Discovery of TRPA1 Antagonist : Derisking Preclinical Toxicity and Aldehyde Oxidase Metabolism with a Potential First-in-Class Therapy for Respiratory Disease

Transient receptor potential ankyrin 1 (TRPA1) is a nonselective calcium ion channel highly expressed in the primary sensory neurons, functioning as a polymodal sensor for exogenous and endogenous stimuli, and has been implicated in neuropathic pain and respiratory disease. Herein, we describe the optimization of potent, selective, and orally bioavailable TRPA1 small molecule antagonists with strong in vivo target engagement in rodent models. Several lead molecules in preclinical single- and short-term repeat-dose toxicity studies exhibited profound prolongation of coagulation parameters. Based on a thorough investigative toxicology and clinical pathology analysis, anticoagulation effects in vivo are hypothesized to be manifested by a metabolite─generated by aldehyde oxidase (AO)─possessing a similar pharmacophore to known anticoagulants (i.e., coumarins, indandiones). Further optimization to block AO-mediated metabolism yielded compounds that ameliorated coagulation effects in vivo, resulting in the discovery and advancement of clinical candidate GDC-6599, currently in Phase II clinical trials for respiratory indications.

Investigating the Utility of Humanized Pregnane X Receptor-Constitutive Androstane Receptor-CYP3A4/7 Mouse Model to Assess CYP3A-Mediated Induction

Clinical induction liability is assessed with human hepatocytes. However, underpredictions in the magnitude of clinical induction have been reported. Unfortunately, in vivo studies in animals do not provide additional insight because of species differences in drug metabolizing enzymes and their regulatory pathways. To circumvent this limitation, transgenic animals expressing human orthologs were developed. The aim of this work was to investigate the utility of mouse models expressing human orthologs of pregnane X receptor, constitutive androstane receptor, and CYP3A4/7 (Tg-Composite) in evaluating clinical induction. Rifampin, efavirenz, and pioglitazone, which were employed to represent strong, moderate, and weak inducers, were administered at multiple doses to Tg-Composite animals. In vivo CYP3A activity was monitored by measuring changes in the exposure of the CYP3A probe substrate triazolam. After the in vivo studies, microsomes were prepared from their livers to measure changes of in vitro CYP3A4 activity. In both in vivo and in vitro, distinction of clinic induction was recapitulated as rifampin yielded the greatest inductive effect followed by efavirenz and pioglitazone. Interestingly, with rifampin, in vivo CYP3A activity was approximately 4-fold higher than in vitro activity. Conversely, there was no difference between in vivo and in vitro CYP3A activity with efavirenz. These findings are consistent with the report that, although rifampin exhibits differential inductive effects between the intestines and liver, efavirenz does not. These data highlight the promise of transgenic models, such as Tg-Composite, to complement human hepatocytes to enhance the translatability of clinical induction as well as become a powerful tool to further study mechanisms of drug disposition. SIGNIFICANCE STATEMENT: Underprediction of the magnitude of clinical induction when using human hepatocytes has been reported, and transgenic models may improve clinical translatability. The work presented here showcases the human orthologs of pregnane X receptor, constitutive androstane receptor, and CYP3A4/7 model, which was able to recapitulate the magnitude of clinical induction and to differentiate tissue-dependent induction observed with rifampin but not with efavirenz. These results not only foreshadow the potential application of such transgenic models in assessing clinical induction but also in further investigation of the mechanism of drug disposition.

Tetrahydrofuran-Based Transient Receptor Potential Ankyrin 1 (TRPA1) Antagonists: Ligand-Based Discovery, Activity in a Rodent Asthma Model, and Mechanism-of-Action via Cryogenic Electron Microscopy

Transient receptor potential ankyrin 1 (TRPA1) is a nonselective calcium-permeable ion channel highly expressed in the primary sensory neurons functioning as a polymodal sensor for exogenous and endogenous stimuli and has generated widespread interest as a target for inhibition due to its implication in neuropathic pain and respiratory disease. Herein, we describe the optimization of a series of potent, selective, and orally bioavailable TRPA1 small molecule antagonists, leading to the discovery of a novel tetrahydrofuran-based linker. Given the balance of physicochemical properties and strong in vivo target engagement in a rat AITC-induced pain assay, compound 20 was progressed into a guinea pig ovalbumin asthma model where it exhibited significant dose-dependent reduction of inflammatory response. Furthermore, the structure of the TRPA1 channel bound to compound 21 was determined via cryogenic electron microscopy to a resolution of 3 Å, revealing the binding site and mechanism of action for this class of antagonists.

