Journal of Neuro-Ophthalmology, March 1991, Volume 11, Issue 1

Magnetic resonance angiography (MRA) of isolated aneurysmal third nerve palsy.

Magnetic resonance angiography (MNA) was compared to conventional intra-arterial digital subtraction angiography in a patient with an isolated third nerve palsy caused by a posterior communicating artery aneurysm. The technique of MRA is briefly discussed.

© 1991 Raven Press, Ltd., New York Magnetic Resonance Angiography ( MRA) of Isolated Aneurysmal Third Nerve Palsy Robert L. Tomsak, M. D., Ph. D., Thomas J. Masaryk, M. D., and James H. Bates, M. D. Magnetic resonance angiography ( MNA) was compared to conventional intra- arterial digital subtraction angiog­raphy in a patient with an isolated third nerve palsy caused by a posterior communicating artery aneurysm. The technique of MRA is briefly discussed. Key Words: Magnetic resonance angiography- Third nerve palsy- Cerebral aneurysm. From the Division of Neuro- ophthalmology, University Hos­pitals of Cleveland and Department of Ophthalmology and Neurology, Case Western Reserve University School of Medi­cine ( R. L. T.); Division of Radiology, Cleveland Clinic Founda­tion, Cleveland, ( T. J. M.); and Department of Ophthalmology, Akron CIty HospItal a. H. B.), Akron, Ohio, U. S. A. Address correspondence and reprint requests to Dr. Robert L. Tomsak at Division of Neuro- ophthalmology, University HospItals of Cleveland, Lakeside 3200 A, Cleveland, Ohio 44106, USA 16 CASE REPORT A 39- year- old woman was referred for neuro­ophthalmologic evaluation because of a painful, isolated, right third nerve palsy of one month du­ration associated with a fixed and dilated pupil ( Fig. 1). She was promptly admitted to the hospital and conventional selective intra- arterial cerebral angiography ( Fig. 2) and magnetic resonance an- FIG. 1. Complete isolated right third nerve palsy with pupil involved. MRA AND ANEURYSMAL THIRD NERVE PALSY 17 FIG. 2. Selective intra- arterial right internal carotid angiogram showing posterior communicating artery aneurysm ( arrow). giography ( MRA) ( Figs. 3 and 4) showed an aneu­rysm at the junction of the right internal carotid artery and posterior communicating artery. The aneurysm was successfully treated by neurosur­gery. DISCUSSION This case shows the excellent ability of MR. A to image the cerebral circulation. In contrast to mag­netic resonance imaging ( MRf) of stationary tissue such as brain tissue, MRA relies on flowing blood for image alteration ( 1). Imaging is made possible by two relatively independent phenomena: a) the effect of flowing protons relative to the timing of the radiofrequency excitation pulse sequence (" time of flight effects"), and b) flow effects related to the signal localizing gradients (" spin- phase phenomena"). The MRA images of our patient were made by a gradient- echo technique using short echo times ( TEs) ( 2- 5). Such scans produce FIG. 4. Magnetic resonance angiogram ( axial. or sub­mentovertex projection) showing aneurysm ( arrow). rectangular three- dimensional computer data sets rather than the traditional two- dimensional ones and allow for vessel imaging in any plane and at any angle. The MRAs are displayed like conven­tional angiograms but are obtained in noninvasive fashion without the need for paramagnetic con­trast enhancement. Imaging time is only minimally longer than conventional MRI, with an increase in overall examination length averaging 12- 20 min­utes ( 5). At this time, MRA can image the circle of Willis and detect aneurysms as small as 3-- 4 mm in size ( 5). Magnetic resonance angiography is still under­going refinement and is being compared with in­tra- arterial digital subtraction angiography for sen­sitivity and specificity in detecting intracranial and extracranial vascular lesions ( 2- 5). It promises to be a powerful, noninvasive technique for evalu­ating a variety of cerebrovascular disorders. FIG. 3. Magnetic resonance an­giogram ( lateral projection) show­ing aneurysm ( arrow head). JClin Nruro- ophthalmol, Vol. 11, No. 1. 1991 R. L. TOMSAK ET AL.. _ ccation: 989; 171: l~ EFERENCES .. to.., ,.,. 11., It" II V ....., K · S. F.. mandl: Z EJ. Spalter C. Ill, .' 1'" ".'" I "" 1' 1,111' flowing l:> lood on magnetic res. .",•.• '.,.,': II" 1~. 14; l. 1167_ 74. ~ l. " I " l,~ h. ,",,' r. R".." IS... I al. [ nlrilCfanial cirroLt­I.. '" :,., 1,,,,,,,.,,,, d, m,', ll rt" Sults with thrl" t"- dlmensionaJ ,".' pWlk I\ · .... n,"...'- · . lnpogrolphy. RtldIlJl" S. yl989; 171: 793- 9. \\, 1"' 11110. 11. M, I<. iI'" MT. Rugglt" ri r. l' 1 ill. Three- dimen-skm, l gradient echo imaging of the ca-: otld prrliminary clinical experierce. RadI% K) 801- 6. 4. Ross IS, Masaryk n. Modic, MT. et ill. Magn~ tic reso~ ance angiography of Ike ... lracranial carotid artenes and mtJa­nolniaJ vessels: .. review. Ntll, oIogy 1989; 39: 1369- 76. 5. Ross J5. Masaryk n. Modic MT. et al. Intracranial aneu­rysms: t'wlluation by MR angiography. AJNR 1990; 11: 449­56. /~-----,