Cross-Sectional Imaging Evaluation of Congenital Temporal Bone Anomalies: What Each Radiologist Should Know.

Hearing loss in pediatric age group is associated with many congenital temporal bone disorders. Aberrant development of various ear structures leads into either conductive or sensorineural hearing loss. Knowledge of the embryology and anatomical details of various compartments of the ear help better understanding of such disorders. In general, abnormalities of external and middle ears result in conductive hearing loss. Whereas abnormalities of inner ear structures lead into sensorineural hearing loss. These abnormalities could occur as isolated or part of syndromes. Temporal bone disorders are a significant cause of morbidity and developmental delays in children. Imaging evaluation of children presented with hearing loss is paramount in early diagnosis and proper management planning. Our aim is to briefly discuss embryology and anatomy of the pediatric petrous temporal bones. The characteristic imaging features of commonly encountered congenital temporal bone disorders and their associated syndromes will be discussed.

Principles of functional magnetic resonance imaging: application to auditory neuroscience.

Functional imaging based on magnetic resonance methods is a new research frontier for exploring a wide range of central nervous system (CNS) functions, including information processing in sensory, motor, cognitive, and linguistic systems. Being able to localize and study human brain function in vivo, in relatively high resolution and in a noninvasive manner, makes this a technique of unparalleled importance. In order to appreciate and fully understand this area of investigation, a tutorial covering basic aspects of this methodology is presented. We introduce functional magnetic resonance imaging (fMRI) by providing an overview of the studies of different sensory systems in response to modality-specific stimuli, followed by an outline of other areas that have potential clinical relevance to the medical, cognitive, and communicative sciences. The discussion then focuses on the basic principles of magnetic resonance methods including magnetic resonance imaging, MR spectroscopy, fMRI, and the potential role that MR technology may play in understanding a wide range of auditory functions within the CNS, including tinnitus-related activity. Because the content of the material found herein might be unfamiliar to some, we provide a broad range of background and review articles to serve as a technical resource.

Cutaneous-evoked tinnitus. II. Review Of neuroanatomical, physiological and functional imaging studies.

Cutaneous-evoked tinnitus is a clinical entity that has not been reported previously in the neurootological literature. Herein, a neuroscience framework that encompasses several distinct areas of research is used to conceptualize and help understand this phenomenon. We review normal neuroanatomical and physiological interactions between auditory and somatosensory systems in mammals. Also considered are mechanistic accounts of lesion-induced changes in the CNS following deafferentation/deefferentation of peripheral sensory or motor structures that may have a relationship to this phenomenon, as well as the role of functional imaging modalities in studying various phantom perceptions.

Cutaneous-evoked tinnitus. I. Phenomenology, psychophysics and functional imaging.

DC00166e and acute unilateral deafferentation of the auditory periphery (auditory and vestibular afferents) can induce changes in the central nervous system that may result in unique forms of tinnitus. These tinnitus perceptions can be controlled (turned on and off) or modulated (changed in pitch or loudness) by performing certain overt behaviors in other sensory/motor systems. Clinical reports from our laboratory and several other independent sources indicate that static change in eye gaze, from a neutral head-referenced position, is one such behavior that can evoke, modulate and/or suppress these phantom auditory events. This report deals with a new clinical entity and a form of tinnitus that can be evoked directly by cutaneous stimulation of the upper hand and fingertip regions. In 2 adults, cutaneous-evoked tinnitus was reported following neurosurgery for space-occupying lesions at the base of the skull and posterior craniofossa, where hearing and vestibular functions were lost completely and acutely in one ear (unilateral deafferentation) and facial nerve paralysis (unilateral deefferentation) was present either immediately following neurosurgery or had occurred as a delayed-onset event. Herein, we focus on the phenomenology of this discovery, provide perceptual correlates using contemporary psychophysical methods and document in one individual cutaneous-evoked tinnitus-related neural activity using functional magnetic resonance imaging. In a companion paper, neuroanatomical and physiological interactions between auditory and somatosensory systems, possible mechanistic accounts and relevant functional neuroimaging studies are reviewed.

