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Show Literature Abstracts Institute, 500 Sherbourne Street, Toronto, Ontario M4X lK9, Canada. Fourteen patients with orbital lesions were studied by magnetic reson,lnce using a Technicare unit with a 0.15-T resistive magnet. Thirteen of these patients underwent CT of the orbits with 5-mm slice thickness and orbital ultrasound (eight examinations with a Xenotec 303 ABX scanner and four examinations with a Cooper 404 Ultrascan, both using 10MHz transducers; one examination was done in a Diasonic scanner using a 7.5-MHz transducer). The orbital space-occupying lesions included two cavernous hemangiomas, one orbital varix, three thyroid ophthalmopathies, two pseudotumors, two sphenoid wing meningiomas, one optic nerve glioma, one solitary plasmacytoma, and one intrascleral epithelial cyst. The major advantage of magnetic resonance over CT is that there is no risk of ionizing radiation from the contrast medium. In addition, utilizing a T2 weighted spin echo with echo delay (TE) of 60 ms and repetition intervals (TR) of 1,000-ms pulse sequence, in some cases, it was possible to characterize fat-containing, fluid-containing, and solid tumors. In conclusion, magnetic resonance provided better anatomical details than can ultrasound but not as well as can CT, and ultrasound provided the best tissue characterization of the three modalities. Therefore, magnetic resonance using a 0.15-T resistive magnet does not show an advantage over the combination of CT and ultrasound in diagnosing orbital space-occupying lesions. Rosendo D. Dia:, M.D. • • • 4. Reference: Tucci, J. M., Maitland, C. G., Pcsolyar, D. W., Thomas, J. R., and Black, J. L.: Carotidcavernous fistula due to traumatic dissection of the extracranial internal carotid artery. A.f.N.R. 5: 828-829, 1984. Reprints: C. G. Maitland, M.D., Department of Neurology, National Naval Medical Center, 4301 Jones Bridge Road, Bethesda, MD 20814. A 4~-year-old man developed throbbing, rightSided neck pam 12 h after being punched in the right side of the neck. Subsequently, he noticed tingling and numbness in the left arm and face, occasional visual blurring, and a sensation of constriction of the visual fields bilaterally. A cerebral angiogram demonstrated a dissecting aneurysm extending from the upper cervical segment to the petrous segment of the right internal carotid artery. There was also concentric narrowing of the precavernous segment of the right internal carotid artery. Intracranially, there was evidence of a low-flow, carotid-cavernous fistula on the right. The patient's sensory symptoms resolved after 6 weeks. Two months later he noted a bruit in the right side of the head and infected right sclera. Physical examination showed a chemotic, congested, and protruded right eye. A repeat cerebral angiogram demonstrated enlargement of the right carotid-cavernous fistula. Most carotidcavernous fistulas occur after head trauma. This case demonstrates that traumatic carotid dissection, re- 200 mote from the cavernous sinus and without associated head trauma, can result in a carotid-cavernous fistula. Rosendo D. Diaz, M.D. • • • 5. Reference: Rothfus, W. E., and Latchaw, R. E.: Nonefficacy of routine removal of CSF during neurodiagnostic procedures. A.f.N.R. 5: 797-800, 1984. Reprints: W. E. Rothfus, M.D., Presbyterian-University Hospital, DeSoto at O'Hara Street, Pittsburgh, PA 15213. The charts of 750 consecutive patients who had had myelograms and cisternograms were reviewed to evaluate the value of routinely removing cerebrospinal fluid (CSF) for chemical and cytologic analysis. Emphasis was placed on the progress notes, laboratory summary sheets, and discharge notes to see how the information from the CSF studies was used by the clinicians. In 80% of the myelograms and 68% of the cisternograms, the CSF studies were completely normal. In most patients having CSF abnormalities, the information added little to the clinical differential diagnosis. A CSF abnormality never led to detection of an occult problem. In very few patients were the results of the CSF examinations documented in writing in the patient's charlo (Seven percent of these 750 patients were referred by the neuro-ophthalmology service and of these patients only 14% had CSF results commented on in writing in their charts.) The authors conclude that removal of CSF during neurodiagnostic procedures should not be automatic but should be tailored to the particular clinical situation. Rosendo D. Diaz, M.D. • • • 6. Reference: Yeates, A. E., Blumenkopf, B., Drayer, B. P., Wilkins, R. H., Osborne, D., and Heinz, E. R.: Spontaneous CSF rhinorrhea arising from the middle cranial fossa: CT demonstration. A./NR. 5: 820-821, 1984. Reprints: A. E. Yeates, M.D., Department of Radiology, Box 3808, Duke University Medical Center, Durham, NC 27710. A 45-year-old woman developed spontaneous ce. rebrospinal fluid (CSF) leakage from the left nostnl 3 weeks prior to admission. The patient del1led havmg trauma. CT metrizamide cisternography was performed and showed an air-metrizamide level in the left sphenoid sinus. The left sphenoid sinus was pneumatized laterally (pterygoid recess); therefore, the floor of the medial portion of the middle cranial fossa formed the roof of the laterally pneumatized sphenoid sinus. In addition, the medical aspects of the floors of both middle cranial fossae were irregular and pitted. High-density CSF (metrizamide) was seen passing through one of these pits ir the left mid~le cranial fossa. A left subtemporal craniotomy confirmed the CT findings. Pitting in the floor of the Journal of Clinical Neuro-ophthalmology middle cranial fossa is probably congenital. The authors speculate