Journal of Neuro-Ophthalmology, March 1987, Volume 7, Issue 1

Congenital ocular motor apraxia without head thrusts.

Congenital ocular motor apraxia is a distinctive disorder that may present initially as apparent cortical blindness, because of the patient's inability to make saccadic eye movements to fixate targets moving in the horizontal plane. Affected children develop a characteristic compensatory head thrust that allows them to fixate and allows the physician to make the diagnosis. Two patients, initially thought to be blind because of a lack of fix or following responses in the horizontal plane, are reported. Although head thrusts were not present because of inadequate head control, the diagnosis of congenital ocular motor apraxia was made because of other diagnostic features. The cases emphasize the need to consider congenital ocular motor apraxia in any child thought to be cortically blind.

lOll mal of Clillical Neuro-opittitalmology 7(1): 26-28, 1987. Congenital Ocular Motor Apraxia Without Head Thrusts Michael L. Rosenberg, M.D., and Edward Wilson, M.D. © 1987 Raven Press, New York Congenital ocular motor apraxia is a distinctive disorder that may present initially as apparent cortical blindness, because of the patient's inability to make saccadic eye movements to fixate targets moving in the horizontal plane. Affected children develop a characteristic com­pensatory head thrust that allows them to fixate and allows the physician to make the diagnosis. Two pa­tients, initially thought to be blind because of a lack of fix or following responses in the horizontal plane, are reported. Although head thrusts were not present be­cause of inadequate head control, the diagnosis of con­genital ocular motor apraxia was made because of other diagnostic features. The cases emphasize the need to consider congenital ocular motor apraxia in any child thought to be cortically blind. Key Words: Congenital ocular motor apraxia-Contra­versive deviation-Head thrust-Cortical blindness. From the Neuro-ophthalmology Section, Departments of Neurology and Surgery, Uniformed Services University of the Health Sciences, Bethesda, Maryland; and Ophthalmology De­partment, Naval HospitaL Bethesda, Bethesda, Maryland. The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the Department of Defense, the Depart­ment of the Navy or the Uniformed Services University of the Health Sciences. Address correspondence and reprint requests to Dr. M. L. Rosenberg, Departments of Neurology and Surgery, Uni­formed Services University of the Health Sciences, Bethesda, MD 20814-4799, U.S.A. 26 In 1952 Cogan reported four cases of a peculiar ocular motility disorder he called congenital ocular motor apraxia (1). Since Cogan's original descrip­tion, more than 40 cases have been reported. Most have been sporadic, but a significant number have been familial, with both sex-linked and autosomal recessive inheritance (2,3). Although most pa­tients are otherwise normal, the condition has been associated with immunodeficiency, agenesis of the corpus callosum, macrocephaly, and poren­cephaly, as well as supra- and infratentorial masses (4-8). Patients with this condition have a striking ab­sence of voluntary horizontal movements of the eyes and yet retain full random movements. Ver­tical pursuits and refixation movements are typi­cally intact, although a single patient has been re­ported with oculomotor apraxia isolated to the vertical plane (9). The absence of normal hori­zontal following or refixation movements in an in­fant despite normal pupillary reflexes has led fre­quently to a misdiagnosis of cortical blindness (1,2). The retention of a normal vestibulo-ocular reflex produces a so-called contraversive deviation of the eyes with head turn that enables the pa­tients to develop compensatory head thrusts and therefore voluntarily fixate an eccentric target. These compensatory head thrusts may be the pre­senting sign and are usually the most character­istic feature leading to the diagnosis of congenital ocular motor apraxia. We report two cases of con­genital ocular motor apraxia diagnosed without head thrusts, and emphasize that prior to devel­opment of full head control this compensatory fix­ation movement will not be seen. As these pa­tients are often thought to be cortically blind, early diagnosis is crucial to decrease family anxieties and to prevent unnecessary testing. CONGENITAL OCULAR MOTOR APRAXIA 27 CASE REPORTS Case 1 An 8-month-old infant girl was seen for the evaluation of cortical blindness. The parents had noted that the child did not fixate well with her eyes at the age of 2 months. Pediatric evaluation at that time found the child to be developmentally delayed with poor head control. There was no evi­dence of any ability to fix or follow any objects; yet, the pupillary reactions were normal. Flash visual evoked responses were flat on the left, and there was only a minimal response on the right. On ophthalmologic examination, no fixation response was detected. The fundi were normal bilaterally. Computed tomography (CT) showed bilateral, mild, diffuse cortical atrophy. The parents were told that the child was cortically blind. At 8 months she was reevaluated because of continued developmental delay. Head control remained poor, and she was not turning or crawling. She was again thought to be cortically blind and was sent for further evaluation. Neuro-ophthalmologic examination confirmed a lack of ability to fix or follow objects within the horizontal plane. In con­trast, the child responded normally to targets moved only in the vertical plane. Further, a full range of motion horizontally was noted with random saccades and after passive movement of the head. Optokinetic nystagmus could not be elicited horizontally but was normal vertically. When the child was rotated at arm's length to ei­ther side, the eyes deviated conjugately towards the direction in which she was rotated. There were no head thrusts. A visual evoked response test was repeated and on this occasion was noted to be normal. A repeat CT scan again showed cortical atrophy. Neurologic defects such as those in this patient are unusual in congenital oculomotor apraxia. However, because of the clear-cut vertical refixation movements and the contraversive ocular