Clear cell carcinoma of the base of the tongue: MR imaging findings

Clear cell carcinoma of the base of the tongue is a rare minor salivary gland neoplasm, and to our knowledge, the MR imaging appearance of this entity has not been described. We present the MR imaging findings in such a case and review the differential diagnosis for tongue base masses in an adult.

Neuropathologic findings in a Guillain-Barré patient with strokes after IVIg therapy

Strokes have been rarely associated with immunoglobulin G (IVIg) therapy. A 70-year-old woman with stable polycythemia vera developed Guillain-Barré syndrome and received IVIg, 8 days following which she became comatose due to bilaterally symmetric cerebral infarcts. Autopsy showed intravascular aggregates of fibrin-IgG but also platelets and a necrotizing microangiopathy in the infarcts.

Diffusion-weighted echo-planar MR imaging of CNS involvement in systemic lupus erythematosus

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the range of findings at diffusion-weighted magnetic resonance (MR) imaging in patients with systemic lupus erythematosus (SLE) and central nervous system involvement.

MATERIALS AND METHODS

Diffusion-weighted MR images were reviewed in 20 patients with SLE and correlated with clinical symptoms and findings at computed tomography, conventional MR imaging, MR angiography, or conventional angiography.

RESULTS

Diffusion-weighted MR imaging showed acute or subacute lesions in nine of 20 patients (45%). In the other 11, it showed no abnormal findings or chronic lesions. In four of the nine patients with lesions, diffusion-weighted imaging primarily showed hyperintense lesions with decreased apparent diffusion coefficient (ADC), which indicates acute or subacute infarcts. In four other patients, it primarily showed iso- or slightly hyperintense lesions with increased ADC, suggesting vasogenic edema. In two of these four patients, the findings were consistent with hypertensive encephalopathy. In the other two, small hyperintense foci on diffusion-weighted images with decreased ADC were seen within the vasogenic edema. These foci presumably represent microinfarcts associated with SLE vasculopathy. In the ninth patient, diffusion-weighted imaging showed a small linear hyperintense lesion with normal ADC in the left parietooccipital region.

CONCLUSION

Diffusion-weighted imaging shows primarily two patterns of acute or subacute parenchymal lesions in patients with SLE: acute or subacute infarction and vasogenic edema with or without microinfarcts.

Diffusion anisotropy of the internal capsule and the corona radiata in association with stroke and tumors as measured by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE

Diffusion-weighted MR images have enabled measurement of directionality of diffusion (anisotropy) in white matter. To investigate differences in the anisotropy for various types of pathologic findings and the association between the anisotropy of tracts and neurologic dysfunction, we compared the anisotropy of the posterior limb of the internal capsule and the corona radiata between patients with stroke and those with tumors and between patients with and without hemiparesis.

METHODS

Thirty-three patients consisting of 11 with tumors and 22 with ischemic disease (16 acute infarction, four old infarction, and two transient ischemic attack) and nine control patients were studied with a 1.5-T MR imager. Diffusion-weighted images were obtained with diffusion gradients applied in three orthogonal directions. The diffusion anisotropy measurements were obtained from regions of interests defined within the internal capsule and the corona radiata.

RESULTS

The diffusion anisotropy was significantly reduced in all internal capsules and coronae radiata involved by infarcts, tumors, and peritumoral edema compared with that of the control patients (P <.0001). This reduction was most prominent in the tracts involved by tumors (P <.05). The anisotropy of the internal capsules and coronae radiata was significantly decreased in cases with moderate-to-severe hemiparesis as compared with those with no or mild hemiparesis (P <.0001). Diffusion anisotropy tended to be also reduced in normal-appearing internal capsules and coronae radiata that were remote from the involved segment of the corticospinal tract.

CONCLUSION

The degree of impaired diffusion anisotropy may vary in different pathologic conditions and correlate with neurologic dysfunction. The measurement of diffusion anisotropy may provide additional information relating to neurologic function and transneuronal effects.

