully awake patients with and without raised ICP and correlated ONSD with continuously measured ICP values. (2) Methods: In a prospective study, intracranial pressure (ICP) was continuously measured in 25 patients with an intraparenchymatic P-tel probe. Ultrasonic measurements were carried out three times for each optic nerve in vertical and horizontal directions. ONSD measurements and ICP were correlated. Patients with ICP of 2.0–10.0 mmHg were compared with patients suffering from an ICP of 10.1–24.2 mmHg. (3) Results: In all patients, the ONSD vertical and horizontal measurement for both eyes correlated well with the ICP (Pearson R = 0.68–0.80). Both measurements yielded similar results (Bland-Altman: vertical bias: −0.09 mm, accuracy: ±0.66 mm; horizontal bias: −0.06 mm, accuracy: ±0.48 mm). For patients with an ICP of 2.0–10.0 mmHg compared to an ICP of 10.1–24.2, ROC (receiver operating characteristic) analyses showed that ONSD measurement accurately predicts elevated ICP (optimal cut-off value 5.05 mm, AUC of 0.91, sensitivity 92% and specificity 90%, p < 0.001). (4) Conclusions: Ultrasonographic measurement of ONSD in awake, spontaneously breathing patients provides a valuable method to evaluate patients with suspected increased ICP. Additionally, it provides a potential tool for rapid assessment of ICP at the bedside and to identify patients at risk for a poor neurological outcome.

Secondary White Matter Injury and Therapeutic Targets After Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is one of the special stroke subtypes with high mortality and mobility. Although the mortality of SAH has decreased by 50% over the past two decades due to advances in neurosurgery and management of neurocritical care, more than 70% of survivors suffer from varying degrees of neurological deficits and cognitive impairments, leaving a heavy burden on individuals, families, and the society. Recent studies have shown that white matter is vulnerable to SAH, and white matter injuries may be one of the causes of long-term neurological deficits caused by SAH. Attention has recently focused on the pivotal role of white matter injury in the pathophysiological processes after SAH, mainly related to mechanical damage caused by increased intracerebral pressure and the metabolic damage induced by blood degradation and hypoxia. In the present review, we sought to summarize the pathophysiology processes and mechanisms of white matter injury after SAH, with a view to providing new strategies for the prevention and treatment of long-term cognitive dysfunction after SAH.

Individualized blood pressure targets in the postoperative care of patients with intracerebral hemorrhage

OBJECTIVE Recent guidelines recommend targeting a systolic blood pressure (SBP) < 140 mm Hg in the early management of patients with spontaneous intracerebral hemorrhage (ICH). The optimal SBP targets for ICH patients after hematoma evacuation (HE) remain unclear. Here, the authors aimed to define the optimal SBP range based on multimodal neuromonitoring data. METHODS Forty poor-grade ICH patients who had undergone HE and then monitoring of intracerebral pressure, brain tissue oxygen tension (PbtO2), and cerebral metabolism (via cerebral microdialysis [CMD]) were prospectively included. Episodes of brain tissue hypoxia (BTH) (1-hour averaged PbtO2 < 20 mm Hg) and metabolic distress (CMD–lactate/pyruvate ratio [LPR] ≥ 40) were identified and linked to corresponding parameters of hemodynamic monitoring (SBP and cerebral perfusion pressure [CPP]). Multivariable regression analysis was performed using generalized estimating equations to identify associations between SBP levels, PbtO2, and brain metabolism. RESULTS The mean patient age was 60 (range 51–66) years and the median [IQR] initial ICH volume was 47 [29–60] ml. In multivariable models adjusted for Glasgow Coma Scale score, probe location, ICH volume, and age, lower SBP was independently associated with a higher risk of BTH (≤ 120 mm Hg: adjusted OR 2.9, p = 0.007; 120–130 mm Hg: adj OR 2.4, p = 0.002; 130–140 mm Hg: adj OR 1.6, p = 0.017) compared to a reference range of 140–150 mm Hg at the level of the foramen interventriculare Monroi, which corresponded to a CPP of 70–80 mm Hg and SBP levels between 150 and 160 mm Hg at the heart level. After exclusion of episodes with mitochondrial dysfunction, SBP targets < 140 mm Hg were associated with higher odds of cerebral metabolic distress (≤ 130 mm Hg: OR 2.5, p = 0.041; 130–140 mm Hg: OR 2.3, p = 0.033). Patients with a modified Rankin Scale score ≥ 5 at neurological ICU discharge more often exhibited BTH than patients with better outcomes (51% vs 10%, p = 0.003). CONCLUSIONS These data suggest that lower SPB and CPP levels are associated with a higher risk for BTH. Further studies are needed to evaluate whether a higher SPB target may prevent BTH and improve outcomes.

