Pilot epinephrine dose-finding study to counter epidural-related blood pressure reduction.

OBJECTIVE: An unwanted side effect associated with epidural analgesia is the reduction in blood pressure (BP) due to the sympathetic blockade. This study evaluated the hemodynamic effects of adding different epinephrine concentrations to epidurally injected local anesthetic solution to counteract sympathectomy. We hypothesized that epinephrine could mitigate the decrease in BP possibly caused by the local anesthetic, specifically decreasing the incidence of hypotension. METHODS: Sixty-six patients were enrolled in a randomized, controlled, quadruple-blinded prospective study into three groups: epidural ropivacaine 0.2% without epinephrine (control) or with 2 µg/mL or 5 µg/mL epinephrine. Our primary outcome was the assessment of differences in hypotension between groups, defined as a >20% decrease in hypotension from baseline to the end of the intraoperative period. RESULTS: Forty-seven patients completed the study, and 19 were withdrawn. Fifteen patients were in the control group, while 16 patients received 0.2% ropivacaine +2 µg/mL epinephrine, and 16 received 0.2% ropivacaine +5 µg/mL epinephrine. The overall rate of hypotension was 21.3% (10/47). There were no statistically significant differences in hypotension rates between the control group (33%) and groups receiving either +2 µg/mL (13%, p=0.165) or +5 µg/mL (19%, p=0.353) of epinephrine. In secondary analyses, respiratory rate showed greater decreases in control groups across the perioperative period compared with treatment groups (p=0.016) CONCLUSION: Adding epinephrine to the epidural local anesthetic did not significantly decrease the rate of hypotension. However, epinephrine mitigated decreases in respiratory rate across the perioperative period. Future studies will focus on increasing group size and higher epinephrine concentrations (10 µg/mL). TRIAL REGISTRATION NUMBER: NCT02722746.

Newly revealed anatomy of the bucinator muscle: An anatomical and histological study.

BACKGROUND: Current anatomical knowledge of the origin of the bucinator muscle (BM), i.e., long thin attachments on the maxilla and mandible and the pterygomandibular raphe (PMR), is not supported by anatomical dissection of this muscle. The aim of this study was therefore to investigate the detailed morphology of the BM and associated structures and to discuss its function. METHODS: The anatomy of the BM and related structures was investigated in 15 cadaveric heads using a surgical microscope and histological analysis. RESULTS: The inferior fibers of the BM originated from a small retromolar area (internal oblique line), which shared a common tendon with the deep tendon of the temporalis. The superior fibers of the BM originated from the maxillary tuberosity. The middle fibers originated the pterygoid hamulus. No PMR was identified in any of the specimens, but the border between the BM and superior pharyngeal constrictor muscle (SC) was clear because the muscle fibers followed different directions. Some horizontal fibers were continuous between the BM and SC. CONCLUSIONS: Our results suggest the need to revise established accounts of the origins of the bucinator (the maxillary tuberosity, conjoint tendon of the temporalis, and pterygoid hamulus without a pterygomandibular raphe. It also needs to be noted that some of its fibers merge directly with the SC.

Anatomical study with clinical significance of communicating and visceral branching of the cervical and upper thoracic sympathetic trunk.

Current advances in the management of the autonomic nervous system in various cardiovascular diseases, and in treatments for pain or sympathetic disturbances in the head, neck, or upper limbs, necessitate a thorough understanding of the anatomy of the cervicothoracic sympathetic trunk. Our objective was to enhance our understanding of the origin and distribution of communicating branches and visceral cervicothoracic sympathetic nerves in human fetuses. This was achieved through a comprehensive topographic systematization of the branching patterns observed in the cervical and upper thoracic ganglia, along with the distribution of communicating branches to each cervical spinal nerve. We conducted detailed sub-macroscopic dissections of the cervical and thoracic regions in 20 human fetuses (40 sides). The superior and cervicothoracic ganglia were identified as the cervical sympathetic ganglia that provided the most communicating branches on both sides. The middle and accessory cervical ganglia contributed the fewest branches, with no significant differences between the right and left sides. The cervicothoracic ganglion supplied sympathetic branches to the greatest number of spinal nerves, spanning from C5 to T2 . The distribution of communicating branches to spinal nerves was non-uniform. Notably, C3 , C4 , and C5 received the fewest branches, and more than half of the specimens showed no sympathetic connections. C1 and C2 received sympathetic connections exclusively from the superior ganglion. Spinal nerves that received more branches often did so from multiple ganglia. The vertebral nerve provided deep communicating branches primarily to C6 , with lesser contributions to C7 , C5 , and C8 . The vagus nerve stood out as the cranial nerve with the most direct sympathetic connections. The autonomic branching pattern and connections of the cervicothoracic sympathetic trunk are significantly variable in the fetus. A comprehensive understanding of the anatomy of the cervical and upper thoracic sympathetic trunk and its branches is valuable during autonomic interventions and neuromodulation. This knowledge is particularly relevant for addressing various autonomic cardiac diseases and for treating pain and vascular dysfunction in the head, neck, and upper limbs.

