COVID-19, post-acute COVID-19 syndrome (PACS, "long COVID") and post-COVID-19 vaccination syndrome (PCVS, "post-COVIDvac-syndrome"): Similarities and differences.

Worldwide there have been over 760 million confirmed coronavirus disease 2019 (COVID-19) cases, and over 13 billion COVID-19 vaccine doses have been administered as of April 2023, according to the World Health Organization. An infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to an acute disease, i.e. COVID-19, but also to a post-acute COVID-19 syndrome (PACS, "long COVID"). Currently, the side effects of COVID-19 vaccines are increasingly being noted and studied. Here, we summarise the currently available indications and discuss our conclusions that (i) these side effects have specific similarities and differences to acute COVID-19 and PACS, that (ii) a new term should be used to refer to these side effects (post-COVID-19 vaccination syndrome, PCVS, colloquially "post-COVIDvac-syndrome"), and that (iii) there is a need to distinguish between acute COVID-19 vaccination syndrome (ACVS) and post-acute COVID-19 vaccination syndrome (PACVS) - in analogy to acute COVID-19 and PACS ("long COVID"). Moreover, we address mixed forms of disease caused by natural SARS-CoV-2 infection and COVID-19 vaccination. We explain why it is important for medical diagnosis, care and research to use the new terms (PCVS, ACVS and PACVS) in order to avoid confusion and misinterpretation of the underlying causes of disease and to enable optimal medical therapy. We do not recommend to use the term "Post-Vac-Syndrome" as it is imprecise. The article also serves to address the current problem of "medical gaslighting" in relation to PACS and PCVS by raising awareness among the medical professionals and supplying appropriate terminology for disease.

Ultrasonic bone cement removal efficiency in total joint arthroplasty revision: A computer tomographic-based cadaver study.

Polymethylmethacrylate (PMMA) removal during septic total joint arthroplasty revision is associated with a high fracture and perforation risk. Ultrasonic cement removal is considered a bone-preserving technique. Currently, there is still a lack of sound data on efficacy as it is difficult to detect smaller residues with reasonable technical effort. However, incomplete removal is associated with the risk of biofilm coverage of the residue. Therefore, the study aimed to investigate the efficiency of ultrasonic-based PMMA removal in a human cadaver model. The femoral components of a total hip and a total knee prosthesis were implanted in two cadaver femoral canals by 3rd generation cement fixation technique. Implants were then removed. Cement mantle extraction was performed with the OSCAR-3-System ultrasonic system (Orthofix®). Quantitative analysis of cement residues was carried out with dual-energy and microcomputer tomography. With a 20 µm resolution, in vitro microcomputer tomography visualized tiniest PMMA residues. For clinical use, dual-energy computer tomography tissue decomposition with 0.75 mm resolution is suitable. With ultrasound, more than 99% of PMMA was removed. Seven hundred thirty-four residues with a mean volume of 0.40 ± 4.95 mm3 were identified with only 4 exceeding 1 cm in length in at least one axis. Ultrasonic cement removal of PMMA was almost complete and can therefore be considered a highly effective technique. For the first time, PMMA residues in the sub-millimetre range were detected by computer tomography. Clinical implications of the small remaining PMMA fraction on the eradication rate of periprosthetic joint infection warrants further investigations.

Human Frontalis Muscle Innervation and Morphology.

Due to its clinical importance and due to a suggestion regarding the afferent innervation, the microscopic appearance of the frontalis muscle was investigated. Methods: From seven human cadavers, serial sections of the frontalis muscle were studied using light microscopy. Immunhistochemistry was performed using antibodies against collagen XXII and neurofilament. Results: The macroscopic appearance of the muscle was in accordance with the literature. At both insertion sides, the muscle fiber endings expressed collagen XXII, a marker for myotendinous junctions, although no tendons were present at the origin side. Neuromuscular junctions were seen in the middle part of the muscle belly (insertion of the nerve fibers of the facialis nerve) and in the cranial part toward the galea aponeurotica (possible afferent fibers?). Conclusions: This study summarizes the microscopic appearance of the frontalis muscle. It is a first example that collagen XXII can be expressed even without tendon formation. It confirms the absence of corpuscular afferent neuronal structures within the muscle.

Aponeurosis linguae-Myocutaneous or myotendinous junctions of skeletal muscle fibres in the human tongue?

