Central Nervous System and Head and Neck Histiocytoses: A Comprehensive Review on the Spectrum of Imaging Findings.

The histiocytoses are a rare group of varied but related disorders characterized by abnormal tissue proliferation of macrophages and dendritic cells within tissues. The purpose of this article was to review the imaging findings in patients presenting with CNS and with head and neck manifestations of these disorders. Histiocytoses include but are not limited to Rosai-Dorfman disease, Erdheim Chester disease, Langerhans cell histiocytosis, histiocytic sarcoma, and juvenile xanthogranuloma. A review of the literature was performed to determine the sites of disease involvement. This article includes the demographics, histopathologic criteria for diagnosis, and imaging features of these histiocytoses, and describes the manifestations in locations known to harbor disease: intraaxial and extra-axial intracranial regions, the calvaria, skull base, hypothalamopituitary axis, orbits, paranasal sinuses, spine, and the head and neck region. Histiocytoses have variable imaging appearances in the CNS and in the head and neck region, and radiologists should be aware of the spectrum of findings to avoid mistaking them for other disease processes. LEARNING OBJECTIVE: To understand the general pathophysiology, clinical presentation, and typical imaging characteristics of the most common histiocytoses; comprehend the morphologic and immunohistochemical characteristics of these histiocytoses and the hallmark findings on pathology; and be able to differentiate between these disorders based on their most common presentations.

Dynamic contrast-enhanced perfusion processing for neuroradiologists: model-dependent analysis may not be necessary for determining recurrent high-grade glioma versus treatment effect.

BACKGROUND AND PURPOSE: Dynamic contrast-enhanced perfusion MR imaging has proved useful in determining whether a contrast-enhancing lesion is secondary to recurrent glial tumor or is treatment-related. In this article, we explore the best method for dynamic contrast-enhanced data analysis. MATERIALS AND METHODS: We retrospectively reviewed 24 patients who met the following conditions: 1) had at least an initial treatment of a glioma, 2) underwent a half-dose contrast agent (0.05-mmol/kg) diagnostic-quality dynamic contrast-enhanced perfusion study for an enhancing lesion, and 3) had a diagnosis by pathology within 30 days of imaging. The dynamic contrast-enhanced data were processed by using model-dependent analysis (nordicICE) using a 2-compartment model and model-independent signal intensity with time. Multiple methods of determining the vascular input function and numerous perfusion parameters were tested in comparison with a pathologic diagnosis. RESULTS: The best accuracy (88%) with good correlation compared with pathology (P = .005) was obtained by using a novel, model-independent signal-intensity measurement derived from a brief integration beginning after the initial washout and by using the vascular input function from the superior sagittal sinus for normalization. Modeled parameters, such as mean endothelial transfer constant > 0.05 minutes(-1), correlated (P = .002) but did not reach a diagnostic accuracy equivalent to the model-independent parameter. CONCLUSIONS: A novel model-independent dynamic contrast-enhanced analysis method showed diagnostic equivalency to more complex model-dependent methods. Having a brief integration after the first pass of contrast may diminish the effects of partial volume macroscopic vessels and slow progressive enhancement characteristic of necrosis. The simple modeling is technique- and observer-dependent but is less time-consuming.

Erdheim-Chester disease of the central nervous system: new manifestations of a rare disease.

BACKGROUND AND PURPOSE: ECD is a rare non-Langerhans-cell histiocytosis, which can involve the CNS; therefore, CNS imaging findings have been described in only a small number of patients. To gain additional insight into the CNS manifestations of ECD, we reviewed the findings on imaging of the brain, head and neck, and spine in patients with ECD who presented to our institution. Here, we illustrate manifestations that have not, to our knowledge, been previously described. MATERIALS AND METHODS: CT, MR imaging, and PET/CT studies of the brain, maxillofacial region, and spine were reviewed in 11 patients with ECD. RESULTS: Four new manifestations of ECD were present, including the following: a stellate appearance of intracranial extra-axial lesions, ependymal enhancement along the lateral ventricle with deep linear extension to the lentiform nucleus, irregular enhancement in the pons, and diffuse involvement of the vertebral column on PET/CT. CONCLUSIONS: ECD has a variety of imaging appearances in the CNS, including new manifestations described herein. Neuroradiologists should be aware of these manifestations to avoid mistaking them for other disease processes.

