ULTRASOUND on WRIST JOINTS

In this issue of Journal of Medical Ultrasound (September 2013), the application of high frequency ultrasound on wrist joints, especially with a focus on De Quervain disease, carpal tunnel syndrome, and ultrasound-guided injection techniques, is intensively reviewed and comprehensively discussed.

De Quervain disease, defined as stenosing tenosynovitis of the first extensor compartment of the wrist, is the most common wrist disorder referred for ultrasound imaging. The best landmark for the transducer placement is on the radial styloid. The longitudinal plane is suitable for dynamic examination of tendon gliding, whereas the transverse view serves as a better window to inspect the retinaculum, internal septa, and accessory tendons [1], [2]. Increased sizes with hypoechoic changes in the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons are typical findings [3]. In the acute inflammatory stage, the synovial sheath may be filled with effusion, and hypervascularity is easily seen under power Doppler sonography. In the chronic phase, synovial hypertrophy, marked thickening, and hypoechoic appearance may be present at and inside the retinaculum of the first compartment.

The most common pattern of tendons inside the first extensor compartment is one or two APLs and one EPB in a single compartment [4]. Many anatomic variations of the first extensor compartment exist that may potentially interfere with the response of a corticosteroid injection. APL tendons frequently have multilamellar texture, whose prevalence was up to 89% of specimens at dissection [3]. The investigator should be cautious about not misdiagnosing multilamellar appearance as longitudinal split tear. Another common variation is the presence of a vertical or oblique linear septum-like structure extending from the extensor retinaculum between the APL and EPB or the presence of completely separate hypoechoic circular rims around the EPB and APL. One study demonstrated 100% sensitivity (95% confidence interval, 74–100%) and 73% positive predictive value (95% confidence interval, 47–91%) in identifying subcompartmentalization by using ultrasound [4]. Another research exhibited a similar diagnostic accuracy of ultrasound in detecting subcompartmentalization and high prevalence (41%) of septum-like structures at asymptomatic contralateral wrists in patients with De Quervain disease [1].

Another diagnosis, named intersection syndrome, is usually confused with De Quervain disease. It is a noninflammatory condition that affects the portion of the distal forearm where the first extensor compartment tendons pass over the tendons in the second extensor compartment (extensor carpi radialis longus and extensor carpi radialis brevis tendons). The typical location of the intersection is proximal to the Lister tubercle of the distal radius, whereas the painful site in De Quervain disease is more distal. The ultrasound findings comprise significant tendon swelling, peritendinous hypervascularity, and effusion within the tendon sheaths at the point of intersection [3]. However, even though the above findings are absent, the diagnosis of intersection syndrome can be made if the pain is elicited through dynamic examination at the crossover region between the first and second extensor compartments.

Application of high-resolution ultrasound on patients with carpal tunnel syndrome is a hot issue for research. Most studies use clinical presentations and electrical diagnostic findings to compare with the designated sonographic parameters. The parameters include morphological changes in median nerves such as cross-sectional area and flattening ratio or estimation of external compression such as the bowing of the flexor retinaculum [5]. All the measurements can be performed from the inlet to the outlet of the carpal tunnel, and the diagnostic accuracy varies according to the site. Several meta-analyses have been published in exploring the sensitivity and specificity of ultrasound in the diagnosis of carpal tunnel syndrome [6], [7], [8]. Most meta-analyses noted that measuring the median nerve cross-sectional area by ultrasound gives complementary information but failed to serve as an alternative to electrodiagnostic testing for diagnosis of carpal tunnel syndrome. A recent meta-analysis demonstrated that using 9 mm² of the cross-sectional area at the carpal tunnel inlet was the best single diagnostic criterion with a diagnostic odds ratio of 40.4 (sensitivity 87.3%, specificity 83.3%) [8]. Although ultrasound may not replace the role of electrodiagnostic testing, it can be considered an easy and useful tool for the screening of carpal tunnel syndrome.

