Accuracy and complications associated with the freehand C-1 lateral mass screw fixation technique: a radiographic and clinical assessment

2013 ◽  
Vol 18 (4) ◽  
pp. 372-377 ◽  
Author(s):  
Yong Hu ◽  
Christopher K. Kepler ◽  
Todd J. Albert ◽  
Zhen-shan Yuan ◽  
Wei-hu Ma ◽  
...  
Keyword(s):  
Spinal Canal ◽  
Ct Scanning ◽  
Ct Scans ◽  
Screw Placement ◽  
Type I ◽  
Type Ii ◽  
Lateral Mass ◽  
Type Iii ◽  
Clinical Records ◽  
The Ideal

Object The aims of this study were to evaluate a large series of posterior C-1 lateral mass screws (LMSs) to determine accuracy based on CT scanning findings and to assess the perioperative complication rate related to errant screw placement. Methods Accuracy of screw placement was evaluated using postoperative CT scans obtained in 196 patients with atlantoaxial instability. Radiographic analysis included measurement of preoperative and postoperative CT scans to evaluate relevant anatomy and classify accuracy of instrumentation placement. Screws were graded using the following definitions: Type I, screw threads completely within the bone (ideal); Type II, less than half the diameter of the screw violates the surrounding cortex (safe); and Type III, clear violation of transverse foramen or spinal canal (unacceptable). Results A total of 390 C-1 LMSs were placed, but 32 screws (8.2%) were excluded from accuracy measurements because of a lack of postoperative CT scans; patients in these cases were still included in the assessment of potential clinical complications based on clinical records. Of the 358 evaluable screws with postoperative CT scanning, 85.5% of screws (Type I) were rated as being in the ideal position, 11.7% of screws (Type II) were rated as occupying a safe position, and 10 screws (2.8%) were unacceptable (Type III). Overall, 97.2% of screws were rated Type I or II. Of the 10 screws that were unacceptable on postoperative CT scans, there were no known associated neurological or vertebral artery (VA) injuries. Seven unacceptable screws erred medially into the spinal canal, and 2 patients underwent revision surgery for medial screws. In 2 patients, unilateral C-1 LMSs penetrated the C-1 anterior cortex by approximately 4 mm. Neither patient with anterior C-1 penetration had evidence of internal carotid artery or hypoglossal nerve injury. Computed tomography scanning showed partial entry of C-1 LMSs into the VA foramen of C-1 in 10 cases; no occlusion, associated aneurysm, or fistula of the VA was found. Two patients complained of postoperative occipital neuralgia. This was transient in one patient and resolved by 2 months after surgery. The second patient developed persistent neuralgia, which remained 2 years after surgery, necessitating referral to the pain service. Conclusions The technique for freehand C-1 LMS fixation appears to be safe and effective without intraoperative fluoroscopy guidance. Preoperative planning and determination of the ideal screw insertion point, the ideal trajectory, and screw length are the most important considerations. In addition, fewer malpositioned screws were inserted as the study progressed, suggesting a learning curve to the technique.

Relevance of early head CT scans following neurosurgical procedures: an analysis of 892 intracranial procedures at Rush University Medical Center

2014 ◽  
Vol 121 (2) ◽  
pp. 307-312 ◽  
Author(s):  
Ricardo B. V. Fontes ◽  
Adam P. Smith ◽  
Lorenzo F. Muñoz ◽  
Richard W. Byrne ◽  
Vincent C. Traynelis
Keyword(s):  
Operating Room ◽  
Neurological Examination ◽  
Medical Center ◽  
Ct Scanning ◽  
Ct Scans ◽  
Type I ◽  
Type Ii ◽  
Head Ct ◽  
Ct Findings ◽  
Neurological Change