A histology guide for performing human cadaveric studies: SQIP 2024 what to look for with light microscopy.

Histological observation under light microscopy has long been used in human cadaveric studies. However, it can distort the interpretations of findings if not used appropriately; there is no guide for its proper use. The aim of this article is to revisit and discuss the correct use of histology in human cadaveric studies, following discussions with experts in multiple fields of medicine, and to create the first guide for such usage. We reached a consensus with the experts, agreeing that when this principle (structure, quantification, interaction, position: SQIP) is applied to histological observations, the findings will be interpreted correctly. Appropriate use of this recommendation can make human cadaveric studies more accurate and informative. This is the first histology guide for human cadaveric studies.

No evidence of fascicular injury following a low-volume intraneural injection of the median nerve: a cadaveric study.

BACKGROUND: The test dose or hydrolocation technique allows rapid detection of spread location. Though its primary aim is to enhance safety in peripheral nerve blocks, evidence on the potential risks of an intraneural test aliquot is lacking. We conducted a cadaveric study to evaluate the risk of fascicular injury following a low-volume (<1 mL) intraneural injection of the median nerve. METHODS: Ten upper limbs from fresh unembalmed human cadavers were studied. In-plane ultrasound-guided intraneural injections of the median nerve were performed at mid, proximal, and distal locations using 1 mL of methylene blue and heparinized blood solution. Nerves were extracted and samples immersed in 10% buffered formalin for 4 weeks. Perpendicular 3 mm slices were obtained for H&E staining and light microscopy analysis. Our main objective was to assess the number of injured fascicles. Secondarily, we evaluated the pattern of intraneural spread. Fascicular injury was defined as the presence perineurium or axonal disruption and/or the presence of erythrocytes inside a nerve fascicle. RESULTS: Thirty injections were performed in 10 median nerves. Sonographic swelling was confirmed in 100% of the cases. 352 histological sections were analyzed to assess study outcomes. The mean number of fascicles on each section of median nerve was 20±6 covering 49%±7% of the nerve area. No evidence of axonal disruption nor intra-fascicular erythrocytes was found in any of the analyzed sections. CONCLUSIONS: Low-volume intraneural injections do not result in evident fascicular injury. Our findings support the use of a test dose in ultrasound-guided regional anesthesia.

Nerve block, nerve damage, and fluid injection pressure: overturning the myth.

Histological and micro-ultrasound evidence rebuffs deep-rooted views on the nature of nerve block, nerve damage, and injection pressure monitoring. We propose that the ideal position of the needle tip for nerve block is between the innermost circumneural fascial layer and outer epineurium, with local anaesthetic passing circumferentially through adipose tissue. Thin, circumferential, subepineural expansion that is invisible to the naked eye was identified using micro-ultrasound, and could account for variability of outcomes in clinical practice. Pressure monitoring cannot differentiate between intrafascicular and extrafascicular injection. High injection pressure only indicates intraneural extrafascicular spread, not intrafascicular spread, because it is not possible to inject into the stiff endoneurium in most human nerves.

Refractory primary and secondary headache disorders that dramatically responded to combined treatment of ultrasound-guided percutaneous suprazygomatic pterygopalatine ganglion blocks and non-invasive vagus nerve stimulation: a case series.