The morphology of the more superficial tissue of the human tongue was investigated and discussed with the clinical appearance of fissures. Three regions could be distinguished according to the presence and shape of the aponeurosis linguae: the central region showed a thick aponeurotic plate with myotendinous muscle fibre insertions. The lateral region showed still an aponeurosis linguae but of reduced thickness and without muscle insertions. The edge-wise and lower region showed no aponeurosis linguae but a fatty subcutis and myocutaneous muscle fibre insertions lacking specific molecules of myotendinous junctions. This system of partially developed exoskeleton seems to underlie but not to be involved in tongue fissures, which are more superficial within the epidermis and dermis.

Muscle spindles in the rhesus monkey platysma.

The platysma of the rhesus monkey consists of two parts: a platysma myoides located similar to the human platysma, and a platysma cervicale passing the dorsal cervical region and being in contact with the cheek pouch. Our investigation showed that the muscle fiber morphology was comparable in both parts. Muscle spindles were only present in regions connected to the cheek pouch and contained only nuclear chain fibers. It is tempting to speculate that they sense the filling of the cheek pouch rather than mimic activities.

In the human, true myocutaneous junctions of skeletal muscle fibers are limited to the face.

Within the panniculus carnosus-associated skeletal muscles in the human, the palmaris brevis and the platysma showed myotendinous/myofascial junctions with clear distance to the corium and the specific connection collagen type XXII. The orbicularis oris muscle, in contrast, contained bundles of striated muscle fibers reaching the corium at two distinct levels: the predominant inner ending was connected to the elastic network of the inner corium and the outer ending was within the more superficial collagen network. At both locations, the striated muscle fibers showed brush-like cytoplasmic protrusions connecting a network which was not oriented toward the muscle fibers. Collagen type XXII was not present.

Long Abductor Digiti Minimi Muscle: Variation of the Hypothenar Muscles and Clinical Consequences.

Variations in the hypothenar muscles influence the susceptibility of Guyon's canal and surgical procedures in this region. The hypothenar regions of both hands of 38 human donors were dissected and the single muscles identified. A semiquantitative evaluation included 19 donors. The opponens digiti minimi and the abductor digiti minimi were constantly present. The flexor digiti minimi showed various appearances: in 58% it formed one belly, in 21% two bellies, and in 21% it was missing. Rare unilateral supernumerary muscles (2.5% in this study) were associated to the abductor digiti minimi. The variation of the flexor digiti minimi and the possible appearance of additional muscles should be recognized for hypothenar region pathologies. Clin. Anat., 33:643-645, 2020. © 2019 Wiley Periodicals, Inc.

Characterization of afferent corpuscular sensors of the human palmaris brevis muscle.

The palmaris brevis muscle contains numerous muscle spindles to control changes of the muscle length but is devoid of tendon-associated neuronal elements (e.g. Golgi tendon organs or Ruffini-like corpuscles) controlling changes in muscle strength. Pacinian bodies, frequently seen in the palm of the hand, show no direct association to the muscle bundles. The observed innervation pattern of the palmaris brevis muscle points to a specific type of neuronal regulation, present in skeletal muscles with no skeletal connection.

The Horizontal Raphe of the Human Retina and its Watershed Zones.

The horizontal raphe (HR) as a demarcation line dividing the retina and choroid into separate vascular hemispheres is well established, but its development has never been discussed in the context of new findings of the last decades. Although factors for axon guidance are established (e.g., slit-robo pathway, ephrin-protein-receptor pathway) they do not explain HR formation. Early morphological organization, too, fails to establish a HR. The development of the HR is most likely induced by the long posterior ciliary arteries which form a horizontal line prior to retinal organization. The maintenance might then be supported by several biochemical factors. The circulation separate superior and inferior vascular hemispheres communicates across the HR only through their anastomosing capillary beds resulting in watershed zones on either side of the HR. Visual field changes along the HR could clearly be demonstrated in vascular occlusive diseases affecting the optic nerve head, the retina or the choroid. The watershed zone of the HR is ideally protective for central visual acuity in vascular occlusive diseases but can lead to distinct pathological features.

Species Differences in the Nutrition of Retinal Ganglion Cells among Mammals Frequently Used as Animal Models.