Object Early postoperative head CT scanning is routinely performed following intracranial procedures for detection of complications, but its real value remains uncertain: so-called abnormal results are frequently found, but active, emergency intervention based on these findings may be rare. The authors' objective was to analyze whether early postoperative CT scans led to emergency surgical interventions and if the results of neurological examination predicted this occurrence. Methods The authors retrospectively analyzed 892 intracranial procedures followed by an early postoperative CT scan performed over a 1-year period at Rush University Medical Center and classified these cases according to postoperative neurological status: baseline, predicted neurological change, unexpected neurological change, and sedated or comatose. The interpretation of CT results was reviewed and unexpected CT findings were classified based on immediate action taken: Type I, additional observation and CT; Type II, active nonsurgical intervention; and Type III, surgical intervention. Results were compared between neurological examination groups with the Fisher exact test. Results Patients with unexpected neurological changes or in the sedated or comatose group had significantly more unexpected findings on the postoperative CT (p < 0.001; OR 19.2 and 2.3, respectively) and Type II/III interventions (p < 0.001) than patients at baseline. Patients at baseline or with expected neurological changes still had a rate of Type II/III changes in the 2.2%–2.4% range; however, no patient required an immediate return to the operating room. Conclusions Over a 1-year period in an academic neurosurgery service, no patient who was neurologically intact or who had a predicted neurological change required an immediate return to the operating room based on early postoperative CT findings. Obtaining early CT scans should not be a priority in these patients and may even be cancelled in favor of MRI studies, if the latter have already been planned and can be performed safely and in a timely manner. Early postoperative CT scanning does not assure an uneventful course, nor should it replace accurate and frequent neurological checks, because operative interventions were always decided in conjunction with the neurological examination.

Primary extradural meningiomas: a report on nine cases and review of the CT-era literature

2000 ◽  
Vol 93 (6) ◽  
pp. 940-950 ◽  
Author(s):  
Frederick F. Lang ◽  
O. Kenneth Macdonald ◽  
Gregory N. Fuller ◽  
Franco DeMonte
Keyword(s):  
Skull Base ◽  
Death Rate ◽  
Benign Tumors ◽  
Data Sets ◽  
Type I ◽  
Type Ii ◽  
Content Type ◽  
Type Iii ◽  
Clinical Records ◽  
Fine Print

Object. Primary meningiomas arising outside the intracranial compartment (primary extradural meningiomas [PEMs]) are rare tumors. To develop a better understanding of these tumors and to establish a comprehensive classification scheme for them, the authors analyzed a series of patients treated at the M. D. Anderson Cancer Center (MDACC) and reviewed all cases reported in the English-language literature since the inception of the use of computerized tomography (CT) scanning.Methods. Clinical records, results of radiographic studies, and histological slides were reviewed for all cases of PEM at MDACC. Demographic features, symptoms, tumor location, histological grade, and patient outcome were assessed in all cases. A comprehensive literature search identified 168 PEMs in 142 patients reported during the CT era. These reports were also analyzed for common features. Tumors for both data sets were classified as purely extracalvarial (Type I), purely calvarial (Type II), and calvarial with extracalvarial extension (Type III). Type II and Type III tumors were further categorized as convexity (C) or skull base (B) lesions.The incidence of PEMs at MDACC was 1.6%, which was consistent with the rate reported in the literature. In both data sets, the male/female ratio was nearly 1:1. The most common presenting symptom was a gradually expanding mass. The age of patients at diagnosis of PEM was bimodal, peaking during the second decade and during the fifth to seventh decades. In all MDACC cases and in 90% of those reported in the literature the PEMs were located in the head and neck. The majority of tumors originated in the skull (70%).In the MDACC series and in the literature review, the majority (67% and 89%, respectively) of tumors were histologically benign. Although fewer PEMs were malignant or atypical (33% at MDACC and 11% in the literature), their incidence was higher than that observed for primary intracranial meningiomas. Distant metastasis was not a common feature reported for patients with PEMs (6% in the literature).Outcome data were available in 96 of the cases culled from the CT-era literature. The combination of the MDACC data and the data obtained from the literature demonstrated that patients with benign Type IIB or Type IIIB lesions were more likely to experience recurrence than patients with benign Type IIC or Type IIIC tumors (26% compared with 0%, p < 0.05). The more aggressive atypical and malignant tumors were associated with a statistically significant higher death rate (29%) relative to benign tumors (4.8% death rate, p < 0.004).Conclusions. Defining a tumor as a PEM is dependent on the tumor's relation to the dura mater and the extent and direction of its growth. Classification of PEMs as calvarial or extracalvarial and as convexity or skull base lesions correlates well with clinical outcome.