Longitudinal analysis of olfactory deficits in HIV infection.

The presence and degree of odor identification deficits in 55 HIV-infected (30 asymptomatic, 25 symptomatic) and 29 HIV-negative at-risk control volunteers were examined longitudinally using the University of Pennsylvania Smell Identification Test (UPSIT). Factors other than HIV infection that could account for olfactory loss (i.e., sinusitis or upper respiratory infection) were also considered by obtaining MRI scans of the nasal passages and information from an olfaction questionnaire. No differences were found among groups at the first administration of the UPSIT, with significant differences among groups emerging at the 1-year and 2-year follow-ups. The symptomatic group showed a significant decline in odor identification scores across time, while means for the asymptomatic and control groups remained stable. The presence of sinusitis or an upper respiratory infection appeared to have no effect on odor identification. The implications for these findings in relationship to cognitive decline in neurodegenerative diseases are discussed.

Neurobiochemical changes from Taxol/Neupogen chemotherapy for metastatic breast carcinoma corresponds with suicidal depression.

A patient under Taxol and granulocyte colony stimulating factor (G-CSF, Neupogen) treatment for metastatic breast carcinoma of the liver experienced repeated suicidal depression on days 10 and 11 of therapy. MRI and MRS were performed during the fifth and sixth cycles of chemotherapy on days 1 and 10. The MRI was normal in all four examinations. The MRS showed normal levels of metabolites on days 1 of therapy, with remarkable reproducible declines in neurobiochemicals myo-inositol (23-27%), choline (20-24%), creatine (10-14%) and glutamate/glutamine (22-39%) on day 10 of therapy. The neurobiochemical declines coincided with the patient's experience of suicidal depression. Patients reporting depression during standard cancer therapy may be experiencing previously undocumented chemotherapeutic neurobiochemical imbalances or neurotoxicity.

Articular cartilage volume in the knee: semiautomated determination from three-dimensional reformations of MR images.

PURPOSE: To determine the accuracy of semiautomated quantification of articular cartilage volume from three-dimensional (3D) reformations of magnetic resonance (MR) images. MATERIALS AND METHODS: Sagittal, fat-suppressed, 3D, spoiled gradient-recalled-echo MR imaging of two bovine and two human cadaver knees was performed. Articular cartilage volume was calculated from 3D reformations of the MR images by using a semiautomated program written at the authors' institution. Calculated volumes were compared with directly measured volumes of the surgically removed articular cartilage. RESULTS: The percentage of error of the MR imaging-determined volumes was 6.53% +/- 4.75 (mean +/- standard deviation). A strong correlation between the two sets of observations was shown (r=.997). Linear regression showed the calculated volumes to be highly accurate (slope=1.002, P>.25). Repeated reformations yielded volumes that were reproducible (mean absolute error, 0.013 mL +/- 0.019) and not significantly different from the measured volume (P>.10). CONCLUSION: Semiautomated quantification of knee articular cartilage from MR images yields highly accurate cartilage volumes.

Clinical MR spectroscopy: fundamentals, current applications, and future potential.

In 1959, Dr. Erik Odeblad, a physician, wrote about nuclear magnetic resonance (NMR): "NMR really seems to possess extensive possibilities to help study, in a non-invasive way, many problems in biology and medicine ... When instruments for NMR become more common and available at medical laboratories, we may expect direct routine clinical diagnosis with this new technique" [1]. This 1959 prediction has become a reality in 1995, when examinations using MR spectroscopy and MR imaging are allowing physicians direct routine clinical diagnoses that were previously unobtainable by other radiologic or clinical tests. Many questions are commonly asked about MR spectroscopy, its use, and its applications. The purpose of this article is to answer some of these questions, provide an introduction to MR spectroscopy, review some current clinical applications, and speculate on the future potential of this technique.

