Orbital Magnetic Resonance Research Articles

Twenty-six cases of dumbbell-shaped orbital dermoids: preoperative diagnosis and management

The authors reviewed 26 cases of dumbbell-shaped orbital dermoids treated at the 1st and 2nd Affiliated Hospitals of Tian Jin Medical College from 1973 to 1992. All 26 cases were diagnosed correctly prior to surgery. The dermoid cysts were located in the posterior 2/3 of the orbit with extension through an interosseous fissure into the frontal sinus or cranial fossa. Complete surgical excision was achieved by a single orbitotomy in each case. A dermoid cyst which extended to the cranial fossa and paranasal sinus was resected simultaneously. When clinical signs such as proptosis, restriction of eye movement or fistula formation indicated a deep orbital tumor, X-ray, ultrasound examination, computed tomography (CT) and magnetic resonance imaging (MRI) were performed. Orbital erosion with a well-defined margin or calcification on X-ray and an uneven compressible orbital mass on ultrasonography are indicative of deep orbital dermoid. CT is of diagnostic value in determining the nature of the mass as well as its extension. In our limited experience, MRI is superior to CT in providing anatomical information for assessing the extent and location of the mass, as well as for confirming its nature.

Atrophy of Bilateral Extraocular Muscles CT and Clinical Features of Seven Patients

Swelling of the extraocular muscles is a common orbital abnormality that is easily demonstrated by computed tomography (CT). However, muscle atrophy is more difficult to identify and is rarely reported in the literature. Bilateral atrophy is extremely rare. We report the CT and clinical features of seven patients showing bilateral extraocular muscle atrophy: four with mitochondrial myopathy (MM) and three with myasthenia gravis (MG). Six patients had clinical histories of muscle involvement > 20 years. An incorrect diagnosis of MG was made initially in two patients with MM because of mildly positive Tensilon testing. The ocular motor abnormalities failed to improve after thymectomy in the myasthenic patients. Orbital appearance on neuroimaging is similar in these disorders. Differentiation between these two disorders is impossible with orbital CT and magnetic resonance imaging (MR) alone.

Metastatic Prostate Cancer to the Optic Canal

Purpose: Optic neuropathies represent a common cause of blindness among patients with cancer. The authors present the clinical and imaging findings and discuss the management of optic nerve involvement from metastatic prostate cancer to the optic canal. Methods: Five patients with advanced metastatic prostate cancer had visual loss. Neurophthalmologic examination and pre- and post-gadolinium orbital and brain magnetic resonance imaging (MRI) were performed. Compressive optic neuropathy secondary to extensive optic canal involvement was demonstrated in all of the patients. Neuropathologic examination was accomplished in two cases. A combination of steroid and focal radiation therapy was used for treatment in four patients. Results: Imaging and neuropathologic findings demonstrated a compressive optic neuropathy secondary to both epidural metastases and to deformity and hypertrophy of the optic canal due to metastatic cancer. Treatment was of benefit in three cases. Conclusion: Acute and subacute unilateral or bilateral optic neuropathy in patients with prostate cancer may be the result of optic canal metastases. Magnetic resonance imaging shows a characteristic pattern of bone hypertrophy and deformity with optic nerve compression. Early combination steroid and radiation therapy may induce long-lasting improvement.

Chronic Paroxysmal Hemicrania and Hemicrania Continua: Orbital Phlebography and MRI Studies

Six patients with chronic paroxysmal hemicrania (CPH) and 10 patients with hemicrania continua (HC), two indomethacin-responsive, unilateral, headache syndromes, were investigated with orbital phlebography and magnetic resonance imaging of the brain. Orbital phlebography apparently showed pathological findings more frequently in CPH than in HC. Such abnormalities did not always show preference for the side of headache. MR scans were grossly normal in these headaches.

Magnetic Resonance Imaging in Diagnosis and Follow-up of Minimal Thyroid Ophthalmopathy.

We report a case of minimal thyroid ophthalmopathy treated with intravenous methylprednisolone, in which precise identification of the involved muscle was possible with the use of surface coil magnetic resonance (MR) imaging. Intravenous methylprednisolone was more effective than the oral prednisolone as judged by orbital MR imaging. MR imaging is one of the useful tools in the diagnosis and assessment of treatment in this field.

The conformational properties of some phenyl esters. Molecular orbital and nuclear magnetic resonance studies

Extensive, geometry-optimized, STO-3G MO computations on phenyl formate imply a strongly nonplanar Z conformer (C=O bond cis to the phenyl group) at ambient temperatures. The internal barrier to rotation about the C(1)—O bond in this conformer is computed as V/kJ mol−1 = (−5.17 ± 0.27) sin2 θ − (2.42 ± 0.27) sin2 2θ, θ being zero for the planar conformer; the twofold is nearly twice as large as the fourfold component. The expectation value of θ is 58° at 300 K. The spin–spin coupling constants over six bonds between 13C and I9F nuclei in 4-fluorophenyl formate, acetate, propionate, and isobutyrate, as well as in the 2,6-dichloro-4-fluorophenyl acetate, are adduced as evidence for nonplanar conformers of these molecules. The magnitudes of these six-bond coupling constants are consistent with internal barriers to rotation about the C(1)—O bonds, which are similar in magnitude to those given by the computations on the Z conformer of phenyl formate. The energies of the planar and nonplanar E conformers, as well as the interconversion energies for [Formula: see text] isomerization, are computed. Small amounts of the nonplanar E conformer are predicted at ambient temperatures. The 13C chemical shifts and the one-bond 13C, 19F coupling constants are consistent, respectively, with only minor variations in the conformational behavior of the ester moieties caused by the fluorine substituent and by changes in the structures of these moieties themselves.