Journal of Neuro-Ophthalmology, March 1982, Volume 2, Issue 1

Abducens paresis. A rare presenting sign of posterior-inferior cerebellar artery aneurysm.

Posterior fossa aneurysms comprise a minority of intracranial aneurysms, but produce a wide array of signs and symptoms. We report a patient with slowly progressive unilateral sixth nerve paresis secondary to a saccular aneurysm of the posterior-inferior cerebellar artery. Neuroradiologic investigation of subarachnoid hemorrhage is discussed, and the literature concerning posterior circulation aneurysms is reviewed.

j. Gin. Neuro-ophthalrnol. 2:55-00, 1982. Abducens Paresis A Rare Presenting Sign of Posterior-Inferior Cerebellar Artery Aneurysm SUSAN DUMAS, M.D. WILLIAM T. SHULTS, M.D. Abstract Posterior fossa aneurysms comprise a minority of intracranial aneurysms, but produce a wide array of signs and symptoms. We report a patient with slowly progressive unilateral sixth nerve paresis secondary to a saccular aneurysm of the posterior-inferior cerebellar artery. Neuroradiologic investigation of subarachnoid hemorrhage is discussed, and the literature concerning posterior circulation aneurysms is reviewed. Intracranial aneurysms may produce cranial nerve pareses; however, aneurysm-induced slow progression of paresis of a single cranial nerve is uncommon. The following case illustrates unilat­eral abducens paresis due to a posterior fossa aneurysm which, although unusual, should be con­sidered in the differential diagnosis of progressive abducens paresis. Case Report A 56-year-old white female educator was re­ferred for neuro-ophthalmic assessment of hori­zontal diplopia. Two years previously, while speaking at a convention, she had developed the sudden onset of a global headache associated with neck stiffness, followed 10 minutes later by bilat­eral anterior chest pain. Emergency room electro­cardiogram (ECG) showed a new left bundle branch block, and the patient was admitted to the coronary care unit. Admission neurological exam­ination was normal, without nuchal rigidity or extraocular motility deficit. Myocardial infarction was ruled out with serial ECG's and serum creatine phosphokinase levels, and the patient was dis­charged on the third hospital day. One day following discharge, the patient saw her family physician, complaining of continued From the Department of Ophthalmology, Oregon Health Sci­ences University (SO, WTSj. and Devers Eye Clinic, Good Samaritan Hospital and Medical Center (WTSj. Portland. Or­egon. March 1982 headache and neck stiffness. Examination revealed nuchal rigidity, prompting lumbar puncture which yielded grossly bloody cerebrospinal fluid. The patient stated that intermittent horizontal diplopia had been present since her first hospitalization. The admitting neurosurgeon found hypesthesia over the right face and minimal weakness of the right corner of the mouth. There was no limitation of ocular motility. Bilateral common carotid and right vertebral arteriography failed to demonstrate an aneurysm, arteriovenous malformation, or in­tracranial mass (Figs. 1 and 2); the left vertebral artery was not visualized. The patient was again discharged. The patient continued to experience diplopia at distance, and consulted her ophthalmologist who measured 9 ~ esotropia at distance and 7 ~ at near. Prism was added to her spectacles, with relief of diplopia for over 2 years, when she again saw her ophthalmologist, complaining of horizontal diplo­pia. Her esotropia had increased to 14 ~ at distance, and an increase in prism was prescribed. Over the next 2 months, her esotropia increased to 24 ~ at distance, and 18 ~ at near. A Tensilon test was negative. The patient was referred for neuro-oph­thalmic