In 1981, Devoghel achieved an 85.6% success rate in treating patients with treatment-refractory cluster headaches with alcoholization of the pterygopalatine ganglion (PPG) via the percutaneous suprazygomatic approach. Devoghel's study led to the theory that interrupting the parasympathetic pathway by blocking its transduction at the PPG could prevent or treat symptoms related to primary headache disorders (PHDs). Furthermore, non-invasive vagus nerve stimulation (nVNS) has proven to treat PHDs and has been approved by national regulatory bodies to treat, among others, cluster headaches and migraines.In this case series, nine desperate patients who presented with 11 longstanding treatment-refractory primary headache disorders and epidural blood patch-resistant postdural puncture headache (PDPH) received ultrasound-guided percutaneous suprazygomatic pterygopalatine ganglion blocks (PPGB), and seven also received nVNS. The patients were randomly selected and were not part of a research study. They experienced dramatic, immediate, satisfactory, and apparently lasting symptom resolution (at the time of the writing of this report). The report provides the case descriptions, briefly reviews the trigeminovascular and neurogenic inflammatory theories of the pathophysiology, outlines aspects of these PPGB and nVNS interventions, and argues for adopting this treatment regime as a first-line or second-line treatment rather than desperate last-line treatment of PDPH and PHDs.

Identification of spread after deliberated intraneural injection in five mammalian species: not all animal models and needle types are valid for studying the effect of intraneural injections in humans.

INTRODUCTION: This research endeavors to investigate the phenomenon of intraneural spread across distinct locations: subcircumneurium, extrafascicular intraneural, intrafascicular intraneural, and intraperineurium after deliberate intraneural injections across five mammalian species. The study also aims to propose determinants influencing this spread. Furthermore, the investigation strives to ascertain the optimal animal species and needle configuration for extrapolating intraneural injection outcomes to human contexts. METHODS: This study examined 60 sciatic nerves from 30 fresh and untreated cadavers of rats, rabbits, dogs, pigs, and sheep. The specimens were organized into five groups, each comprising an equal number of nerves. Histological assessments were performed on 30 nerves, involving fascicle metrics. The remaining 30 nerves underwent intentional intraneural injections, facilitated by 19G and 23G needles under ultrasound and direct visualization guidance.Heparinized erythrocytes combined with a methylene blue solution were used as a marker to analyze the extent and patterns of intraneural spread. Needle orifice measurements were obtained, and these data were overlaid onto images of both nerves and needles. This enabled a comparative evaluation of sizes and an assessment of marker diffusion. RESULTS: The findings indicated that sciatic nerves in rats, rabbits, and dogs were oligofascicular, characterized by larger fascicles, whereas pigs and sheep exhibited polyfascicular nerves comprised of numerous smaller fascicles. Fascicular diameters were variable across species, with dogs presenting the largest measurements. While intraneural spread was observed and documented, intrafascicular marker spreading was rare, occurring only in one rabbit specimen. Needle orifice attributes were scrutinized and visually depicted. CONCLUSIONS: Despite the formidable challenges associated with the practical realization of intrafascicular injection, the utilization of animal models possessing monofascicular or oligofascicular nerves, such as rats, rabbits, and dogs, in conjunction with needles featuring aperture dimensions surpassing those of the fascicles, likely contributes to the compromised reliability of investigations into intraneural injection outcomes.

The anatomy of the tendon of abductor pollicis longus and its morphological variations: An anatomical approach emphasizing the clinical relevance.

PURPOSE: The anatomical literature describes the abductor pollicis longus as a muscle with a single tendon inserting on the base of the first metacarpal bone, but investigations have shown that it often exhibits morphological variations. However, methodological approaches used to describe these variations have not been useful in a clinical context. Therefore, the purpose of this investigation was to study and relate such anatomical variations in a clinical context. BASIC PROCEDURES: Thirty upper limbs from the body donation program were dissected using standard procedures to identify the number of abductor pollicis longus (APL) tendons, their position, site of insertion, length, width and thickness. The presence or absence of the extensor pollicis brevis muscle was also noted. Inter and intra-observer reliability was analysed. MAIN FINDINGS: A total number of 71 tendons from the APL muscle were found in the thirty limbs. The most frequent distribution pattern was a main tendon inserted on the base of the first metacarpal and an accessory tendon inserted into the abductor pollicis brevis muscle. These tendons could divide into various tendinous slips that could insert in different locations. Also, clustering algorithms and classical statistical tests showed tendons inserting on the first metacarpal were longer than tendons not inserting on the first metacarpal (p = 0.03), while medial tendons and tendons from an APL muscle with supernumerary tendons were narrower (p < 0.001). The absence of the extensor pollicis brevis muscle was not related to the presence of supernumerary APL tendons. CONCLUSIONS: Radiological and surgical implications of these results are important when examining this region of the hand and wrist. The pathophysiology and treatment of de Quervain's tenosynovitis, trapeziometacarpal arthritis and trapeziometacarpal subluxation or laxity could be influenced by the results of our findings.