Airway Development Relevant to Cranial Vault Suture Synostosis Subtype in Apert Syndrome

FACE ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 89-96
Author(s):  
Xiaona Lu ◽  
Antonio Jorge Forte ◽  
Kitae Eric Park ◽  
Omar Allam ◽  
Derek M. Steinbacher ◽  
...  
Keyword(s):  
Nasal Cavity ◽  
Cranial Base ◽  
Apert Syndrome ◽  
Ct Scans ◽  
Type I ◽  
Nasal Airway ◽  
Type Ii ◽  
Cross Sectional ◽  
Type Iii ◽  
Pharyngeal Airway

Introduction: Based on an established classification system of Apert syndrome subtypes, we aim to directly analyze the correlation between segmented airway volume changes and different skull suture synostosis, so as to provide individualized surgical planning for each subgroup of Apert patients. Methods: CT scans of 44 unoperated Apert syndrome and 53 controls were included and subgrouped as: type I. Bilateral coronal synostosis; type II. Pansynostosis; type III. Perpendicular combinations of cranial vault synostosis. CT scans were measured using Mimics and 3-matics software. Results: Type I developed a 41% ( P = .116) reduction in the nasal cavity, yet a normal sized pharyngeal airway. The reduced nasal airway was linked to the decreased cross sectional area ( r = 0.598, P = .001), vertical dimension ( r = 0.719, P < .001), and narrower width ( r = 0.727, P < .001). Type II developed proportionally reduced nasal airway and pharyngeal airway volumes (both 47%, P = .113 and P = .041), along with the proportionally restricted cross sectional areas at choana and condylion levels by 62 to 65%. This reduction is related to the cranial base length ( r = 0.712, P = .048), and also cranial base angulation ( r = 0.780, P = .023). Nasal and pharyngeal airway developed normal volume in type III. However, the cross sectional areas at the gonion level diminished by 74% ( P < .001). Conclusion: Airway development is influenced by subtype of Apert suture synostosis. Type II pansynostosis Apert patients developed synchronous reduced nasal and pharyngeal airways, which is correlated with the slightly flattened cranial base. Type I bicoronal patients have a smaller nasal cavity, but normally sized hypopharynx. Yet, type III patients developed normal nasopharyngeal airway volume overall.

Microsurgical anatomy of the superior petrosal venous complex: new classifications and implications for subtemporal transtentorial and retrosigmoid suprameatal approaches

2007 ◽  
Vol 106 (6) ◽  
pp. 1041-1050 ◽  
Author(s):  
Necmettin Tanriover ◽  
Hiroshi Abe ◽  
Albert L. Rhoton ◽  
Masatou Kawashima ◽  
Galip Z. Sanus ◽  
...  
Keyword(s):  
Petrous Apex ◽  
Type I ◽  
Microsurgical Anatomy ◽  
Type Ii ◽  
Drainage Pattern ◽  
Type Iii ◽  
Working Space ◽  
Surgical Exposure ◽  
Transtentorial Approach ◽  
The Ideal

Object The purpose of this study was to define the patterns of drainage of the superior petrosal venous complex (SPVC) along the petrous ridge in relation to the Meckel cave and internal acoustic meatus (IAM) and to delineate its effect on the surgical exposures obtained in subtemporal transtentorial and retrosigmoid suprameatal approaches. Methods The patterns of drainage of the SPVC along the petrous ridge were characterized according to their relation to the Meckel cave and the IAM based on an examination of 30 hemispheres. Subtemporal transtentorial and retro-sigmoid suprameatal approaches were performed in three additional cadavers to demonstrate the effect of the drainage pattern on the surgical exposures. Conclusions The SPVC emptied into the superior petrosal sinus (SPS) within a distance of 1 cm from the midpoint of the Meckel cave. The patterns of drainage of the SPVC were classified into three groups. Type I emptied into the SPS above and lateral to the boundaries of the IAM. The most common type, Type II, emptied between the lateral limit of the trigeminal nerve at the Meckel cave and the medial limit of the facial nerve at the IAM, within an area of approximately 13 mm. Type III emptied into the SPS above or medial to the Meckel cave. The ideal SPVC for a subtemporal transtentorial approach (with or without anterior extradural petrosectomy) seems to be a Type I. In SPVC Type III and those Type II cases in which the SPVC is located near the Meckel cave, the amount of working space is significantly limited in a subtemporal transtentorial approach. In contrast, the ideal type of SPVC for a retrosigmoid suprameatal approach would be a Type III, and the SPVC must be divided in the majority of Type I and II cases for a satisfactory surgical exposure along the Meckel cave and middle fossa dura. The proposed modified classification system and its effect on the surgical exposure may aid in planning the approach directed along the petrous apex and may reduce the probability of venous complications.

