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Show Journal of Neuw- Ophthalmology 19( 4): 242- 245, 1999. © 1999 Lippincott Williams & Wilkins, Inc., Philadelphia Divergence Paresis: A Nonlocalizing Cause of Diplopia Frederick E. Lepore, M. D. Objectives: To determine the causes, clinical characteristics, and localizing value of divergence paresis, which is characterized by acquired and uncrossed diplopia when viewing distant targets, fusion when viewing near targets, and no limitation of ocular ductions. Controversy persists regarding the diseases underlying divergence paresis and the existence of a divergence " center." Materials and Methods: The charts of 15 patients with divergence paresis examined between 1983 and 1998 were reviewed. All patients underwent neuroimaging and detailed ocular motility testing, with measurement of esotropia in prism diopters in 14 patients. Results: Divergence paresis in 15 patients was idiopathic in three patients, was associated with central nervous system microangiopathy or infarct in seven patients, and clivus lymphoma, chronic lymphocytic leukemia with sinusitis, Wernicke ophthalmoplegia, Parkinson disease, myasthenia gravis, cryptic cerebellar vascular malformation, and childhood esotropia in one patient each ( two patients had two diagnoses). The mean maximum esotropia was 10.4 prism diopters, and there was no significant correlation ( Fisher exact test) between the magnitude of esotropia and vasculopathic etiology or posterior fossa lesion site. Although six patients had posterior fossa disease, neuroimaging showed no common circumscribed lesion site or evidence of increased intracranial pressure. Conclusions: Divergence paresis is an uncommon cause of acquired diplopia. Divergence paresis is associated with diverse central nervous system diseases and can be mimicked by myasthenia. The absence of a single consistent lesion in our study, which is the largest reported series, suggests that divergence paresis is a nonlocalizing cause of horizontal diplopia and that multiple or diffusely distributed neural structures may govern divergence. Alternatively, elusive divergence " centers" may not exist, and divergence paresis may arise from impaired inhibition or from defective passive antagonism of orbital structures to convergence. Key Words: Abducens paresis- Diplopia- Divergence weakness. Manuscript received August 23, 1999; accepted September 17, 1999. From the Department of Neurology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, New Jersey, U. S. A. Presented in part at the 51sl annual meeting of the American Academy of Neurology, April 1999, Toronto, Ontario, Canada. Address correspondence and reprint requests to Frederick E. Lepore, M. D., Department of Neurology, Robert Wood Johnson Medical School, 97 Paterson Street, New Brunswick, NJ 08901. Duane's ( 1) 1905 report of 11 patients with " very troublesome cases of esophoria" clearly delineated the clinical entities of divergence paralysis and paresis, which had initially been described by Parinaud ( 2) in 1883. Distinguishing features of this disorder of ocular motility included marked esophoria, insuperable or varying homonymous ( uncrossed) diplopia for distance, normal or nearly normal relations for near, and no impairment of outward nor excess of inward rotations of the eyes ( 3). More than a century later, controversy persists regarding whether disorders of ocular divergence may aid in neuroanatomic localization. The important clinical questions surrounding the frequency of associated neurologic diseases, the implications of the varying severity of divergence weakness, and the relationship of divergence paresis to disorders of the abducens nerve remain, in addition to discerning the anatomic underpinnings of divergence paresis. This study of 15 patients with divergence paresis uses neuroimaging and detailed measurements of esotropia to reconcile existing definitions of divergence paresis with the phenomena actually encountered by clinicians, to document the frequency of associated neurologic diseases, and to speculate on the neural substrate for ocular divergence. MATERIALS AND METHODS I reviewed the charts of 15 patients with ocular esode-viation for distant targets, fusion for near targets, and full ocular ductions. The study included all patients with divergence paresis who were evaluated in the author's university- based, neuro- ophthalmology out- patient practice between 1983 and 1998. A complete neuro- ophthalmo-logic examination was performed on each patient, and prism diopter measurements of distance esotropia in different fields of gaze were obtained for 14 patients. All patients underwent neuroimaging ( 14 patients underwent magnetic resonance imaging, and one patient underwent computed tomography). RESULTS The mean age of the 15 patients ( nine men and six women) was 58.6 ( range, 14 to 80 years). All eyes tested had better than 20/ 30 visual acuity. Divergence paresis was isolated in three patients; was associated with central 242 DIVERGENCE PARESIS 243 nervous system ( CNS) microangiopathy or infarct in seven patients; and was associated with clivus lymphoma, chronic lymphocytic leukemia with