Innervation of the heart: Anatomical study with application to better understanding pathologies of the cardiac autonomics.

Current advances in management of the cardiac neuroaxis in different cardiovascular diseases require a deeper knowledge of cardiac neuroanatomy. The aim of the study was to increase knowledge of the human fetal extrinsic cardiac nervous system. We achieved this by systematizing the origin and formation of the cardiac nerves, branches, and ganglia and their sympathetic/parasympathetic connections. Thirty human fetuses (60 sides) were subjected to detailed sub-macroscopic dissection of the cervical and thoracic regions. Cardiac accessory ganglia lying on a cardiac nerve or in conjunction with two or more (up to four) nerves before entering the mediastinal cardiac plexus were observed in 13 sides. Except for the superior cardiac nerve, the sympathetic cardiac nerves were individually variable and inconstant. In contrast, the cardiac branches of the vagus nerve appeared grossly more constant and invariable, although the individual cardiac branches varied in number and position of origin. Each cervical cardiac nerve or cardiac branch of the vagus nerve could be singular or multiple (up to six) and originated from the sympathetic trunk or the vagus nerve by one, two, or three roots. Sympathetic nerves arose from the cervical-thoracic ganglia or the interganglionic segment of the sympathetic trunk. Connections were found outside the cardiac plexus. Some cardiac nerves were connected to non-cardiac nerves, while others were connected to each other. Common sympathetic/parasympathetic cardiac nerve trunks were more frequent on right (70%) versus left sides (20%). The origin, frequency, and connections of the cardiac nerves and branches are highly variable in the fetus. Detailed knowledge of the normal neuroanatomy of the heart could be useful during cardiac neuromodulation procedures and in better understanding nervous pathologies of the heart.

Human lumbar sympathetic blockade: An anatomical study to address potential block failure.

The lumbar sympathetic block is often used to treat complex regional pain syndrome, but it seems to have a high failure rate. This study seeks anatomical explanations for this apparent failure in order to refine our block procedure. Two simulated sympathetic trunk blocks were carried out on four fresh, cryopreserved unembalmed human cadavers under fluoroscopic control at the L2 vertebral body level, followed by two further simulated blocks at the L4 vertebral body level on the other side. Dye was injected, and the areas were dissected following a specific protocol. We then describe the anatomy and the spread of the dye compared to the spread of the contrast medium on fluoroscopy. The ganglia were differently located at different vertebral levels, and differed among the cadavers. Following this anatomical clarification, we now prefer to perform lumbar sympathetic blocks at the fourth lumbar vertebra level, using an extraforaminal approach at the caudal end of ​​the vertebra, avoiding the anterolateral margin of the vertebral body at the midpoint.

Prone Position MRI of the Lumbar Spine in Patients With Low Back Pain and/or Radiculopathy Refractory to Treatment.

BACKGROUND: There are patients with limiting low back pain (LBP) with or without radicular pain in whom conventional supine magnetic resonance imaging (MRI) show no causative pathology. Despite the limitations of dynamic axially loaded MRI examinations, these imaging studies have shown a striking ability to diagnose pathology unrecognized by conventional MRI. The difference in findings between supine and prone MRI with patient symptom correlation has not been studied. METHODS: Nineteen patients suffering from chronic moderate-to-severe LBP and/or radicular pain nonresponsive to conventional therapy or interventional treatment, were included in this study. Both supine and prone MRIs were performed and analyzed by a neuroradiologist. Specific supine and prone measurements were registered, including spinal canal area, lateral recess diameter, foraminal area, and ligamentum flavum thickness. Three-dimensional  MRI reconstructions of varying pathology patterns were created. RESULTS: The mean patient age was 48.7 years (range [R]: 30-69), 63% of patients were women. The mean numeric pain score  was 6.5 (R: 4-8). In 52.6% of cases, disc pathology/increased disc pathology was seen only on prone imaging. We observed significant buckling and increased thickness of the ligamentum flavum in 52.6 % of cases in the prone position that was absent from the supine MRIs. We also documented varying grades of spondylolisthesis and facet joint subluxation resulting in significant foraminal stenosis in 26.3% of prone cases not seen from supine MRIs. CONCLUSIONS: Four patterns of pathological findings have been identified by MRI performed in the prone position. These findings were not observed in the supine position. Prone MRI can be a significant and useful tool in the diagnosis and treatment of patients with back pain refractory to treatment whose conventional supine MRIs appeared unremarkable.