that a prerequisite to the development of spontaneous CSF rhinorrhea from the middle cranial fossa is to have the bone in the base of these pits thinned and forming the roof of a laterally pneumatized sphenoid sinus. Thus, when studying patients with CSF rhinorrhea it is important to examine the full extent of the sphenoid sinuses, not just the anterior fossa. RO:'l'lldo D. Dia:, M. D. • • • I. Ref,'W/lt': Davis, P. C, Hoffman, J. C Jr., Tindall, G. T., and Braun, I. F.: Prolactin-secreting pituitary microadenomas: inaccuracy of high-resolution cr imaging. A./.N.R. 5: 721-726, 1984. Reprints: P. C Davis, M.D., Department of Radiology, Emory University School of Medicine and Emorv Clinic, 1365 Clifton Road, N.E., Atlanta, GA 3032i Fifty-one patients suspected of harboring a prolactin- secreting pituitary adenoma were studied with CT of the selJa and subsequently underwent transsphenoidal surgery. The surgical findings were retrospectively correlated with the CT findings. AlJ the patients had hyperprolactinemia (more than 25 nglml) with symptoms attributed to high prolactin levels such as amenorrhea, galactorrhea, infertility, and/or decreased libido. CT scans of the sella were performed in the coronal projection with continuous 1.5-mm sections immediately after a bolus of 100 ml of 60% intravenous contrast medium. After the bolus injection, a drip infusion of 30% intravenous contrast medium was kept open during the study. The bestknown indicators for diagnosing microadenomas by CT were evaluated. These were (1) a pituitary gland height greater than 8 mm, (2) a diffuse or focal, superiorly convexed diaphragma sellae, (3) a displaced infundibulum, (4) erosion of the sella floor, and (5) a focal lesion (either hyperdense or hypodense) within the enhancing pituitary gland. Of these, the only statistically Significant indicator for a microadenoma was a focal lesion. Nevertheless, six path<!llogically proven cases of microadenomas had normal CT scans, and a significant number of patients with surgically proven microadenomas had few of these findings. The authors conclude that these CT indicators are neither sensitive nor specific for microadenomas. Rosendo D. Diaz, M.D. • • • 8. Reference: Kapila, A., Steinbaum, S., and Chakeres, D. W.: Case report. Meckel's cave epidermoid with trigeminal neuralgia: cr findings. J. Comput. Assist. Tomogr. 8: 1172-1174, 1984. Reprints: A. Kapila, M.D., Department of Radiology, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78284. The authors describe a 42-year-old woman with throbbing right facial pain for 4 years. On physical examination she had two trigger points on the September 1985 Literature Abstracts right, one in the body of the mandible and the other in the nasolabial fold. She also had decreased pain sensation in the face and decreased corneal reflex, both on the right. CT showed a nonenhancing, lowattenuation ( - 66 HU) mass in the medial portion of the right middle cranial fossa extending into the posterior fossa over the right petrous apex. A CT metrizamide cisternogram accurately demonstrated the lesion within Meckel's cave. This mass was resected via a right subtemporal craniotomy, and the microscopic diagnosis was epidermoid with no dermal components. What is unique about this case is that, first, it is rare to find epidermoids with fat density. Actually, a negative CT attenuation is a feature used to differentiate dermoids and lipomas, typically having fat density, from epidermoids, which usually have a mixed CT attenuation. This is because of the relative concentration of high-denSity keratin and low-density cholesterol in epidermoids. Second, CT metrizamide cisternography showed the tumor to be within Meckel's cave, important preoperative information for the surgeon, since Meckel's cave is usually not in direct view. In this case, if significant tumor were left in Meckel's cave, the patient's trigeminal neuralgia could have persisted. Rosendo D. Diaz, M.D. • • • 9. Reference: Towle, V. L., Sutcliffe, E., and Sokol, S.: Diagnosing functional visual deficits with the P300 component of the visual evoked potential. Arch. Ophtha/mol. 103: 47-50, 1985. Reprints: V. L. Towle, M.D., Department of Neurology, Box 425, University of Chicago, 5841 Maryland Ave., Chicago, IL 60637. The authors attempt to show that a "cognitive component" of the visual evoked response called P300 (a positive deflection that occurs at about 300 ms) can be used to assess the validity of the patient's evoked response performance. The P300 wave is emitted when the brain is "identifying infrequently presented stimuli" and is not generated by visual cortex or degraded by poor fixation or blurred image. Horizontal and vertical stripes were used as stimuli, with the former presented 15% (i.e., infrequently) and the latter 85% of the time. Their traces first showed a normal subject's response when asked to either "attend" the horizontal stripes or simply to watch the TV. When attending, the P300 is readily evident. The same subject generated a P300 wave with a +11 diopter lens placed over the eye but not with a +45 diopter lens. Three patients with clinically diagnosed factitious visual loss were tested. Even when each claimed to be unable to see the horizontal stripes, a P300 wave was recorded, although the amplitude was less than in the normal subject and the timing and wave forms looked quite different on different tracings. The authors conclude that the presence of the P300 wave, when the patient denies being able to see the stimulus, bespeaks a functional visual loss, even though absence of the P300 wave does not confirm absence of vision. To the skeptic, this article offers a refinement in visual evoked response testing, 201 |