Human herpesvirus 6-meningoencephalitis in an HIV patient with progressive multifocal leukoencephalopathy

Human herpesvirus 6 (HHV6) has been reported as a rare cause of meningoencephalitis and leukoencephalitis. We present an HIV-infected patient with lesions of progressive multifocal leukoencephalopathy (PML), but also meningoencephalitis apparently due to HHV6. Immunohistochemistry for HHV6 antigens and in situ polymerase chain reaction for HHV6 genome showed many positive lymphocytes and microglia in the meningeal and cortical lesions. More importantly, dead and dying neurons were conspicuous; some were undergoing neuronophagia and some displayed evidence of HHV6 infection. A pathogenic role for this almost universal, and usually commensal, virus in inflammatory brain lesions and PML is briefly discussed.

MR volumetric analysis of the human basal ganglia: normative data

RATIONALE AND OBJECTIVES

The authors undertook this study to identify a precise, semiautomated, reproducible magnetic resonance (MR) imaging technique for measuring the basal ganglia, to establish normative volumetric data, and to verify the presence of previously reported asymmetries.

MATERIALS AND METHODS

Twenty-eight healthy adults underwent cranial MR examination. The volumes of the various components of the basal ganglia were measured by means of a combination of thresholding and manual tracing techniques performed with specialized software. The validity of these measurements was assessed by fashioning, imaging, and measuring a practical basal ganglia phantom. Measurement accuracy was also established by means of inter- and intrarater reliability indexes. Normalized volumes were statistically analyzed with analysis of variance and paired t tests.

RESULTS

The absolute values of the various components of the basal ganglia varied widely even though the volumes were normalized to differences in intracranial volume. The right caudate nucleus volume was significantly (P < .000001) larger than the left in both men and women and in both right-handed and non-right-handed subjects. This asymmetry led to an increase in the overall volume of the basal ganglia on the right.

CONCLUSION

The authors have defined a precise, reproducible technique for measuring various components of the basal ganglia and have established normative data. The basal ganglia, similar to other brain structures, exhibit hemispheric lateralization.

Diffusion-weighted echo-planar MR imaging: clinical applications and pitfalls -- a pictorial essay

Diffusion-weighted imaging (DWI) provides unique information about various pathological changes of the brain. DWI is sensitive for the detection of hyperacute infarcts, and useful in distinguishing acute or subacute infarcts from chronic infarcts. DWI is useful in differentiating cytotoxic edema from vasogenic or interstitial edema, which may help to determine prognosis. DWI is useful in differentiating cystic or necrotic tumors from abscesses or epidermoids. DWI can discriminate nonenhanced tumor infiltration from vasogenic edema, and differentiate dysmyelination from demyelination.

Efficacy of targeted CT angiography in evaluation of intracranial internal carotid artery disease

RATIONALE AND OBJECTIVES

This study evaluated the efficacy of targeted computed tomographic (CT) angiography in the diagnosis of intracranial internal carotid artery (ICA) disease and compared the results of routine and targeted CT angiography.

MATERIALS AND METHODS

Fifty-four patients (24 male and 30 female patients aged 2 months to 87 years) were examined with CT angiography. Digital subtraction angiography (DSA) was performed in 42. CT angiograms were reconstructed with the maximum-intensity projection (MIP) algorithm. Targeted CT angiography was performed by individually reconstructing a single ICA territory. Each ICA was divided into four segments, and findings of routine MIP CT angiography, routine MIP plus targeted CT angiography, and DSA were reviewed independently by two neuroradiologists for vascular lesions involving each segment. Routine and targeted CT angiograms were also evaluated to determine how well both ICAs were visualized.

RESULTS

Routine CT angiography was rated good or excellent for ICA visualization in 64% of cases, compared with 81% for targeted CT angiography (P = .0005). The overall agreement between routine CT angiography and DSA and between routine plus targeted CT angiography and DSA was 92% and 94%, respectively. There was no statistically significant difference between the percentages of vascular lesions detected with routine CT angiography alone and with routine plus targeted CT angiography. Both methods tended to show false-positive findings of steno-occlusive disease, but targeted CT angiography showed details of aneurysms and stenotic lesions that were easily overlooked with routine CT angiography alone.