sinusitis, Wernicke ophthalmoplegia, Parkinson disease, myasthenia gravis, cryptic cerebellar vascular malformation, and childhood esotropia in one patient each ( two patients had two diagnoses) ( Table 1). The mean maximum esotropia for distant target was 10.4 prism diopters ( range, 1 to 20 prism diopters), and there was no significant correlation ( Fisher exact test) between the magnitude of esotropia and vasculopathic etiology, posterior fossa lesion site, or isolated divergence paresis. In different positions of gaze upon a distant target, variation of esodeviation was equal or less than 6 prism diopters in 12 patients and greater than 6 prism diopters in two patients. Six patients had posterior fossa disease, with cerebellar lesions in a patients 6 and 11, rostral brainstem disease in patients 3 and 4, clivus lymphoma in patient 1, and pontine ischemia in patient 10. Neuroimaging showed no patients with evidence of increased intracranial pressure. DISCUSSION Divergence paresis is an uncommon cause of acquired diplopia. Divergence paresis is associated with diverse CNS diseases ( 4), although in the present series, a peripheral origin for divergence paresis was proposed for patient 7, who had myasthenia gravis, a disorder that can mimic central gaze disturbances, such as internuclear Patient number 1 2 3 4 5 6 7 Age/ Sex 32/ M 62/ F 78/ M 79/ F 76/ M 76/ M 18/ F TABLE 1. Patients with divergence paresis Distance esotropia Esodeviation on alternate cover test, full ductions 10 PD in right/ primary/ left gaze 6 PD in right/ 8- 10 PD in primary/ 20 PD in left gaze 6 PD in right/ esophoria in primary/ 8- 10 PD in left gaze 10 PD in right and primary/ 4 PD in left gaze 2 PD in right/ 4 PD in primary/ 6 PD in left gaze 20 PD in right and left Neuroimaging ( MRI, unless otherwise stated) Clivus mass with erosion Sphenoid sinusitis with equivocal cavernous sinus involvement Cerebral atrophy Increased periventricular signal on T2 sequences, 4 x 5 mm pituitary microadenoma Atrophy and subcortical microangiopathic changes Atrophy, left cerebellar infarct, increased periventricular signal on T2 sequences Normal Diagnosis CNS lymphoma Chronic lymphocytic leukemia with sinusitis Wernicke ophthalmoplegia Parkinson disease and CNS microangiopathy CNS microangiopathy Cerebellar infarction and CNS microangiopathy Myasthenia gravis Comment Developed left sixth- nerve palsy 6 weeks later Convergence insufficiency also found Mild optic neuropathy OS History of coronary artery disease History of coronary artery disease, Type 11 DM, and hyperlipidemia Developed esotropia at 12 13 14 gaze/ esophoria in primary gaze 14/ F 14 PD in right and left gaze/ 16 PD in primary gaze 53/ M 4 PD in right downgaze/ 2 PD in direct and left downgaze 76/ F 6 PD in right gaze/ 8 PD in primary gaze/ 6- 8 PD in left gaze 65/ M 4 PD in right and left gaze/ 2 PD in primary gaze 31/ F 12 PD in right, primary, and left gaze 68/ M 6 PD in right gaze/ fusion to 4 PD in primary gaze/ 4 PD in left gaze 71/ M 4 PD in right and left gaze/ fusion to 1 PD in primary gaze 80/ M 10 to 12 PD in right gaze/ 10 PD in primary gaze/ fusion in left gaze near within 2 years Normal Few scattered foci of increased periventricular signal on T2 sequences Cerebral atrophy, periventricular, and pontine microangiopathy Left cerebellar cryptic AVM Hyperintense focus in right corona radiata Left ganglionic/ capsular lacune Hyperintense signal in left frontal white matter Cerebral atrophy on CT Isolated divergence paresis Isolated divergence paresis Vertebrobasilar ischemia Cryptic cerebellar vascular malformation Lacunar CVA, childhood esotropia Lacunar CVA CNS microangiopathy Isolated divergence paresis Convergence insufficiency also found Convergence insufficiency also found PD, prism diopters; CNS, central nervous system, CT, computed tomography; AVM, arteriovenous malformation; CVA, cerebrovascular accident; DM, diabetes mellitus. J Neiim- Oplithalniol, Vol. 19. No. 4, 1999 244 F. E. LEPORE ophthalmoplegia ( 5). The condition most frequently associated with divergence paresis ( found in 7 patients) was CNS microangiopathy or infarction. In contrast with Krohel's series, in which only 27% of patients had concomitant neurologic diseases ( 6), 80% of patients in the present series had neurologic or neuromuscular disorders. None of the patients in our study had clinical or neuroimaging evidence of increased intracranial pressure, which was a common finding in older reports ( 7,8). Although prior reports have stressed the concomitance of esodeviation in all fields of gaze ( 4), this was not a consistent finding in the present series. In the absence of detailed measurements of esodeviation in standard positions of gaze in the overwhelming majority of reports ( including reports 4, 6, 7, and 8), it is exceedingly difficult to determine the stringency of concomitance as a defining feature of divergence paresis. A minor degree of incomitance in divergence paresis was deemed acceptable in Duane's original report ( 1), and Bielschowsky ( 9) observed that the angle of squint would increase or decrease when looking down or up, respectively. Visual target distance from the patient is critical in assessing