The diffusion rate for proper nutrition of the inner retina depends mainly on four factors which are discussed in this review: 1. The diffusion distance between blood and retinal ganglion cells shows morphological variants in different mammalian species, namely a choroidal nutrition type, a retinal nutrition type, and a mixture of both types. 2. Low oxygen concentration levels in the inner retina force the diffusion of oxygen especially in the choroidal nutrition type. Other nutrients might be supplied by surrounding cells, mainly Müller cells. 3. Diffusion in the eye is influenced by the intraocular pressure, which is vital for the retinal ganglion cells but might also influence their proper function. Again, the nutrition types established might explain the differences in normal intraocular pressure levels among different species. 4. Temperature is a critical feature in the eye which has to be buffered to avoid neuronal damage. The most effective buffer system is the increased blood turnover in the choroid which has to be established in all species.

The human platysma contains numerous muscle spindles.

The mimic muscles are usually described as containing no muscle spindles. In the present publication the human platysma was reinvestigated concerning its content of corpuscular sensors. Serial sections through the platysma of seven donors revealed numerous muscle spindles but no Pacini corpuscules. The muscle spindles were located in the cranial two-thirds of the platysma, and were evenly distributed with a tendency to have more spindles in the lateral part of the muscle. Immunohistochemical staining with S46 antibodies revealed a predominance of nuclear bag fibers. The results point to an extended function of the platysma as an afferent center of the lower face mimic muscles.

Hypothesis: Watershed zones in the human eye are a key for understanding glaucomatous retinal damage.

The pathogenesis of glaucoma is complex which has led to numerous hypothesizes concerning the important factors creating this specific type of inner retinal degeneration namely apoptosis of retinal ganglion cells. We favor a primary vascular etiology and provide evidence that the pathogenesis of glaucoma should not be confined to changes exclusively at the optic nerve head but must include changes occurring in the peripheral retina with particular emphasis on the watershed zones of both the retina and choroid. This focus may help to sharpen ones awareness for early glaucoma treatment particularly in patients with minimal findings suggestive of glaucoma.

The peripheral and Central Humphrey visual field - morphological changes during aging.

BACKGROUND: To define age-related changes in the visual field by comparing 'standard' central and unique peripheral visual field measurements in healthy volunteers. METHODS: In a single center, retrospective, Cross-sectional, observational study, 20 volunteers with no retinal diseases or risk factors, ranging in age between 30 and 94 years (four age groups: 30's, 50's, 70's, 90's) were measured in one eye (preferentially the right one) using a Humphrey visual field 24-2 and 60-4. RESULTS: While the central visual field remained relatively well preserved during aging showing only a mild reduction in sensitivity, a profound loss of the peripheral visual field was observed beginning in the fifth decade of life and decreasing continuously up to the 90ies. CONCLUSIONS: The peripheral visual field declined substantially from the 4th decade onward while the central visual field remained quite stable.

Nutrition and Vascular Supply of Retinal Ganglion Cells during Human Development.

PURPOSE: To review the roles of the different vascular beds nourishing the inner retina [retinal ganglion cells (RGCs)] during normal development of the human eye, using our own tissue specimens to support our conclusions. METHODS: An extensive search of the appropriate literature included PubMed, Google scholar, and numerous available textbooks. In addition, choroidal and retinal NADPH-diaphorase stained whole mount preparations were investigated. RESULTS: The first critical interaction between vascular bed and RGC formation occurs in the sixth to eighth month of gestation leading to a massive reduction of RGCs mainly in the peripheral retina. The first 3 years of age are characterized by an intense growth of the eyeball to near adult size. In the adult eye, the influence of the choroid on inner retinal nutrition was determined by examining the peripheral retinal watershed zones in more detail. CONCLUSION: This delicately balanced situation of RGC nutrition is described in the different regions of the eye, and a new graphic presentation is introduced to combine morphological measurements and clinical visual field data.

Influence of Caloric Vestibular Stimulation on Body Experience in Healthy Humans.

The vestibular system has more connections with and influence on higher cortical centers than previously thought. These interactions with higher cortical centers and the phenomena that they elicit require a structural intact cerebral cortex. To date, little is known about the role and influence of the vestibular system on one's body experience. In this study we show that caloric vestibular stimulation (CVS) in healthy participants has an effect on the perceptive component of one's body experience. After CVS all participants showed a statistically significant difference of thigh width estimation. In contrast to previous studies, which demonstrated an influence of CVS on higher cortical centers with an intact cerebral cortex both the cognitive and affective component of body experience were not effected by the CVS. Our results demonstrate the influence of the vestibular system on body perception and emphasize its role in modulating different perceptive-qualities which contributes to our body experience. We found that CVS has a limited influence on one's conscious state, thought process and higher cortical functions.

