Jugular Foramen: Anatomic and Computed Tomographic Study

The computed tomographic (eT) appearance of the jugular foramen was examined in detail, and anatomic and CT sections were correlated. The pars nervosa and pars vascularis were identified, and , with intravenous contrast enhancement, a rapid sequence of scans at a gantry angle of +30° to the canthomeatal line demonstrated cranial nerves IX, X, and XI. The osseous margins of the jugular foramen were best shown by CT at planes of sections parallel and positive (0°_30°) to the canthomeatal line . CT can be used to evaluate osseous anatomy and the jugular foramen with precision sufficient to confidently exclude an intracanalicular mass. The computed tomographic (CT) appearance of glomus jugul are tumors has been described [1 -3], but th e normal configuration of the foramen and its contents has not yet been completely analyzed by CT. We undertook a correlative study with head and skull specimens and c lini cal subjects . Materials, Subjects, and Methods In preliminary studi es, we found th at a plane of secti on 30° cephal ad to th e can th omeatal line (CML) just below th e internal auditory canal, was nearly tang ential to th e endocrani al opening of th e jugular foramen ( To determine th e CT appearance of the jugular foramen, we im aged a dry sk ull and some patients at several planes between -15° and +30° to th e CML (figs. 6-8). We also reviewed the appearance of th e j ugular foramen in our co nve ntional poste ri or fossa CT studies, done at -15° w ith respect to the CML Four patients with symptoms of a jugular foram en lesion (pul satil e tinnitu s, cra ni al nerves IX, X, and / or XI deficit , etc.) were placed supine in th e GE CT / T 8800 scanner w ith th eir heads elevated about 30° on a foam pad . CT images were obtained at a p lane +30° to th e CML determined with th e lateral localize r scan. On th e basis of our anatomi c d issec ti ons, thi s plane is perpendi cular to th e intraforamin al co urse of c rani al nerves IX-X I. Fi ve-and 1 .5-mm-ttiick sections we re obtain ed about 5 mm below th e internal auditory ca nal to locate th e jugular foram en. We injec ted 50 ml of 60% iodin ated co ntrast agent manuall y and rapidly in an antecubital ve in via an 18 gauge Angi o-cath need le. CT im ages we re obtain ed at a single level; th e first scan was 5 sec after th e initiati on of th e injection and th en every 10-15 sec until four scans were obt ain ed. Tec hnical fac tors in c lu ded 1 .5 mm collimation, 120 kVp, 9 .6 sec scan tim e, pulse width of 2 msec, and 356 or 409 mAs (figs . 9 and 10). Subsequently , 150 ml of 30% iod in ated co ntrast agent was infused and con ti guous CT scans were obtained through th e region of interest. Results and Discussion The anatomic and radiographic appearance of th e jugul ar foramen has been described in detai

Magnetic Resonance Imaging of the Cavernous Sinus 187

The magnetic resonance (MR) appearance of the cavernous sinus was studied by correlating the MR images of normal volunteers and cryomicrotomic sections from six cadavers. In addition, MR images of patients with parasellar masses were compared with corresponding intravenously enhanced computed tomographic (CT) scans. The MR appearance of the cranial nerves in the cavernous sinuses is demonstrated, as well as MR signs of a parasellar mass, including obliteration of intracavernous venous spaces, displacement of the intracavernous internal carotid artery, and bulging of the lateral wall of the cavernus sinus. MR proved to be more effective than CT in delineating the parts of the cavernous sinus. Magnetic resonance (MR) imaging has the potential to demonstrate the intracavernous segments of cranial nerves in contrast to the negligible signals of flowing blood. Our article describes the normal MR appearance of the cavernous sinuses and the MR signs of cavernous sinus lesions. Materials and Methods Six fresh frozen cadaver heads were embedded in styrofoam boxes with a solution of carboxymethyl cellulose gel. The orbitomeatal lines and sellae turcicae were identified with fluoroscopy. With a horizontally cutting heavy-duty sledge cryomicrotome (LKB 2250) and serial photography of the surfaces of the specimens (1), anatomic images of the cavernous sinuses were obtained in planes parallel or perpendicular to the orbitomeatal line. In the anatomic images, the intracavernous segments of cranial nerves III-VI and of the internal carotid arteries (ICAs) were identified using published anatomic, computed tomographic (CT), and MR literature (2-6). A group of seven normal volunteers and 15 patients were chosen for MR imaging. The patients included two with pituitary adenomas involving cavernous sinuses and one with a parasellar aneurysm . The diagnoses were verified with conventional clinical, CT , angiographic, and surgical (two cases) findings . The volunteers and patients were studied in prototype 1.3, 1.4, or 1.5 T General Electric MR scanners. Initially , a partial saturation (PS) sagittal image was used to determine locations for axial and coronal PS , inversion recovery (IR ), and spin-echo (SE) imaging . Sections parallel (axial plane) and/or perpendicular (coronal plane) to the orbitomeatal line were obtained

Differentiation of Intramedullary Neoplasms and Cysts by MR

527 To determine the MR criteria that are effective for differentiating intramedullary neoplasms from syringo-or hydromyelia, we reviewed MR scans made on prototype and commercial imagers of 33 patients with surgically confirmed cord abnormalities, including nine intramedullary neoplasms and 20 cysts (syringo-or hydromyelia). Two radiologists who did not know the clinical and radiologic diagnoses were asked to evaluate the scans with respect to (1) cord expansion, (2) distinctness of the disease margin, (3) homogeneity, and (4) signal intensity. These observations were correlated with the proved diagnoses. The combination of distinct margins and uniform signal intensity equal to that of CSF correlated consistently (88%) with spinal cord cysts. Other combinations were less reliable for diagnosing a cyst or tumor

