Functional brain imaging in apraxia.

BACKGROUND: An extensive literature describes structural lesions in apraxia, but few studies have used functional neuroimaging. We used positron emission tomography (PET) to characterize relative cerebral glucose metabolism in a 65-year-old, right-handed woman with progressive decline in ability to manipulate objects, write, and articulate speech. OBJECTIVE: To characterize functional brain organization in apraxia. DESIGN AND METHODS: The patient underwent a neurological examination, neuropsychological testing, magnetic resonance imaging, and fludeoxyglucose F 18 PET. The patient's magnetic resonance image was coregistered to her PET image, which was compared with the PET images of 7 right-handed, healthy controls. Hemispheric regions of interest were normalized by calcrine cortex. RESULTS: Except for apraxia and mild grip weakness, results of the neurological examination were normal. There was ideomotor apraxia of both hands (command, imitation, and object) and buccofacial apraxia. The patient could recognize meaningful gestures performed by the examiner and discriminate between his accurate and awkward pantomime. The magnetic resonance image showed moderate generalized atrophy and mild ischemic changes. Positron emission tomographic scans showed abnormal fludeoxyglucose F 18 uptake in the posterior frontal, supplementary motor, and parietal regions, the left affected more than the right. Focal metabolic deficit was present in the angular gyrus, an area hypothesized to store conceptual knowledge of skilled movement. CONCLUSIONS: Greater parietal than frontal physiological dysfunction and preserved gesture recognition are not consistent with the theory that knowledge of limb praxis is stored in the dominant parietal cortex. Gesture comprehension may be more diffusely distributed.

The value of ultrasound with ultrasound-guided fine-needle aspiration biopsy compared to computed tomography in the detection of regional metastases in the clinically negative neck.

PURPOSE: Head and neck oncologists have not reached consensus regarding the role of contemporary imaging techniques in the evaluation of the clinically negative neck in patients with head and neck squamous cell carcinoma (HNSCC). The purpose of the present study was to compare the accuracy of ultrasound with guided fine-needle aspiration biopsy (UGFNAB) and computed tomography (CT) in detecting lymph node metastasis in the clinically negative neck. METHODS AND MATERIALS: Sixty-four neck sides of patients with HNSCC were examined preoperatively by ultrasound/UGFNAB and CT at one of five participating tertiary care medical centers. The findings were correlated with the results of histopathologic examination of the neck specimen. RESULTS: Ultrasound with guided fine-needle aspiration biopsy was characterized by a sensitivity of 48%, specificity of 100%, and overall accuracy of 79%. Three cases had nondiagnostic aspirations using UGFNAB and were excluded. CT demonstrated a sensitivity of 54%, specificity of 92%, and overall accuracy of 77%. UGFNAB detected two additional metastases not visualized on CT, whereas CT detected no metastases not seen on UGFNAB. The results of UGFNAB were similar between the participating centers. CONCLUSIONS: Approximately one half of the clinically occult nodal metastases in our patient group were identified by both CT and UGFNAB. Overall, UGFNAB and CT demonstrated comparable accuracy. The sensitivity of CT was slightly better than UGFNAB, but the latter remained characterized by a superior specificity. The results of CT and UGFNAB did not appear to be supplementary. The choice of imaging modality for staging of the clinically negative neck depends on tumor site, T-stage, and experience and preference of the head and neck oncologist. If CT is required for staging of the primary tumor, additional staging of the neck by UGFNAB does not provide significant additional value.

Physiological perturbation of ocular and cerebral blood flow as measured by scanning laser ophthalmoscopy and color Doppler imaging.