Neurology/neurosurgery

In this chapter on neurosurgery and anaesthesia, the authors give clear guidance for the management of time critical brain and neurological conditions, including raised intracerebral pressure, severe head injury, subarachnoid and intracerebral haemorrhage, sodium disturbances, venous air embolism, acute spinal cord injury, spinal shock, autonomic dysreflexia, dystonic reactions, and status epilepticus. In addition, the definitions, presentation, management strategies, investigations, risk factors, exclusions and causes, and any special considerations for each potential neurosurgical and neurologically related situation are given. Lists of up-to-date online resources and further reading are also provided here, offering invaluable know-how to encourage the reader to broaden their knowledge.

Noninvasive Transfontanelle Monitoring of the Intracerebral Pressure in Comparison With an Invasive Intradural Intracranial Pressure Device: A Prospective Study

BACKGROUND: We previously introduced a novel noninvasive technique of intracranial pressure (ICP) monitoring in children with open fontanelles. OBJECTIVE: To compare the ICP obtained by our new technique to the ICP derived from an intradurally implanted ICP measurement device (external ventricular drain, subdural ICP device). METHODS: Children with open fontanelles and need of intracranial monitoring were included in this study. A standard ICP probe was placed upon the frontal fontanelle and data were compared with the values recorded by an already invasively implanted subdural ICP technique. The 2 methods of ICP measurement were evaluated using the correlation coefficient, Bland and Altman method and method comparison by Carstensen. RESULTS: Five children under the age of 1 year with an open frontal fontanelle were included in this study. Three were male and 2 were female. Mean age was 7 months. A total of 139 pairs of measurements were assessed. Mean transfontanelle ICP was 7.6 mm Hg. Mean ICP measured subdurally was 5.4 mm Hg. The correlation analysis showed a correlation coefficient of 0.7. The Bland-Altman plot revealed a good accuracy of the new method with &gt;95% of the values within the limits of agreement. An additional method comparison analysis confirmed the finding of accurate ICP measurements between both applied methods. CONCLUSION: The noninvasive transfontanelle ICP monitoring method displayed a high validity and reliability as proven by correlation analysis. This novel technique might therefore be an interesting and promising tool for noninvasive ICP monitoring in children. But further research is necessary to evaluate the accuracy of this technique in children with elevated ICP.

Surgical Treatment for Leptomeningeal Disease

Background Advancements in cancer treatment have led to more cases of leptomeningeal disease, which requires a multimodal approach. Methods Treatment modalities are reviewed from a neurosurgical standpoint, focusing on intrathecal chemotherapy and shunting devices. Potential complications and how to avoid them are discussed. Results The Ommaya reservoir and the chemoport are used for administering intrathecal chemotherapy. Use of ventriculo-lumbar perfusion can efficiently deliver chemotherapeutic agents and improve intracerebral pressure. Shunting systems, in conjunction with all of their variations, address the challenge of hydrocephalus in leptomeningeal carcinomatosis. Misplaced catheters, malfunction of the system, and shunt-related infections are known complications of treatment. Conclusions From an oncological perspective, the surgical treatment for leptomeningeal disease is limited; however, neurosurgery can be used to aid in the administration of chemotherapy and address the issue of hydrocephalus. Minimizing surgical complications is important in this sensitive patient population.