Quantitative impact of using different criteria for the laboratory diagnosis of type 1 von Willebrand disease.

INTRODUCTION: Only ± 50% of patients with type 1 von Willebrand disease (VWD) have recognized molecular defects and diagnosis still rests on demonstrating low plasma von Willebrand factor (VWF) protein/function. However, no generalized consensus exists regarding the type and number of VWF variables that should be considered for diagnosis. AIM: To compare the quantitative impact of four different criteria to diagnose type 1 VWD. METHODS: We tested four laboratory criteria on 4298 laboratory studies during a 5-year period. The first was the National Heart, Lung, and Blood Institute recommendation, which diagnoses type 1 VWD with plasma VWF antigen (VWF:Ag) and VWF ristocetin cofactor (VWF:RCo) < 30 IU dL(-1) and possible VWD/'low VWF' with values between 30 and 50 IU dL(-1) . Second, diagnosis was established when two of three variables, VWF:Ag, VWF:RCo, VWF collagen binding assay (VWF:CB), were ≤ 2.5th percentile. Diagnostic criterion for possible VWD/'low VWF' using percentiles was also described. The third criterion (European Group on von Willebrand Disease, EUVWD), uses a plasma level of VWF:RCo (or VWF:CB) ≤ 40 IU dL(-1) for diagnosis. Finally, the Zimmerman Program for the Molecular and Clinical Biology of VWD (ZPMCBVWD) diagnoses VWD if VWF:Ag or VWF:RCo are ≤ 40 IU dL(-1) . RESULTS: The three assays had high correlation and excellent agreement at levels < 120 IU dL(-1) . The National Heart, Lung, and Blood Institute recommendation was followed to diagnose 122 (2.8%) patients with type 1 VWD and 704 (16.4%) with possible VWD/'low VWF.' Using percentiles, the diagnosis of type 1 VWD increased to 280 (6.5%) patients; 169 (3.9%) patients had possible VWD and 180 (4.2%) patients had 'low VWF.' Diagnoses using EUVWD and ZPMCBVWD criteria increased to 339 (7.9%) and 357 (8.3%) patients, respectively. DISCUSSION: Identical data, analyzed using different criteria, led to almost three-fold difference (2.8-8.3%) in diagnostic rate. This increase is mostly explained by increasing the cut-off values of VWF measurements from < 30 to ≈ 40 IU dL(-1) . Further refinement of the laboratory diagnosis of type 1 VWD is a priority.

Determinación de péptidos solubles relacionados a mesotelina para la detección precoz del mesotelioma maligno / Soluble mesothelin-related protein for malignant pleural mesothelioma screening

Introduction: Malignant Pleural Mesothelioma (MPM) is a tumor of the mesothelial cells related to asbestos exposure. This malignancy is extremely aggressive, with poor response to different treatment modalities, and it has a mean survival of 8 months since diagnosis. With the introduction of new chemotherapeutic agents and trimodality protocols, five-year survival of 40 percent in initial stages has been reported. Serum detection of Soluble Mesothelin-related Protein (SMRP) could be used for screening of MPM. Using the MESOMARK® test, 53 percent of MPM patients had levels greater than 1,5 nM, while 99 percent of control patients had lower concentrations. The aim of this study is to evaluate the use of this test in Chile and determine its utility for screening ofMPM. Methods: Quantitative blind measurement of serum SMRP by MESOMARK® test. We studied 3 groups: 8 workers exposed to asbestos, 5 patients with diagnosed MPM and 14 age matched workers without known exposure to asbestos. Participants were informed of the study. Results: Mean +/- standard deviation SMRP levels in the control group was 0,53 +/- 0,4 nM, 0,89 +/- 0,46 nM in patients exposed to asbestos and 10,68 +/- 10,28 nM in MPMpatients. Differences between the groups were statistically significant (p = 0,02). In the MPM group, 3 patients were found to have SMRP levels greater than 1,5 nM (17,27 nM; SD 6,95) and 2 patients normal values (0,79 nM; SD 0,32). Using a cut-off value of 1,5 nM, sensitivity of the test was 60 percent and specificity was 100 percent. Conclusions: Detection of SMRP levels allowed to identify patients with MPM, three of whom had very high concentrations. The sensitivity and specificity found is similar to that previously reported. If our results are confirmed in greater studies, SMRP detection could be used for screening of MPM.

