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Biomedical subjects

D Norman

Publications and source records attributed to D Norman.

At least 163 records · Page 9Linked to original sources
PubMed1988

MR evaluation of large intracranial aneurysms using cine low flip angle gradient-refocused imaging.

MR imaging has proved to be useful in evaluating large intracranial aneurysms. The parent artery and patent lumen can be identified as flow voids and differentiated from thrombus. However, in the presence of slow flow, even-echo rephasing, and motion artifact, increased intraluminal signal may be present, which may be difficult to distinguish from thrombus. Aneurysms are also dynamic lesions and exert pulsatile mass effect on adjacent structures. Further definition of vascular anatomy and physiology may aid in therapeutic planning and assessment. Cine MR is a new technique using a movie loop of sequential GRASS (gradient-recalled acquisition in the steady state) images obtained during various points in the cardiac cycle. The combination of GRASS images and cardiac gating thus allows cinegraphic display of vascular structures. A comparison of this method with routine T1- and T2-weighted MR imaging and angiography was made in a group of 13 patients with intracranial aneurysms greater than 1.5 cm in diameter. Eight of these patients underwent transvascular detachable balloon occlusion. With cine MR, flowing blood has high intensity due to flow-related enhancement. Turbulent and high-velocity flow can be recognized on the basis of signal loss, which occurs during systole. Thrombus demonstrated variable signal intensity, which remained unchanged during the cardiac cycle. Compared with routine MR sequences, there was less image degradation from phase-encoding artifacts and improved visualization of the neck of the aneurysm. Pulsatile mass effect was uniquely assessed. After transvascular embolization, cine MR demonstrated improved conspicuity of acute thrombus and higher contrast between flowing blood and the occlusion balloon when compared with routine MR. Confirmation of flow within the parent vessel, residual aneurysm lumen, and distal arterial branches is possible. If the parent vessel was occluded, cine MR yielded greater information than angiography. Cine MR provides additional anatomic and physiologic data in the evaluation and assessment of therapy of intracranial aneurysms. Information can be obtained that is not available with either routine MR or angiography. The inherent limitations of this new technique include partial-volume artifacts, less than optimal flow-related enhancement or spatial resolution, and poor data acquisition due to cardiac arrhythmias.

Adolescent↗
PubMed1988

Anomalies of the corpus callosum: correlation with further anomalies of the brain.

The MR imaging studies of 68 patients who had brain anomalies were reviewed retrospectively to evaluate specific anatomic abnormalities of the corpus callosum. The corpus callosum was abnormal in 32 (47%) of the 68 patients. Excluding patients with the Chiari I malformation, callosal anomalies were present in 30 (68%) of 44 patients. Callosal dysgenesis was most common, followed by callosal atrophy or hypoplasia and complete agenesis. The anterior commissure was present in all patients. On the basis of the known temporal sequence of brain and callosal embryogenesis, we deduced the following regarding the pathogenesis of developmental anomalies: (1) callosal dysgenesis occurs as a result of insults during the formation of its precursors, not during formation of the corpus callosum itself; (2) the Dandy-Walker malformation sometimes occurs as a result of an insult in the eighth week of gestation, several weeks later than has been generally accepted; (3) sphenoidal encephaloceles probably occur as a result of faulty disjunction of neuroectoderm and cutaneous ectoderm at the anterior neuropore; and (4) a complete but atrophic corpus callosum results from an insult to the cortex or white matter after formation of the corpus callosum is complete (18-20 weeks). Callosal anomalies, easily identified on MR, are an important indicator of additional brain anomalies. Analysis of the corpus callosum provides important information about the embryogenesis of brain anomalies and may assist in distinguishing between in utero and perinatal brain insults.

Adolescent↗
PubMed1988

MR imaging of cavernous sinus involvement by pituitary adenomas.

The ability of high-resolution MR imaging (1.5 T) to detect invasion of the cavernous sinuses by pituitary adenoma was determined through a retrospective review of 74 patients. These patients were divided into three groups: 25 normal subjects, 24 subjects with invasive pituitary adenomas, and 25 subjects with noninvasive pituitary adenomas. A fourth group of 30 patients, who subsequently underwent surgery for pituitary adenoma, was evaluated prospectively by MR for the presence or absence of cavernous sinus invasion. Several features were analyzed: (1) the detectability of the medial and lateral dural margins of the cavernous sinus (2) the size and variation in intensity of compartments within the cavernous sinus (3) the relationship of endocrine function to the surgical and MR appearance of the cavernous sinus and (4) carotid artery displacement or encasement by tumor. The normal cavernous sinuses were usually symmetric, but their sizes varied. The lateral dural margin of the cavernous sinus was always recognized on MR as a linear, discrete, low-intensity area. The medial dural margin (pituitary capsule) was seen on MR in only two of the 25 normal patients. In all 24 patients with cavernous sinus invasion involvement was unilateral and was most common with laterally positioned prolactin or adrenocorticotropic hormone secretory adenomas. Invasion of the cavernous sinus was suspected by MR in only two of the 13 invasive microadenomas and was questionable in three. In 10 of the 11 macroadenomas with surgically proved dural invasion, MR demonstrated an asymmetric increase in size and intensity of the superior and inferior cavernous sinus compartments. Noninvasive macroadenomas compressed and displaced the cavernous sinus bilaterally. The prospective MR evaluation of 30 patients undergoing surgery for pituitary tumor revealed a sensitivity for predicting cavernous sinus invasion of 55%, a specificity of 85.7%, a positive predictive value of 62.5%, and a negative predictive value of 81.8%. No feature permitted certain distinction between invasive and noninvasive microadenomas, as the medial dural wall of the cavernous sinus could not be reliably identified. The most specific sign of cavernous sinus invasion was carotid artery encasement.