CONCLUSION

Routine plus targeted CT angiography, while providing superior image quality, did not have much clinical effect; further assessment may be needed.

Characteristics and pitfalls of contrast-enhanced, T1-weighted magnetization transfer images of the brain

RATIONALE AND OBJECTIVES

This study was undertaken to clarify the difference in signal pattern on contrast material-enhanced T1-weighted magnetic resonance (MR) magnetization transfer (MT) images between enhancing and nonenhancing lesions in various intracranial diseases and to determine the necessity of nonenhanced MT images for evaluating lesional contrast enhancement.

MATERIALS AND METHODS

MR images of 116 patients who underwent nonenhanced T1-weighted imaging, nonenhanced MT imaging, and contrast-enhanced MT imaging were reviewed. The increase in signal intensity of lesions relative to normal brain was compared between nonenhanced T1-weighted images and contrast-enhanced MT images. Signal intensity of lesions was compared with that of the striate nucleus and white matter on contrast-enhanced MT images. True enhancement was determined by comparison with nonenhanced MT images.

RESULTS

In all, 143 lesions, including 86 enhancing and 57 nonenhancing lesions, were identified among 63 patients. Almost all (99%) of the enhancing lesions were hyperintense to striate nucleus on contrast-enhanced MT images, and most (>87%) showed moderate to marked signal intensity increase from nonenhanced T1-weighted images to contrast-enhanced MT images. Most (>95%) of the nonenhancing lesions showed mild or no increase in relative signal intensity, and most (75%) were iso- or hypointense to striate nucleus on contrast-enhanced MT images. A few nonenhancing lesions (4%-6%), however, showed increase in signal intensity that was indistinguishable from true enhancement without comparison to non-enhanced MT images.

CONCLUSION

Nonenhanced MT images should be obtained to assess pathologic enhancement accurately.

Heschl and superior temporal gyri: low signal intensity of the cortex on T2-weighted MR images of the normal brain

PURPOSE

To study the normal signal intensity pattern in the primary auditory cortex (first Heschl gyrus [HG]) and the surrounding cortices in the superior temporal gyrus (STG) and middle temporal gyrus (MTG) on T2-weighted magnetic resonance (MR) images.

MATERIALS AND METHODS

Coronal T2-weighted fast spin-echo MR images in 30 neurologically normal patients (60 hemispheres) were retrospectively analyzed. Two raters evaluated the cortical signal intensity of the first HG and the neighboring STG and compared them with those of the MTG and the subcortical white matter. The cortical signal intensities between the first HG and the STG were also directly compared. Coronal MR images, which included images of the anterior and posterior halves of the first HG, were evaluated separately.

RESULTS

All first HGs were hypointense to the MTG and were either iso- or hypointense to the STG. Cortical hypointensity was especially prominent in the posterior half; the first HG was isointense to the white matter in 33 (55%) hemispheres. The STG was hypointense to the MTG in 54 (90%) hemispheres and in the anterior halves of 36 (60%) hemispheres.

CONCLUSION

These findings demonstrate lower signal intensity of the cortex on T2-weighted images in the first HG and surrounding STG compared with that of the MTG.

Central brain herniation secondary to juvenile diabetic ketoacidosis

We present the CT, MR, and autopsy findings of central brain herniation in a 9-year-old boy undergoing treatment for diabetic ketoacidosis (DKA). Severe cerebral edema resulting in central brain herniation is an uncommon complication of the treatment of DKA but carries with it high morbidity and mortality. Radiologic imaging and autopsy findings in this case revealed striking infarctions of central brain structures.

