Trigeminal and concurrent glossopharyngeal neuralgia secondary to lateral medullary infarction.

A 69-year-old woman developed acute pain in the left trigeminal and glossopharyngeal nerve distributions. MR imaging demonstrated a left lateral medullary infarction (LMI) involving the left spinotrigeminal nucleus and tract, nucleus ambiguus, and solitary nucleus. Most patients presenting with trigeminal neuralgia will have disease involving the trigeminal nerve or ganglion or the primary sensory nucleus in the pons. We discuss the unusual finding of LMI associated with concurrent trigeminal and glossopharyngeal neuralgia.

A clinical comparison of the safety and efficacy of MultiHance (gadobenate dimeglumine) and Omniscan (Gadodiamide) in magnetic resonance imaging in patients with central nervous system pathology.

RATIONALE AND OBJECTIVES: The safety and diagnostic efficacy of MultiHance (gadobenate dimeglumine) in the central nervous system (CNS) were evaluated in a double-blind, multicenter, phase III clinical trial. METHODS: Two hundred five patients highly suspected of having a CNS lesion (by previous imaging exam) were enrolled at 16 sites in the United States. Patients were randomized to one of three incremental dosing regimens. Magnetic resonance imaging with Omniscan (gadodiamide) at doses of 0.1 and 0.3 mmol/kg was compared with MultiHance (gadobenate dimeglumine) at doses of 0.05 and 0.15 mmol/kg and at 0.1 and 0.2 mmol/kg. RESULTS: Compared with predose images alone, efficacy was demonstrated in each of the gadobenate dimeglumine and gadodiamide groups (single and cumulative doses) as indicated by the level of diagnostic information, number of lesions detected, and contrast-to-noise ratio measurements. The level of diagnostic information from gadobenate dimeglumine at 0.1 mmol/kg was equivalent to that with gadodiamide at the same dose. One of the two blinded reviewers found equivalence between the gadobenate dimeglumine 0.05 mmol/kg dose and gadodiamide at 0.1 mmol/kg. Both reviewers found the level of diagnostic information to be equivalent after the second dose of contrast for all three dosing regimens. The cumulative doses of gadobenate dimeglumine were well tolerated and as safe as gadodiamide. CONCLUSIONS: Gadobenate dimeglumine is comparable to gadodiamide in terms of safety and efficacy for imaging of CNS lesions, with a possible advantage in imaging applications owing to enhanced T1 relaxivity.

Corticotropin- and thyrotropin-secreting pituitary microadenomas: detection by dynamic magnetic resonance imaging.

Hormone-secreting pituitary microadenomas are often not visible on magnetic resonance imaging (MRI). Diagnosis requires confirmatory endocrine test results and often an invasive procedure, inferior petrosal sinus sampling (IPSS). Improved pituitary imaging may eliminate the need for IPSS in some patients, as shown in the 2 women in this report. The first patient with hirsutism, weight gain, and hypertension had intermittent elevations of urinary free cortisol, abnormal results on a low-dose dexamethasone suppression test, and positive results on a dexamethasone-suppressed ovine corticotropin-releasing hormone test (corticotropin, increase of 122%; cortisol, increase of 118%). Gadolinium-enhanced MRI showed no focal lesion, but dynamic MRI (sequential images beginning immediately after contrast injection) revealed a right-sided 5-mm microadenoma, confirmed by transsphenoidal surgery. The second patient had a goiter, anxiety, increased free thyroxine and triiodothyronine levels, and a normal thyrotropin value with no response to thyrotropin-releasing hormone. Magnetic resonance imaging showed no lesion, but dynamic MRI detected an 8-mm microadenoma. Although about 8% to 10% of healthy persons have incidental pituitary lesions that are 3 mm or larger on MRI, identification of a distinct lesion and positive results on a dexamethasone-suppressed ovine corticotropin-releasing hormone test should decrease the probability of a false-positive result on an imaging study. We recommend that dynamic MRI be performed in any patient with a suspected microadenoma, before IPSS is performed.

Hemangioma of the mandibular branch of the trigeminal nerve in the Meckel cave presenting with facial pain and sixth nerve palsy.

In a 25-year-old woman with episodic periorbital-temporal pain who eventually developed a sixth nerve palsy, magnetic resonance imaging revealed a lesion predominantly in the Meckel cave that was found to be a capillary hemangioma arising from the mandibular division of the trigeminal nerve. Hemangiomas of the Meckel cave must be considered in cases of facial pain with a sixth nerve palsy. even if there are no clinical findings of trigeminal neuropathy.

Imaging of the spine. Techniques of MR imaging.

Recently, magnetic resonance (MR) imaging has become the preferred method of evaluation for spinal disorders. The vertebrae, intervertebral disks, ligaments, spinal canal, and neural foramen may all be evaluated using current MR imaging techniques. MR imaging with paramagnetic contrast has developed into a valuable technique for diagnosing a tumor, an infection, or a degenerative disease. Computed tomography remains the procedure of choice for examining fine cortical bone detail including evaluation of spine fractures and assessing neural foraminal size, but it is not sensitive for detecting marrow-infiltrating disorders.