Specific densified regions in the postlaminar human glaucomatous optic nerve.

PURPOSE: To describe 'densified regions' in human postlaminar optic nerves of donors with the clinical diagnosis of primary open angle glaucoma (POAG) and pseudoexfoliation glaucoma (PEXG). METHODS: Optic nerves of 25 eyes with POAG and of 19 eyes with PEXG were investigated. Clinical data and axon counts of Epon-embedded semi-thin sections were used to determine the stage of the disease. Ultrathin sections were performed of selected areas and studied with an electron microscope. Immunofluorescence staining of paraffin sections was performed including antibodies against glial fibrillary acidic protein (GFAP), neural cellular adhesion molecule, vimentin and laminin. RESULTS: Early changes in both types of glaucoma showed increased numbers of areas with a densified appearance. The lack of GFAP staining and of ultrastructurally light nuclei within these areas indicated loss of astroglia. CONCLUSION: For the first time, a special type of neurodegeneration in optic nerves with mild glaucomatous changes is described.

The male bulbospongiosus muscle and its relation to the external anal sphincter.

PURPOSE: The bulbospongiosus muscle is part of the superficial muscular layer of the perineum and pelvic floor. Its morphology remains controversial in the literature. Therefore, we reinvestigated the fascial arrangement and fiber courses of the bulbospongiosus muscle and its topographical relation to the external anal sphincter. MATERIALS AND METHODS: The perineum was dissected in 9 male cadavers (mean ± SD age 78.3 ± 10.7 years). Select samples were obtained for histology and immunohistochemistry. In 43 patients (mean age 60.7 ± 12 years) the topographical relation between the bulbospongiosus muscle and the external anal sphincter was determined by magnetic resonance imaging. RESULTS: The perineum contains several fascial layers consisting of elastic and collagen fibers as well as bundles of smooth muscle cells. The bulbospongiosus muscle was subdivided into a ventral and dorsal portion, which developed in 4 variants. The ventral insertion formed a morphological unity with the ischiocavernous muscle while the dorsal origin had a variable relation to the external anal sphincter (5 variants). A muscle-like or connective tissue-like connection was frequently present between the muscles. However, in some cases the muscles were completely separated. CONCLUSIONS: We suggest a concept of variations of bulbospongiosus muscle morphology that unifies the conflicting literature. Its ventral fiber group and the ischiocavernosus muscle form a functional and morphological unity. While the bulbospongiosus muscle and the external anal sphincter remain independent muscles, their frequent connection might have clinical implications for perineal surgery and anogenital disorders.

Muscle spindles in the human bulbospongiosus and ischiocavernosus muscles.

INTRODUCTION: Muscle spindles are crucial for neuronal regulation of striated muscles, but their presence and involvement in the superficial perineal muscles is not known. METHODS: Bulbospongiosus and ischiocavernosus muscle specimens were obtained from 31 human cadavers. Serial sections were stained with hematoxylin and eosin, Sirius red, antibodies against Podocalyxin, myosin heavy chain isoforms (MyHC-slow tonic, S46; MyHC-2a/2x, A4.74), and neurofilament for the purpose of muscle spindle screening, counting, and characterization. RESULTS: A low but consistent number of spindles were detected in both muscles. The muscles contained few intrafusal fibers, but otherwise showed normal spindle morphology. The extrafusal fibers of both muscles were small in diameter. CONCLUSIONS: The presence of muscle spindles in bulbospongiosus and ischiocavernosus muscles supports physiological models of pelvic floor regulation and may provide a basis for further clinical observations regarding sexual function and micturition. The small number of muscle spindles points to a minor level of proprioceptive regulation.

Distribution of caveolin in the muscle spindles of human skeletal muscle.

The aim of the present study was to demonstrate the location of the different members of the caveolin (cav) family in human muscle spindles. Twenty spindles of three human muscles (vastus medialis, ischiocavernosus, bulbospongiosus) from 12 cadavers were immunohistochemically stained for cav-1, cav-2, and cav-3, and the equatorial and polar regions evaluated. All layers of the outer and inner spindle capsule and all blood vessels within the spindle stained for cav-1 and cav-2. In the muscle spindle, intrafusal muscle fibres stained selectively for cav-3, but with a patchy appearance. Caveolinopathies may therefore also include changes in muscle spindle function.