Fibro-osseous lesions of the central nervous system: report of four cases and literature review

Fibro-osseous lesions, also reported as calcifying pseudoneoplasms of the neural axis, are uncommon lesions of the CNS. We report four additional cases: two extraaxial and two intraaxial, in patients ages 33, 47, 49, and 59 years at presentation. Fibro-osseous lesions involving the CNS demonstrate variable proportions of fibrous stroma, bone, palisading spindle to epithelioid to multinucleated cells in association with a highly distinctive, perhaps pathognomonic, chondromyxoid-like matrix often distributed in a nodular pattern. This histopathologically distinctive lesion can be seen in many regions of the neuraxis, often with a dural association, and most commonly along the vertebral column. It appears to be a slow-growing lesion and, with wide excision, the prognosis is excellent. The etiology remains unclear, but the preponderance of data favors a reactive rather than neoplastic process. If this putative pseudotumor is not recognized histopathologically, a neoplastic or infectious differential might result in inappropriate investigations and potentially harmful therapies.

Functional MRI study of auditory and visual oddball tasks

To seek neural sources of endogenous event-related potentials, brain activations related to rare target stimuli detection in auditory and visual oddball tasks were imaged using a high temporal resolution functional MRI technique. There were multiple modality specific and modality non-specific activations. Auditory specific activations were seen in the bilateral transverse temporal gyri and posterior superior temporal planes while visual specific activations were seen in the bilateral occipital lobes and their junctions with the temporal lobes. Modality non-specific activations were seen in multiple areas including the bilateral parietal and temporal association areas, bilateral prefrontal cortex, bilateral premotor areas, bilateral supplementary motor areas and anterior cingulate gyrus. Results were consistent with previous intracranial evoked potential recording studies, and supported the multiple generator theory of the endogenous event-related potentials.

Value of CT angiography in the evaluation of a peripheral anterior inferior cerebellar artery aneurysm: case report

We report a case of a peripheral anterior inferior cerebellar artery (AICA) aneurysm in a 66-year-old woman. Computed tomography angiography (CTA) demonstrated a saccular aneurysm in the left AICA. A subsequent vertebral digital subtraction angiography using our standard injection technique failed to demonstrate the aneurysm. However, the aneurysm was visualized on a follow-up injection performed with an increased contrast dose and injection rate. CTA proved to be critical in the detection of this aneurysm which could have been easily overlooked on a conventional angiogram.

Fibro-osseous lesions involving the brain: MRI

We present the MRI findings in two patients with "fibro-osseous lesions" involving the central nervous system. A left temporal lobe mass was present in one patient and an extra-axial mass at the skull base in the other. In both cases, calcification was present, with low signal intensity on T1- and T2-weighted images.

Cerebral giant aneurysm with extensive vasogenic edema

An unusual presentation of a giant intracranial aneurysm is demonstrated. The patient was a 58-year-old woman who developed sudden onset of headache followed by generalized seizures. CT scan showed a high-density lesion in the middle cranial fossa with extensive vasogenic edema. Possible mechanisms for the edema are discussed.

A case of subacute combined degeneration: MRI findings

The specific spinal cord lesion caused by vitamin B12 deficiency is known as subacute combined degeneration (SCD). Neuropathological studies of SCD show lesions mainly in the posterior and lateral columns, involving the cortico-spinal and spino-cerebellar tracts. We report a case of SCD in a 19-year-old man who presented with 4 weeks history of gradually progressing tingling in both hands. MRI of the cervical spine demonstrated symmetrical areas of T2 signal abnormality involving the dorsal columns of the cervical cord from the C2 through C5 levels associated with spinal cord expansion. He was treated with vitamin B12 supplements and experienced gradual improvement in his clinical symptoms. Repeat MRI of the cervical spine after 2 months revealed slight decrease in the area of abnormal signal.

MR imaging of the mamillothalamic tract

PURPOSE

To demonstrate the normal and abnormal appearance of the mamillothalamic tract (MTT) on cranial magnetic resonance (MR) images.

MATERIALS AND METHODS

Two formalin-fixed normal human brain specimens sectioned in axial and coronal planes were used to demonstrate the normal anatomy of the MTT. MR images were obtained in 32 volunteers. Proton-density-weighted coronal and axial pulse sequences were used. The images were evaluated for visualization quality and size and signal intensity of the MTTs in correlation with the specimens. Abnormal MTTs were identified on cranial MR images in two patients, and the imaging findings were analyzed. The clinical history of the patients was also reviewed to determine the effect of these findings on patient care.