A TRPA1 inhibitor suppresses neurogenic inflammation and airway contraction for asthma treatment

Despite the development of effective therapies, a substantial proportion of asthmatics continue to have uncontrolled symptoms, airflow limitation, and exacerbations. Transient receptor potential cation channel member A1 (TRPA1) agonists are elevated in human asthmatic airways, and in rodents, TRPA1 is involved in the induction of airway inflammation and hyperreactivity. Here, the discovery and early clinical development of GDC-0334, a highly potent, selective, and orally bioavailable TRPA1 antagonist, is described. GDC-0334 inhibited TRPA1 function on airway smooth muscle and sensory neurons, decreasing edema, dermal blood flow (DBF), cough, and allergic airway inflammation in several preclinical species. In a healthy volunteer Phase 1 study, treatment with GDC-0334 reduced TRPA1 agonist-induced DBF, pain, and itch, demonstrating GDC-0334 target engagement in humans. These data provide therapeutic rationale for evaluating TRPA1 inhibition as a clinical therapy for asthma.

Preclinical Safety Assessment of a Highly Selective and Potent Dual Small-Molecule Inhibitor of CBP/P300 in Rats and Dogs

Cyclic adenosine monophosphate-response element (CREB)-binding protein (CBP) and EP300E1A-binding protein (p300) are members of the bromodomain and extraterminal motif (BET) family. These highly homologous proteins have a key role in modulating transcription, including altering the status of chromatin or through interactions with or posttranslational modifications of transcription factors. As CBP and p300 have known roles for stimulating c-Myc oncogenic activity, a small-molecule inhibitor, GNE-781, was developed to selectively and potently inhibit the CBP/p300 bromodomains (BRDs). Genetic models have been challenging to develop due to embryonic lethality arising from germline homozygous mutations in either CBP or P300. Hence, the purpose of this study was to characterize the role of dual inhibition of these proteins in adult rats and dogs. Repeat dose toxicity studies were conducted, and toxicologic and pathologic end points were assessed. GNE-781 was generally tolerated; however, marked effects on thrombopoiesis occurred in both species. Evidence of inhibition of erythroid, granulocytic, and lymphoid cell differentiation was also present, as well as deleterious changes in gastrointestinal and reproductive tissues. These findings are consistent with many preclinical (and clinical) effects reported with BET inhibitors targeting BRD proteins; thus, the current study findings indicate a likely important role for CBP/p300 in stem cell differentiation.

Magnetic resonance imaging findings of golf-related injuries

Injuries related to participation in golf are becoming more common given the increasing popularity of the sport itself. Golf is considered to be an activity associated with a moderate risk for sports injuries. Golf injuries are usually attributable to overuse or traumatic mechanisms and primarily occur at the elbow, wrist, shoulder, and lumbar spine. None of these injuries are unique to golf, but each of these injuries represent the most common injuries associated with golfing. This article reviews a wide range of injuries that are encountered in golfers and describes the magnetic resonance imaging findings of each of these injuries.

Assessing hERG channel inhibition using PatchXpress

PatchXpress, an automated 16-channel parallel patch clamp system, was used to determine inhibition of human ether-a-go-go related gene (hERG) potassium channels by known blockers. A monoclonal cell line stably expressing hERG potassium channels was generated in CHO-K1 cells. Results were compared to conventional patch clamp experiments using similar voltage protocols and solutions. Success rates were evaluated for cell recordings under a variety of conditions, including Accumax versus trypsin treatment to harvest cells, single versus double compound additions, and polystyrene versus glass-coated compound plates. Finally, polystyrene versus glass-coated compound plates were evaluated, and the authors found that for some compounds (but not all), preparation of compound samples in glass-coated plates resulted in inhibition that more closely matched data obtained by conventional experiments.