Imaging and clinical features of an intra-axial brain stem schwannoma.

A 68-year-old man presented with a highly symptomatic brain stem tumor originally thought to be a brain stem glioma. Intraoperative MR imaging guidance was used to resect the tumor, and real-time evoked potentials improved during surgery. Pathology findings unexpectedly indicated that the tumor was an intra-axial brain stem schwannoma, a condition reported, to our knowledge, only 6 times previously in the literature. The patient made an excellent recovery with reversal of his symptoms.

Multidetector CT-Guided Lumbar Puncture in Patients with Cancer.

SUMMARY: Lumbar puncture can be performed for therapeutic purposes, to instill intrathecal chemotherapy for leptomeningeal cancer treatment or prophylaxis. This technique is generally performed blindly or under fluoroscopic guidance. However, in certain situations, lumbar puncture using multidetector CT (MDCT)-guided imaging may be beneficial, when other options have been exhausted or depending on the requirements of the performing radiologist's institution. The purpose of this article is to describe the technique and to evaluate outcomes of MDCT-guided lumber puncture for diagnostic and therapeutic purposes in patients with cancer. We conclude that MDCT-guided lumbar puncture is an effective and safe guiding modality for thecal sac access in patients with cancer, particularly where other methods of intrathecal access have failed.

Hematogenous pyogenic facet joint infection.

STUDY DESIGN: Retrospective. OBJECTIVES: To determine the incidence, clinical presentation, diagnostic laboratory values, imaging characteristics, and optimal treatment of hematogenous pyogenic facet joint infections. SUMMARY OF BACKGROUND DATA: There are 27 documented cases of hematogenous pyogenic facet joint infections. Data regarding incidence, clinical presentation, diagnosis, and treatment response are incomplete because of the paucity of reported cases. METHODS: This is a retrospective study of all cases of hematogenous pyogenic facet joint infection treated at one institution. Data from previous publications were combined with the present series to identify pertinent clinical characteristics and response to treatment. RESULTS: A total of six cases (4%) of hematogenous pyogenic facet joint infection were identified of 140 cases of hematogenous pyogenic spinal infection at our institution. Combining all reported cases reveals the following: The average patient age is 55 years. Ninety-seven percent of cases occur in the lumbar spine. Epidural abscess formation complicates 25% of the cases of which 38% develop severe neurologic deficit. Erythrocyte sedimentation rate and C-reactive protein are elevated in all cases. Staphylococcus aureus is the most common infecting organism. Magnetic resonance imaging is accurate in identifying the septic joint and associated abscess formation. Percutaneous drainage of the involved joint has a higher rate of success (85%) than treatment with antibiotics alone (71%), but the difference is not significant (P = 0.37). CONCLUSIONS: Hematogenous pyogenic facet joint infection is a rare but underdiagnosed clinical entity. Facet joint infections may be complicated by abscess formation in the epidural space or in the paraspinal muscles. Uncomplicated cases treated with percutaneous drainage and antibiotics may fare better than those treated with antibiotics alone. Cases complicated by an epidural abscess and severe neurologic deficit should undergo immediate decompressive laminectomy.

A fuzzy logic approach to identifying brain structures in MRI using expert anatomic knowledge.

We report a novel computer method for automatic labeling of structures in 3D MRI data sets using expert anatomical knowledge that is coded in fuzzy sets and fuzzy rules. The method first identifies major structures and then uses spatial relationships to these landmarks to recognize other structures. This labeling process simulates the iterative process that we ourselves use to locate structures in images. We demonstrate its application in three data sets, labeling brain MRI by locating the longitudinal and lateral fissures and the central sulci and then determining boundaries for the frontal lobes. Our method is adaptable to the identification of other anatomical structures.