Plasmacytoma manifesting as recurrent cellulitis and hematic cyst of the orbit.

PURPOSE: To describe a patient with recurrent periorbital cellulitis and orbital blood cyst as the initial manifestation of primary extramedullary plasmacytoma. METHODS: The chart, imaging studies, and histopathologic examination results and literature on the subject were reviewed. RESULTS: Orbital surgery disclosed a hematic cyst along with a solitary plasma cell tumor. CONCLUSIONS: Periorbital cellulitis and pain can be a manifestation of a plasma cell tumor. Bleeding may occur within a necrotic orbital tumor.

Hyaline cartilage: truncation artifact as a cause of trilaminar appearance with fat-suppressed three-dimensional spoiled gradient-recalled sequences.

PURPOSE: To investigate the cause of the trilaminar appearance within hyaline cartilage observed on magnetic resonance (MR) images obtained with a fat-suppressed three-dimensional spoiled gradient-recalled sequence. MATERIALS AND METHODS: The knees of three asymptomatic volunteers were imaged with a fat-suppressed, three-dimensional, spoiled gradient-recalled sequence. The field of view, number of phase-encoding steps, and phase-encoding direction were varied. On each image, the thickness of the patellar and trochlear cartilage was measured in millimeters and divided by the pixel dimension, which effectively expressed the thickness as the number of pixels. Finally, the number of pixels was compared with the number of alternating hyperintense and hypointense lines depicted. RESULTS: The number of truncation lines increased as pixel dimension was reduced by either decreasing the field of view or increasing the number of phase-encoding steps. The accuracy for predicting more than three lines with use of an anteroposterior phase-encoding direction varied between 83% and 92%. The appearance of the cartilage was altered when phase- and frequency-encoding directions were exchanged, but truncation lines were still evident. CONCLUSION: The trilaminar appearance depicted within hyaline cartilage on MR images obtained with this sequence is predominantly attributable to truncation artifact rather than to histologic zonal anatomy.

Three-dimensional time-of-flight MR angiography with a surface coil: evaluation in 12 subjects.

We compared three-dimensional time-of-flight MR angiograms obtained with head coils and then with surface coils in five patients with intracranial vascular lesions and in seven normal volunteers to determine if imaging of intracranial vascular anatomy could be improved with the use of a surface coil. Visualization of small peripheral vessels was consistently better with a surface coil than with a head coil at identical small fields of view (FOVs). The surface-coil technique allowed small-FOV imaging of peripheral vascular lesions with higher spatial resolution and signal-to-noise ratio similar to that of large-FOV head-coil images. The use of a surface coil introduced the problem of signal falloff; centrally located vessels were visualized as well or better when a standard head coil was used. We conclude that surface-coil MR angiography can serve as a useful adjunct to routine head-coil MR angiography in the evaluation of peripheral vascular abnormalities.

High-intensity signals within the posterior pituitary fossa: a study with fat-suppression MR techniques.

Five different theories have been proposed to explain the high-intensity signals within the posterior pituitary fossa seen on MR: (1) a paramagnetic effect of phospholipids in the posterior lobe, (2) lipid in pituicytes in the posterior lobe of the pituitary, (3) neurosecretory granules in the posterior lobe, (4) fat within the sella but outside the pituitary gland, and (5) fat in bone marrow in the dorsum sellae. Previous reports have contained conflicting evidence on which of these structures is the cause of the high-intensity signals within the posterior sella. The purpose of this study was to examine the high-intensity signals of the normal posterior sella with fat-suppression MR techniques to reevaluate the contribution of fat to those signals. The sellae of 19 normal volunteers and two cadavers were imaged with MR with a commercially available unit and a research fat- water-suppression technique. High-intensity signals in the posterior sella were observed in all 21 subjects on conventional T1-weighted MR images. In two volunteers, the high-intensity signals in the posterior sella were suppressed with fat-suppression techniques; in 17 subjects the signals were suppressed with water-suppression techniques. In two volunteers the results were indeterminate. The high-intensity signals in the posterior sella do not behave like lipid in the majority of cases. Our study supports the conclusion that high-intensity signals in the posterior sella may have more than one source. It appears that most of these sources do not suppress with fat-suppression techniques.

MR imaging of optic nerve lesions: value of gadopentetate dimeglumine and fat-suppression technique.