Magnetic resonance imaging of the collateral ligaments and the anatomic quadrants of the knee

Injuries to the lateral and medial supporting structures of the knee can be significantly disabling and somewhat difficult to detect and evaluate clinically. An accurate imaging evaluation of these structures requires the use of the appropriate MR imaging sequences and the detailed knowledge of the anatomic structures that are present in these locations. Normal function is dependent on the integrity of the complex functional structures and effective clinical treatment, including surgical repair, of these structures is predicated on an optimal diagnostic evaluation. A successful diagnostic evaluation can expedite treatment and provide the best opportunity for a favorable long-term outcome.

Case for diagnosis. Elbow synovial fold syndrome

The following report reviews presentation, pathophysiology, characteristic imaging findings and current treatment options for elbow synovial fold syndrome. We present the case of a 17 year old female with clinical and MR imaging evidence of this condition and provide a comprehensive review of the limited peer-reviewed literature.

Systematic approach to interpretation of the lumbar spine MR imaging examination

The lumbar spine MR imaging study is one of the most frequently ordered MR imaging examinations in the United States. Numerous possible causes exist for low back pain, which contributes to the diagnostic challenge that imagers face in arriving at clinically relevant diagnoses from the anatomic information provided by MR imaging. In this article, the authors suggest a systematic approach to MR imaging interpretation. The evaluation may be altered, based on individual preferences and the specific clinical scenario. The author also highlights commonly encountered disease processes, pertinent MR imaging anatomy, and some common diagnostic pitfalls. Normal and abnormal spine MR images are also shown.

Extramedullary Intradural Spinal Tumors: A Pictorial Review

Defining the location of tumors and mass lesions of the spine in relation to the spinal cord and the dura is of the utmost importance as certain types of lesions tend to occur in certain locations. The differential diagnostic considerations will vary according to location of the mass lesion as will the treatment and prognosis of these various lesions. The category of extramedullary intradural masses includes a variety of lesions from meningiomas and nerve sheath tumors (neurofibromas, schwannomas) to less common tumors (hemangiopericytoma), metastases, benign tumors (lipoma, dermoid, epidermoid), inflammatory disorders (arachnoid adhesions, sarcoidosis), vascular lesions (spinal-dural arteriovenous fistula), and cystic lesions (perineural or Tarlov cysts). Characteristic magnetic resonance imaging findings are helpful for localization and characterization of these lesions before treatment, as well as for follow-up after treatment. We present a pictorial review of the various extramedullary intradural lesions of the spine, with pathologic correlation. We discuss imaging features that are typical for the various entities and describe various therapeutic options that are important considerations for surgical treatment of these lesions.

Magnetic resonance imaging of the collateral ligaments and the anatomic quadrants of the knee

Injuries to the lateral and medial supporting structures of the knee can be significantly disabling and somewhat difficult to detect and evaluate clinically. An accurate imaging evaluation of these structures requires the use of the appropriate MR imaging sequences and the detailed knowledge of the anatomic structures that are present in these locations. Normal function is dependent on the integrity of the complex functional structures and effective clinical treatment, including surgical repair, of these structures is predicated on an optimal diagnostic evaluation. A successful diagnostic evaluation can expedite treatment and provide the best opportunity for a favorable long-term outcome.

Bone Tumor Mimics: Avoiding Misdiagnosis

Whether discovered incidentally or as part of a focused diagnostic evaluation, the finding of a benign osseous lesion that has radiologic features resembling a bone tumor is not uncommon. Some of the more common benign and nonneoplastic entities that can sometimes be confused with tumors are the following: cortical desmoid, Brodie abscess, synovial herniation pit, pseudocyst, enostosis, intraosseous ganglion cyst, fibrous dysplasia, stress fracture, avulsion fracture (healing stage), bone infarct, myositis ossificans, brown tumor, and subchondral cyst. Accurate diagnosis and management of these lesions require a basic understanding of their epidemiology, clinical presentations, anatomic distributions, imaging features, differential considerations, and therapeutic options. This in-depth review of 13 potential bone tumor mimics will assist the radiologist in correctly identifying these benign lesions and in avoiding misdiagnosis and related morbidity. This review will also aid the radiologist in making appropriate recommendations to the referring physician for management or further imaging.