scholarly journals Classification of unilateral cervical locked facet with or without lateral mass-facet fractures and a retrospective observational study of 55 cases

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chao Tang ◽  
Yuan He Fan ◽  
Ye Hui Liao ◽  
Qiang Tang ◽  
Fei Ma ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Closed Reduction ◽  
Injury Mechanism ◽  
Neurological Deficits ◽  
Type I ◽  
Type Ii ◽  
Lateral Mass ◽  
Fracture Type ◽  
Type Iii ◽  
Articular Process

AbstractThis study describes a morphology-based unilateral cervical facet interlocking classification in an attempt to clarify the injury mechanism, instability, neurological deficits, radiological features, and determine optimum management strategies for these injuries. A total of 55 patients with unilateral cervical locked facet (UCLF) involving C3 to C7 were identified between January 1, 2012 and December 1, 2019. The injuries were classified into three types, and they were further divided into six subtypes using three-dimensional computed tomography. The injury mechanism, clinical features, neurological deficits, and imaging characteristics were analyzed, and the appropriate treatment strategies for UCLF were discussed. UCLFs were divided into the following six subtypes: UCLF without lateral mass-facet fracture (type I) in nine cases, with superior articular process fracture (type II A) in 22, with inferior articular process fracture (type II B) in seven, both superior and inferior articular process fractures (type II C) in four, with lateral mass splitting fracture (type III A) in three, and with lateral mass comminution fractures (type III B) in ten. A total of 22 (40.0%) of the 55 patients presented with radiculopathy, and 23 patients (41.8%) had spinal cord injuries. The subtype analyses showed high rates of radiculopathy in types II A (68.2%) and II C (75.0%), as well as significant spinal cord injury in types I (77.8%) and III (61.5%). Destruction of the facet capsule was observed in all patients, but the injury of disc, ligamentous complex, and vertebra had a significant difference among the types or subtypes. The instability parameters of the axial rotation angle, segmental kyphosis, and sagittal displacement showed significant differences in various types of UCLF. Closed reduction by preoperative and intraoperative general anesthesia traction was achieved in 27 patients (49.1%), and successful rate of closed reduction in type I (22.2%) was significantly lower than that in type II (51.5%) and type III (61.5%). A total of 35 of 55 patients underwent a single anterior fixation and fusion, 10 patients were treated with posterior pedicle and (or) lateral mass fixation, and combined surgery was performed in ten patients. Ten patients (18.2%) with a poor outcome were observed after first surgery. Among them, 3 patients treated with a single anterior surgery had persistent or aggravated radiculopathy and posterior approach surgery with ipsilateral facet resection, foramen enlargement, and pedicle and (or) lateral mass screw fixation was performed immediately, 5 patients treated with a short-segment posterior surgery showed mild late kyphosis deformity, and 2 patients with vertebral malalignment were encountered after anterior single-level fusion during the follow-up. This retrospective study indicated that UCLF is a rotationally unstable cervical spine injury. The classification proposed in this study will contribute to understanding the injury mechanism, radiological characteristics, and neurological deficits in various types of UCLF, which will help the surgeons to evaluate the preoperative closed reduction and guide the selection of surgical approach and fusion segment.