Practice effects with the NIMH AIDS abbreviated neuropsychological battery.

The degree of practice effects with the Brief NIMH Neuropsychological Battery for HIV Infection and AIDS is reported using a 7-10 day test-retest interval. The patient groups were asymptomatic and symptomatic of HIV while the control group was made up of "at risk" volunteers. Statistically significant practice effects were obtained on the California Verbal Learning Test, the Paced Auditory Serial Addition Task and the Visual Search Test among the infected individuals. The controls subjects demonstrated statistically significant practice effects on all of the neuropsychological tests. The implications of these findings in prospective studies are discussed.

Fat-suppressed spoiled GRASS imaging of knee hyaline cartilage: technique optimization and comparison with conventional MR imaging.

OBJECTIVE: We studied healthy volunteers with fat-suppressed three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR) to determine parameters that maximize positive contrast between knee articular cartilage and fluid, marrow fat, and muscle; and we compared the technique with conventional MR imaging sequences. The purpose was to determine if fat-suppressed 3D SPGR imaging is useful for detecting abnormalities of the articular cartilages. SUBJECTS AND METHODS: The knees of 10 healthy volunteers were imaged in the axial plane. Fat-suppressed 3D SPGR imaging was performed with a TR of 60 msec, a TE ranging from 5 to 15 msec, and a flip angle ranging from 20 degrees to 80 degrees. This was followed by a similar set of fat-suppressed two-dimensional (2D) SPGR images, and conventional T1- and T2-weighted spin-echo and multiplanar gradient studies. Contrast-to-noise (C/N) ratios were determined for cartilage versus a saline fluid phantom, marrow fat, and muscle. Optimal parameters were determined both quantitatively and by a blinded subjective analysis. RESULTS: A TE of 5 msec and a flip angle of 40 degrees demonstrated the greatest C/N ratio between the signals for cartilage and for fluid, marrow, and muscle. C/N ratios in the 3D sequences were higher than in the 2D, spin-echo, and gradient series, although the absolute C/N ratio values for the T2-weighted spin-echo sequence were higher than those for the 3D fat-suppressed SPGR sequence. Subjective analysis showed articular cartilage to have a consistent trilaminar appearance, and independent interpreters favored a 3D fat-suppressed SPGR sequence with a TE of 5 msec and a flip angle of 40 degrees. Three subjects with incidental joint fluid had C/N ratios within a 95% confidence range for cartilage versus the fluid phantom. CONCLUSION: When a fat-suppressed 3D SPGR sequence of 60/5/40 degrees (TR/TE/flip angle) is used, MR images can show high positive contrast between articular hyaline cartilage and adjacent structures. This convenient technique is different from standard MR imaging sequences because it demonstrates greater signal intensity in cartilage than in fluid, marrow fat, and muscle, and because it consistently shows an organized internal architecture of hyaline cartilage. Fat-suppressed 3D SPGR imaging therefore has promise for detecting abnormalities of the articular cartilage.

Alzheimer dementia: quantification of energy metabolism and mobile phosphoesters with P-31 NMR spectroscopy.

To determine whether high-energy phosphate metabolism and mobile phosphoester indexes of membrane metabolism are altered in Alzheimer disease and to help resolve some inconsistencies in the literature, brain phosphate metabolite concentrations and ratios were measured in 11 patients with mild to severe dementia of the probable Alzheimer type and 14 healthy subjects. Fully relaxed, spatially localized, phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy and proton (hydrogen-1) MR imaging were performed. No significant differences were found in the concentrations and relative ratios of phosphocreatine, nucleoside triphosphate, inorganic phosphate, phosphomonoester, and phosphodiesters in whole axial sections through the lateral cerebral ventricles of the brain that could not be accounted for by atrophy. There was no correlation between P-31 NMR indexes and the severity of dementia as assessed with neuropsychologic testing. High-energy phosphate and membrane metabolism, as detected in vivo with P-31 NMR spectroscopy in whole-brain sections, do not appear to play a major role in the disease process, except as a direct consequence of atrophy quantified with H-1 MR imaging.