divergence paresis, and the issue of incomitance versus concomitance may be further obscured when gaze measurements reveal esotropia for distance, fusion for near, and exotropia for test objects proximal to fusion distance because of the frequent association of convergence insufficiency with divergence paresis ( 9), such as was recorded in three patients in this series. Based on present ( 10) and past ( 1,9) clinical observations of gaze incomitance, pure concomitance may be regarded justifiably as a minor criterion of divergence paresis, and greater diagnostic weight should be assigned to the clinical triad of uncrossed diplopia at distance, no diplopia at near, and full versions and ductions ( 6). Another widely held diagnostic tenet of disorders of divergence is that these disorders constitute a distinct entity that usually can be separated from bilateral lateral rectus muscle palsies ( 6). Although bilateral abducens palsies can be distinguished readily from divergence paresis by features such as limitation of abduction or esotropia at near ( 10), this study and others ( 1,11) suggest that divergence paresis and bilateral abducens palsies may be part of a continuum of esodeviation. Patients 2 and 7 developed lateral rectus palsies following initial presentation with divergence paresis. Similarly, Duane's ( 1) original description noted that " bilateral abducens paralysis may be converted into a divergence-paralysis, and, on the other hand a divergence- paralysis may pass into a paresis of the abducens." These observations support the close relationship of divergence paresis and abducens palsy but suggest a distinct class of abducens dysfunction producing the features of divergence insufficiency without other signs of sixth- nerve palsy ( 11). No etiologic significance could be attributed to the magnitude of esotropia in this study. Although the quantity of esotropia was used by Duane ( 1) to distinguish divergence paralysis from divergence insufficiency, he too did not attempt to correlate cause with severity of esotropia. Alternatively, Duke- Elder ( 12) differentiated divergence paralysis from insufficiency on the basis of organic disease or functional origin, respectively, and not on the size of esotropia. The variety of criteria and vague nomenclature create an artificial and arbitrary classification that does not foster clinical precision. Consequently, this study uses the single term " divergence paresis" to identify divergence dysfunction of all magnitudes and etiologies. Despite detailed neuroimaging in this study there was no single site of pathology to account for divergence paresis. The absence of a consistently demonstrable lesion supports the investigations of Scobee and Green ( 13) and others ( 10) who have argued against the existence of a divergence center. Although there are case reports of clinicopathologic identification of a divergence center, these cases were almost invariably characterized by a posterior fossa lesion and by evidence of increased intracranial pressure ( 7,8,14). In such cases, the operative mechanism may simply be raised intracranial pressure, which can produce the classic features of divergence paresis ( 11). With no compelling evidence for a single divergence center, alternative explanations of divergence paresis include dysfunction of multiple or diffusely distributed neural structures governing divergence, impaired inhibition of convergence mechanisms, e. g., convergence spasms ( 9), or defective passive antagonism of orbital structures to convergence, e. g., the elasticity theory ( 13). Although Mays ( 15) identified divergence neurons in the mesencephalic reticular formation of rhesus monkeys, a discrete nucleus for divergence in the human has yet to be unequivocally identified. Like the other proposed vergence center, Periia's nucleus of convergence, the " divergence nucleus," may be a candidate for neurologic mythology ( 16). At present, clinicians should regard divergence paresis as a nonlocalizing cause of diplopia, and divergence paresis should be classed among other causes of heterotropia that defy precise neuroanatomic localization, such as skew deviation, convergence insufficiency, abduction paresis because of increased intracranial pressure, and nonparalytic strabismus. REFERENCES 1. Duane A. Paralysis of divergence. Ophthalmology 1905; 2: 1- 19. 2. Parinaud MH. Paralysie des mouvements associes des yeux. Arch de Neurol 1883; 5: 145- 72. 3. Duane A. The extra- ocular muscles. In: Posey WC, Spiller WG, eds. The eye and nervous system. Philadelphia: JB Lippincott, 1906: 178- 284. 4. Stern RM, Tomsak RL. Magnetic resonance images in a case of " divergence paralysis." Surv Ophthalmol 1986; 30: 397- 401. 5. Glaser JS. Myasthenic pseudo- internuclear ophthalmoplegia. Arch Ophthalmol 1966; 75: 363- 6. 6. Krohel GB, Tobin DR, Hartnett ME, Barrows NA. Divergence paralysis. 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Neural control of vergence eye movements: convergence and divergence neurons in midbrain. J Neurophysiol 1984; 31: 1091- 108. 16. Warwick R. The so- called nucleus of convergence. Brain 1955; 78: 92- 114. J Neuro- Ophthalnwl, Vol. 19, No. 4, 1999 |
