The effects of carbon dioxide on measuring cerebral spinal fluid pressure

Cerebrospinal fluid pressure dynamics across the intra- and postoperative setting: Retrospective study of a spine surgery cohort

Timely and sufficient decompression are critical objectives in degenerative cervical myelopathy (DCM) and spinal cord injury (SCI). We previously investigated intraoperative cerebrospinal fluid pressure (CSFP) for determining surgical outcomes. However, confounding factors during the intra- and postoperative setting need consideration. These are related to type of respiration (i.e., artificial vs. natural) and anesthesia, which affect CSFP dynamics through the interaction between the cardiorespiratory system and the CSF compartment. This retrospective cohort study (NCT02170155) aims to systematically investigate these factors to facilitate CSFP interpretation. CSFP was continuously measured through a lumbar catheter, intra- and postoperatively, in 21 patients with DCM undergoing decompression surgery. Mean CSFP and cardiac-driven CSFP peak-to-valley amplitude (CSFPp) were analyzed throughout the perioperative period, including the immediate extubation period in eight patients. Intraoperative mean CSFP had a median value and {interquartile range} of 10.8 {5.5} mmHg and increased 1.6-fold to 16.9 {7.1} mmHg postoperatively (p < 0.001). CSFPp increased 3-fold from 0.6 {0.7} to 1.8 {2.5} mmHg (p = 0.001). Increased CSFP persisted overnight. During extubation, there was a notable increase in CSFP and CSFPp of 14.0 {5.8} and 5.1 {3.1} mmHg, respectively. From case-based analysis, this was attributed to an arterial pCO2 increase. There was no correlation between respirator settings and CSFP metrics. There were distinct and quantifiable changes in CSFP dynamics from the intra- to postoperative setting related to type of respiration, anesthesia, and level of consciousness. When monitoring CSFP dynamics in spine surgery across these settings, cardiorespiratory factors must be controlled for.

How to use lumbar puncture manometry in children

Measurement of cerebrospinal fluid pressure through lumbar puncture (LP) manometry is an essential practical skill all paediatricians should possess competency in. The ability to perform manometry is crucial in the diagnosis of idiopathic intracranial hypertension and can provide critical information on raised (or lowered) intracranial pressure in other clinical scenarios. Practitioners should be familiar with the procedure and in particular with equipment available to them locally. In this article, we will describe an approach to LP manometry. The online supplemental material includes an instructional video as well as supporting practical information.

Pseudotumor Cerebri Syndrome in Children

PURPOSE OF REVIEW

Pseudotumor cerebri syndrome (PTCS) may affect both children and adults; however, the risk factors and clinical presentation vary greatly between these populations. This review aims to highlight the entity of PTCS in children and the unique considerations in this population; review the epidemiology and demographics; discuss the clinical presentation, revised diagnostic criteria, and approach to evaluation; review management strategies; and discuss the prognosis and long-term outcomes in children with PTCS.

RECENT FINDINGS

Clinical presentation can be variable in children and may be less obvious than in their adult counterparts. Papilledema can also be challenging to diagnose in this population. The upper limits for opening pressure on lumbar puncture differ in children, with a cut-off of 25 cm H20 (or 28 cm H2O in a sedated or obese child). Morbidity related to visual loss, pain and reduced quality of life lends urgency towards accurately identifying, evaluating and managing children with PTCS. There are no randomised controlled studies to allow for evidence-based recommendations for the management of PTCS in children. Further studies are needed to clarify and consolidate management approaches in this population.

Pediatric Intracranial Hypertension: a Current Literature Review

PURPOSE OF REVIEW

The purpose of this review is to provide an update on pediatric intracranial hypertension.