consultation, which confirmed a moderate left lateral rectus paresis. Contrast-enhanced computerized tomographic (CT) brain scan demonstrated a sharply circum­scribed circular extraaxial lesion in the area of the left cerebellopontine angle (Figs. 3 and 4). Left vertebral arteriography defined a 2 X 1 cm bilobed aneurysm at the origin of the left posterior inferior cerebellar artery (PICA) (Figs. 5 and 6). At the time of surgery, the neck of the aneurysm was identified just distal to the origin of the PICA, and success­fully clipped. The patient's postoperative course was uneventful except for hoarseness, and exami­nation 2 months later showed only minimal left sixth nerve paresis and mild hoarseness. Comment Focal neurologic deficit may be the first sign of intracranial aneurysm. Although Drakel states that small intact saccular aneurysms are usually unher- 55 Figure 1. Cerebral angiography. Right vertebral artery injection, an­teroposterior view. Contrast material does not reflux into the left vertebral artery or its branches. Figure 2. CPrcbr.ll .mgiography. Right vertebral artery injection, lateral view. Journal of Clinical Neufo-ophthalmology March 1982 Figure 3. Computerized tomography. axial view, demonstrates ring-like en­hancing leSIon in the region of the left cerebelloponline angle. Figure 4. Computerized tomography, coronal and sagitt.ll reconstructions, suggest extra-axial 100.,lion of lesion s{'en in Fig. 3. 57 figure 5. Cerebral angiography. Left vertebral artery injection. anteroposterior view, demonstrates saccular aneurysm (arrow) near origin of the left PICA. figure 6. Cerebral <mgiography. Left vertebral artery injection, lateral view. Arrow points to left PICA dneurysm. Journal of Clinical Neuro-ophthalmology aided before rupture occurs, many reports exist of symptoms prior to rupture. Okawara~ reported warning signs presumed secondary to aneurysm expansion, minor bleeding, or ischemia in 54 of 112 patients with single aneurysm prior to rupture; none of the five reported posterior fOsS.1 aneu­rysms, however, produced neurologic.11 signs. Oie­mann'l believes that patients with compression of a cranial nerve comprise the I.ugest group with symptomatic unruptured single aneurysms seen by the neurosurgeon. Transient focal ischemic def­icits, possibly thromboembolic, .lssoci.lted with un­ruptured intracranial aneurysms have been re­ported. 4 . [, Saccular aneurysms of the posterior circulation may simulate posterior fossa tu­mors, t>-1lI and chiasmal syndrome due to basilar artery aneurym has recently been reported. II Pathologic study by Hyland and Barnettl~ of aneurysms clinically affecting cranial nerves re­vealed a nearly equal incidence of direct involve­ment by the aneurysm and indirect involvement secondary to hemorrhage. Abrupt aneurysmal di­latation without rupture, or incorporation of the nerve within the aneurysm wall are possible mech­anisms of impairment of nerve function. Hyland and Bamete~ state that "leakage of blood, or the accompanying acute dilatation of the sac, may provide the additional trauma necessary to cause loss of function in a nerve which has been able to function previously, although damaged by aneu­rysm pressure." Posterior fossa aneurysms are uncommon, n. 14 comprising 10-15% of intracranial aneurysms; PICA aneurysms are rarer still. Of 2672 cases of single aneurysm reported by Locksley in a large cooperative study, 5.5% were within the posterior circulation, and only 0.5% involved the PICA. 15 Acquired sixth nerve paresis is rarely due to intracranial aneurysm. In Rucker's series of 2000 cases of paralysis of the third, fourth, and sixth cranial nerves, 924 cases involved the abducens nerve alone, of which 31 (3.3%) were due to aneu­rysm. I~. 