[Structure of the arachnoid layer of the human spinal meninges: a barrier that regulates dural sac permeability]

Unforeseen Complications: A Case of Subdural Anesthesia Post-epidural Insertion

Subdural anesthesia, although rare, is a significant complication of epidural anesthesia. This case report presents a 28-year-old female patient who developed sudden unconsciousness following epidural anesthesia administration for labor pain. Despite no evident contraindications to epidural anesthesia, she lost consciousness shortly after the initial test dose, leading to an emergency cesarean section under general anesthesia. The neonate showed signs of fetal bradycardia post-epidural and required intensive care. The patient made a complete recovery with no postpartum complications. This report underlines the need for vigilant monitoring and the importance of swift interventions in case of complications arising from epidural anesthesia.

Intrathecal Drug Delivery: Advances and Applications in the Management of Chronic Pain Patient

Advances in our understanding of the biology of spinal systems in organizing and defining the content of exteroceptive information upon which higher centers define the state of the organism and its role in the regulation of somatic and automatic output, defining the motor response of the organism, along with the unique biology and spatial organization of this space, have resulted in an increased focus on therapeutics targeted at this extracranial neuraxial space. Intrathecal (IT) drug delivery systems (IDDS) are well-established as an effective therapeutic approach to patients with chronic non-malignant or malignant pain and as a tool for management of patients with severe spasticity and to deliver therapeutics that address a myriad of spinal pathologies. The risk to benefit ratio of IDD makes it a useful interventional approach. While not without risks, this approach has a significant therapeutic safety margin when employed using drugs with a validated safety profile and by skilled practioners. The present review addresses current advances in our understanding of the biology and dynamics of the intrathecal space, therapeutic platforms, novel therapeutics, delivery technology, issues of safety and rational implementation of its therapy, with a particular emphasis upon the management of pain.

Did she have an epidural? The long-term consequences of postdural puncture headache and the role of unintended dural puncture

OBJECTIVE

This narrative literature review examines the long-term impact of postdural puncture headache (PDPH) in postpartum women following an unintended dural puncture (UDP) with a large bore needle commonly used for epidural catheter placement. It seeks to bridge the knowledge gap for the neurologist as to the mounting body of obstetric anesthesia literature on the development of chronic headache after PDPH with this unique needle.

BACKGROUND

Headache is the most common complication of dural puncture, and the risk is greatest in the parturient population. Preexisting risk factors for this population include youth and sex, and after UDP with a large bore needle, almost 70%-80% report a headache. Additionally, there appears to be a significant cohort who experience long-term, persistent headache after UDP.

METHODS

We performed a narrative review of literature using PubMed, searching terms that included long-term follow-up after UDP with a large bore needle in the postpartum population.

RESULTS

In women who had UDP with a large bore needle used for epidural catheter placement at delivery, the rate of chronic debilitating headache is around 30% in the months following delivery and may persist for up to a year or longer.

CONCLUSION

Based on the existing literature, we have mounting evidence that UDP with the large bore needle used to place an epidural catheter should be understood as a high-risk inciting event for the development of long-term headaches not simply a high risk of acute PDPH. Additionally, consideration should be given to stratifying the etiology of PDPH, based on needle type, and recognizing the entity of chronic PDPH, thus allowing for improvements in research and diagnosis.

Validation of a bioabsorbable device that seals perforations after Tuohy needle dural puncture in an ovine model

BACKGROUND

We designed a device to close accidental dural puncture via the offending puncturing epidural needle directly after diagnosis of the puncture and before removing the needle. The aim of this study was to quantify this device's ability to seal cerebrospinal fluid leakage.

METHODS

Forty-six anesthetized adult sheep were studied in a single-blind randomized controlled fashion in two equal groups.An intentional dural puncture was performed with an 18-gage Tuohy needle on all the sheep between L6 and S1 levels. Contrast medium was injected through the needle. Twenty-three animals receive treatment with the sealing device. Two minutes after device placement, or dural puncture in the control group, a CT scan was performed on the animals to estimate contrast material leakage. A region of interest (ROI) was defined as the region that enclosed the subarachnoid space, epidural space, and neuroforaminal canal (the vertebral body above and half of its equivalent height in sacrum below the puncture site). In this region, the total contrast volume and the volumes in the epidural space (EPIDURAL) were measured. The primary outcome measure was the EPIDURAL/ROI ratio to ascertain the proportion of intrathecally injected fluid that passed into the epidural space in both groups. The secondary outcomes were the total amount of contrast in the ROI and the EPIDURAL.