RECENT FINDINGS

The annual pediatric incidence is estimated at 0.63 per 100,000 in the USA and 0.71 per 100,000 in Britain. The Idiopathic Intracranial Hypertension Treatment Trial found improvement in visual fields, optical coherence tomography, Frisen grade, and quality of life with acetazolamide compared to placebo in adult patients, and these findings have been translated to the pediatric population. Pediatric intracranial hypertension is a disorder that if left untreated can lead to poor quality of life and morbidity. There are no current treatment studies in pediatrics, but adult data suggests acetazolamide remains an acceptable first-line medication.

Pediatric Intracranial Hypertension

Primary (idiopathic) intracranial hypertension has been considered to be a rare entity, but with no precise estimates of the pediatric incidence in the United States. There have been attempts to revise the criteria over the years and adapt the adult criteria for use in pediatrics. The clinical presentation varies with age, and symptoms tending to be less obvious in younger individuals. In the prepubertal population, incidentally discovered optic disc edema is relatively common. By far the most consistent symptom is headache; other symptoms include nausea, vomiting tinnitus, and diplopia. Treatment mainstays include weight loss when appropriate and acetazolamide. Furosemide may exhibit a synergistic benefit when used in conjunction with acetazolamide. Surgical interventions are required relatively infrequently, but include optic nerve sheath fenestration and cerebrospinal fluid shunting. Pain and permanent vision loss are the two major complications of this disorder and these manifestations justify aggressive treatment. Once intracranial hypertension has resolved, up to two thirds of patients develop a new or chronic headache type that is different from their initial presenting headache.

Interpretation of lumbar puncture opening pressure measurements in children

BACKGROUND

Understanding the reference range of cerebrospinal fluid opening pressure (CSFOP) in children is essential to the diagnosis of elevated intracranial pressure. Recent studies have highlighted several clinical elements that need to be considered when interpreting CSFOP measures.

EVIDENCE ACQUISITION

This review and recommendations are based on peer-reviewed literature, primarily from the past decade, as well as the author's clinical and research experience.

RESULTS

CSFOP measures ≤28 cm H2O can be considered "normal" for most children. The patient's depth of sedation, body mass index, and sedation medication can sometimes result in small increases in CSFOP. Patient age and leg position (flexed vs extended) in the lateral decubitus position do not seem to significantly impact CSFOP measures.

CONCLUSIONS

The threshold of a normal CSFOP should not be interpreted in isolation, but instead, in concert with other clinical and examination findings to help the physician make a well-informed assessment of whether a child has elevated intracranial pressure.

Fifteen-minute consultation: the child with idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is a rare condition where intracranial hypertension is found in the context of normal brain parenchyma and no mass lesion, ventriculomegaly, underlying infection, or malignancy. Our understanding of this condition has greatly improved in the recent years with neuroimaging features and normal values for lumbar puncture opening pressure now well defined. This article provides a review of IIH in children and revised diagnostic criteria based on recent evidence and published opinion. We have also presented an algorithmic approach to the child with possible IIH.

Reference range of cerebrospinal fluid opening pressure in children: historical overview and current data

The lumbar puncture and cerebrospinal fluid (CSF) opening pressure (OP) in children remains an essential diagnostic test for children with suspected elevated intracranial pressure. Recent prospective data have revised the normative CSF OP values and described how clinical variables such as age, depth of sedation, and obesity may influence the measurements. In addition, the new normative data are now reflected in revised diagnostic criteria for idiopathic intracranial hypertension/pseudotumor cerebri syndrome. This review highlights the recently published data and provides guidance on how it may impact clinical management.

A prospective photographic study of the ocular fundus in obstructive sleep apnea

BACKGROUND

The prevalence of optic nerve and retinal vascular changes within the obstructive sleep apnea (OSA) population are not well-known, although it has been postulated that optic nerve ischemic changes and findings related to an elevated intracranial pressure may be more common in OSA patients. We prospectively evaluated the ocular fundus in unselected patients undergoing overnight diagnostic polysomnography (PSG).

METHODS

Demographic data, medical/ocular history, and nonmydriatic fundus photographs were prospectively collected in patients undergoing PSG at our institution and reviewed for the presence of optic disc edema for which our study was appropriately powered a priori. Retinal vascular changes were also evaluated. OSA was defined using the measures of both sleep-disordered breathing and hypoxia.