The relationship between cardiac function and metabolism in acute adriamycin-treated perfused rat hearts studied by 31P and 13C NMR spectroscopy.

Acute adriamycin cardiotoxicity was studied in the isolated, perfused rat heart by 31P and 13C NMR spectroscopy at flow rates of 15 and 5 ml/min. Treated hearts received a total dose of 13.5 mg of adriamycin. 31P NMR spectra were collected at the beginning and end of each experiment, and cardiac function was recorded throughout. Hearts were perfused with [1-13C]glucose, and 13C NMR spectra were recorded in the presence and absence of the drug. At normal flow (15 ml/min), adriamycin caused a decline in cardiac function which was reversible when the drug was removed. There were no changes in high energy phosphate levels. The labeling of glutamate was unchanged in the presence of adriamycin; however, there was a slight increase in the labeling of lactate and alanine. At reduced flow (5 ml/min), control hearts exhibited a small decrease in ATP and phosphocreatine levels, and cardiac function was depressed. These changes were reversible when normal flow was restored. Nevertheless, adriamycin treatment at low flow caused an irreversible decline in function and in hydrolysis of ATP and phosphocreatine. At reduced flow, the control and drug-treated hearts showed similar labeling of the glutamate pool; however, there was significantly greater labeling of lactate and alanine during adriamycin treatment. These results indicate that adriamycin is more toxic under reduced flow conditions. Impairment of cardiac function by adriamycin without changes in glutamate labeling suggests that this drug alters the relationship between cardiac function and energy production.

AIDS dementia complex: brain high-energy phosphate metabolite deficits.

To test whether compromised high-energy phosphate metabolism is implicated in the neurologic impairment of acquired immunodeficiency syndrome dementia complex (ADC), brain phosphate metabolite concentrations and ratios were measured noninvasively in 12 patients with mild to moderate ADC and 29 healthy volunteers by use of localized phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy and proton (hydrogen-1) magnetic resonance (MR) imaging. In patients, brain phosphocreatine (PCr) and nucleoside triphosphate (NTP) concentrations in sections through the centrum semiovale that were seen with NMR spectroscopy were reduced significantly from normal values of 4.92 mmol/kg wet weight +/- .13 (standard error of the mean) and 2.79 mmol/kg +/- .11, respectively, to 3.33 mmol/kg +/- .26 and 1.99 mmol/kg +/- .13 (P less than .0001). The ratios of metabolites detectable with P-31 NMR spectroscopy did not differ significantly from those of control subjects. The magnitude of the PCr and NTP deficits in ADC was not explicable by focal abnormalities or cerebral atrophy quantified in images of the same regions. These results are consistent with the hypothesis of a generalized virus-associated toxic process affecting brain cell function in ADC. Noninvasive measurement of metabolite concentrations with NMR spectroscopy provides new functional information that may help quantify disease progression and response to therapy.

Glycolytic activity in the human cornea monitored with nuclear magnetic resonance spectroscopy.

This study confirms the feasibility of using nuclear magnetic resonance (NMR) spectroscopy to assess, noninvasively, glucose metabolism in isolated corneal tissue. Glycolytic activity of human corneas was analyzed by high-resolution NMR spectroscopy and spectrophotometric coupling assays. Glucose utilization and lactate formation were readily demonstrated in incubating intact and deepithelialized human corneas utilizing an NMR spectrometer with an array of spectra taken at ten-minute intervals over a period of nine hours. The lactate formation rate by biochemical coupling assays was determined to be approximately 0.50 mumol/hr in the intact cornea and 0.20 mumol/hr in the de-epithelialized cornea. Analysis by NMR spectroscopy of the rate of glucose utilization and lactate formation may be a useful means of determining human donor corneal viability.