Calcaneal osteochondroma

Osteochondromas are essentially the most common primary bone tumors. These benign cartilage producing neoplasms are generally asymptomatic and have a relatively small potential for adverse effects. HME, the familial form of this tumor, is associated with a greater incidence of complications, the most significant of which is sarcomatous degeneration to secondary chondrosarcomas. Various imaging techniques can be used to characterize these lesions, but in the absence of symptoms or signs of complications, plain-film radiography is usually sufficient for diagnosis as this tumor has a characteristic radiographic appearance. Once this benign tumor is identified and more serious forms of tumor are ruled out, treatment is generally not needed. If a malignancy is suspected, however, complete surgical excision is the preferred treatment as this usually ensures long term survival.

Infected dermoid sinus tract mimicking recurrent sinusitis in an adolescent male

Nasal dermoid sinus cysts are the most common congenital midline nasofrontal masses, but they can easily be confused with simple recurrent sinusitis upon clinical presentation. We report the case of a 14-year-old male who was initially diagnosed with frontal sinusitis and treated with antibiotics but, after multiple episodes of recurrence, was later sent for imaging. Computed tomography and magnetic resonance imaging showed an infected dermoid sinus tract. Subsequent surgery removed the mass and pathologic investigation proved the diagnosis.

Disruption of the inferior popliteomeniscal ligamentous fascicle

The superior popliteomeniscal ligamentous fascicular injury association with lateral meniscal injury has been previously documented in the literature. Both superior and inferior popliteomeniscal ligamentous injuries have demonstrated associations with lateral meniscal motion, and these ligaments can be disrupted in posterolateral corner knee injuries as well. The current case demonstrates an unusual case of isolated inferior popliteomeniscal ligamentous fascicular injury. We examine and discuss its association with the superior popliteomeniscal ligament, posterolateral corner injuries and the fascicular relationship to lateral meniscal tears.

Magnetic resonance imaging of the rotator cuff interval

The rotator cuff interval (RCI) is an important and anatomically complex region of the rotator cuff that is critically important to normal glenohumeral function. Recognition of common pathologies in this region on imaging examinations is especially important as injuries may be difficult to detect on clinical examination and even at arthroscopy. Familiarity with the magnetic resonance imaging appearance of the normal and abnormal RCI and the ability to convey findings to orthopedic and sports medicine referrers are essential to facilitate prompt creation of effective treatment plans.

Carpal tunnel syndrome resulting from hydroxyapatite deposition

Hydroxyapatite deposition disease (HADD) is a rare cause of carpal tunnel syndrome. This is a case report of a 55-year-old male who presented with symptoms of carpal tunnel syndrome and was subsequently found to have HADD. The diagnosis of HADD is made by the identification of poorly defined cloudy calcifications on radiography of the hand and wrist. Management is usually with nonsteroidal anti-inflammatory drugs, but if the pain is refractory, more invasive methods are utilized.

The accuracy of magnetic resonance imaging in the assessment of glenohumeral articular degenerative disease

Degenerative joint disease is a major source of disability in the world with over 43 million individuals suffering from the affliction in the United States alone. It is the most common cause of activity limitation in individuals over 65 years of age. While much of the focus in recent years has been on osteoarthritis of the hips and knees, shoulder degenerative disease is becoming a more commonly recognized source of morbidity with a wide range of associated lifestyle-limiting disabilities. At the same time therapeutic options for treatment of degenerative joint disease are rapidly increasing, both medically and surgically. This combination of factors makes it necessary to determine a reliable, noninvasive means by which to accurately diagnose the early changes of shoulder degenerative disease. The clinical diagnosis of shoulder osteoarthritis is extremely challenging. There are numerous existing mimickers such as rotator cuff injuries, bursitis, and impingement syndrome. While the conventional radiographic findings are well recognized, they are generally late developments in the course of the disease when therapeutic options are more limited and less effective. Additionally, plain film evaluation has poor sensitivity for the detection of many of the alternative diagnoses that may underlie chronic shoulder pain. Though correlative findings are seen in MR imaging, its role in evaluating glenohumeral degenerative changes has been limited, with much of the focus being on the identification of tendinous and ligamentous disease or osseous tumors. A retrospective analysis is presented which demonstrates the efficacy of MR imaging in assessing GHJ OA, as well as shows that dedicated evaluation for specific degenerative findings results in improved detection rates of GHJ degenerative disease. It is believed that with improved detection and reporting, improved clinical care for this prevalent disorder may be achieved.