RESULTS

The device was deployed successfully in all but two instances, where it suffered from manufacturing defects.Leakage was less in the study group (1.0 vs 1.4 mL, p=0.008). The median EPIDURAL/ROI ratio was likewise less in the study group (29 vs 46; p=0.013; 95% CI (-27 to -3.5)).

CONCLUSION

This novel dural puncture-sealing device, also envisaged to be used in other comparable iatrogenic leakage scenarios to be identified in the future, was able to reduce the volume of cerebrospinal fluid that leaked into the epidural space after dural puncture. The device is possibly a valuable way of preventing fluid leakage immediately after the recognition of membrane puncture.

Spinal arachnoid sleeves and their possible causative role in cauda equina syndrome and transient radicular irritation syndrome

INTRODUCTION

We have previously described arachnoid sleeves around cauda equina nerve roots, but at that time we did not determine whether injections could be performed within those sleeves. The purpose of this observational study was to establish whether the entire distal orifice of a spinal needle can be accommodated within an arachnoid sleeve.

MATERIALS AND METHODS

We carefully dissected the entire dural sacs off four fresh cadavers, opened them by longitudinal incision, and immersed them in saline. Under direct vision, we penetrated the cauda equina roots nerves traveling almost vertically downward at 30 locations each with a 27- and a 25-G pencil-point needle (60 punctures total). We captured the images with a stereoscopic camera.

RESULTS

The nerve root offered no noticeable resistance to needle entry. Although the arachnoid sleeves could not be identified with the naked eye, they were translucent but visible under microscopy. In 21 of 30 attempts with a 27-gauge needle, and in 20 of 30 attempts with a 25-gauge needle, the distal orifice of the spinal needle was completely within the arachnoid sleeve.

CONCLUSION

It seems possible to accommodate the distal orifice of a 25- or a 27-gauge pencil-point spinal needle completely within the space of the arachnoid sleeve. An injection within this sleeve could potentially lead to a neurological syndrome, as we have previously proposed.

Can Platelet Count and Mean Platelet Volume be Used as Markers of Postdural Puncture Headache in Obstetric Patients?

Objective

In this study, considering the importance of platelet function in inflammatory processes, we explored whether there are relationships of platelet indices with postdural puncture headache (PDPH) and pain developing after use of spinal needles and whether patient characteristics contribute to the development of PDPH.

Methods

This prospective, observational study included 76 patients (Group 1) with PDPH and 93 patients (Group 2) without PDPH. The postoperative hemoglobin, hematocrit, platelet count (PC), and mean platelet volume (MPV) values were recorded, along with age, blood type, Rh factor, gravida, parity, and gestational age. In addition, the time of the onset of pain was recorded in patients who complained of a postspinal headache.

Results

Hemoglobin and hematocrit values in Group 1 were significantly lower than in Group 2 (both, p=0.024). The PC of Group 1 was significantly higher than that of Group 2 (p < 0.001), whereas the MPV was significantly lower (p < 0.001). The area under the curve (AUC) values were significant for hemoglobin, hematocrit, PC, and MPV (p=0.022, p=0.024, p < 0.001, and p < 0.001, resp.). For MPV, the AUC value was 0.293, sensitivity was 1%, and specificity was 99%. The highest likelihood ratio (LR+) value was 1.22 at a cut-off value of 13.3 fL. For the PC, the AUC value was 0.666, the sensitivity was 9%, and the specificity was 99%, while the highest LR + value was 8.56 at a cut-off value of 352 × 10⁹/L. There was no significant relationship between the parameters examined and the onset of pain.

Conclusion

In this study, the PC was higher and MPV was lower in obstetric patients with PDPH compared with the control group. However, we also found that these two values cannot be used as markers of PDPH.