Imaging of brain tumors in AIDS patients by means of dual-isotope thallium-201 and technetium-99m sestamibi single-photon emission tomography.

Our aim was to evaluate the use of dual-isotope thallium-201 (Tl) and technetium-99m sestamibi (sestamibi) simultaneous acquisition in brain single-photon emission tomography (SPET) for the differentiation between brain lymphoma and benign central nervous system (CNS) lesions in AIDS patients. Thirty-six consecutive patients with enhancing mass lesions on magnetic resonance (MR) imaging were included in the study. SPET of the brain was performed to obtain simultaneous Tl and sestamibi images. Regions-of-interest were drawn around the lesion and on the contralateral side to calculate uptake ratios. The final diagnosis was reached by pathologic findings in 17 patients and clinical and/or MR follow-up in 19 patients. Of the 36 patients, 11 had brain lymphoma, 1 glioblastoma multiforme, 15 toxoplasmosis and 9 other benign CNS lesions. Correlation between SPET and the final diagnosis revealed in 10 true-positive, 23 true-negative, 1 false-positive and 2 false-negative studies. All patients with toxoplasmosis had negative scans. A patient with a purulent infection had positive scans. Tl and sestamibi scans were concordant in every lesion. The same lesions that took up Tl were also visualized with sestamibi. However, sestamibi scans showed higher lesion-to-normal tissue uptake ratios (3.7 +/- 1.8) compared with those of Tl (2.3 +/- 0.8, P < 0.002). Simultaneous acquisition of Tl and sestamibi can help differentiate CNS lymphoma from benign brain lesions in AIDS patients.

Neuroimaging of the aging brain.

Age-related white matter injury has been recognized increasingly with the improvement of brain imaging technology. Arteriosclerosis and venous collagenosis, which occur with aging, result in a spectrum of white matter changes that range from periventricular to subcortical and deep white matter hyperintensities best seen on T2 weighted magnetic resonance imaging. These white matter changes are associated not only with aging, but with hypertension and silent infarctions. Loss of brain volume and accumulation of iron in putamen occur with normal, healthy aging. This article discusses the imaging appearance of healthy aging and pathological correlates of similar appearing alterations. The imaging findings of the most common neurodegenerative disorders, Alzheimer's and Parkinson's disease, are highlighted.

Neuroradiologic findings in children with mitochondrial disorders.

PURPOSE: We report the neuroradiologic findings in 25 children with various mitochondrial diseases. METHODS: Twenty-two children with a mitochondrial disorder had MR imaging of the brain and three children had CT studies. In all cases, the diagnosis was based on examination of muscle morphology, analysis of oxygen consumption and respiratory chain enzyme activity in isolated muscle mitochondria, and analysis of rearrangements of the mitochondrial DNA. RESULTS: Fifteen patients were found to have the classical syndromes of mitochondrial diseases. Four children had Kearns-Sayre syndrome, but only one had the typical neuroradiologic findings of basal ganglia and brain stem lesions, T2 hyperintensity of the cerebral white matter, and cerebellar atrophy; the others had nonspecific or normal findings. Eight patients had Leigh syndrome, and all showed changes in the putamina. Involvement of the caudate nuclei, globus pallidi, thalami, and brain stem was common, and diffuse supratentorial white matter T2 hyperintensity was seen in two of these patients. Three patients had mitochondrial encephalopathy with lactic acidosis and strokelike episodes (MELAS), with infarctlike lesions that did not correspond to the vascular territories. Ten children with complex I or IV deficiencies and abnormal muscle morphology had nonspecific imaging findings, such as atrophy and abnormal or delayed myelination. One patient with combined complex I and IV deficiency had extensive white matter changes. None of the patients with clinical encephalopathy had normal findings. CONCLUSION: MR imaging is helpful in the diagnosis of the classical mitochondrial diseases; however, nonspecific findings are common.

MR and TL-210 spect imaging with pathologic correlation for the assessment of CNS lymphoma vs. toxoplasmosis in AIDS patients.