Microscopy of structures surrounding typical acupoints used in clinical practice and electron microscopic evaluation of acupuncture needles.

Although the general functionality and structures of acupoints have been studied, there has been little insight into their underlying morphology and physical characteristics. We describe the microanatomical structures surrounding acupoints, the electron microscopic appearance of the needles, and the physical effects of acupuncture needling on the fascia. We injected heparinized blood solution through thin needles at seven known and commonly used "sweat acupoints" in eight fresh, unembalmed, cryopreserved human cadavers to mark the needle positions, and later, during histological examination, to identify them. After the solution was injected, samples were dissected and prepared for histological examination. We examined 350 cross-sections of five different paraffin wax sections from each acupoint microscopically. Acupuncture needles were photographed and superimposed on the cross-sectioned tissues at similar magnifications. Needles were also examined under a scanning electron microscope to judge the roughness or smoothness of their surfaces. A greater conglomeration of nerve endings surrounded the acupoints than in tissues more than 1-3 cm distant from them. Nerve endings and blood vessels were in close contact with a complex network of membranes formed by interlacing collagen fibers, and were always enclosed within those collagen membranes. Nerve endings were found within hypodermis, muscles, or both. Scanning electron microscopy demonstrated the three-dimensional shapes and sizes of the needles, and the degree of roughness or smoothness of their polished external surfaces. We demonstrate a delicate arrangement of nerve endings and blood vessels enclosed within complex collagen membrane networks at acupoints within the hypodermis and muscle. This arrangement could explain why needling is an essential step in the acupuncture process that provides favorable outcomes in clinical practice.

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.

Anatomical basis of fascial plane blocks.

Fascial plane blocks (FPBs) are regional anesthesia techniques in which the space ("plane") between two discrete fascial layers is the target of needle insertion and injection. Analgesia is primarily achieved by local anesthetic spread to nerves traveling within this plane and adjacent tissues. This narrative review discusses key fundamental anatomical concepts relevant to FPBs, with a focus on blocks of the torso. Fascia, in this context, refers to any sheet of connective tissue that encloses or separates muscles and internal organs. The basic composition of fascia is a latticework of collagen fibers filled with a hydrated glycosaminoglycan matrix and infiltrated by adipocytes and fibroblasts; fluid can cross this by diffusion but not bulk flow. The plane between fascial layers is filled with a similar fat-glycosaminoglycan matric and provides gliding and cushioning between structures, as well as a pathway for nerves and vessels. The planes between the various muscle layers of the thorax, abdomen, and paraspinal area close to the thoracic paravertebral space and vertebral canal, are popular targets for ultrasound-guided local anesthetic injection. The pertinent musculofascial anatomy of these regions, together with the nerves involved in somatic and visceral innervation, are summarized. This knowledge will aid not only sonographic identification of landmarks and block performance, but also understanding of the potential pathways and barriers for spread of local anesthetic. It is also critical as the basis for further exploration and refinement of FPBs, with an emphasis on improving their clinical utility, efficacy, and safety.

Visceral versus somatic pain: an educational review of anatomy and clinical implications.

Somatic and visceral nociceptive signals travel via different pathways to reach the spinal cord. Additionally, signals regulating visceral blood flow and gastrointestinal tract (GIT) motility travel via efferent sympathetic nerves. To offer optimal pain relief and increase GIT motility and blood flow, we should interfere with all these pathways. These include the afferent nerves that travel with the sympathetic trunks, the somatic fibers that innervate the abdominal wall and part of the parietal peritoneum, and the sympathetic efferent fibers. All somatic and visceral afferent neural and sympathetic efferent pathways are effectively blocked by appropriately placed segmental thoracic epidural blocks (TEBs), whereas well-placed truncal fascial plane blocks evidently do not consistently block the afferent visceral neural pathways nor the sympathetic efferent nerves. It is generally accepted that it would be beneficial to counter the effects of the stress response on the GIT, therefore most enhanced recovery after surgery protocols involve TEB. The TEB failure rate, however, can be high, enticing practitioners to resort to truncal fascial plane blocks. In this educational article, we discuss the differences between visceral and somatic pain, their management and the clinical implications of these differences.