Resumen Introducción: El Mesotelioma Maligno (MM) es un tumor de las células mesoteliales relacionado a la exposición a asbesto, altamente agresivo, con pobre respuesta al tratamiento y con una sobrevida promedio de 8 meses después del diagnóstico. Sin embargo, nuevos agentes quimioterapéuticos y protocolos de terapia trimodal han logrado sobrevidas de hasta 40 por ciento en etapas iniciales. La detección en sangre periférica de Péptidos Solubles Relacionados a Mesotelina (SMRP) podría ser útil para el diagnóstico precoz de MM. Utilizando el test MESOMARK® para la determinación de SMRP, 53 por ciento de los pacientes con MM tenían valores mayores a 1,5 nM mientras que 99 por ciento de los controles mostraron valores inferiores. El objetivo del presente trabajo es evaluar la implementación de este test en Chile y determinar su utilidad para el diagnóstico precoz en MM. Métodos: Medición cuantitativa de SMRP en suero humano por test MESOMARK®. Se realizaron mediciones en forma ciega a 8 trabajadores con exposición a asbesto, a 5 pacientes con MMy a 14 voluntarios sin exposición. Todos los participantes fueron informados del estudio. Resultados: El promedio +/- desviación estándar de SMRP en el grupo control fue de 0,53 +/- 0,4 nM, de 0,89 +/- 0,46 nM en los expuestos sin MMy de 10,68 +/- 10,28 nM en el grupo con MM; encontrándose una diferencia estadísticamente significativa entre los valores de estos tres grupos (p = 0,02). En el grupo con MM, 3 pacientes tuvieron concentraciones mucho mayores a 1,5 nM (17,27 nM; DS 6,95) y 2 valores normales (0,79 nM; DS 0,32). Utilizando un valor de 1,5 nM como punto de corte, la sensibilidad fue de 60 por ciento y la especificidad de 100 por ciento. Conclusiones: La medición de SMRP permitió diferenciar a los pacientes con MM, presentando 3 de ellos concentraciones muy elevadas. La sensibilidad y especificidad encontrada es similar con datos previamente reportados. De confirmarse estos resultados en estudios con mayor ...

Reproducibility and performance of one or two samples of salivary cortisol in the diagnosis of Cushing's syndrome using an automated immunoassay system.

The purpose of this article is to evaluate the variability and reproducibility of late night salivary cortisol (LNSC) using electrochemiluminescence immunoassay (ECLIA) and compare the accuracy of one or two samples in diagnosis of Cushing's syndrome (CS). We prospectively included 64 healthy volunteers (HV), 35 patients with clinically suspected CS (S), and 26 patients with confirmed CS. Nine patients in the CS group had 24-h urinary free cortisol (UFC) less than two times the upper limit of normal (mild CS). UFC and two consecutive LNSC (LNSC1, LNSC2) were collected at home. All patients in the S group had normal UFC and low-dose dexamethasone suppression test. No differences were found between the HV and S groups in UFC, LNSC1, and LNSC2. Intra-individual variability between the two samples of LNSC was 22% in HV (1.6-91%), 32% in the S group (1.6-144%), and 51% (1.6-156%) in the CS group. Variability was higher in CS patients than those in the HV (P < 0.001) and S groups (P = 0.05). The AUC of LNSC1 was 0.945 (IC 95% 0.880-1.004); when considering the highest LNSC, the AUC was 0.980 (IC 95% 0.954-1.007) (P < 0.01). We found 23% of discordant LNSC in the S group and 11% in the CS group. Three patients with CS had only one elevated LNSC, all of them with mild CS. Our results suggest that LNSC is variable, and reproducibility is affected in both CS and S patients. We found significant improvements in the diagnostic accuracy of the LNSC measurement by obtaining two samples.

Template bleeding time and PFA-100 have low sensitivity to screen patients with hereditary mucocutaneous hemorrhages: comparative study in 148 patients.