Three-Dimensional Evaluation and Classification of the Anatomy Variations of Vertebral Artery at the Craniovertebral Junction in 120 Patients of Basilar Invagination and Atlas Occipitalization

2019 ◽  
Vol 17 (6) ◽  
pp. 594-602 ◽  
Author(s):  
Teng Li ◽  
Yi-heng Yin ◽  
Guang-yu Qiao ◽  
Hua-wei Wang ◽  
Xin-guang Yu
Keyword(s):  
Craniovertebral Junction ◽  
Basilar Invagination ◽  
Posterior Arch ◽  
Type I ◽  
Type Ii ◽  
Lateral Mass ◽  
Type Iii ◽  
Different Types ◽  
Type V ◽  
Abnormal Anatomy

Abstract BACKGROUND Patients with basilar invagination and atlas occipitalization usually present abnormal anatomy of the vertebral arteries (VAs) at the craniovertebral junction (CVJ). OBJECTIVE To describe and further classify different types of VA variations at the CVJ with 3D visualization technology. METHODS One hundred twenty patients with basilar invagination and atlas occipitalization who had undergone 3-dimensional computed tomographic angiography (3D-CTA) were retrospectively studied. Imaging data were processed via the separating, fusing, opacifying, and false-coloring-volume rendering technique. Abnormal anatomy of the VA at the CVJ was categorized and related anatomic parameters were measured. RESULTS Seven different types were classified. Type I, VAs enter the cranium after leaving VA groove on the posterior arch of atlas (26.7% of 240 sides); Type II, VAs enter an extraosseous canal created in the assimilated atlas lateral mass-occipital condyle complex before reaching the cranium (53.3%); Type III, VA courses above the axis facet or curves below the atlas lateral mass then enter the cranium (11.7%); Type IV, VAs enter the spinal canal under the axis lamina (1.3%); Type V, high-riding VA (31.3%); Type VI, fenestrated VA (2.9%); Type VII, absent VA (4.2%). Distance from the canal of Type II VA to the posterior facet surface of atlas lateral mass (5.51 ± 2.17 mm) means a 3.5-mm screw can be safely inserted usually. Shorter distance from the midline (13.50 ± 4.35) illustrates potential Type III VA injury during exposure. Decreased height and width of axis isthmus in Type V indicate increased VA injury risks. CONCLUSION Seven types of VA variations were described, together with valuable information helpful to minimize VA injury risk intraoperatively.

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

scholarly journals Perforator preservation technologies (PPT) based on a new neuro-interventional classification in endovascular treatment of perforator involving aneurysms (piANs)

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chen Li ◽  
Ao-Fei Liu ◽  
Han-Cheng Qiu ◽  
Xianli Lv ◽  
Ji Zhou ◽  
...  
Keyword(s):  
Endovascular Therapy ◽  
Saccular Aneurysm ◽  
Type I ◽  
Type Ii ◽  
Fusiform Aneurysm ◽  
Type Iii ◽  
Perforating Artery ◽  
Protection Technology ◽  
Perforating Arteries

Abstract Background Treatment of perforator involving aneurysm (piAN) remains a challenge to open and endovascular neurosurgeons. Our aim is to demonstrate a primary outcome of endovascular therapy for piANs with the use of perforator preservation technologies (PPT) based on a new neuro-interventional classification. Methods The piANs were classified into type I: aneurysm really arises from perforating artery, type II: saccular aneurysm involves perforating arteries arising from its neck (IIa) or dome (IIb), and type III: fusiform aneurysm involves perforating artery. Stent protection technology of PPT was applied in type I and III aneurysms, and coil-basket protection technology in type II aneurysms. An immediate outcome of aneurysmal obliteration after treatment was evaluated (satisfactory obliteration: the saccular aneurysm body is densely embolized (I), leaving a gap in the neck (IIa) or dome (IIb) where the perforating artery arising; fusiform aneurysm is repaired and has a smooth inner wall), and successful perforating artery preservation was defined as keeping the good antegrade flow of those perforators on postoperative angiography. The periprocedural complication was closely monitored, and clinical and angiographic follow-ups were performed. Results Six consecutive piANs (2 ruptured and 4 unruptured; 1 type I, 2 type IIa, 2 type IIb, and 1 type III) in 6 patients (aged from 43 to 66 years; 3 males) underwent endovascular therapy between November 2017 and July 2019. The immediate angiography after treatment showed 6 aneurysms obtained satisfactory obliteration, and all of their perforating arteries were successfully preserved. During clinical follow-up of 13–50 months, no ischemic or hemorrhagic event of the brain occurred in the 6 patients, but has one who developed ischemic event in the territory of involving perforators 4 h after operation and completely resolved within 24 h. Follow-up angiography at 3 to 10M showed patency of the parent artery and perforating arteries of treated aneurysms, with no aneurysmal recurrence. Conclusions Our perforator preservation technologies on the basis of the new neuro-interventional classification seem feasible, safe, and effective in protecting involved perforators while occluding aneurysm.