Intrathecal drug delivery in the era of nanomedicine

Administration of substances directly into the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord is one approach that can circumvent the blood-brain barrier to enable drug delivery to the central nervous system (CNS). However, molecules that have been administered by intrathecal injection, which includes intraventricular, intracisternal, or lumbar locations, encounter new barriers within the subarachnoid space. These barriers include relatively high rates of turnover as CSF clears and potentially inadequate delivery to tissue or cellular targets. Nanomedicine could offer a solution. In contrast to the fate of freely administered drugs, nanomedicine systems can navigate the subarachnoid space to sustain delivery of therapeutic molecules, genes, and imaging agents within the CNS. Some evidence suggests that certain nanomedicine agents can reach the parenchyma following intrathecal administration. Here, we will address the preclinical and clinical use of intrathecal nanomedicine, including nanoparticles, microparticles, dendrimers, micelles, liposomes, polyplexes, and other colloidalal materials that function to alter the distribution of molecules in tissue. Our review forms a foundational understanding of drug delivery to the CSF that can be built upon to better engineer nanomedicine for intrathecal treatment of disease.

Microanatomy Relevant to Intrathecal Drug Delivery

This chapter describes the microanatomy of the spinal cord that is relevant to intrathecal drug delivery started with covering of the spinal cord that are pierced to enter the intrathecal space. The dural sac is mostly constituted by the outer layer of dura and the inner layer called arachnoid membrane, which regulates diffusion of drugs into the intrathecal space. The pia matter surrounding the spinal cord is a permeable structure allowing the passage of drugs through intercellular spaces. The relationship between nerve roots, CSF, and subarachnoid catheters determines the passage of an intrathecal catheter which can cause damage to nerve roots and spinal cord. Multiple factors may be involved in the mechanisms of drug diffusion across the membranes of the spinal cord, as well as in their dilution with the CSF, which will lead to the final drug distribution and availability at nerve roots and the spinal cord.

The rising root sign: the magnetic resonance appearances of post-operative spinal subdural extra-arachnoid collections

We present a case series of symptomatic post-operative spinal subdural extra-arachnoid collections that displace the cauda equina roots anteriorly. This is described as the "rising root sign".

Oblique Intrathecal Injection in Lumbar Spine Surgery: A Technical Note

OBJECTIVES

Intrathecal morphine (ITM) is an efficacious method of providing postoperative analgesia and reducing pain associated complications. Despite adoption in many surgical fields, ITM has yet to become a standard of care in lumbar spine surgery. Spine surgeons' reticence to make use of the technique may in part be attributed to concerns of precipitating a cerebrospinal fluid (CSF) leak.

METHODS

Herein we describe a method for oblique intrathecal injection during lumbar spine surgery to minimize risk of CSF leak. The dural sac is penetrated obliquely at a 30° angle to offset dural and arachnoid puncture sites. Oblique injection in instances of limited dural exposure is made possible by introducing a 60° bend to a standard 30-gauge needle.

RESULTS

The technique was applied for injection of ITM or placebo in 104 cases of lumbar surgery in the setting of a randomized controlled trial. Injection was not performed in two cases (2/104, 1.9%) following preinjection dural tear. In the remaining 102 cases no instances of postoperative CSF leakage attributable to oblique intrathecal injection occurred. Three cases (3/102, 2.9%) of transient CSF leakage were observed immediately following intrathecal injection with no associated sequelae or requirement for postsurgical intervention. In two cases, the observed leak was repaired by sealing with fibrin glue, whereas in a single case the leak was self-limited requiring no intervention.

CONCLUSIONS

Oblique dural puncture was not associated with increased incidence of postoperative CSF leakage. This safe and reliable method of delivery of ITM should therefore be routinely considered in lumbar spine surgery.

Rapid fluorescence imaging of spinal cord following epidural administration of a nerve-highlighting fluorophore

Iatrogenic spinal cord injury (SCI) is the most devastating complication of spine surgery, which usually results in permanent and serious disabilities of patients. Improvement of the visualization and discrimination of the spinal cord is critical for accuracy and safety during surgery; however, to date, there is no suitable technology to fulfill this clinical need. Here, we first show an efficient and rapid fluorescence imaging of the spinal cord in rabbit by epidural administration of a nerve-highlighting fluorophore, i.e. (E, E)-1,4-bis(p-aminostryl)-2-methoxy benzene (BMB). The BMB is firstly encapsulated into polymeric micelles to form a BMB-micelle (BMB-m) formulation with well-dispersion in normal saline solution. After epidural administration of BMB-m, BMB is transported by the flow of cerebrospinal fluid (CSF) and binds to the peripheral region of the white matter thus facilitating rapid staining of the spinal cord. Furthermore, this BMB imaging technology also holds great potential for visually monitoring the integrity of the spinal cord in real time and promptly identifying acute SCI during spine surgery.