Retinal blood flow regulation in health remains poorly described. We hypothesized that retinal perfusion is controlled to provide constant O2 delivery to that tissue, and that changes in retinal blood flow in response to chemical stimuli parallel changes in carotid and retrobulbar perfusion. Accordingly, in 11 young adults with normal eye examinations, we measured retinal blood flow indices (via scanning laser ophthalmoscopy [SLO] during fluorescein angiography) and carotid, ophthalmic, and central retinal arterial blood flow indices (via Doppler imaging [CDI]) under control, hypoxic (alveolar PO2 = 55 +/- 3 mmHg) and hyperoxic (alveolar PO2 = 655 +/- 18 mmHg) conditions. The three conditions were counterbalanced in order and isocapnia was maintained in each. Retinal arterial mean dye velocity and arteriovenous passage time, as measured by SLO, were slowed by hyperoxia and accelerated by hypoxia, in rough proportion to the changes in arterial O2 content (+/- 10%; p < 0.05). In the seven subjects in which relative measurements of retinal arterial diameters were obtained, neither hypoxia nor hyperoxia significantly altered vessel diameter. At the same time, mean retinal capillary transit velocity was independent of PO2, suggesting that, in health, retinal capillaries may be recruited as PO2 falls. O2-induced changes in carotid, ophthalmic, or central retinal arterial blood flow velocities (via CDI) were not found, though a wide coefficient of variation (30% for CDI vs. 14% for SLO) may have contributed to this failure. We conclude that, under isocapnic conditions, retinal perfusion may be regulated to provide constant O2 delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial hypophosphatemic rickets causing ocular calcification and optic canal narrowing.

In a case of familial hypophosphatemic rickets, marked bone thickening caused narrowing of the optic canals, resulting in bilateral optic atrophy. The case also showed metastatic calcification in the walls of both globes.

Central nervous system cryptococcosis: parenchymal calcification and large gelatinous pseudocysts.

In an 11-year-old immunocompetent girl with protracted cryptococcal infection of the central nervous system, CT showed multiple areas of parenchymal calcification. MR imaging showed large gelatinous pseudocysts around the brain stem. These imaging features and the child's age are unusual for intracranial cryptococcosis.

Meningeal myelomatosis: CT and MR appearances.

Meningeal myelomatosis is a rare feature of multiple myeloma. We report a case of IgG-kappa myeloma presenting as bilateral intracranial extraaxial masses.

Engorged anterior epidural venous plexus mimics an anterior epidural mass.

A 48-year-old woman presented with severe neck pain on flexion 1 week after a reportedly uncomplicated lumbar puncture, and with a slightly elevated white blood cell count. Magnetic resonance imaging showed an anterior epidural mass that was thought to represent an epidural abscess. At surgery, the epidural "mass" was due to an engorged anterior epidural venous plexus.

Neurosarcoidosis resembling meningioma: MRI characteristics and pathologic correlation.

A 37-year-old woman had visual changes. Magnetic resonance imaging showed an extraaxial mass in the anterior clinoid region that was presumed to be meningioma. There was no evidence of systemic or leptomeningeal disease. Pathologic findings were consistent with sarcoidosis. Isolated mass-like neurosarcoidosis, without systemic or leptomeningeal disease is difficult to diagnose preoperatively.

The spectrum of neuroimaging abnormalities in solvent abuse and their clinical correlation.

The brain magnetic resonance (MR) images and medical records of 6 patients with a history of chronic toluene abuse were reviewed retrospectively. The imaging findings were correlated with clinical impairment. The major findings consisted of atrophy (6 patients), white matter T2 hyperintensity (6 patients), and T2 hypointensity involving the basal ganglia and thalami (5 patients). Also seen was focal enhancement, previously unreported for patients who abused toluene. This study showed a correlation between the degree of neurological impairment and extent of white matter disease. There was no correlation between the severity of white matter changes on MR images and the presence of T2 hypointensity or duration of toluene abuse. There was no definite clinical evidence of damage to the basal ganglia and thalami despite the MR imaging finding of T2 hypointensity. Temporal evidence against the theory that toluene accumulation causes the T2 hypointensity was found.

Sarcoid myelopathy.