OBJECTIVES AND PATIENTS: We compared the template bleeding time (BT) and closure time (CT) in the PFA-100 as screening tests in 148 consecutive patients with unequivocal mucocutaneous bleeding and positive family history. EXCLUSION CRITERIA: drug intake, concomitant diseases including minor infections, low platelet count, diseases of secondary hemostasis. RESULTS: Type 1 von Willebrand disease (VWD-1) was diagnosed in 26 patients, primary platelet secretion defect (PSD) in 33, VWD-1 + PSD in nine, whereas 80 patients did not comply with the criteria for known hemostatic disorders (UD, unknown diagnosis). BT and CT were prolonged in 35.8% and 29.7% of all the patients, respectively (P = 0.23). Sensitivity increased to 48% if an abnormality of BT and/or CT was considered. Same comparisons for BT and CT in each diagnostic category were, respectively: 42 vs. 61.5% in VWD-1 (P = 0.18), 42 vs. 24% in platelet secretion defects (P = 0.11), 67 vs. 89% in VWD-1 + PSD (P = 0.50), and 27.5 vs. 15% in UD (P = 0.06). CONCLUSION: Both tests were relatively insensitive and not significantly different in detecting incoming patients with mucocutaneous hemorrhages. In patients with VWD-1, the PFA-100 performed slightly better, whereas the opposite occurred in those patients with platelet secretion defects. In the UD group, both tests lost sensitivity, but the BT detected 1.8 times more patients than the PFA-100. Given the large proportion of undiagnosed bleeders and the overall low sensitivity of these tests, clinical decisions still rely on the medical history and etiological diagnosis of the bleeding disorder.

Clinical aspects of round window membrane permeability under normal and pathological conditions.

Current research and an overall review of 25 years of round window membrane studies are presented. The approach, rationale and concepts that have evolved from these studies are described. Ultrastructural studies of the round window membrane of humans, monkeys, felines and rodents have disclosed three basic layers: an outer epithelium, a middle core of connective tissue and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thickest in humans. Morphologic evidence suggests that the layers of the round window participate in resorption and secretion of substances to and from the inner ear, and that the membrane could play a role in the defense system of the ear. Different substances, including antibiotics and tracers, when placed in the middle ear side traverse the membrane. Tracers placed in perilymph become incorporated into the membrane by the inner epithelial cells. Permeability is selective and factors affecting permeability include size, concentration, electrical charge, thickness of the membrane and tacilitating agents. Passage of substances through the membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the membrane. Round window membrane studies have provided increased knowledge of the anatomy and function of this structure, as well as new insights into pathology and pathogenesis. The concepts that have evolved from these studies are potentially useful for understanding middle and inner ear interactions, and for eventual drug delivery (based on permeability) to the inner ear.

Gland formation in otitis media. An ultrastructural study in humans.

In an effort to evaluate mechanisms of new gland formation in otitis media, 14 human middle ear mucoperiostial tissue samples were obtained from 7 patients with a history of this disease. In areas of inflammatory reaction, especially in the promontory and anterior wall, the mucoperiosteum acquires polyploidal characteristics, with occasional epithelial breaks. The epithelium becomes thicker and the cells develop increased secretory activity. The invaginated portion of these polyploidal formations can be observed as pits lined by secretory epithelium. The cells in these invaginated areas: (i) fuse in areas of epithelial ruptures, leaving spaces into which cells secrete; (ii) develop dense cellular nests that bud off the epithelium, leaving empty spaces into which cells secrete. It is proposed that new gland formation can occur by means of fusion and formation of cellular nests that bud off the epithelium.

Evaluación de métodos diagnósticos para sífilis congénita / Evaluation of diagnostic methods for congenital syphilis

La sífilis congénita es un problema relevante en nuestro país. Actualmente no existen exámenes de uso rutinario que permitan confirmar su diagnóstico. En este estudio prospectivo multicéntrico se evaluaron 60 binomios madre-RN que presentaban test no treponémicos (TNT) reactivos. En todas las muestras se realizaron 2 TNT (VDRL y RPR) y 7 test treponémicos (TT): dos evaluaban IgM, uno IgG y cuatro IgM + IgG. La concordancia entre los tests que evaluaban IgG o IgG + IgM fue de 90 por ciento y entre los que evaluaban IgM fue de 87,5 por ciento. Un resultado IgG positivo se observó en 100 por ciento de los binomios cuyas madres presentaron sífilis durante el embarazo o portaban serología residual. La IgM fue positiva en 64 por ciento de las madres con sífilis adecuadamente tratada durante el embarazo, siendo sus neonatos todos IgM negativa. Aquellas madres con un tratamiento inadecuado tuvieron IgM positiva en 82.3 por ciento y sus RN tuvieron IgM positivas en 11,8 por ciento. En conclusión, la IgM materna no aporta al diagnóstico de sífilis congénita, pues su positividad no se correlaciona con el riesgo de que el RN presente este cuadro. La Igm en el RN es útil para el diagnóstico precoz de sífilis congénita, pero su ausencia no descarta esta patología