17 Rush and Younge lH recently reported a further series of 1000 cases of ocular motor paral­ysis, 419 involving the sixth nerve alone, of which 15 (3.6%) were due to aneurysm. Of 65 patients with ocular involvement in cerebral aneurysms reported by Dailey et al.,19 none presented with an isolated abducens nerve paralysis. Hook et al. 2I1 reported 28 cases of saccular ver­tebrobasilar aneurysm, one associated with unilat­eral abducens paresis which the authors felt rep­resented elevated intracranial pressure rather than a focal neurologic sign. Duvoisin and Yahr7 de­scribed one patient with a 4-day course of bilateral abducens paresis associated with rupture of a ver­tebral aneurysm at the origin of the PICA. Of 27 patients with vertebrobasilar aneurysm, Sharr and Kelvin21 reported one case with bilateral sixth nerve palsy and pinpoint pupils secondary to hem- March 1982 Dumas, Shults orrhage from a basilar bifurcation aneurysm. One patient with a fusiform posterior circulation aneu­rysm and multiple left-sided symptoms described by Pribram et al. llJ had previously undergone sur­gical correction of idiopathic left sixth nerve palsy. Michacl" reported two cases more closely resem­bling our pJtient. The first, a 41-year-old woman with diplopia due to a partial sixth nerve lesion, underwent negative carotid angiography. Twenty­one months later, she returned with persistent left abducens paresis, left lower facial weakness, and absent left corneal reflex; vertebral angiography demonstrated a large basilar aneurysm. The second patient, a 58-year-old woman with subarachnoid hemorrhage and no localizing signs, underwent negative bilateral carotid and right vertebral an­giography. Three years later, she returned with signs of cervical cord compression producing a Brown-Sequard syndrome; left vertebral angiog­raphy demonstrated an aneurysm of unspecified location. Four-vessel cerebral angiography after subarach­noid hemorrhage is negative in approximately 15% of cases.22 . 2'1 In 122 patients with subarachnoid hemorrhage reported by Sharr and Kelvin,21 uni­lateral vertebral angiography after negative bilat­eral carotid angiography yielded 18 aneurysms (16%); in 77 patients studied by Sutton and Trickey/3 16 aneurysms (21%) were found with unilateral vertebral angiography after negative ca­rotid studies; and in 60 such cases reported by Spatz and Bull/4 vertebral study revealed another 8 aneurysms (13%). Sutton and Tricke/'l caution against accepting a negative three-vessel study in subarachnoid hemorrhage, as the terminal segment of the contralateral vertebral artery with its PICA branch "in most cases can only be shown if the correct vertebral artery is injected. Occasionally the termination of both vertebrals can be shown by injection of one vertebral artery because of reflux down the contralateral vertebral artery. This phenomenon however is more likely to occur with a healthy vertebral artery than with one which has been associated with recent subarachnoid hemor­rhage." Based on results of this study of 113 pa­tients with subarachnoid hemorrhage investigated by four-vessel angiography Biorkesten~~ recom­mends complete angiographic studies even after one aneurysm has been found, if that lesion does not explain the clinical findings. The patient reported here demonstrates an un­common lesion presenting in an unusual manner, and underscores the necessity of complete angio­graphic study in patients with subarachnoid hem­orrhage. CT scanning may be helpful in detecting intracranial aneurysms, but is by no means diag­nostic. In unexplained progressive abducens pa­resis, particularly in patients with a history sugges­tive of subarachnoid hemorrhage, posterior fossa aneurysm should be considered. 