Eleven patients with known or suspected optic nerve lesions and eight normal subjects were examined with spin-echo technique at 1.5 T with unenhanced T1-weighted imaging, IV gadopentetate-dimeglumine-enhanced T1-weighted imaging, and enhanced T1-weighted imaging with fat suppression. Two pathologically proved and four presumed optic nerve meningiomas demonstrated significant enhancement and were best seen with the fat-suppression technique. None of the three presumed optic nerve gliomas nor the optic nerves of normal subjects demonstrated qualitative enhancement. We conclude that the use of a fat-suppression technique with gadopentetate dimeglumine enhancement improves delineation of enhancing optic nerve lesions. This technique should be useful for evaluating other anatomic regions where enhancing tissue marginates fat.

MR imaging of optic nerve lesions: value of gadopentetate dimeglumine and fat-suppression technique.

Eleven patients with known or suspected optic nerve lesions and eight normal subjects were examined with spin-echo technique at 1.5 T with unenhanced T1-weighted imaging, IV gadopentetate-dimeglumine-enhanced T1-weighted imaging, and enhanced T1-weighted imaging with fat suppression. Two pathologically proved and four presumed optic nerve meningiomas demonstrated significant enhancement and were best seen with the fat-suppression technique. None of the three presumed optic nerve gliomas nor the optic nerves of normal subjects demonstrated qualitative enhancement. We conclude that the use of a fat-suppression technique with gadopentetate dimeglumine enhancement improves delineation of enhancing optic nerve lesions. This technique should be useful for evaluating other anatomic regions where enhancing tissue marginates fat.

MR appearance of gray and white matter at the cervicomedullary region.

To study the appearance of gray and white matter in the cervicomedullary region, six fresh cadavers were imaged with a 1.5-T MR scanner and then sectioned with a cryomicrotome. The pyramidal tracts, fasciculus cuneatus and gracilis, inferior olivary nuclei, supraspinal nuclei, spinal trigeminal nuclei, and medial lemnisci were identified by MR in the cervicomedullary region.

Contrast enhancement in spinal MR imaging.

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.

MR imaging of facial nerve enhancement in Bell palsy or after temporal bone surgery.

The authors evaluated magnetic resonance (MR) images obtained with intravenously administered gadolinium in ten patients who had facial paralysis and no facial nerve tumor. In patients with either Bell palsy (four patients) or facial paralysis after temporal bone surgery (six patients), intratemporal facial nerve enhancement was seen. Facial nerve enhancement on MR images proved to be a nonspecific finding.

Gradient recalled echo MR imaging of superior sagittal sinus occlusion.

With T1-weighted gradient recalled echo (GRE) MR images and flow compensation, we studied the superior sagittal sinus in 3 normal volunteers and 3 patients with sinus occlusion. In these images, sites of patency of the superior sagittal sinus were identified due to the high signal intensity of the normal sinus. Tumor invading the sinus was nearly isointense with cerebral gray matter. T1-weighted GRE imaging proves to be an effective technique to evaluate sinus blood flow.

Characteristic features of MR truncation artifacts.

Truncation artifacts occur in MR imaging because Fourier transforms are used to process MR signal data. These artifacts may alter the intensity, shape, and anatomic detail of structures in the spine. Ring artifacts (Gibb phenomenon) occurring near highly contrasting interfaces represent but one manifestation of truncation artifacts visible on MR images. We review truncation phenomena by providing graphic and phantom models. Ways in which truncation artifacts alter the MR appearance of the spine are discussed. We found that truncation phenomena are reduced most effectively by using a 256 x 256 matrix whenever feasible.

Cervical neural foramina: correlative anatomic and MR imaging study.

Accurate diagnosis of diseases affecting the cervical neural foramina with magnetic resonance (MR) imaging requires an appreciation of the normal anatomic appearance of the foramen. The MR appearance of the foramen was studied in cadavers and healthy volunteers and was correlated with cadaver cryomicrotome sections. With gradient-echo techniques, foraminal soft tissues are highlighted relative to adjacent bone, making gradient-echo images valuable for evaluating the overall size and contents of the neural foramina. Intravenously administered gadolinium DTPA produces enhancement of all foraminal soft tissues, including the dorsal root ganglion. The nerve roots do not enhance with Gd-DTPA. Gradient-echo pulse sequences and intravenous use of Gd-DTPA represent promising techniques for the evaluation of the cervical foramina.

MR imaging of the cavernous sinus: value of spin echo and gradient recalled echo images.

A detailed evaluation of the MR appearance of the pituitary gland-cavernous sinus junction has not been described. In a series of coronal T1-weighted spin echo images without and with IV gadolinium, we noted the variable size and signal intensity of cavernous venous spaces adjacent to the pituitary gland and the inconsistent visualization of the dural membrane just lateral to the gland. Correlation of coronal T1-weighted spin echo and gradient recalled echo images (the latter with high-signal-intensity vascular structures) proved to be an effective means of identifying cavernous venous spaces, connective tissue and cranial nerves, and the lateral margins of the pituitary gland, and of differentiating tumor tissue from cavernous venous spaces. Further work is needed to develop criteria to distinguish cavernous sinus compression from actual tumor invasion.