Surgical treatment of vertigo by utriculostomy: an experimental study in sheep.

The objective of this study was to develop and test an endolabyrinthic microsurgical procedure for treatment of vertigo, the utriculostomy. This involves the application of local heat for obtaining a fistula in the membranous labyrinth, so as to establish communication between the endolymphatic and perilymphatic spaces at the utricle level. Before the procedure, an experimental model using quail eggs was built for pre-evaluation, and macroscopic and histological studies were performed in the temporal bones of three healthy sheep. Following this, the utriculostomy was performed through the oval window in 12 sheep. A microthermocautery was conceived by the first author and developed at Hospital de Clinicas de Porto Alegre. This equipment allows for control of temperature and duration of exposure to heat. Three months after the surgery, the animals were killed. A histological study of the temporal bones was performed to assess whether communication had been created between the endolymphatic and perilymphatic spaces, or whether a neomembrane had developed in the cauterized region. Histological sections of the vestibule of eight animals (three normal, five surgical) were analysed. All non-surgical cases presented a normal utricle wall. Three surgical cases (60%) presented a neomembrane. The absence of identifiable perforations in the utricle wall and the presence of neomembrane areas in 60% of the operated bones suggest that utriculostomy is a promising procedure for the treatment of Meniere's disease.

Mastoid and tympanomastoid procedures in otitis media: classic mastoidectomy (simple, modified, and radical) and current adaptations; open-cavity, closed-cavity, and intact-bridge tympanomastoidectomy.

Otitis media is a multifactorial, multifaceted disease that manifests itself in the middle ear, mastoid, and eustachian tube. To select a rational therapy, physicians must have an understanding of the anatomy, function, and pathology of the organs involved and of the mechanisms of disease. The purpose of this article is to provide surgical principles in tympanomastoidectomy and an overall concept of the procedures available. Simple mastoidectomy is described in detail as a general approach.

The theory of the trigger, the bridge and the transmigration in the pathogenesis of acquired cholesteatoma.

The purpose of the study was to evaluate factors in the otitis media process that could play a role in the pathogenesis of acquired cholesteatoma. The study was divided in two parts: firstly the temporal bones of 75 cats and 15 chinchillas with induced otitis media, and 78 human bones with otitis media were evaluated. Special emphasis was placed on epithelial breaks. These breaks were commonly observed, leaving areas of connective tissue of the mucoperiostium in direct contact with the middle ear effusion. As these changes progressed, the effusion became organized, serving as a bridge for granulation tissue. In later stages these areas became totally or partially covered with epithelium. Areas of epithelial breaks became connected to each other through the organized effusion. Cholesteatomas in humans seem to spread using the connective tissue as scaffolding. Secondly, we reviewed 15 chinchillas in which a chemically modified membrane was placed leading from the external auditory canal to the promontory, through a tympanic membrane perforation. Squamous epithelial migration with cholesteatoma formation occurred through the tympanic membrane perforation, collagen membrane, organized effusion and granulation tissue in 53.5% of the experimental animals. The authors propose the theory that for transmigration of squamous epithelium to occur, a trigger (inflammatory process) and a bridge (granulation tissue and organized effusion) are needed in a predisposed subject.

Round window membrane. Structure function and permeability: a review.

The ultrastructure of the round window membrane of humans, monkeys, felines, and rodents discloses three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thicker in humans. Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Different substances, including antibiotics, local anesthetics, and tracers such as cationic ferritin, horseradish peroxidase, and 1 mu latex microspheres, are placed in the middle ear side traverse the membrane. Cationic ferritin and 1 micron microspheres placed in perilymph become incorporated by the inner epithelial cells of the membrane. Permeability is selective; factors include size, concentration, liposolubility, electrical charge, and thickness of the membrane. Passage of substances through the round window membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the round window membrane.