Ultrasound-guided injection therapy has emerged as a mainstream approach in musculoskeletal pain medicine [9]. The guided injection has been shown to lead to a resolution of symptoms in 97% of wrists with De Quervain disease in a case series [10]. A randomized controlled trial further indicated a more significant decrease in the ultrasound-guided group than in the manual injection group from baseline to 4 weeks after injection [11]. Because the existence of septum inside the first compartment is common in wrists with De Quervain disease and hinders the diffusion of steroids, the guided injection can direct the medication to each subspace and results in treatment success. Regarding carpal tunnel syndrome, a local steroid injection is effective for short-term symptom relief. The benefit of guided therapy is the precise targeting of the soft tissue adjacent to the median nerve without injury to the nerve [12]. However, to date, only a few studies can demonstrate the better effectiveness of guided injections against carpal tunnel syndrome compared with the blind approach.

In the current special issue of Journal of Medical Ultrasound, we published an interesting study regarding the measurement of tendon thickness of the first and second extensor compartments at the intersection region in asymptomatic volunteers. The article is important to the background knowledge of ultrasound assessment of wrist joints. We expect that in the near future, further studies will emerge to demonstrate the quantitative findings of symptomatic intersection syndrome and the effectiveness of guided injection to this specific wrist disorder.

 

NHÂN CA BRONCHOGENIC CYST @ MEDIC

Xem BRONCHOGENIC CYST

Bronchogenic cyst

Dr Yuranga Weerakkody and Dr Jeremy Jones et al.     http://radiopaedia.org/articles/bronchogenic-cyst

Discussion

http://www.ijri.org/article.asp?issn=0971-3026;year=2004;volume=14;issue=4;spage=391;epage=394;aulast=Smitha

Bronchogenic cyst result from an anomalous super numerary budding of the ventral or tracheal diverticulum of the foregut during the sixth week of gestation and is thus part of the spectrum of broncho pulmonary foregut malformations [1].

The most frequent location is mediastinal and subcarinal [1].They usually contact the carina or main bronchi, but may be seen anywhere along the course of trachea and larger airways. They frequently project into the middle or posterior mediastinum and rarely into anterior mediastinum [2],[3].

Extra mediastinal bronchogenic cysts may be located in the lung parenchyma, diaphragm or pleura [3]. Intra pulmonary cysts are usually found in the perihilar areas or rarely peripherally in the lower lobe [1]. Bronchogenic cysts have also been reported near the midline in the upper thoracic or lower cervical chest wall [1].

Lesions may be classified as anterior mediastinal if located anterior to heart or great vessels (prevascular space), posterior mediastinal if located in either para spinal regions and middle mediastinal if located in the para tracheal or subcarinal regions or along the course of the esophagus [3].

Bronchogenic cysts vary in size and maybe quite large [2]. They are usually discrete and unilocular [4]. The cyst contents usually consist of thick mucoid material. The cysts can grow very large without causing symptoms, but may compress surrounding structures, particularly the airway and give rise to symptoms .In rare cases, they become infected or hemorrhage occurs into the cyst. These complications may be life threatening, particularly in infants and young children [2].

In the work by Mc Adams et al, most affected patients presented in the first few decades of life. Presentation beyond 50 years is distinctly unusual. Most of the patients were symptomatic at presentation and chest pain was the most common complaint. Symptoms were likely related to mass effect on adjacent structures. Maximal cyst diameter ranged from 1.3 to 11 cms with a mean of 4.8 cms [3].

In young children, they tend to compress or distort the trachea and bronchi resulting in clinically obvious respiratory compromise. Compression of a single bronchus may result in focal pulmonary hyperinflation, mimicking congenital lobar emphysema on x rays [4].

Bronchogenic cysts usually do not present in the neonatal period, although they can do so when located near major airways and undergoing rapid expansion. More commonly, they present with recurring episodes of infection or wheezing or can be asymptomatic and discovered serendipitously [1].