Adenoma↗
PubMed1988

Falx ossification--MR visualization.

While falx calcification is rarely demonstrated using magnetic resonance, falx ossification, when seen, is characteristic. On magnetic resonance images, falx ossification exhibits a typical appearance consisting of a central marrow-containing portion with signal intensity similar to fat, surrounded by low signal intensity representing cortical bone. Falx ossification was seen in 0.7% of patients and should not be confused with a falx lipoma, a rare congenital entity.

Brain Diseases↗
PubMed1987

Giant intracranial aneurysms: MR imaging.

Fifteen patients with giant intracranial aneurysms were examined with magnetic resonance (MR) imaging, computed tomography (CT), and angiography. MR imaging revealed a rounded extraaxial mass with evidence of intraluminal blood flow in 12 of the 15 cases. Signal void within the lumen was seen in all 12 of these cases. Other flow effects, such as even-echo rephasing, were seen in some cases. Complete thrombosis was seen in three giant aneurysms in which high signal intensity on T1- and T2-weighted images filled the lumen, and no flow effects were seen. Partial thrombosis was detected in four aneurysms as persistent areas of medium to high signal intensity within the lumen on T1- and T2-weighted images. In five cases, the cause of the intraluminal signal that was present was difficult to determine. The ability of MR to indicate flow within the lumen in 12 of 15 cases provided for greater diagnostic confidence than with CT, which was strongly suggestive of an extraaxial tumor in nine patients. Calcification of the wall of the aneurysm was better detected with CT.

Adult↗
PubMed1987

Dural fistulas involving the cavernous sinus: results of treatment in 30 patients.

Thirty symptomatic indirect carotid cavernous fistulas were treated between 1978 and 1986 with a variety of treatment modalities. Combined carotid artery and jugular vein compression resulted in a complete cure in seven of 23 patients (30%) and improvement in one additional patient. There were no complications from this treatment, which is performed by the patient on an outpatient basis. Patients in whom carotid jugular compression therapy failed or who demonstrated cortical venous drainage or visual decline were treated with intravascular embolization. Embolization resulted in complete cure in 17 of 22 (77%) and improvement in four of 22 (18%). One patient required surgical excision of the involved dura after embolization to achieve complete cure. There was one permanent complication (stroke), which resulted in mild weakness caused by clot formation on a catheter.

Adult↗
PubMed1987

Dural fistulas involving the transverse and sigmoid sinuses: results of treatment in 28 patients.

Twenty-eight symptomatic dural fistulas involving the transverse and sigmoid sinuses were treated between 1978 and 1986 with a variety of treatment modalities. Occipital artery compression therapy resulted in a complete cure in two of nine patients (22%) and improvement in three of nine (33%). There were no complications from this treatment. Patients who were excluded or in whom compression therapy failed were treated with embolization alone or in conjunction with surgery. Of the 17 patients who underwent embolization alone, ten were cured and six were improved. Six patients had a combination of embolization and surgery; four patients were cured and two improved. There were three complications in this series, one related to surgery and two related to embolization.

Adult↗
PubMed1987

Posterior pituitary gland: appearance on MR images in normal and pathologic states.

T1-weighted magnetic resonance (MR) images of the pituitary gland and sella turcica routinely demonstrate a region of high signal intensity in the neurohypophysis. High-resolution MR imaging studies of the sella turcica in 200 subjects with a normal or abnormal sella were analyzed. The hyperintensity was found in the images of about 90% of healthy subjects and patients with microadenoma, in only 43% of patients with macroadenoma, and in 12% of patients with empty sellae. The signal was absent in several patients with functional or anatomic abnormalities of the hypothalamic-hypophyseal axis. It is concluded that the high signal intensity in the posterior lobe of the pituitary gland is present in most healthy individuals and that its absence in many patients with large intrasellar masses and empty sellae is due to compression of posterior lobe tissue. Its absence in diabetes insipidus further suggests a relationship between hyperintensity and the functional status of the hypothalamic-hypophyseal axis.

