Focal Areas Of High Signal Intensity Research Articles

FOCAL AREAS OF HIGH-SIGNAL INTENSITY ON BRAIN T2-WEIGHTED MAGNETIC RESONANCE IMAGING SCANS ARE SIGNIFICANT FOR THE DIAGNOSIS OF NEUROFIBROMATOSIS VON RECKLINGHAUSEN TYPE 1

INTRODUCTION: Neurofibromatosis von Recklinghausen type 1 (NF1) is characterized by the following National Institutes of Health (NIH) diagnostic criteria: café au lait spots, freckling, neurofibromas, Lisch nodules, optic glioma, distinct osseous lesions, and first-degree relative with NF1. Focal areas of high-signal intensity (FASI) in white matter and deep gray matter are typical brain MRI findings in children with NF1. OBJECTIVE: This study evaluated the frequency of FASI and the possibility of using FASI as a diagnostic criterion. METHODS: In a group of 160 children, the diagnosis of NF1 was confirmed in keeping with the NIH criteria. All children had MRI examination of the brain. The MRI findings of FASI in the children with NF1 were compared both with the brain MRI findings of the control group of 160 children with different diagnoses and with frequencies of the NIH diagnostic criteria. RESULTS: In 137 (86%) patients with NF1, ≥1 FASI were found. The difference between frequency of FASI in the NF1 group and in the control group (14 [9%]) is highly significant. The frequencies of the diagnostic criteria were as follows: café au lait spots: 157 (98%); freckling: 123 (77%); neurofibromas: 112 (70%); NF1 relatives: 89 (56%); Lisch nodules: 71 (44%); optic glioma: 45 (28%); and osseous lesions: 15 (9%; only partial examination of the group). CONCLUSIONS: The findings of FASI in T2-weighted images of the brain MRI are significantly frequent in children with NF1. Frequency of FASI is comparable with frequency of NIH diagnostic criteria. FASI could be proposed as an additional or new criterion for the NF1, mainly in childhood.

Magnetic Resonance Imaging and Histologic Findings of Acute and Subacute Stage of Experimental Cerebral Fat Embolism in Cats

Purpose: To determine the magnetic resonance imaging (MRI) findings and natural history of cerebral fat embolism in a cat model, and to correlate the MRI and histologic findings. Materials and Methods: Using the femoral arterial approach, the internel carotid artery of 11 cats was injected with 0.1 ml of triolein. T2-weighted (T2WI), T1-weighted (T1WI) and Gd-enhanced T1-weighted (Gd-T1WI) images were obtained serially at 2 hours, 1 and 4 days and 1, 2 and 3 weeks after embolization. Any abnormal signal intensity (SI) was evaluated. After MR imaging at 3 weeks, brain tissue was obtained for light microscopic (LM) examination using hematoxylin-eosin and Luxol fast blue staining, and for electron microscopic (EM) examination. The histologic and MRI findings were correlated. Results: At 2 hours, lesions showed high SI at T2WI, iso- or low SI at T1WI, and strong enhancement at Gd-T1WI. The high SI seen at T2WI decreased thereafter, and most lesions became iso-intense. At week 3, however, small focal areas of high SI were seen in the grey matter of eight cats and in the white matter of three. The low SI noted at acute-stage T1W1 subsequcntly became normal, though in the areas in which T2W1 had depicted high SI, focal areas of low SI remained. Lesion enhancement demonstrated by Gd-T1WI decreased continuously from day 1, and at week 3, weak enhancement was seen at the margin of the remained hypointense lesions in the gray matter in five cats. At LM examination with hematoxylin-eosin staining revealed normal histologic findings in the greater park of an embolized lesion. Cystic change was observed in the gray matter of eight cats, and in the gray and white matter of three of the eight. At LM examination, Luxol fast blue, staining demonstrated demyelination around the cystic change occurring in the white matter, and EM examination of the embolized cortex revealed sporadic intracapillary fat vacuoles (n=11) and disruption of the blood-brain barrier (n=4). Most lesions were normal, however, and perivascular interstitial edema and cellular swelling were mild compared with the control side. Conclusion: Experimental cerebral fat embolism was clearly demonstrated by T2WI and Gd-T1WI images obtained at all time points. The greater part of an embolized lesion showed reversible findings at MR and histologic examination; irreversible focal necrosis was, however, observed in gray and white matter at week 3.