Complications include superior vena cava syndrome, tracheal compression, pneumothorax, pleurisy and pneumonia [5]. In the typical case, there is no bronchial communication and the cyst is fluid filled. Repeated infection can cause erosion into a neighboring airway and also an air fluid level. Rhabdomyosarcoma arising in a congenital bronchogenic cyst also has been reported [1].

On plain film examinations, bronchogenic cysts present as spherical or oval masses with smooth outlines and soft tissue density projecting from either side of the mediastinum [2],[4]. [Figure - 1]

CT is an excellent method for demonstrating the size, shape, position and margin characteristics of cyst. It is also useful for evaluation of mass effect on adjacent structures, cyst attenuation, homogeneity, calcification and patterns of enhancement following intra venous contrast administration of iodinated contrast material [2].[3].

The cysts are classified as water attenuation if their attenuation is less than 20 HU and tissue attenuation if more than 20 HU. Further Mc Adams et al classified bronchogenic cysts as follows: a) cystic - if attenuation is less than that of surrounding soft tissue, lesion is internally homogenous, if there is no internal enhancement and if there is a well defined thin wall. b) Solid: if attenuation is similar to surrounding soft tissues, lesion is internally heterogeneous and if there is no well defined thin wall. c) Indeterminate: if the cysts did not meet above mentioned criteria [3].

Indeterminate borders may be due to obscuration of the margins by associated atelectasis. Mass effect on surrounding structures such as bronchi, esophagus or mediastinal vessels and associated atelectasis or consolidation may also be observed [3].

The bronchogenic cysts appear as round or ovoid masses intimately related to the airway [4]. They frequently push the carina forward and the esophagus backward - displacements that are almost never seen with other masses [2]. When the cyst has attenuation similar to soft tissues and therefore tumor, the differential diagnosis becomes wider. Rarely the cyst may show uniformly high attenuation, probably due to high protein content or a very high density due to high calcium content (milk of calcium) within [2]. Calcification observed rarely may be in the cyst wall or within the cyst [3].

David S. Mendelson et al studied bronchogenic cysts with CT numbers more than 30 HU and found that they contain turbid mucoid fluid as well as clear and serous fluid. The turbid fluid results in a high CT number . Rarely the cysts become infected and this may also contribute to the relatively high attenuation coefficients [6]. Hence high Hounsfield units do not exclude the diagnosis of bronchogenic cysts. Infection may also result in thick wall and air fluid level within the cyst. [7].

In the case presented above, a completely extra dural neurogenic tumor too was considered. These are of lower attenuation on CT than muscle, because of their lipid or mucinous matrix or because of cystic degeneration [8]. They are usually para vertebral in location and may cause smooth expansion of a vertebral foramen [9]. Density varies from hypo to slightly hyperdense. Calcification and hemorrhage are rare[10].

Attenuation differences between mediastinal soft tissues and the cyst contents are accentuated following administration of contrast. The cyst contents do not enhance. Mural enhancement may be seen in some and helps to delineate a thin wall [3].

A thick or irregular wall suggests necrotic tumor or lymph adenopathy .If the lesion is heterogeneous or enhances centrally, neoplasia must be excluded. MRI can be useful to differentiate high attenuation cysts on CT from soft tissue masses. Such cysts are typically iso intense or hyper intense to CSF with all pulse sequences. A lesion that is hypo intense to CSF on T2 W images should be viewed with caution. [3]. Minimal wall enhancement is expected with gadolinium enhancement [4].

Surgery maybe considered as the treatment of choice even when the cyst is asymptomatic, since complications are not uncommon and definitive diagnosis can be established only on surgical specimen [5,12]. Observation may be indicated for small, classic, asymptomatic cysts or high-risk patients. Per cutaneous catheter, drainage, sterile alcohol ablation or trans bronchial cyst aspiration have been performed in selected cases [3],[11].