Adenoma↗
PubMed1987

Rathke cleft cysts: CT, MR imaging, and pathologic features.

The authors retrospectively reviewed the clinical, computed tomography (CT), and magnetic resonance (MR) imaging findings in seven patients with pathologically proved Rathke cleft cysts. All the cysts were located in the anterior sella turcica or the anterior suprasellar cistern. Five cysts had both intra- and suprasellar components, one was entirely intrasellar, and the other was predominantly suprasellar in location. The size of the cysts ranged from 8 to 20 mm. CT scans demonstrated low-density homogeneous lesions in four cases. On MR images of three of these four cases, the cysts had the same intensity as cerebrospinal fluid on T1- and T2-weighted images, while in the fourth case, the cyst was hyperintense on the T1-weighted images. In the remaining three cases, CT showed slight hyperdensity relative to brain parenchyma, suggestive of contrast enhancement. MR showed signal heterogeneity of these lesions with focal components of diminished signal intensity of T2-weighted images. These same foci appeared iso- to slightly hyperintense on T1-weighted images.

Adult↗
PubMed1987

MR imaging of paragangliomas.

MR imaging of 15 paragangliomas in 10 patients was compared with CT of 13 of the lesions in eight patients. All lesions were confirmed with angiography. All lesions were detected by MR and CT with the exception of one small glomus tympanicum tumor that was seen only in retrospect with MR. CT better demonstrated subtle osseous changes of the skull base and the relation of the tumor to the middle ear structures. MR better demonstrated the relation of the tumor to the adjacent internal jugular vein and carotid artery. The paragangliomas had a characteristic MR appearance based on their vascularity. Serpiginous areas of signal void representing high vascular flow were interspersed among areas of high signal intensity caused by slowly flowing blood and tumor cells. This "salt-and-pepper" pattern was seen in all lesions greater than 2 cm in maximal dimension. MR was therefore able to accurately characterize the tumors as highly vascular. Multiplanar imaging and good tissue contrast and anatomic detail permitted display of the relations of these neoplasms to surrounding carotid sheath vessels and to intracranial structures better than did CT. In this experience, the MR appearance of paragangliomas was quite characteristic and differed markedly from meningiomas, neuromas, and metastatic disease of the skull base.

Carotid Body Tumor↗
PubMed1987

The role of MR imaging in evaluating metastatic spinal disease.

Fifty-eight patients with suspected epidural metastases were evaluated with MR imaging. Six patients were examined on two separate occasions. MR was judged to be diagnostic in 60 of the 64 examinations. Twenty-two patients also underwent myelography. MR was as diagnostic as myelography in all cases of epidural metastases. In addition, MR offered several advantages over myelography in the evaluation of metastatic spinal disease, including demonstration of paravertebral tumor extension, identification of additional osseous metastatic lesions, and visualization of areas of spinal cord compression occurring between areas of myelographic blocks. We conclude that MR imaging is the examination of choice for evaluating suspected metastatic spinal disease.

Adolescent↗
PubMed1987

Localizing studies in patients with persistent or recurrent hyperparathyroidism.

Preoperative localizing studies are essential for patients with persistent or recurrent hyperparathyroidism requiring reoperation, because of loss of normal tissue planes and because the hyperfunctioning parathyroid tissue that remains is more likely to be situated in an ectopic position. The value of noninvasive and invasive localizing techniques was evaluated in 59 consecutive patients undergoing reoperation for persistent (40 patients) or recurrent (19 patients) hyperparathyroidism. Magnetic resonance imaging was performed in 17 patients; 11 results (65%) were positive, 3 (18%) were negative, and 3 (18%) were false-positive. Ultrasonography was performed in 52 patients; 29 (56%) were positive, 16 (31%) were negative, and 7 (13%) were false-positive. Computed tomography was performed on 41 patients; 19 (46%) were positive, 16 (39%) were negative, and 6 (15%) were false-positive. Thallium chloride 201-technetium 99m pertechnetate scans were used in 39 patients; 19 (49%) were positive, 11 (28%) were negative, and 9 (13%) were false-positive. One or more of these noninvasive tests was positive in 78% of the cases. Highly selective venous catheterization with measurement of immunoreactive parathyroid hormone concentration localized the abnormal parathyroid gland in 20 of 28 patients (71%) overall and in 8 of the 14 patients (57%) whose tumors were not identified by the noninvasive techniques. Since false-positive results were common, a combination of localizing studies was helpful in identifying the abnormal gland. Fifty-three of the 59 patients (90%) were successfully treated at the initial reoperation and three were successfully treated at a second reoperation. Advances in parathyroid localization have contributed to the improved surgical results in patients with persistent or recurrent hyperparathyroidism.

Adult↗