Jason N. Nixon

Imaging of Pediatric Renal Transplants and Their Complications: A Pictorial Review

Renal transplantation is the treatment of choice for end-stage renal disease in children. As a technically demanding surgery with complex medical management, it is associated with a number of complications. Anatomic imaging including ultrasonography with color and spectral Doppler and functional assessment with renal perfusion scintigraphy are complementary for the detection and characterization of posttransplant complications. Complications can be characterized by the time of appearance after transplantation (immediate, early, or late) or the anatomic site of origin (perinephric, vascular, urologic, or renal parenchymal). Perinephric fluid collections include hematomas and seromas, abscesses, lymphoceles, and urinomas. Noninfected collections frequently resolve spontaneously but should be monitored to exclude progression. Vascular complications are more prevalent in pediatric patients because of the small vessel caliber and include vascular thrombosis and stenosis. Arteriovenous fistulas and pseudoaneurysms can complicate biopsy and are typically transient. Common urologic complications include urine leak and urinary tract obstruction. Renal perfusion scintigraphy can be invaluable in elucidating the nature of such complications. Renal parenchymal abnormalities include acute tubular necrosis, rejection, and toxic effects of medication. Imaging features of renal parenchymal abnormalities can overlap, and the primary role of imaging is to exclude alternative causes of renal dysfunction. Renal and nonrenal mass lesions are more common in immunosuppressed patients after transplantation. Familiarity with the normal imaging appearance of the renal allograft and the appearances of common complications facilitates accurate diagnosis and timely treatment, with the ultimate goal of increasing graft survival. This goal is particularly crucial in children, given their greater number of projected life years.

The Diagnostic Value of CT Myelography, MR Myelography, and Both in Neonatal Brachial Plexus Palsy

BACKGROUND AND PURPOSE: Although most infants with brachial plexus palsy recover function spontaneously, approximately 10–30% benefit from surgical treatment. Pre-operative screening for nerve root avulsions is helpful in planning reconstruction. Our aim was to compare the diagnostic value of CT myelography, MR myelography, and both against a surgical criterion standard for detection of complete nerve root avulsions in birth brachial plexus palsy. MATERIALS AND METHODS: Nineteen patients who underwent a preoperative CT and/or MR myelography and subsequent brachial plexus exploration were included. Imaging studies were analyzed for the presence of abnormalities potentially predictive of nerve root avulsion. Findings of nerve root avulsion on surgical exploration were used as the criterion standard to assess the predictive value of imaging findings. RESULTS: Ninety-five root levels were examined. When the presence of any pseudomeningocele was used as a predictor, the sensitivity was 0.73 for CT and 0.68 for MR imaging and the specificity was 0.96 for CT and 0.97 for MR imaging. When presence of pseudomeningocele with absent rootlets was used as the predictor, the sensitivity was 0.68 for CT and 0.68 for MR imaging and the specificity was 0.96 for CT and 0.97 for MR imaging. The use of both CT and MR imaging did not increase diagnostic accuracy. Rootlet findings in the absence of pseudomeningocele were not helpful in predicting complete nerve root avulsion. CONCLUSIONS: Findings of CT and MR myelography were highly correlated. Given the advantages of MR myelography, it is now the single technique for preoperative evaluation of nerve root avulsion at our institution.

Diagnostic imaging of posterior fossa anomalies in the fetus and neonate: part 2, posterior fossa disorders

This second portion of a two-part review illustrates examples of posterior fossa disorders detectable on prenatal ultrasound and MRI, with postnatal or pathology correlation where available. These disorders are discussed in the context of an anatomic classification scheme described in Part 1 of this posterior fossa anomaly review. Assessment of the size and formation of the cerebellar hemispheres and vermis is critical. Diagnoses discussed here include arachnoid cyst, Blakes pouch cyst, Dandy-Walker malformation, vermian agenesis, Joubert syndrome, rhombencephalosynapsis, Chiari II malformation, ischemia, and tumors.

Diagnostic imaging of posterior fossa anomalies in the fetus and neonate: part 1, normal anatomy and classification of anomalies.

This article is the first portion of a two-part review that illustrates the normal appearance of the cerebellum and posterior fossa on prenatal ultrasound and MRI and on postnatal diagnostic imaging studies. Classification and terminology of posterior fossa abnormalities in the literature are confusing due to evolution of concepts and sometimes lack of consensus. Accurate classification of posterior fossa anomalies is important for predicting fetal outcome and for appropriate counseling. In Part 1 of this review, prenatal and postnatal imaging techniques for assessing the posterior fossa will be discussed, followed by a discussion of how cerebellar malformations may be classified.

Absent cavum septum pellucidum: a review with emphasis on associated commissural abnormalities

The cavum septum pellucidum (CSP) is an important fetal midline forebrain landmark, and its absence often signifies additional underlying malformations. Frequently detected by prenatal sonography, absence of the CSP requires further imaging with pre- or postnatal MRI to characterize the accompanying abnormalities. This article reviews the developmental anatomy of the CSP and the pivotal role of commissurization in normal development. An understanding of the patterns of commissural abnormalities associated with absence of the CSP can lead to improved characterization of the underlying spectrum of pathology.

Brachial Plexus Birth Palsy: Multimodality Imaging of Spine and Shoulder Abnormalities in Children

OBJECTIVE. The purpose of this article is to provide a comprehensive overview of the imaging of brachial plexus palsy, including both pathologic conditions of the spine and shoulder and clinical background and management. CONCLUSION. Brachial plexus birth palsy can result in permanent disability and limb deformity. Identifying the lesion type and associated sequelae is important in clinical management aimed at optimizing outcome. The imaging algorithms used are guided by clinical presentation and are designed to assess the extent of injury to guide possible surgical intervention.

Presyrinx in a child with acquired Chiari I malformation

Spinal cord signal abnormality resulting from alterations in cerebrospinal fluid flow at the craniocervical junction has been termed a presyrinx state. This condition has been described in the adult literature in association with a variety of conditions that cause obstruction to normal cerebrospinal fluid flow. We present a case of presyrinx in a child in the setting of acquired Chiari I malformation caused by lumboperitoneal overshunting. Awareness of the potentially reversible nature of this condition might allow for intervention before irreversible neurological damage has occurred.

Primary choriocarcinoma of the bilateral basal ganglia presenting in a teenaged male

Primary intracranial choriocarcinoma (PICCC), a type of germ-cell tumor, is a very rare primary tumor of the central nervous system that generally arises in the pineal or suprasellar region. We present a case of a teenage boy with PICCC of the bilateral basal ganglia, an anatomic site for which we were unable to find the previous reports. We offer discussion of the differential diagnosis, imaging characteristics, and prognosis of PICCC and germ-cell tumors of the basal ganglia, in the hope that it will increase awareness and allow for early detection.

Delayed-Onset Movement Disorder and Encephalopathy After Oxycodone Ingestion

We present the case of a 14-year-old girl with a biphasic course after oxycodone ingestion. Clinically, she had a rapid return to baseline after initial ingestion and presented a week later with new-onset ballism, akathisia, and encephalopathy. Neuroimaging demonstrated bilateral globi pallidi and cerebellar lesions with a relative decrease of metabolite peaks on magnetic resonance spectroscopy. Her movement disorder was treated successfully with valproic acid and clonidine. Her cognitive functioning returned to baseline 3 months after ingestion.