Radiology corner. Answer to last month's radiology case and images: Schistosomiasis japonicum involving the liver and colon

Abdominal radiography showed subtle curvilinear densities overlying the left lower quadrant and central within the pelvis (Fig. 1a). This was confirmed on intravenous contrast-enhanced abdominopelvic CT to be caused by thin mucosal surface calcifications within the descending and sigmoid colons (Fig. 1b, c). Incidental note is made of thin right hepatic lobe capsule calcifications (Fig. 1d). These colonic and hepatic calcifications are characteristic of Schistosomiasis infection of the gastrointestinal tract. Liver biopsy confirmed Schistosomiasis japonicum infection.

Gnathodiaphyseal dysplasia

Gnathodiaphyseal dysplasia (GDD) is an orthopedic condition involving cemento-osseous lesions of jaw bones, sclerosis, bowing of tubular bones, and overall bone fragility. This is a case report of GDD in which an 18-year-old female presented with a several-year history of bony abnormalities of the jaw and long bones. Radiographs demonstrated endosteal thickening, bowing of long bones, and abnormalities of the skull. These findings, along with the patient's known maxillary region cementoma, led to a diagnosis of GDD.

Intervertebral disk cyst: a case report

This case describes a patient who presented with chronic low back pain which developed over the course of 1 year. Imaging revealed a 1.1-cm cystic lesion at the L4-L5 vertebral level posterior to the intervertebral disk. Following both magnetic resonance and computed tomography imaging, diagnosis of intervertebral disk cyst was confirmed by both imaging modalities. A computed tomography-guided aspiration of the lesion was performed, and the patient was given a course of steroid injections with complete resolution of the lesion.

Cavernous Angioma of the Cerebellopontine Angle

Although cavernous hemangiomas are commonly found supratentorially, their presence in the internal auditory canal is uncommon. We describe a case that was initially mistaken for a vestibular schwannoma due to its location in the cerebellopontine angle. Although there can be overlap in their presentations, familiarity with the characteristic magnetic resonance imaging findings of both entities will aid in their differentiation and potentially affect preoperative planning.

Multiple Focal Nodular Hyperplasia: Atypical Imaging Characteristics in the Setting of Hepatic Steatosis

Focal nodular hyperplasia is an uncommon, benign lesion of the liver most often affecting women of childbearing age. It can present clinically with chronic, intermittent right upper quadrant pain and nausea, with associated liver enzyme abnormalities. The presence of characteristic sonographic and computed tomography imaging findings can help to differentiate this entity from other hepatic masses. This article describes an unusual case of multifocal disease that demonstrates atypical imaging findings in the background of hepatic steatosis.

Postoperative imaging of the hip

The number and type of operative procedures involving the hip continue to increase, placing a greater emphasis on characterizing patient postoperative condition accurately. Optimal postoperative imaging evaluation may involve multiple modalities, including conventional radiography, radionuclide scintigraphy, and cross-sectional imaging. Many of the surgical procedures involve the placement of metallic joint replacements or fixation that can make the imaging evaluation of the postoperative anatomy challenging. Clinical examination of patients combined with the type of procedure performed direct the appropriate imaging evaluation; adequate clinical knowledge of these procedures and how to optimally image them provide an opportunity to attain the most accurate evaluation possible.

The transverse humeral ligament: a separate anatomical structure or a continuation of the osseous attachment of the rotator cuff?