PURPOSE: Analyze the value of TL-201 (Tl) brain single-photon emission computed tomography (SPECT), to differentiate CNS lymphoma from toxoplasmosis in AIDS patients. MATERIAL AND METHODS: Twenty-four AIDS patients with MR enhancing lesion(s), underwent a brain Tl SPECT. Final diagnosis was established by pathology and clinical/MR follow-up. RESULTS: Nine patients had CNS tumor, 9 toxoplasmosis and 6 other non-tumorous lesions. The sensitivity of T1 to diagnose CNS tumor was 77% and the specificity 93%. Two false negative studies correspond to tumors with significant necrosis. CONCLUSIONS: T1 proved useful for differentiating brain neoplasm from toxoplasmosis. Tumors with significant necrosis, did not show the expected increase in T1 uptake. Determination of T1 uptake ratios help detect tumor with faint tracer uptake.

CNS lymphoma in an AIDS patient involving the posterior fornix case report.

We report an unusual presentation of CNS lymphoma involving the posterior fornix in a patient with AIDS. The patient's initial symptoms included progressive cognitive impairment, consistent with AIDS dementia, as well as impotence and urinary retention suggestive of myelopathy. An MR scan with gadolinium-DTPA enhancement demonstrated enhancing lesions in the cerebellum and in the posterior fornix. At autopsy, the later lesions proved to be lymphoma. This case demonstrates the unusual clinical features that may occur with lesions in the limbic system and importance of gadolinium-enhanced MRI in the evaluation of symptoms of cognitive impairment in patients with advanced HIV infection.

Pseudoprogression of cerebral cavernous angiomas: the importance of proper magnetic resonance imaging technique.

Magnetic resonance imaging (MRI) is the method of choice to detect cerebral cavernous angiomas. Specifically tailored MRI studies are necessary to evaluate patients with cerebral cavernous angiomas. The patient described here, for whom serial MRIs performed on different scanners falsely suggested rapid disease progression, illustrates the point.

Laminar cortical necrosis in MELAS syndrome: MR and neuropathological observations.

Laminar cortical necrosis has been described in many conditions of cellular energy depletion, such as hypoxia and hypoglycemia. In MELAS, a genetic defect in mitochondrial protein synthesis leads to impairment of oxidative phosphorylation, with subsequent insufficient energy production within the cell. Neurons are more vulnerable to energy depletion than glial cells and vascular elements, and among the layers of the cerebral cortex the lower laminae are more vulnerable than the superficial layers. We studied a child with severe MELAS syndrome two months before death with MR and compared the images to autopsy findings, including macroscopic specimens and light and electron microscopy. The MR images showed an excellent correlation with the neuropathological results and displayed the various degrees of damage to the brain tissue caused by deficient energy production. Acute laminar cortical necrosis was seen as swelling of the cortex with intracortical hyperintense bands in T2-weighted images. The subacute stage with focal cortical hemorrhage was displayed as hyperintensity of the gyral surface in T1-weighted and hypointensity in T2-weighted images, with T2-hyperintensity and swelling of the rest of the cortex and underlying white matter. Severe cortical atrophy represented the chronic stage.

Cognitive performance and regional brain volume in human immunodeficiency virus type 1 infection.

BACKGROUND: Brain atrophy has been reported to occur in advancing human immunodeficiency virus (HIV) infection, particularly in patients with HIV-related dementia. Atrophy of the caudate region, as assessed by magnetic resonance imaging measures, has been reported to correlate with cognitive impairment in patients with HIV infection; however, differences in the severity of HIV-induced immunosuppression may have contributed to these findings. OBJECTIVE: To determine the relationship between regional brain volumes and cognitive performance in individuals with HIV infection. PATIENTS AND METHODS: We evaluated 11 patients with advanced HIV disease by using neuropsychologic tests and quantitative magnetic resonance imaging volume analysis. SETTING: University hospital, involving patients from a clinical trial. RESULTS: Caudate volume, expressed as a ratio of total intracranial volume, correlated with performance on the Trails A and Grooved Pegboard tests, but not with other tests of memory, motor speed, or mood (adjusted for age and education). Hippocampal volume did not correlate with any of the neuropsychologic tests. CONCLUSIONS: Caudate volume in patients with advanced HIV disease is associated with poor performance on neuropsychologic tests of complex motor and sequencing skills. Hippocampal volume does not appear to be related to impairment on neuropsychologic tests. These findings are independent of the degree of immunosuppression and the overall extent of brain atrophy; however, these results must be interpreted with some caution, given the limited sample size.