deviations on rotation, a diagnosis of congenital ocular motor apraxia was confidently made even in the absence of head thrusts. Case 2 A 6-month-old infant boy was referred from the pediatric clinic for presumed cortical blindness and developmental delay. CT scan had shown scattered areas of cortical atrophy. Developmen­tally, head control was poor, and he was unable to crawl or turn over. The results of general neuro­logical examination were otherwise normal. The pupils were normal with brisk light reaction. Random extraocular movements were full; how­ever, no fixation or following movements could be demonstrated in the horizontal plane. A diagnosis of cortical blindness was made. Neuro-ophthalmo­logic evaluation confirmed these findings but also noted that fix and follow responses were clearly present within the vertical plane. Rotation pro­duced contraversive deviation without nys­tagmus. No head thrusts were present. The diag­nosis of congenital ocular motor apraxia was made. By the age of 10 months, development had progressed and head control was greatly im­proved. Head thrusts were now readily employed as a refixation strategy. DISCUSSION Congenital ocular motor apraxia is a disorder with rather stereotyped eye and head movements (1). Random ocular motility is intact, as are vertical saccades and pursuit movements. Horizontal sac­cades to eccentric targets are absent, and hori­zontal following movements may be impaired. In infants, the lack of a fix and follow response to visually presented targets may lead to the impres­sion of blindness (1,2). Although visual evoked re­sponses have been suggested to be helpful in the diagnosis (10), it has been our experience (as in Case 1 and others) that such responses may be falsely abnormal in an infant, "confirming" the er­roneous diagnosis of blindness. This lack of corre­lation has been previously documented in children with cortical blindness by Frank and Torres (11). Patients with congenital ocular motor apraxia have a marked contraversive deviation of the eyes with any head movement (1). This pattern is used by the infant to develop a compensatory mecha­nism for the fixation of eccentric targets. The head is thrust to the side of the target, causing the eyes to deviate in the opposite direction. The head con­tinues to turn past the target, until the eyes are dragged up to the target. Once fixation is set, the head is then moved back towards the target while fixation is maintained. The head movement past the object of regard is referred to as a head thrust. This striking clinical sign is very characteristic of congenital ocular motor apraxia and has been the hallmark for diagnosis. In only a few patients has the diagnosis been made without head thrusts. In 1982 Gittinger reported three infants who were thought to be cortically blind (10). The diagnosis was first suggested when visual evoked potentials suggested normal visual acuity. Vertical saccades or following movements were difficult to demon­strate at first in these cases. All patients later de- 1Clin Neuro-ophthalmol, Vol. 7, No.1, 1987 28 M. L. ROSENBERG AND E. WILSON veloped very characteristic head thrusts, and the diagnosis was confirmed. Visual evoked re­sponses in our cases was misleading at a time when vertical following and vertical optokinetic nystagmus were demonstrated. Manson reported a patient he examined at 4 months of age without head thrusts, but did not definitively diagnose congenital ocular motor apraxia until head thrusts developed at 8 months of age (12). Others have documented head thrusts as early as 3 months of age (rarely), and many as early as 5 or 6 months (1,5). Zaret et al. reported a child with a clinical pic­ture of congenital ocular motor apraxia who was noted at 8 months to have compensatory head thrusts (6). On readmission to the hospital at the age of 12.5 months, the child had had a deteriora­tion in his neurologic status with evidence of a brainstem neoplasm and no longer had notable head thrusts. Although the authors did not so speculate, this was presumably due to a deteriora­tion in head control. Head thrusts as a compensa­tory mechanism do not occur until head control has developed. We believe that the diagnosis of congenital oc­ular motor apraxia can be comfortably and reliably made in the absence of characteristic head thrusts by demonstrating contraversive eye movements on head rotations as well as noting intact fix and follow responses in the vertical plane. Congenital ocular motor apraxia should be considered in the differential diagnosis of all infants thought to have cortical blindness. Increased awareness of the dis- Oin NClIro·"phthallllof, Vol. 7, No. 1. 1987 order and all of its characteristics will lead to an increased accuracy in diagnosis, In contrast, reli­ance on the visual evoked potential may be signifi­cantly misleading. REFERENCES 1. Cogan OG. A type of congenital ocular motor apraxia pre­senting jerky head movements. Trans Am Acad Ophthalmol OtolaryngoI1952;Nov-Oec:853-62. 2. Rendle-Short J, Appleton B, Peam J. Congenital ocular motor apraxia: pediatric aspects. Aust Pediatr J 1973;9: 263-8. 3. Moe Pc. Ocular motor apraxia in three families. Neurology (Minneap) 1971;21:451. 4. Narbona L Crisci CO, Villa I. Familial congenital ocular motor apraxia and immune deficiency. Arch Neural 1980;37:325. 5. Orrison WW, Robertson WC Jr. Congenital ocular molor apraxia. Arch Neural 1979;36:29-31. 6. Zaret CR, Behrens MM, Eggers HM. Congenital ocular motor apraxia and brainstem tumor. Arch Ophthalmol 1980;98:328-30. 7. Lyle OJ. A discussion of ocular motor apraxia with a case presentation. Trans Am Ophthalmol Soc 1961;59:274-85. 8. Smith JL. Cited by Walsh F, and Hoyt W. Clinical Neuro­Ophthalmology, vol 1, 3rd ed. Baltimore: Williams & Wilkins, 1969:214. 9. Hughes JL, O'Connor PS, Larsen PO, Mumma JV. Con­genital vertical ocular motor apraxia. J Clin Neuro Oph­thalmoI1985; 5:153-7. 10. Gittinger JW Jr, Sokol S. The visual-evoked potential in the diagnosis of congenital ocular motor apraxia. Am J Oph­thalmoI1982; 93:700-3. 11. Frank Y, Torres F. Visual evoked potentials in the evalua­tion of "cortical blindness" in children. Ann Neural 1979;6:126-9. 12. Manson JI. Ocular motor apraxia in childhood. Proc Aust Assac NellroI1973;10:27 -9. ,.===.