BACKGROUND

No study to date has isolated the anatomical nature of the transverse humeral ligament and its relationship to the biceps tendon and the anterosuperior portion of the rotator cuff.

HYPOTHESIS

There is no separate identifiable transverse humeral ligament, but rather the fibers covering the intertubercular groove are composed of a sling formed by fibers from the subscapularis and supraspinatus tendons.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 14 shoulder examinations were performed on 7 matched pairs of fresh-frozen cadaveric shoulders. Magnetic resonance imaging scans were performed, followed by gross and microscopic anatomical dissection.

RESULTS

In the location of the transverse humeral ligament, magnetic resonance imaging and gross dissection revealed the continuation of superficial fibers of the subscapularis tendon from the tendon body across the intertubercular groove to attach to the greater tuberosity, whereas deeper fibers of the subscapularis tendon inserted on the lesser tuberosity. Longitudinal fibers of the supraspinatus tendon and the coracohumeral ligament were also noted to travel the length of the groove, deep to the other interdigitating fibers but superficial to the biceps tendon. Histologic studies confirmed these gross dissection patterns of fiber attachment and also revealed the absence of elastin fibers, which are more commonly seen in ligamentous structures and are typically absent from tendinous structures.

CONCLUSION

There is no identifiable transverse humeral ligament, but rather the fibers covering the intertubercular groove are composed of a sling formed mainly by the fibers of the subscapularis tendon, with contributions from the supraspinatus tendon and the coracohumeral ligament.

CLINICAL RELEVANCE

According to our findings, dislocations of the long head of the biceps must disrupt at least the deep fibers of the annular sling created mainly by the subscapularis tendon insertion. This finding provides anatomical support for the findings of a positive biceps tendon subluxation or dislocation and subscapularis tear during glenohumeral arthroscopy with a normal-appearing subscapularis during open surgery or subacromial arthroscopy.

A case of osteochondritis dissecans in rickets

Rickets and the decreased ossification associated with it can give rise to abnormally low bone density and weakened osseous structures. Despite this association, rickets has rarely been associated with osteochondral defects, and the imaging findings of this association have not been previously described on magnetic resonance (MR) imaging. This case report presents an adolescent male with a clinical history of rickets and recent-onset knee pain that was determined to be caused by bilateral osteochondritis dissecans. Prompt recognition of osteochondritis dissecans is important, as this entity is a treatable cause of knee pain.

Massive recurrent synovial sarcoma of the hip: radiologic-histologic correlation in a case of failed magnet therapy

We report the unusual case of a recurrent, massive synovial sarcoma of the hip, following magnet therapy failure.

Imaging findings of femoroacetabular impingement syndrome

Femoroacetabular impingement syndrome (FAI) is a pathologic entity which can lead to chronic symptoms of pain, reduced range of motion in flexion and internal rotation, and has been shown to correlate with degenerative arthritis of the hip. History, physical examination, and supportive radiographic findings such as evidence of articular cartilage damage, acetabular labral tearing, and early-onset degenerative changes can help physicians diagnose this entity. Several pathologic changes of the femur and acetabulum are known to predispose patients to develop FAI and recognition of these findings can ultimately lead to therapeutic interventions. The two basic mechanisms of impingement-cam impingement and pincer impingement-are based on the type of anatomic anomaly contributing to the impingement process. These changes can be found on conventional radiography, MR imaging, and CT examinations. However, the radiographic findings of this entity are not widely discussed and recognized by physicians. In this paper, we will introduce these risk factors, the proposed supportive imaging criteria, and the ultimate interventions that can help alleviate patients' symptoms.

Cystic masses of the knee: magnetic resonance imaging findings

Cystic masses of the knee comprise a diverse group of pathologic entities ranging from simple cysts to complications of underlying disease to tumors. Although their presentations may be similar, the appropriate treatment and patient management can differ greatly. In this article, we review radiographic and magnetic resonance imaging characteristics of both common and uncommon cystic masses of the knee.