Contrast Enhancement in Spinal MR Imaging 633

We evaluated 44 patients with suspected spinal tumors or previous laminectomies with gadolinium-DTPA MR imaging in order to characterize the enhancement in normal, postoperative, and neoplastic intraspinal tissue. Using the signal intensity of CSF as an internal control, we calculated the percentage increase in signal intensity from pre-to postgadolinium studies. Tumors (astrocytoma, ependymoma, schwannoma) enhanced 70-350%; epidural scar, normal epidural venous plexus, and dorsal root ganglion enhanced up to 200%. Contrast enhancement does not per se distinguish neoplastic from normal tissue. Enhancement with gadolinium-DTPA appeared to increase the conspicuousness of intramedullary tumors but not intraosseous metastases. We believe that gadolinium-enhanced MR imaging is a valuable adjunct to routine MR imaging in the evaluation of intraspinal neoplastic processes and may be useful in delineating normal and postoperative structures in the spinal canal. Gadolinium (Gd)-DTPA is under evaluation by the FDA as a contrast medium tor MR imaging of the spine. Enhancement of spinal tumors has been shown previously Materials and Methods Forty-two patients were studied under two different phase Ill protocol s. In one protocol (group 1), 22 patients with suspected spinal tumors were studied. Of the 22 enrolled, 15 had surgical or postmortem verification of the diagnosis. Among these patients there were th ree astrocytomas, three ependymomas, three schwannomas, two metastases , and four cysts not associated with a tumor. One of the 15 patients had previously undergone resection of an ependymoma and was evaluated for a presumed recurrence but has not yet been reoperated . Four of the 22 patients had negative MR studies without anatomic confirmation, and three had positive studies . In a second protocol (group II), 20 patients who had previously undergone laminectomy were studied to investigate possible scar tissue or recurrent disk herniations. Eight patients with MR evidence of epidural scar at one or more levels had surgical confirmation of epidural scar (with or without herniated disk). Measurements of contrast enhancement were made in the 14 tumor tissues in group I, in epidural scar in group II , and in normal tissues in both groups. MR was performed on a 1.5-T cryogenic imager with surface coil s. Each patient had sagittal or axial images with 800/20/2 (TR /TE jexcitations) , then with 2500/25/2 and 2500/ 80/2 plus additional images as needed. Gd-DTPA was injected intravenously in a dose of 0.1 mmjkg body weight. The 800/20 images were then repeated in the same planes with the same number of acquisitions, field of view , and so on. Transmit and receive attenuation were optimized with the system 's automatic tuning software for both pre-and post-Gd-DTPA acquisitions. The signal intensity was measured in reg ions of interest in the images pre-and post-Gd-DTPA. The signal intensity of CSF (which was assumed not to enhanc

Mesencephalic Anatomy: Demonstration by Computed Tomography 65

Although gray and white matter are distinguished by computed tomography (CT) in the cerebrum and cerebellum, their resolution in the mesencephalon has not been reported. CT and anatomic sections of the mesencephalon were compared to determine the relative densities of the superior cerebellar peduncles (white matter) and red nuclei and central gray matter. The normal low attenuation of the superior cerebellar peduncle should not be misinterpreted as infarction or demyelination. The mesencephalon contains both white (superior cerebellar peduncle and smaller fiber tracts) and gray (the red and other small nuclei and the central gray matter) matter. We studied structures of the mesencephalon that are normally distinguished by computed tomography (CT), measuring the relative densities of the structures on cross sections of brain specimens and correlated these sections with CT images . In this paper the appearances of substantia nigra, superior cerebellar penducle, and central gray matter are illustrated. Materials and Methods Three fi xed brain specimens were cut into 5 mm thic k axial sections with an electri c slicer. The slices were photographed on each side and radiographed in a Fa xitron cabin et radiographic unit with minoR low dose film , 20 kV, and about 18 sec exposure. Xe roradiographs were also obtained of some section s. The ph otographs and radiograph s were compared to determine the relative density of the mesencephalic tissues. CT images of patients were compared with the radiograph s. All CT im ages were obt ain ed on a GE CT / T 8800 scanner with consecutive 5 mm , or occ asionall y 1.5 mm , thi ck sli ces. For imaging the mesencephalon , the patients were positioned supine with th eir heads slightly hyperextended in the head holder. Th e gantry was tilted (top of gantry toward patient's feet) to produce a plane of section about -15 0 with respect to th e infraorbitomeatal line. For contrast enhancement , 200 ml of 3 0 % iodinated contrast medium was infused intravenously over 5 min immediately before scanning and 100 ml was infused slowly during scanning . Technical factors for CT scan s in cluded 10 sec scan tim e, 1 ,15 0 mA , and 120 kV . Results The structures that can be demonstrated radiographically within the mesencephalon include superior cerebellar peduncle , substanti a nigra, aqueduc t , ce ntral (periaqueductal) gray matter, and red nuclei . The anatomy of th e mesencephalon and in particular the red nuclei and superior ce rebell ar pedun cles is described in detail elsewhere Since the mesencephalon is 15-20 mm long, a CT study with 5-10 mm thi ck slices includes two or more slices through it. Therefore, it is conveni ent t