Background and PurposeDifferentiating between infectious and neoplastic focal brain lesions that are detected by conventional structural magnetic resonance imaging (MRI) may be a challenge in routine practice. Brain perfusion-weighted MRI (PWI) may be employed as a complementary non-invasive tool, providing relevant data on hemodynamic parameters, such as the degree of angiogenesis of lesions. We aimed to employ dynamic susceptibility contrast-enhanced perfusion MR imaging (DSC-MRI) to differentiate between infectious and neoplastic brain lesions by investigating brain microcirculation changes.Materials and MethodsDSC-MRI perfusion studies of one hundred consecutive patients with non-cortical neoplastic (n = 54) and infectious (n = 46) lesions were retrospectively assessed. MRI examinations were performed using a 1.5-T scanner. A preload of paramagnetic contrast agent (gadolinium) was administered 30 seconds before acquisition of dynamic images, followed by a standard dose 10 seconds after starting imaging acquisitions. The relative cerebral blood volume (rCBV) values were determined by calculating the regional cerebral blood volume in the solid areas of lesions, normalized to that of the contralateral normal-appearing white matter. Discriminant analyses were performed to determine the cutoff point of rCBV values that would allow the differentiation of neoplastic from infectious lesions and to assess the corresponding diagnostic performance of rCBV when using this cutoff value.ResultsNeoplastic lesions had higher rCBV values (4.28±2.11) than infectious lesions (0.63±0.49) (p<0.001). When using an rCBV value <1.3 as the parameter to define infectious lesions, the sensitivity of the method was 97.8% and the specificity was 92.6%, with a positive predictive value of 91.8%, a negative predictive value of 98.0%, and an accuracy of 95.0%.ConclusionPWI is a useful complementary tool in distinguishing between infectious and neoplastic brain lesions; an elevated discriminatory value for diagnosis of infectious brain lesions was observed in this sample of patients when the rCBV cutoff value was set to 1.3.

ContribuiÇÃo da SeQÜÊnCia difuSÃo da Mr no diagnÓStiCo e aCoMpanhaMento da enCefalopatia por doenÇa da urina eMMaple syrup urine disease (MSUD) or leucinosis is caused by a deficiency of the catalytic components of the α-ketoacid-dehydrogenase complex, which is responsible for the catabolism of branched-chain amino acids (leucine, isoleucine, and valine) 1,2 . It is an inherited genetic disease with an autosomal recessive pattern affecting approximately 1 out of 120,000-500,000 infants worldwide 3,4 . Diagnosis is made clinically based on the peculiar maple syrup odor or sugar burnt of the urine, encephalopathy, increased levels of branched-chain amino acids in the plasma and urine, and the presence of α-hydroxyacid and branched-chain α-ketoacids in urine. The presence of plasma L-alloisoleucine and urinary α-hydroxyisovalerate are pathognomonic for MSUD 2 . According to the literature, five forms of MSUD have been described: classic, intermediate, intermittent, thiamine-responsive, and dihydrolipoyl dehydrogenase-deficient. The commonest and severest form of the disease is the classic type, which is characterized by a neonatal onset of encephalopathy 2 . Magnetic resonance imaging (MRI) studies in the acute phase of classic MSUD are characterized by diffuse edema corresponding to both myelinated and unmyelinated areas of the brain [3][4][5][6] . The purpose of this case report is to show conventional MRI and diffusion-weighted imaging (DWI) findings of the different evolutionary phases in MSUD of a newborn that evolved with brain white matter lesions. CaSeA full-term male infant born from an uneventful pregnancy and delivery, with a birth weight of 3.245g and Apgar scores of 9/10 (at 1 and 5 min, respectively), was hospitalized because of sucking difficulties, weak cry, and lethargy. At 10 days of life, the baby had episodes of seizures, bradycardia, and apnea, leading to coma. Biochemical examinations showed hypoglycemia and metabolic ketoacidosis. Brain MRI at 10 days of life showed hypersignal lesions on DWI and corresponding hyposignals on ADC maps throughout the white matter of the brainstem, cerebella and internal capsules (Fig 1).At 20 days of life the clinical condition of the baby became critical and maple syrup odor or sugar burnt was noted in the urine. A repeat MRI at this time showed increasing myelinating white matter lesions and new hypersignal lesions on T2-weighted sequences and hyposignal on the diffusion-weighted images located in the unmyelinated white matter of the frontal, parietal and temporal lobes (Fig 2).At 25 At 8 months of age, a follow-up MRI was performed that showed persisting white matter lesions in the frontal, parietal and temporal lobes with associated hypersignal on DWI and hy-

Meningiomas are tumors of benign histological nature which represent 13 to 26% of all primary intracranial neoplasia 1 . Approximately 20% of intracranial meningiomas present extracranial dissemination at sites such as the orbit, middle ear, nasal cavity, nasopharynx and paranasal sinuses 2 . Primary extracranial meningiomas are histologically identical to intracranial meningiomas. They usually occur in 40 to 60-year-old patients and are rare in the pediatric age group. Primary extracranial meningiomas represent 1 to 2% of all meningiomas [1][2][3][4][5] . We to report the case of a 13-year-old girl with a primary extracranial meningioma of the ethmoid sinus, including the main findings of the imaging examination and a brief review of the literature. CaseA 13-year-old girl was referred to our service with a 30-day history of constant and strong frontal headache, nasal obstruction, and progressive proptosis of the left eye without signs of phlogiston or alterations in visual acuity.At rhinoscopy, a lesion of the soft tissues was observed occupying the left superior meatus of the nasal cavity with a smooth pink surface.In light of these findings, a CT of the skull and face sinuses was performed showing an extensive hypodense non-calcified lesion measuring 2.0x2.0 cm located in the left ethmoid sinus. The lesion presented heterogeneous iodinated contrast enhancement and demonstrated remodeling of the adjacent bone structures (Fig 1).MRI of the facial sinuses was requested to evaluate the involvement of the soft structures as well as the invasion of the adjacent structures and resection planes. The lesion in the left ethmoid sinus was hypointense in T1 and T2-weighted sequences, with heterogeneous paramagnetic contrast enhancement, determining a mass effect on the adjacent structures, lateral divergence of the medial rectus muscle of the left orbit, but with- out invasion (Fig 2). Additionally, maxillary and sphenoidal sinus disease was observed.The patient was submitted to excision of the lesion by external and endoscopic ethmoidectomy with a complete cure of the exophthalmus in the postoperative period. Diagnosis of atypical meningioma was attained by histopathological examination. disCussionThe present study shows the clinical and imaging aspects of primary extracranial meningioma of the ethmoid sinuses in a child. Primary extracranial meningioma of the nasal cavity or paranasal sinuses is rare, especially in children. The paranasal sinuses most commonly affected are the frontal, maxillary, ethmoid and sphenoid sinuses 2,3,5 .