[Hemophilia A: analysis of intron 18 and intron 7 of factor VIII gene and their role in a diagnostic strategy for carrier detection in a Chilean population]. / Hemofilia A: análisis del intron 18 e intron 7 del gen del factor VIII y su rol en una estrategia de diagnóstico de portadoras en una población chilena.

Hemophilia A is an X-linked disorder of coagulation caused by a deficiency of factor VIII. A larger number of different mutations in the VIII gene have been identified. Thus, the detection of female carriers, depends upon the analysis of DNA polymorphisms in and near the factor VIII gene. Our aim was to develop a strategy, earlier reported, for carrier testing in families at risk of hemophilia A. In this study, we analyzed the DNA polymorphisms in 26 affected families, with use of the factor VIII intragenic polymorphisms identified by the restriction enzymes BclI and AlwNI, and by differential hybridization with sequence-specific oligonucleotide probes recognizing BclI and AlwNI polymorphism. While the DNA polymorphism detected by BcilI site in intron 18 of the factor VIII gene was informative for 38% families studied, the AlwNI/intron 7 polymorphism provided additional information (4%). The carrier status of the remaining 58% could be determined utilizing the other polymorphisms suggested by strategy. The two polymorphic sites used combined with the other polymorphisms, intragenic and extragenic, can generate levels of informativeness greater than 98%. We concluded that the strategy for carrier testing would be a good alternative in genetic counselling for hemophilia A, but its limitations must be carefully taken into account.

[Activated C protein resistance: laboratory study and prevalence of the defect in the Chilean population]. / Resistencia a la proteina C activada: estudio de laboratorio y prevalencia del defecto en la población chilena.

Activated protein C resistance (APCR) or Factor V Leiden has been recently described as the most prevalent hemostatic abnormality associated with venous thrombosis. In patients with familial thrombophilia, the prevalence of APCR is 19-60% and around 20% in sporadic venous thrombosis. APCR is usually measured by the degree of prolongation of Activated Partial Thromboplastin Time (APTT) on patient's plasma, induced by addition of APC in comparison to normal plasma. At the molecular level the defect is caused by a single-point mutation in the gene for factor V (FV) (G1.691-->A), that predicts the replacement of Arg506 by Glutamine. This mutation makes activated factor V resistant to inactivation by APC. Since the prevalence of the defect is highly variable among different populations, the objective of this work was to study its frequency in our population and in patients with thrombophilia. We defined the normal range for APTT ratio (APTT + APC/APTT - APC) in a group of 73 healthy volunteers in whom the presence of FV Q506 mutation was searched using Mull enzyme digestion of PCR amplified genomic fragment containing the nucleotide 1.691. The lower limit of APTT ratio established in this group was 2.13. APCR was found in 6 out of 159 control subjects (3.8%) and in 14/50 (28%) of patients with thrombosis. In 13 cases as a single defect and in one associated to type I protein C deficiency. All the APCR patients and control subjects were heterozygotes by gene analysis. The results demonstrate that in our population APCR is also the most common defect associated with thrombosis, in accordance with a high prevalence in the population. The ability to screen for this defect will permit the identification of carriers that would benefit of preventive therapy at risk situations.

Oval and round window membrane changes in otitis media in the human. An ultrastructural study.

An ultrastructural study of oval and round window changes in otitis media in humans was done. Ten cases were evaluated. In this first ultrastructural study of oval and round windows in otitis media, done at different stages of the disease, the round window membrane changes were similar to those of the mucoperiostium. Morphologic evidence suggests that the round window membrane layers participate in absorption and secretion of substances to and from the inner ear, such that the entire membrane could play a role in a middle and inner ear "defense system." Although the middle ear side of the footplate of the stapes had histopathological changes, the vestibular side remained essentially unchanged.

Prevalence of microfissures in the human temporal bone: a report of 1000 temporal bones.