Plasmacytoma of the proximal humerus

This is the case report of a 67-year-old man who developed a solitary lytic lesion of the proximal humerus. Through further studies that included MR imaging of the affected upper extremity and biopsy, a final diagnosis of plasmacytoma was given. We present the clinical, imaging, and histologic findings and review the general characteristics of this neoplastic condition.

Magnetic Resonance Imaging Findings of Chronic Lateral Ankle Instability

The ankle inversion injury is one of the most common types of injury that is encountered in athletes and active individuals. There are a wide variety of acute injuries associated with ankle inversion, including peroneal tendon tears, osteochondritis dessicans of the talus, anterior talofibular ligament avulsion, peroneal retinaculum avulsion, and calcaneofibular ligament tears. Chronic sequelae include impingement, posttraumatic degenerative arthritis, and an attenuated peroneal retinaculum. Most inversion injuries to the ankle have multiple associated injuries and isolated ligament injuries are uncommon. Chronically, the injured ankle usually demonstrates the injuries found at the time of the initial injury. Subsequently, there is a high frequency of these injuries in patients evaluated for symptoms of chronic lateral ankle instability. A high index of suspicion for the specific types of injuries associated with ankle inversions may result in a higher rate of injury detection and more expeditious and accurate diagnoses. Given the persistence of these injuries seen in patients with chronic posterolateral instability, injury patterns of ankle inversion are important to recognize even in the absence of acute trauma. We review the various types of injuries with their associated magnetic resonance (MR) imaging characteristics seen in patients with chronic lateral ankle instability.

MRI diagnosis of occult ganglion compression of the posterior interosseous nerve and associated supinator muscle pathology

Occult interosseous ganglions in the proximal forearm can result in pain and decreased supination. We will describe the magnetic resonance imaging (MRI) diagnosis of an interesting case of supinator atrophy secondary to compression of the posterior interosseous branch of the radial nerve. A brief review of this entity follows.

MR imaging of the elbow A spectrum of common pathologic conditions

The following pictorial essay is a review of common elbow pathology as seen on elbow MR imaging. These include pathologic conditions that involve tendons, ligaments, osseous structures, bursa and other miscellaneous and incidentally detected lesions.

Overuse Injuries of the Upper Extremity in the Competitive Athlete: Magnetic Resonance Imaging Findings Associated with Repetitive Trauma

Overuse injuries are a very common cause of pain in athletes, accounting for a significant loss of training time and missed competitions. Magnetic resonance imaging (MRI) is playing an increasing role in facilitating the expeditious and safe return of these individuals to their preinjury level of physical performance by allowing accurate diagnosis. Sports physicians are increasingly relying on the exquisite anatomic detail afforded by this technique to formulate diagnoses that assist with the optimal management of these athletic injuries. Some upper extremity overuse entities are well recognized; two examples are medial epicondylitis, classically appearing in baseball pitchers, and lateral epicondylitis, in tennis players. Other less well-known injuries of the upper extremity, such as intersection syndrome in rowers and distal clavicular stress fractures in weightlifters, are frequent occurrences in certain circles of athletes. The following article is a pictorial review of the MRI findings of upper extremity overuse injuries encountered in the competitive athlete, with an emphasis on the sports scenarios in which they occur. We will depict mechanisms of injury and applicable anatomy and show characteristic imaging findings. A wide range of entities are addressed, including but not limited to overuse injuries occurring in baseball, swimming, gymnastics, weightlifting, bowling, and cycling.

The symptomatic accessory navicular bone: a report and discussion of the clinical presentation

An accessory navicular bone is a congenital anomaly caused by aberrant ossification. Usually asymptomatic, they are relatively common in our population. They can present in several different locations, which can have an impact on the clinical presentation and the degree of dysfunction. Occasionally, these can become symptomatic, which can manifest as chronic or acute on chronic foot pain. Diagnosis of this condition relies on radiographic evaluation. The 45-degree eversion oblique view of the foot is the most important view for identifying this condition, although several different imaging techniques can be used. Treatment of this condition includes both surgical and nonsurgical options. Ultimately, surgery yields the best outcome for young patients, though conservative management has relevance for less active patients. The following case demonstrates the presence of a symptomatic accessory navicular bone in a young athlete.