Nanda Venkatanarasimha

MRI appearance of muscle denervation

Muscle denervation results from a variety of causes including trauma, neoplasia, neuropathies, infections, autoimmune processes and vasculitis. Traditionally, the diagnosis of muscle denervation was based on clinical examination and electromyography. Magnetic resonance imaging (MRI) offers a distinct advantage over electromyography, not only in diagnosing muscle denervation, but also in determining its aetiology. MRI demonstrates characteristic signal intensity patterns depending on the stage of muscle denervation. The acute and subacutely denervated muscle shows a high signal intensity pattern on fluid sensitive sequences and normal signal intensity on T1-weighted MRI images. In chronic denervation, muscle atrophy and fatty infiltration demonstrate high signal changes on T1-weighted sequences in association with volume loss. The purpose of this review is to summarise the MRI appearance of denervated muscle, with special emphasis on the signal intensity patterns in acute and subacute muscle denervation.

Imaging features of ductal plate malformations in adults

Ductal plate malformations, also known as fibrocystic liver diseases, are a group of congenital disorders resulting from abnormal embryogenesis of the biliary ductal system. The abnormalities include choledochal cyst, Carolis disease and Carolis syndrome, adult autosomal dominant polycystic liver disease, and biliary hamartoma. The hepatic lesions can be associated with renal anomalies such as autosomal recessive polycystic kidney disease (ARPKD), medullary sponge kidney, and nephronophthisis. A clear knowledge of the embryology and pathogenesis of the ductal plate is central to the understanding of the characteristic imaging appearances of these complex disorders. Accurate diagnosis of ductal plate malformations is important to direct appropriate clinical management and prevent misdiagnosis.

Imaging features of therapeutic drug-induced musculoskeletal abnormalities.

Increasing use of a wide variety of therapeutic drugs with known musculoskeletal side-effect profiles necessitates a rigorous understanding and approach when evaluating imaging features suggestive of drug-induced musculoskeletal abnormalities. The etiology of such abnormalities is diverse, and the clinical and imaging manifestations may be nonspecific. The recognition of adverse effects depends, first, on the physicians vigilant review of clinical information for relevant drug history and indicative signs, and second, on the radiologists ability to detect musculoskeletal changes consistent with known potential effects of specific drugs. Musculoskeletal abnormalities induced by therapeutic drugs may be broadly categorized as embryopathic, juvenile, or postmaturation. Embryopathic skeletal abnormalities result from the teratogenic effects of drugs administered to pregnant women (eg, thalidomide, anticonvulsants). Other therapeutic agents characteristically lead to abnormalities during postnatal skeletal maturation (eg, high-dose vitamins or prostaglandin) either because they are used exclusively in children or because they have idiosyncratic effects on immature musculoskeletal structures. Many drugs (eg, statins) may have musculoskeletal side effects that, although independent of the stage of skeletal maturation, are most often seen in adults or elderly people because they are commonly prescribed for people in these age groups. Drug-induced musculoskeletal abnormalities may be further characterized according to the predominant skeletal manifestations as osteomalacic, proliferative, or osteoporotic and according to the involvement of soft tissues as musculotendinous or chondral.

Potential pitfalls of a double PCL sign

The double posterior cruciate ligament (PCL) sign is seen on a midline sagittal MR image of the knee as a low-signal-intensity linear band paralleling the antero-inferior part of the PCL. Although the sign has a high specificity for a displaced bucket-handle tear of the medial meniscus, it can be mimicked by several normal and abnormal structures in the intercondylar region. Familiarity with these variants and identifying the other features supportive of meniscal injury will help to make a confident diagnosis of bucket-handle tear of the medial meniscus

The varied sonographic appearances of focal fatty liver disease: Review and diagnostic algorithm

Focal fat infiltration and focal fat sparing of the liver are less common than diffuse fat infiltration but present a greater diagnostic conundrum. Although typical features of these conditions are well described, there is a wide variety of different appearances. These atypical patterns present significant difficulty in differentiation from other pathological processes and often require additional investigation. We present an innovative diagnostic algorithm and illustrate its effectiveness in diagnosing focal fatty liver disease with typical and atypical examples.

Proximal ulna stress fracture and stress reaction of the proximal radius associated with the use of crutches: a case report and literature review.

We report a case of complete stress fracture of the ulna and stress reaction of the radius resulting from the use of crutches in an overweight patient with severe lower extremity arthritis. Plain radiograph showed an undisplaced complete fracture of the proximal metaphysis of the ulna. Magnetic resonance imaging (MRI) was performed to exclude a pathological cause in view of the unusual fracture site, which confirmed the plain radiographic findings and additionally demonstrated a stress reaction in the proximal radius. There are three cases of stress fracture of the ulnar diaphysis resulting from the use of crutches reported previously in the English literature and a further case of bilaterally symmetrical ulnar diaphysial fracture reported in the Danish literature. We report the first case of ulnar metaphysis stress fracture with concomitant stress reaction of the radius.

Pictorial review: computed tomography features of cardiovascular emergencies and associated imminent decompensation

Multi-detector computed tomography (MDCT) scanner is available in most hospitals and is increasingly being used as the first line imaging in trauma and suspected cardiovascular emergencies, such as acute coronary syndrome, pulmonary artery thrombo-embolism, abdominal aortic aneurysm and acute haemorrhage (Ryan et al. Clin Radiol 60:599–607, 2005). A significant number of these patients are haemodynamically unstable and can rapidly progress into shock and death. Recognition of computed tomography (CT) signs of imminent cardiovascular decompensation will alert the clinical radiologist to the presence of shock. In this review, the imaging findings of cardiovascular emergencies in both acute traumatic and non-traumatic settings with associated signs of imminent decompensation will be described and illustrated.

Case 175: Testicular Lipomatosis in Cowden Disease

US practitioners should be aware of the characteristic appearance of testicular lipomatosis to prevent misdiagnosis of a more sinister disease; the radiologist may be the first to suggest a diagnosis of Cowden disease.

Use of the term “superficial femoral vein” in ultrasound

To determine the frequency of use of the term “superficial femoral vein” (SFV) in the radiologic reports from a sample of sonographic investigations for suspected deep vein thrombosis and to assess the potential for clinical error in their interpretation.

Usual and unusual causes of splaying of the carotid artery bifurcation: the lyre sign—a pictorial review

The ‘Lyre’ sign describes the characteristic splaying of the carotid artery bifurcation due to a carotid body tumour (paraganglioma) on conventional carotid angiography. In this pictorial review, we describe and illustrate two cases demonstrating the equivalent Lyre sign on multi-detector computed tomography (MDCT) and ultrasound resulting from carotid body tumour and extra-cranial internal carotid artery pseudoaneurysm. Both of these pathologies can manifest acutely and warrant accurate diagnosis to prevent potential catastrophic consequences. We also emphasise the added value of MDCT in making a definitive diagnosis and discuss other differential considerations splaying the carotid bifurcation.