A total of 1000 human temporal bones were studied to determine the prevalence of two microfissures: 1. the one between the facial canal and the vestibule, 2. the microfissure between the round window niche (RWN) and the posterior semicircular canal (PSC). Additionally, this study compares the prevalence according to temporal bone age and sex. The microfissure between the facial canal and the vestibule was observed in 470 (47%) temporal bones, with a bilateral presence of 77.2%. The prevalence of this microfissure increases linearly with age. It was not found in any bone within the 0 to 2 age group. It was present in 3 (7.3%) bones from the 2 to 9 age group, as opposed to 374 (54.8%) bones from the 40 and over group. The microfissure between the RWN and the PSC was detected in 915 (91.5%) temporal bones. This second microfissure was found to be an overwhelmingly bilateral entity. The prevalence of this other microfissure also increases with age. This microfissure was also not present in any temporal bone within the 0 to 2 age group. It was found in 28 (68.3%) bones from the 2 to 9 age group, in contrast to 678 (99.4%) temporal bones from the 40+ group.

Prevalence of carotid canal dehiscence in the human middle ear: a report of 1000 temporal bones.

A total of 1000 human temporal bones were used to study the prevalence of carotid canal dehiscence, microdehiscence, and thin bony coverage. Additionally, this study compares the prevalence according to sex and temporal bone age. A carotid canal dehiscence was detected in 77 (7.7%) bones. It was present bilaterally in 23.2% of the paired temporal bones. The prevalence of carotid canal dehiscence decreases with increasing temporal bone age. It was found in 10 (15.9%) bones in the younger than 2 age group, as opposed to 43 (6.3%) bones from the 40 and older group. The concept of microdehiscence of the carotid canal is introduced. A carotid canal microdehiscence was found in 74 (7.4%) bones. Microdehiscences were noted to occur bilaterally in 12.3% of the paired bones. The prevalence of carotid canal microdehiscence also decreases with increasing temporal bone age. It was detected in 7 (11.1%) bones in the younger than 2 age group, in contrast to 51 (7.5%) bones in the 40 and older group. A total of 134 (15.5%) temporal bones were found to have a thin bony coverage, without the presence of a dehiscence or microdehiscence. The prevalence of thin coverage was noted to increase linearly with age. A thin carotid canal was found in 2 (8.3%) bones from the younger than 2 age group, whereas 113 (17.3%) temporal bones from the 40 and older group exhibited this entity. To the best of our knowledge, this is the first systematic study of histologic sections of a large number of temporal bones that looks at these entities.

Sustained release of antimicrobials in the middle ear using a biodegradable support.

The ototoxicity of a poly-L-lactic acid biodegradable support incorporating a therapeutically releasable amount of ampicillin was studied. This device has a shape that allows placement in the middle ear via a myringotomy incision. Once in the middle ear, it expands without mechanical interference and provides extended release of ampicillin. In vitro studies documented sustained release of ampicillin, and in vivo efficacy was demonstrated in otitis media induced in chinchillas and cats. Previous histopathologic studies showed a lack of inflammatory reaction from the device itself and documented its biodegradable characteristics. There was no evidence of ototoxicity on morphometry of the organ of Corti (hair cell counts) in chinchillas exposed to these devices for 3 weeks with and without ampicillin.

Overall view and rationale for surgical alternatives for incapacitating peripheral vertigo.

This article describes an overall view and the rationale for the different surgical alternatives available for treating incapacitating peripheral vertigo. The authors emphasize that the number of patients requiring surgery is very small, and that the surgical procedures available do not provide 100% relief nor are they free of risks. A need for individualized attention to patients and a careful selection of the most appropriate surgical procedure for each particular case are strongly stressed.

Prevalence of facial canal dehiscence and of persistent stapedial artery in the human middle ear: a report of 1000 temporal bones.

A total of 1000 temporal bones were used to study the prevalence of facial canal dehiscence and of persistent stapedial artery in detail. Of the temporal bones studied, 560 (56%) contained at least one facial canal dehiscence. There was a 76.3% prevalence of bilaterality of this canal wall gap. The most common site of dehiscence was the oval window area. The concept of microdehiscence of the facial canal is introduced. One third of the temporal bones observed had a microdehiscence of the facial canal, usually located at the oval window area (74.9%) and found bilaterally 40% of the time. The authors found a 0.48% prevalence (5 out of 1045) of persistent stapedial artery. This is the first histological study of temporal bones to report a prevalence of this vascular anomaly.