Benjamin Y. Huang

Hypoxic-Ischemic Brain Injury: Imaging Findings from Birth to Adulthood

Global hypoxic-ischemic injury (HII) to the brain is a significant cause of mortality and severe neurologic disability. Imaging plays an important role in the diagnosis and treatment of HII, helping guide case management in the acute setting and providing valuable information about long-term prognosis. Appropriate radiologic diagnosis of HII requires familiarity with the many imaging manifestations of this injury. Factors such as brain maturity, duration and severity of insult, and type and timing of imaging studies all influence findings in HII. Severe hypoxia-ischemia in both preterm and term neonates preferentially damages the deep gray matter, with perirolandic involvement more frequently observed in the latter age group. Less profound insults result in intraventricular hemorrhages and periventricular white matter injury in preterm neonates and parasagittal watershed territory infarcts in term neonates. In the postnatal period, severe insults result in diffuse gray matter injury, with relative sparing of the perirolandic cortex and the structures supplied by the posterior circulation. Profound hypoxia-ischemia in older children and adults affects the deep gray matter nuclei, cortices, hippocampi, and cerebellum. Because findings at conventional imaging may be subtle or even absent in the acute setting, particularly in neonates, magnetic resonance spectroscopy can help establish the diagnosis of HII. Promising new neuroprotective strategies designed to limit the extent of brain injury caused by hypoxia-ischemia are currently under investigation.

Endoscopic pedicled nasoseptal flap reconstruction for pediatric skull base defects

A prospective study of endoscopic expanded endonasal approaches (EEA) with nasoseptal flap reconstructions revealed anecdotal evidence of less available relative septal length in pediatric patients. Our goal is to use radioanatomic analysis of computed tomography (CT) scans to determine limitations of the nasoseptal flap in pediatric skull base reconstruction and to describe clinical outcomes after using the nasoseptal flap in six pediatric patients.

Lesions of the Petrous Apex: Classification and Findings at CT and MR Imaging

The petrous apex is a complex region of the central skull base that is surrounded by a number of important vascular and neural structures and can be home to a wide range of disease processes. Lesions arising in or spreading to the petrous apex cause varied and occasionally severe clinical sequelae, which typically result from mass effect or direct invasion of the cranial nerves, brainstem, or internal carotid artery. Because the petrous apex is not amenable to direct examination, cross-sectional imaging with computed tomography and magnetic resonance (MR) imaging plays an important role in diagnosis and characterization of lesions occurring there. Petrous apex lesions can be classified on the basis of their origin into the following categories: developmental lesions, inflammatory lesions, benign tumors, malignant tumors, vascular lesions, and osseous dysplasias. The most common lesions arising in the petrous apex are cholesterol granulomas, which can be reliably diagnosed with MR imaging due to their high signal intensity on both T1-weighted images and T2-weighted images. In addition, one should also be familiar with anatomic variants or pseudolesions in the petrous apex that can be mistaken for pathologic conditions.

Nonadenomatous Tumors of the Pituitary and Sella Turcica

Abstract: While pituitary adenomas make up over 90% of all sellar masses, there are a number of less known tumors, both malignant and benign, which may arise within the sella turcica. These include relatively common tumors such as meningiomas and craniopharyngiomas, as well as extremely rare tumors such as pituitary astrocytomas and granular cell tumors. Unfortunately, many of these tumors lack characteristic imaging features, often making it extremely difficult to distinguish them by imaging alone from the more common pituitary adenoma. In this article, we review several nonadenomatous tumors of the sella, with a focus on their clinical features and typical MR imaging characteristics.

Imaging Characteristics of Children With Auditory Neuropathy Spectrum Disorder

Objective: To identify and define the imaging characteristics of children with auditory neuropathy spectrum disorder (ANSD). Design: Retrospective medical records review and analysis of both temporal bone computed tomographic (CT) and magnetic resonance images (MRI) in children with a diagnosis of ANSD. Setting: Tertiary referral center. Patients: One hundred eighteen children with the electrophysiologic characteristics of ANSD with available imaging studies for review. Interventions: Two neuroradiologists and a neurotologist reviewed each study, and consensus descriptions were established. Main Outcome Measures: The type and number of imaging findings were tabulated. Results: Sixty-eight (64%) MRIs revealed at least 1 imaging abnormality, whereas selective use of CT identified 23 (55%) with anomalies. The most prevalent MRI findings included cochlear nerve deficiency (n = 51; 28% of 183 nerves), brain abnormalities (n = 42; 40% of 106 brains), and prominent temporal horns (n = 33, 16% of 212 temporal lobes). The most prevalent CT finding from selective use of CT was cochlear dysplasia (n = 13; 31%). Conclusion: Magnetic resonance imaging will identify many abnormalities in children with ANSD that are not readily discernable on CT. Specifically, both developmental and acquired abnormalities of the brain, posterior cranial fossa, and cochlear nerves are not uncommonly seen in this patient population. Inner ear anomalies are well delineated using either imaging modality. Because many of the central nervous system findings identified in this study using MRI can alter the treatment and prognosis for these children, we think that MRI should be the initial imaging study of choice for children with ANSD.