Parietal occipital edema in hypertensive encephalopathy: a pathogenic mechanism.

Eight patients with hypertensive encephalopathy from diverse etiologies developed cerebral edema in the vertebrobasilar distribution which resolved after blood pressure was lowered. Parietal occipital edema is a recognized feature of hypertensive encephalopathy. The explanation for this regional pathological variation in hypertensive encephalopathy remains undefined. Some evidence suggests that sympathetic innervation of the anterior cerebral vasculature may be protective, and conversely, the relative lack of sympathetic innervation in the vertebrobasilar vasculature may predispose the parietal occipital region to the development of cerebral edema in hypertensive encephalopathy.

Putaminal Iron Depositionin HIV Infection.

PURPOSE: T2 shortening (hypointensity) in magnetic resonance (MR) images of the putamen, which may be associated with iron deposition, only occurs in normal subjects over the age of 60 years. Increased or premature putaminal iron deposition may be related to brain injury. We sought to determine the correlation between MR putaminal hypointensity in HIV-infected patients and brain iron deposition. METHODS: Eleven T2-weighted axial MR scans were retrospectively rated for the extent of putaminal hypointensity from patients who also had neuropathological examination for the extent of putaminal iron disposition. Correlations between MR putaminal hypointensity and brain iron were obtained. RESULTS: Neuropathological examination in 9 of 10 patients with putaminal hypointensity demonstrated putaminal iron deposition, predominantly in a perivascular pattern. CONCLUSIONS: Premature putaminal iron deposition occurs in patients with HIV infection and may be detected by MR imaging.

Infantile-onset spinocerebellar ataxia: MR and CT findings.

PURPOSE: To report the MR and CT findings in a hereditary disease, infantile-onset spinocerebellar ataxia (IOSCA). METHODS: We studied the brains of 17 patients with infantile-onset spinocerebellar ataxia with CT and/or MR to determine the presence of cerebellar and brain stem atrophy and parenchymal lesions. RESULTS: Cerebellar cortical atrophy was seen in 13 patients. The degree of atrophy correlated with increasing age and clinical deterioration. Brain stem atrophy was seen in 8 patients. It was never severe, and the basis pontis was not flattened even in the most severe cases. Hyperintense lesions were noted within the white matter of cerebellum, in the dentate nuclei, and in the middle cerebellar peduncles in 3 patients. The upper cervical cord was seen in 9 patients and showed mild to moderate atrophy in 4. The basal ganglia and cerebral hemispheres were normal, except in 2 patients transient cortical and subcortical lesions developed during episodes of status epilepticus; mild cortical brain atrophy subsequently developed. CONCLUSION: The brain MR and CT findings of patients with infantile-onset spinocerebellar ataxia correspond to the neuropathologic entities of cerebellar cortical atrophy, olivopontocerebellar atrophy, and spinocerebellar atrophy. The appearance of the findings followed a uniform time sequence from cerebellar cortical atrophy in the early stage of the disease to olivopontocerebellar atrophy and spinocerebellar atrophy in the later stage. The severity of atrophy correlated with clinical deterioration.

Duplication of the extracranial internal carotid artery.

We describe a case of duplication of the left internal carotid artery from a point 1 cm distal to the origin to the proximal petrous segment where the vessel reunites. Duplication and fenestration of the internal carotid artery are discussed. A review of embryologic development is presented. Identification of these entities is important, especially in patients who require surgical intervention involving the internal carotid artery.