59 Abdu(C'ns I'.!resis References I. Dr.lkl', CG.: Man.lgement of .Ineurysms of posterior circul.ltion. In Neuro/ogic.!1 Surgery, J.R. Youman, Ed. W. B S.lUndC'rs, I'hil.ldelphiJ, 1973, pp. 787­BOb. ~ O".lW.H.l, S.H.: W.Hning signs prior to rupture of an intr.lu,1I1i.ll .lnC'urysm. /. Neurosurg. 38: 575-580, 1Q73. 3. Ojem.lnn, R.G.: Editorial: Management of the un­ruptured intrJcrJnial aneurysm. N. Engl. /. Med. 304: 725-72b, 19B!. -to Stew.Ht. R.M., Samson, D., Diehl, J., Hinton, R., and Ditmore, O.M.: Unruptured cerebral aneurysms presenting as recurrent transient neurologic deficits. Neurology 30: 47-51, 19BO. 5. Fisher, M., Davidson, R.I., and Marcus, E.M.: Tran­sient focal cerebral ischemia as a presenting mani­festation of unruptured cerebral aneurysms. Ann. Neurol. 8: 367-372, 19BO. 6. Michael, W.F.: Posterior fossa aneurysms simulating tumours. j. Neuro/. Neurosurg. Psychiatry 37: 21B­223, 1974. 7. Duvoisin, R.C., and Yahr, M.D.: Posterior fossa aneurysms. Neurology 15: 231-241,1965. B. Yaskin, H.E., and Alpers, B.J.: Aneurysm of the vertebral artery. Report of a case in which the aneu­rysm simulated a tumor of the posterior fossa. Arch. Neurol. Psychiatry 51: 271-281, 1944. 9. Alexander, E., Davis, CT., and Pikula, L.: Aneurysm of the posterior inferior cerebellar artery filling the fourth ventricle. Case report. j. Neurosurg. 24: 99­101, 1966. 10. Pribram, H.F.W., Hudson, J.D., and Joynt, R.J.: Pos­terior fossa aneurysms presenting as mass lesions. AIR. 105: 334-340, 1969. 11. Rush, J.A., Balis, G.A., and Drake, CG.: Bitemporal hemianopsia in basilar artery aneurysm. j. Clin. Neuro-ophtha/mo/. 1: 129-133, 19B1. 12. Hyland, H.H., and Barnett, H.J.M.: The pathogenesis of cranial nerve palsies associated with intracranial aneurysms. Proc. R. Soc. Med. 47: 141-146, 1954. 13. Chason, J.L., and Hindman, W.M.: Berry aneurysms of the circle of Willis. Results of a planned autopsy study. Neurology 8: 41-44, 1958. . 14. McDonald, CA., and Korb, M.: Intracramal aneu­rysms. Arch. Neurol. Psychiatry 42: 298-328, 1939. 15. Locksley, H.B.: Natural history of subarachnOId hemorrhage, intracranial aneurysms and arterIove­nous malformations. Based on 6368 cases III the cooperative study. j. Neurosurg. 25: 219-239, 1966. 16. Rucker, C W.: Paralysis of the third, fourth and Sixth cranial nerves. Am. j. Ophthalmol. 46: 787-794, 195B. 17. Rucker, C W.: The causes of paralysis of the third, fourth and sixth cranial nerves. Am. j. Ophthalmol. 61: 1293-1298, 1966. lB. Rush, J.A., and Younge, B.R.: Paralysis of cranial nerves lII, IV, and VI. Cause and prognosis in 1,000 cases. Arch. Ophthalmo/. 99: 76-79, 1981. 19. Dailey, E.).. Holloway, J.A., Murto, R.E, and Schle­zinger, N.5.: Evaluation of ocular signs and symp­toms in cerebral aneurysms. Arch. Ophthalmol. 71: 463-474, 1964. 20. Hook, 0., Norlen, G., and Guzman, J.: Saccular aneurysms of the vertebral-basilar arterial system. A report of 28 cases. Acta Neurol Scand. 39: 271-304, 1964. 21. Sharr, M.M., and Kelvin, F.M.: Vertebrobasilar aneurysms. Experience with 27 cases. Eur. Neurol. 10: 129-143, 1973. 22. Bjorkesten, G., and Halonen, V.: Incidence of intra­cranial vascular lesions in patients with subarach­noid hemorrhage investigated by four-vessel angiog­raphy. f. Neurosurg. 23: 29-32, 1965. 23. Sutton, D., and Trickey, S.L Subarachnoid hae­morrhage and total cerebral angiography. Clin. Ra­diol. 13: 297-303, 1962. 24. Spatz, E.L., and Bull, J. W.D.: Vertebral arteriography in the study of subarachnoid hemorrhage. f. Neu­rosurg. 14: 543-547, 1957. Write for reprints to: William T. Shults, M.D., 2282 N.W. Northrup No. 33, Portland, Oregon 97210. Journal of Clinical Neuro-ophthalmology