The present study reports two histologically proven cases of pulmonary paracoccidioidomycosis where a reversed halo sign was found. The reversed halo, initially described as a pathognomonic sign of cryptogenic organizing pneumonia, has later been found and described in paracoccidioidomycosis.

Keywords: Reversed halo sign, Paracoccidioidomycosis, Cryptogenic organizing pneumonia

The use of signs or analogies for interpretation and description of medical images is an old and common practice among radiologists. Comparison of findings with animals, food or objects is not unprecedented and routinely performed. Many signs are quite specific and, in some cases, pathognomonic. Indeed, notwithstanding their degree of specificity, signs may help in the characterization of certain diseases. Several neuroradiological signs have been already described. The authors will present 15 neuroradiology signs in the present essay, approaching their main characteristics, the significance of their role in the clinical practice, as well as their respective imaging findings.

Keywords: Radiological signs; Neuroradiology; Computed tomography; Magnetic resonance imaging.

The use of signs for interpretation of images in neuroradiology is extremely useful. Some signs are quite specific and, in some cases, pathognomonic. In this second part of their essay, the authors describe 15 additional neuroradiological signs. Main characteristics of imaging findings will be approached and the significance of their role in the clinical practice will be discussed.

Keywords: Radiological signs; Neuroradiology; Computed tomography; Magnetic resonance imaging.

The development of the paranasal sinuses is an intricate process that begins in the intrauterine life and terminates in early adulthood. Among the paranasal sinuses, the ethmoid cells or labyrinth are probably the most complex structures, being associated with the highest number of normal variants. Variations in the pattern of pneumatization of the ethmoid cells can be divided into intra- and extramural cells. Intramural cells are those which develop within the ethmoid labyrinth. Extramural cells are those that develop isolatedly. Computed tomography is the most useful tool in the evaluation of inflammatory processes of the paranasal sinuses. Computed tomography also plays a relevant role in the preoperative planning as well as in the postoperative follow-up, since it demonstrates exact anatomical details of normal structures with accuracy in the detection of variants. In the present pictorial essay, the authors describe the most common anatomical variants of the ethmoid labyrinth and their relationship with adjacent structures. Endoscopic sinonasal surgery has become increasingly less invasive, requiring more detailed anatomical imaging of this region.

Keywords: Computed tomography; Ethmoid sinus.

DWI/ADC is a completely non-invasive technique that has been successfully conducted for many years in brain imaging and is currently being studied for the assessment of other organs, such as the abdomen and pelvis and in particular the head and neck structures. Even though DWI and the ADC measurement are able provide tissue information at the cellular level, most imaging centers have not yet adopted them as part of their routine evaluation of the head and neck. DWI has demonstrated usefulness to discriminate specific histological tumor types, especially to differentiate benign solid lesions from malignant masses, to evaluate lymph nodes, particularly to differentiate benign disease from malignancy, to differentiate postradiation changes from residual tumor and potentially to predict therapy success. Moreover DWI seems to be a safer and more affordable method considering the absence of radiation and to the higher cost of FDGPET to localize tumors and to differentiate benign from malignant masses. Given all these advantages and strengths, DWI will certainly become part of the routine in the MR imaging of the head and neck.

Keywords: Head and neck; Tumors; Squamous cell carcinoma; Diffusion weighted imaging; Apparent diffusion coefficient map; Exponential diffusion weighted imaging.

Disc herniation with posterior epidural migration is a rare and often symptomatic entity. Multiple are the natural barriers that prevent this pattern of migration. Enhanced magnetic resonance imaging is the diagnostic modality of choice in these cases. The diagnostic dilemma in this case was the contraindication to the use of contrast since the patient was known to have chronic renal failure.

Keywords: Lumbar hernia; Complication; Epidural space; Posterior; Magnetic resonance imaging; Contrast.