Localized amyloidosis of the head and neck was found retrospectively in the nasopharynx (n = 3) and orbit (n = 1) of four female patients (mean age, 32 years), three of whom had a prior history of antigenic stimulation. In all patients, computed tomography revealed a slightly high absorption and a relatively homogeneous, partially calcified mass. In the one patient who underwent magnetic resonance (MR) imaging, a distinctive loss of signal intensity was seen on the long repetition time/echo time sequence. This enhanced T2 relaxation may be due to (a) static or slowly fluctuating internal magnetic fields arising from adjacent amyloid protons held in relatively fixed positions within the beta-pleated sheet, resulting in quick phase dispersion; (b) chemical exchange and spin-spin interaction with adjacent water protons; and (c) diffusion through differences in diamagnetic susceptibility. This unusual appearance at MR imaging may improve the ability of radiologists to distinguish focal amyloidosis from many other diseases that affect the head and neck.

An 8-year-old boy with neurofibromatosis type 1 (NF1) and a biopsy-proven juvenile pilocytic astrocytoma of the hypothalamic/chiasmatic region was followed with serial MRIs over 4 years. Spontaneous tumor regression was followed by progression and biopsy; 6 months later, the tumor regressed again. This bimodal regression is rare, but highlights the variable natural history of low-grade gliomas in children with NF1 and the difficulty in evaluating response of such tumors to therapy.

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Summary Identification of the structural lesions that underlie pediatric epilepsy can be challenging. Careful evaluation of the gray–white matter interface is crucial, and necessitates multiplanar thin images of high resolution that can differentiate focal lesions from partial volume averaging artifacts created by the innate gyral configuration. Careful evaluation of the hippocampus and of the myelination patterns can further increase the diagnostic yield of the study. Magnetization transfer imaging can call attention to a lesion that is either very subtle or not evident on conventional sequences. Detection of cortical anomalies is best performed early in infancy, preferably before 6 months of age. If the initial magnetic resonance imaging (MRI) scan is performed between 9 and 18 months of age and is negative, a repeat scan after 2 years of age may be necessary.

MR technology is constantly improving. Functional imaging techniques such as MR spectroscopy, perfusion imaging, diffusion imaging and diffusion tensor imaging are increasingly utilized in the pediatric patient with a brain tumor. However estimate of tumor size remains the primary imaging endpoint in the evaluation of response to treatment; validation across institutions and vendor platforms of MRI functional parameters is necessary given the relative uncommon occurrence of brain tumors in children. Pediatric neuroimaging can be challenging, and the optimal way to image children with CNS tumors is not uniformly applied across all centers. Application of proper scanning techniques and validation of functional imaging techniques should lead to improved care of children with CNS tumors Throughout the past century, great strides have been made in the use of imaging techniques to localize and characterize brain tumors. Major milestones include the first reported injection of air into the lateral ventricles by Dandy in 1918 1 ; the routine use of pneumoencephalography and angiography starting in the 1940s; the arrival of computed tomography (CT) starting in the early 1970s; and, in the mid 1980s, the advent of magnetic resonance imaging (MRI) techniques. Our ability to evaluate pediatric patients with tumors of the central nervous system (CNS) continues to evolve.MRI is by far the most useful and employed technique nowadays, due to its exquisite intrinsic ability to differentiate tissue character. In addition, MRI techniques can estimate multiple tissue parameters -based on anatomy and functional/metabolic features of cerebral tissue. This paper will focus on recent advances in the field of MRI, and will illustrate many of the multiparametric capabilities of MRI. The technical and logistical challenges we face in increasing the application of these new techniques to the pediatric patient will be outlined. Tumor definition, stagingIn the majority of children with CNS neoplasms, MRI can clearly define the location, size and extent of a tumor. With the use of multichannel phased array coils, images of very high anatomical resolution can now routinely be obtained. These high quality images can be put to use in the operative setting, allowing the neurosurgeon the ability to perform image-guided surgical navigation. MR images are acquired intraoperatively (intraoperative MR) in an increasing number of medical centers.In most centers, tumor size is assessed manually and reported using linear scalar measurements; to report tumor size and assess tumor response, bi-directional measurements (maximal length and perpendicular width) are preferred over unidimentional approaches (e.g. RECIST criteria). At many research centers, software programs are available to determine tumor volumes (3D) in a semiautomatic fashion. These techniques depend on clear margins between tumor tissue and surrounding parenchyma; this is simple for focal, well marginated tumors. However, in NIH Public Access