A 45-year-old woman with history of iritis, uveitis, and sarcoidosis of the skin presented with a subacute cervical myelopathy. Magnetic resonance imaging (MRI) showed patchy, multifocal, gadolinium-enhancing intramedullary lesions of the spinal cord, and extramedullary lesions of the basal cisterns and fourth ventricle. Symptoms and MRI abnormalities were improved within 1 month of corticosteroid therapy.

Solitary plasmacytoma of the mastoid bone presenting as coalescent mastoiditis.

Acute mastoiditis is a complication of acute otitis media that produces air cell opacification and coalescence on computed tomographic (CT) imaging. This appearance, however, is nonspecific and may be seen in patients with infection and tumor. Magnetic resonance imaging (MRI) can aid in differentiating the two on the basis of differences in tissue signal characteristics and by showing the presence or absence of an associated soft-tissue mass. In this report, we demonstrate the utility of MRI as a complementary imaging modality to CT in the diagnosis of a solitary plasmacytoma of the temporal bone that was initially thought to be coalescent mastoiditis.

Hypoxic-ischemic encephalopathy in areas of primary myelination: a neuroimaging and PET study.

The stage of regional structural and biochemical development of the central nervous system appears as a critical factor determining the distribution of hypoxic-ischemic lesions during the perinatal period. We describe the brain lesions in 12 patients who suffered hypoxia-ischemia during the perinatal period. The gestational age ranged from 35 to 42 weeks and the age at death from 2 to 16 weeks. There is one patient alive at age 18 years and a second patient at age 1 year. The cerebral cortical damage is mainly restricted to areas of primary myelination and adjacent subcortical white matter. In addition, there is thalamic, basal ganglia, brainstem, and spinal cord damage. It is postulated that selective damage occurs in those areas which at the moment of the hypoxic-ischemic insult had achieved higher rates of oxygen-glucose utilization. This hypothesis is supported by studies utilizing positron emission tomography which indicates that glucose utilization in the normal human neonatal brain follows a phylogenetic order. Regions that achieved higher levels of glucose consumption are those that suffered the brunt of the damage in our term neonates.

Clinical and surgical application of reformatted high-resolution CT of the temporal bone.

High resolution CT has played a pivotal role in temporal bone imaging since the early 1980s. Although the appearance of MR imaging technology with its superior demonstration of fluid-containing spaces of the inner ear and the posterior fossa structures, CT continues to offer distinct advantages for the evaluation of conductive hearing loss, and petrous apex lesions. With the advent of helical scanning techniques, CT is increasingly the imaging study of choice for definitive preoperative temporal bone imaging.

FLAIR and HASTE imaging in neurologic diseases.

The need to develop faster imaging techniques has led to the implementation of fast spin-echo imaging, EPI, and hybrid imaging techniques. This article discusses two of these faster imaging techniques, fast fluid-attenuated inversion-recovery (FLAIR) imaging and half-Fourier acquisition single-shot turbo spin-echo (HASTE) imaging, and their potential clinical application in neurologic diseases. FLAIR imaging, in particular, has demonstrated considerable promise for the evaluation of intracranial pathology. HASTE imaging can be used for rapid imaging of the brain or spine in those patients who are claustrophobic or who have difficulty remaining still, but it does not yet have a primary role in clinical neuroradiology.

Increased intracranial pressure and the cerebrospinal fluid spaces.

Increased intracranial pressure is a frequent accompaniment to many of the disease processes affecting the brain and its coverings. Such increased pressure is associated with significant morbidity and mortality. This article briefly reviews the pathophysiology of increased intracranial pressure and addresses the clinical and neuroradiological presentation of increased pressure. As part of the discussion, the concept of hydrocephalus and its treatment and complications are addressed.

Neuroradiologic review of intracranial infection.

The detection of intracranial infection continues to be a common reason for neuroradiologic examination. This review covers the neuroradiologic findings of the variety of common infections. It includes meningitis and its complications, as well as bacterial, viral, tuberculous, fungal, and parasitic diseases. Finally, a review of the common infections associated with AIDS is presented. With an increased ability to recognize such infections, radiologists should be able to supply their clinical colleagues with more specific diagnoses.