RESULTS

Normal MTTs were easily identified on MR studies of cadaveric brains and of the brains of the human volunteers. On MR images, normal MTTs were commonly symmetric in appearance, with signal intensity equal to that of other normal fiber tracts. The abnormal MTTs showed high signal intensity on images obtained with a long repetition time or asymmetric volume loss and were associated with atrophy of the ipsilateral mamillary body.

CONCLUSION

Normal MTTs are readily visible on conventional MR images. Abnormality of the MTT is a very subtle finding but may be a marker of a limbic system abnormality.

Perirolandic cortex in infants: signal intensity on MR images as a landmark of the sensorimotor cortex

PURPOSE

To correlate the perirolandic low signal intensity seen on T2-weighted magnetic resonance (MR) images in neonates and infants with the anatomically located sensorimotor cortex.

MATERIALS AND METHODS

Axial T2-weighted MR images of 146 consecutive patients less than 6 months old were reviewed. The sensorimotor cortex was located by identifying the central sulcus. Two independent readers attempted to identify the central sulcus using two anatomic methods independently and in combination. The location of the central sulcus was compared with that of the perirolandic low signal intensity.

RESULTS

Seventy-two normal hemispheres in 36 patients and 91 abnormal hemispheres in 47 patients showed clear perirolandic low signal intensity. The central sulcus was located anatomically in 70 and 72 normal hemispheres (97% and 100%, respectively) and 90 and 91 abnormal hemispheres (99% and 100%, respectively). In all normal hemispheres, the identified central sulcus correlated with the perirolandic low signal intensity. In contrast, an apparent mismatch was found in two hemispheres in a patient with Dandy-Walker syndrome.

CONCLUSION

The perirolandic low signal intensity seen on T2-weighted MR images is located exactly in the anatomic sensorimotor cortex in normal brains, whereas a mismatch can occur in abnormal brains.

Pseudoaneurysm of the petrous internal carotid artery after skull base infection and prevertebral abscess drainage

A 37-year-old woman with a skull base infection sustained massive oropharyngeal bleeding after incisional nasopharyngeal biopsy and drainage of a prevertebral abscess. A pseudoaneurysm originating at the petrous portion of the internal carotid artery was initially misinterpreted on MR images as typical postoperative change within a resolving abscess cavity. Follow-up MR imaging and conventional angiography ultimately disclosed the pseudoaneurysm.

Benign fibrous histiocytoma of the nasal cavity in a newborn: MR and CT findings

Benign fibrous histiocytoma of the nasal cavity in a newborn is rare, and the MR imaging appearance of this entity has not been reported. We present the MR and CT findings in such a case and review the differential diagnosis for intranasal masses in the neonate.

Cervical spinal meningioma with unusual MR contrast enhancement

A 16-year-old girl had progressive neck pain and weakness in the left hand. MR images showed a dumbbell-shaped spinal tumor with a prominently enhancing intradural component and a minimally enhancing extradural component. Pathologic examination revealed a meningioma with an intradural transitional component and an extradural syncytial component. The tumor showed no significant cystic change or necrosis.

Initial experience with helical CT and 3D reconstruction in therapeutic planning of cerebral AVMs: comparison with 3D time-of-flight MRA and digital subtraction angiography

PURPOSE

We report our initial experience with helical CT and CT angiography (CTA) in evaluating cerebral arteriovenous malformations (AVMs) in comparison with time-of-flight MR angiography (MRA) and digital subtraction angiography (DSA).

METHOD

Twelve AVMs were studied with CTA, non-gadolinium-enhanced MRA, and DSA. Reconstructed images were obtained in three display methods (maximum intensity projection, shaded surface black and white, shaded surface color). Shaded surface color display was obtained by assigning different colors to vessels and "presumed" nidus. The number of feeding arteries and draining veins associated with each AVM was independently counted in each modality. The relative ease of depicting the nidus and vessels was also determined in each display method. AVM nidus dimensions were measured on CTA and MRA source images and interobserver differences were compared.