RESULTS

Of 250 patients evaluated in the sleep center, fundus photographs were performed on 215 patients, among whom 127 patients (59%) had an apnea/hypopnea index (AHI) ≥ 15 events per hour, including 36 with severe OSA. Those with AHI <15 served as the comparison group. None of the patients had optic disc edema (95% confidence interval [CI]: 0%-3%). There was no difference in rates of glaucomatous appearance or pallor of the optic disc among the groups. Retinal arteriolar changes were more common in severe OSA patients (odds ratio: 1.09 per 5 unit increase in AHI; 95% CI, 1.02-1.16; P = 0.01), even after controlling for mean arterial blood pressure.

CONCLUSIONS

We did not find an increased prevalence of optic disc edema or other optic neuropathies in our OSA population. However, retinal vascular changes were more common in patients with severe OSA, independent of blood pressure.

The tympanic membrane displacement analyser for monitoring intracranial pressure in children

PURPOSE

Raised intracranial pressure (ICP) is a potentially treatable cause of morbidity and mortality but tools for monitoring are invasive. We sought to investigate the utility of the tympanic membrane displacement (TMD) analyser for non-invasive measurement of ICP in children.

METHODS

We made TMD observations on normal and acutely comatose children presenting to Kilifi District Hospital (KDH) at the rural coast of Kenya and on children on follow-up for idiopathic intracranial hypertension at Evelina Children's Hospital (ECH), in London, UK.

RESULTS

We recruited 63 patients (median age 3.3 (inter-quartile range (IQR) 2.0-4.3) years) at KDH and 14 children (median age 10 (IQR 5-11) years) at ECH. We observed significantly higher (more negative) TMD measurements in KDH children presenting with coma compared to normal children seen at the hospital's outpatient department, in both semi-recumbent [mean -61.3 (95 % confidence interval (95 % CI) -93.5 to 29.1) nl versus mean -7.1 (95 % CI -54.0 to 68.3) nl, respectively; P = 0.03] and recumbent postures [mean -61.4 (95 % CI -93.4 to -29.3) nl, n = 59) versus mean -25.9 (95 % CI -71.4 to 123.2) nl, respectively; P = 0.03]. We also observed higher TMD measurements in ECH children with raised ICP measurements, as indicated by lumbar puncture manometry, compared to those with normal ICP, in both semi-recumbent [mean -259.3 (95 % CI -363.8 to -154.8) nl versus mean 26.7 (95 % CI -52.3 to 105.7) nl, respectively; P < 0.01] and recumbent postures [mean -137.5 (95 % CI -260.6 to -14.4) nl versus mean 96.6 (95 % CI 6.5 to 186.6) nl, respectively; P < 0.01].

CONCLUSION

The TMD analyser has a potential utility in monitoring ICP in a variety of clinical circumstances.

Magnetic resonance imaging changes in idiopathic intracranial hypertension in children

To evaluate the usefulness of neuroimaging in children with idiopathic intracranial hypertension, brain magnetic resonance imaging (MRI) scans of children with idiopathic intracranial hypertension and age-matched controls were reviewed. Compared with controls, patients with idiopathic intracranial hypertension had flattening of the posterior sclera in 61% versus 40% of cases, distension of perioptic subarachnoid space in 65% versus 35%, intraocular protrusion of pre-laminar optic nerve in 17% versus 0%, tortuosity of optic nerve in 30% versus 5%, and an empty sella in 26% versus 5% of cases. The presence of 3 or more of the MRI features is 95% specific in predicting idiopathic intracranial hypertension. The observed general anesthetic effect on these neuroimaging features are also minimized when multiple features are taken into account. Magnetic resonance imaging features can assist in suspecting the diagnosis of idiopathic intracranial hypertension in children, provided caution is applied when interpreting imaging performed under a general anesthesia.