scholarly journals Intracellular and Extracellular Markers of Lethality in Osteogenesis Imperfecta: A Quantitative Proteomic Approach

2021 ◽  
Vol 22 (1) ◽  
pp. 429
Author(s):  
Luca Bini ◽  
Domitille Schvartz ◽  
Chiara Carnemolla ◽  
Roberta Besio ◽  
Nadia Garibaldi ◽  
...  
Keyword(s):  
Osteogenesis Imperfecta ◽  
Type I Collagen ◽  
Type I ◽  
Tandem Mass ◽  
Type Ii ◽  
Type Iii ◽  
Bioinformatic Tools ◽  
Proteomic Approach ◽  
Fibrillin 1 ◽  
Heritable Disorder

Osteogenesis imperfecta (OI) is a heritable disorder that mainly affects the skeleton. The inheritance is mostly autosomal dominant and associated to mutations in one of the two genes, COL1A1 and COL1A2, encoding for the type I collagen α chains. According to more than 1500 described mutation sites and to outcome spanning from very mild cases to perinatal-lethality, OI is characterized by a wide genotype/phenotype heterogeneity. In order to identify common affected molecular-pathways and disease biomarkers in OI probands with different mutations and lethal or surviving phenotypes, primary fibroblasts from dominant OI patients, carrying COL1A1 or COL1A2 defects, were investigated by applying a Tandem Mass Tag labeling-Liquid Chromatography-Tandem Mass Spectrometry (TMT LC-MS/MS) proteomics approach and bioinformatic tools for comparative protein-abundance profiling. While no difference in α1 or α2 abundance was detected among lethal (type II) and not-lethal (type III) OI patients, 17 proteins, with key effects on matrix structure and organization, cell signaling, and cell and tissue development and differentiation, were significantly different between type II and type III OI patients. Among them, some non–collagenous extracellular matrix (ECM) proteins (e.g., decorin and fibrillin-1) and proteins modulating cytoskeleton (e.g., nestin and palladin) directly correlate to the severity of the disease. Their defective presence may define proband-failure in balancing aberrances related to mutant collagen.

scholarly journals Brachial supporting structure of Spiriferida (Brachiopoda)

2020 ◽  
pp. 1-15
Author(s):  
Zhiwei Yuan ◽  
Wen Guo ◽  
Dan Lyu ◽  
Yuanlin Sun
Keyword(s):  
Mantle Cavity ◽  
Family Type ◽  
Type I ◽  
Type Ii ◽  
Feeding Apparatus ◽  
Single Family ◽  
Supporting Structure ◽  
Type Iii ◽  
Type Iv ◽  
Evolutionary Lineages

Abstract The filter-feeding organ of some extinct brachiopods is supported by a skeletal apparatus called the brachidium. Although relatively well studied in Atrypida and Athyridida, the brachidial morphology is usually neglected in Spiriferida. To investigate the variations of brachidial morphology in Spiriferida, 65 species belonging to eight superfamilies were analyzed. Based on the presence/absence of the jugal processes and normal/modified primary lamellae of the spiralia, four types of brachidium are recognized. Type-I (with jugal processes) and Type-II (without jugal processes), both having normal primary lamellae, could give rise to each other by losing/re-evolving the jugal processes. Type-III, without jugal processes, originated from Type-II through evolution of the modified lateral-convex primary lamellae, and it subsequently gave rise to Type-IV by evolving the modified medial-convex primary lamellae. The evolution of brachidia within individual evolutionary lineages must be clarified because two or more types can be present within a single family. Type-III and Type-IV are closely associated with the prolongation of the crura, representing innovative modifications of the feeding apparatus in response to possible shift in the position of the mouth towards the anterior, allowing for more efficient feeding on particles entering the mantle cavity from the anterior gape. Meanwhile, the modified primary lamellae adjusted/regulated the feeding currents. The absence of spires in some taxa with Type-IV brachidium might suggest that they developed a similar lophophore to that in some extant brachiopods, which can extend out of the shell.

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