RESULTS

CTA-reconstructed images depicted more veins but fewer arteries than MRA. Shaded-surface color displays best delineated vessels and nidus. Nidus dimension measurement was possible on CTA in all AVMs but impossible on MRA in four AVMs due to interference by methemoglobin (three AVMs) and phase artifact (one AVM). The interobserver difference in nidus dimension as measured on CTA was significantly smaller than that on MRA.

CONCLUSION

Reconstructed CTA images and CTA source images seem to be valuable adjuncts or alternatives to MRA.

Symptomatic vertebral hemangioma: atypical spoke-wheel trabeculation pattern

We present a case of symptomatic vertebral hemangioma in a 49-year-old woman who presented with abrupt onset of left lower extremity symptoms. MR images showed an unusual spoke wheel trabeculation pattern on the axial CT and MR images. Because the entire vertebral body was involved, exclusion of malignant tumor was necessary.

CT angiography in the evaluation of acute stroke

PURPOSE

To determine the worth of CT angiography of the circle of Willis as a supplement to routine CT in the examination of patients with symptoms of acute stroke in terms of its depiction of the number and distribution of arterial stenoses or occlusions. We also sought to compare the accuracy of CT angiography with MR angiography and/or digital subtraction angiography (DSA).

METHODS

One hundred forty-five patients with symptoms of acute stroke were examined with routine head CT and CT angiography of the circle of Willis. MR angiography was also performed in 27 patients and DSA in 28 patients. CT and MR angiograms and DSAs were reviewed for stenoses or occlusions involving the vessels about the circle of Willis. MR and CT angiograms were also evaluated for image quality, and the corresponding routine CT and MR studies were evaluated for the presence of arterial infarction.

RESULTS

CT angiograms were rated good or excellent in 89% of cases whereas MR angiograms were rated good or excellent in 92% of cases. Arterial stenoses or occlusions were present on 43% of CT angiograms, 48% of MR angiograms, and 21% of DSAs. Findings were in agreement in 98% of the vessels analyzed by CT angiography and MR angiography. Similarly, there was overall agreement of findings in 99% of vessels analyzed by CT angiography and DSA. None of the patients had any immediate adverse reactions after administration of intravenous nonionic iodinated contrast material.

CONCLUSION

CT angiography is an accurate and safe method for evaluating arterial stenoses or occlusions in the vessels about the circle of Willis. CT angiography should be used in patients with symptoms of acute stroke for whom evaluation of the intracranial vasculature is desirable.

Unusual manifestation of a vein of Galen malformation: value of CT angiography

We describe a neonate with aneurysmal dilatation of the vein of Galen with arteriovenous fistulous sites located at the superior vermian vein. Helical CT angiography was useful for evaluating the anomalous vessels.

Infarcted spinal schwannoma: an unusual MR finding

We present a case of infarcted schwannoma of the thoracic spine in a patient with acute cord compression. MR images did not enhance after contrast administration, which is highly atypical for schwannoma, but was in keeping with the pathologic findings in this case.

Fixation of complement by anti-F(ab')2 antibodies or ssDNA when added to systemic lupus erythematosus sera

A solid phase total hemolytic complement assay was used to quantitatively determine the % complement fixation by anti-F(ab')2 antibodies or ssDNA when added to serum from patients with systemic lupus erythematosus (SLE). Both autologous and homologous anti-F(ab')2 antibodies with demonstrated anti-anti-ssDNA activity fixed complement when added to SLE sera and normal human complement. Furthermore, comparable amounts of anti-F(ab')2 antibodies with minimal anti-anti-ssDNA activity fixed zero or minimal amounts of complement when added to the same lupus sera. When measured by the same assay with the same sera, ssDNA fixed greater amounts of complement than did comparable amounts of any of the anti-F(ab')2 antibodies.