Failed Endoscopic Sinus Surgery: Spectrum of CT Findings in the Frontal Recess

Since its introduction over 2 decades ago, functional endoscopic sinus surgery (FESS) has revolutionized the surgical management of chronic sinusitis. Performed over 200,000 times annually in the United States to treat medically refractory sinusitis, FESS has success rates as high as 98%. When surgical failure occurs, it is typically due to postoperative scarring or unaddressed outflow tract obstruction in the region of the frontal recess. The most common causes of surgical failure in the frontal recess include remnant frontal recess cells, a retained uncinate process, middle turbinate lateralization, osteoneogenesis, scarring or inflammatory mucosal thickening, and recurrent polyposis. Computed tomography (CT) of the paranasal sinuses has become indispensable in evaluation of patients with FESS failure, particularly in the frontal recess, a location that can be difficult to visualize at endoscopy. Familiarity with the complex anatomy of the frontal recess and knowledge of the most common causes of surgical failure are essential for proper interpretation of sinus CT images obtained in patients being considered for revision FESS of the frontal sinus.

Brain stem and inner ear abnormalities in children with auditory neuropathy spectrum disorder and cochlear nerve deficiency.

BACKGROUND AND PURPOSE: Cranial abnormalities, including CND, are common in children with ANSD. The purpose of this study was to assess whether CND is associated with brain or inner ear abnormalities in a cohort of children with ANSD. MATERIALS AND METHODS: Two neuroradiologists retrospectively reviewed cranial MR imaging examinations in 103 children with ANSD. Brain, cochlear nerve, and temporal bone abnormalities were described and tabulated. Findings were stratified on the basis of the presence and laterality of CND, and differences in the presence of associated inner ear or intracranial abnormalities were assessed by using 2-tailed Fisher exact tests. RESULTS: CND was identified in 33.0% of children and 26.9% of ears with ANSD. Significantly more patients with bilateral CND had intracranial abnormalities than those with unilateral CND (60.0% versus 15.8%; P = .012). Forty percent of patients with bilateral CND, 0% of patients with unilateral CND, and 10.1% of those without CND demonstrated hindbrain malformations. Patients with bilateral CND were more likely to demonstrate hindbrain malformations than patients with normal nerves (P = .01) or unilateral CND (P = .004). Labyrinthine abnormalities were significantly more common in patients with bilateral CND than in those without CND (P ≤ .001). Cochlear anomalies were more common in patients with bilateral versus unilateral CND (P = .01). IAC and cochlear aperture stenosis were more common in those with unilateral and bilateral CND than those without CND (both P < .001). CONCLUSIONS: Cochlear and hindbrain abnormalities are significantly more common among patients with ANSD with bilateral CND compared with those with at least 1 intact cochlear nerve.

Soft Tissue Tumors of the Head and Neck: Imaging-based Review of the WHO Classification

The World Health Organization (WHO) system for defining and classifying soft tissue tumors is usually applied to lesions that occur in the trunk and extremities, but it also provides an excellent framework for characterizing nonepithelial extraskeletal tumors of the head and neck. Although nonepithelial extraskeletal tumors are in the minority among head and neck lesions, they are by no means rare. The WHO classification system recognizes nine major types based on histologic differentiation: adipocytic, fibroblastic or myofibroblastic, fibrohistiocytic, smooth muscle, skeletal muscle, vascular, pericytic, and chondro-osseous tumors, as well as soft tissue tumors of uncertain differentiation. Tumors of each histologic type may be further subclassified on the basis of their biologic behavior as benign, intermediate (ie, having malignant potential), or malignant. Imaging plays an important role in the noninvasive diagnosis and characterization of nonepithelial soft tissue tumors of the head and neck, providing clues about tumor grade, composition, extent, and involvement of adjacent structures. Although the imaging characteristics of many such tumors are nonspecific, consideration of the clinical history in concert with the imaging findings may help limit the differential diagnosis or even allow reliable diagnosis of some of these tumors.

Pediatric Sensorineural Hearing Loss, Part 2: Syndromic and Acquired Causes

SUMMARY: This article is the second in a 2-part series reviewing neuroimaging in childhood SNHL. Previously, we discussed the clinical work-up of children with hearing impairment, the classification of inner ear malformations, and congenital nonsyndromic causes of hearing loss. Here, we review and illustrate the most common syndromic hereditary and acquired causes of childhood SNHL, with an emphasis on entities that demonstrate inner ear abnormalities on cross-sectional imaging. Syndromes discussed include BOR syndrome, CHARGE syndrome, Pendred syndrome, Waardenburg syndrome, and X-linked hearing loss with stapes gusher. We conclude the article with a review of acquired causes of childhood SNHL, including infections, trauma, and neoplasms.

Pediatric Sensorineural Hearing Loss, Part 1: Practical Aspects for Neuroradiologists

SUMMARY: SNHL is a major cause of childhood disability worldwide, affecting 6 in 1000 children. For children with prelingual hearing loss, early diagnosis and treatment is critical to optimizing speech and language development, academic achievement, and social and emotional development. Cross-sectional imaging has come to play an important role in the evaluation of children with SNHL because otolaryngologists routinely order either CT or MR imaging to assess the anatomy of the inner ears, to identify causes of hearing loss, and to provide prognostic information related to potential treatments. In this article, which is the first in a 2-part series, we describe the basic clinical approach to imaging of children with SNHL, including the utility of CT and MR imaging of the temporal bones; we review the most recent proposed classification of inner ear malformations; and we discuss nonsyndromic congenital causes of childhood SNHL.