European Journal of Paediatric Neurology (2003) 7, 173–175 www.elsevier.com/locate/ejpn CASE STUDY A case of disturbed vertical gaze Heidi Browna, Harry E. Willshawb,* a Birmingham and Midlands Eye Centre, Birmingham, UK Birmingham Children’s Hospital, Steel House Lane, Birmingham, UK b Received 24 January 2003; accepted 9 April 2003 KEYWORDS Saccades; Ocular motor apraxia; Optokinetic nystagmus Summary A 10-month-old boy with vertical ocular motor apraxia (OMA) is presented. An optokinetic projector confirmed absence of downward saccades. No case of idiopathic vertical OMA has previously been described. A review of the MRI, initially reported as normal, showed pathology in areas known to be involved with vertical eye movements: the cerebellum and thalamus. Q 2003 European Paediatric Neurology Society. Published by Elsevier Science Ltd. All rights reserved. Introduction Case study Ocular motor apraxia (OMA) was first described by Cogan in 1952 and is often, now, referred to as saccadic initiation defect. OMA most commonly affects horizontal eye movements and is not associated with any underlying CNS pathology. Acquired forms of horizontal OMA and vertical forms have also been reported with the same eye and head movement characteristics as first described by Cogan. We present a child with vertical OMA (absence of downward saccades only) and ischaemic lesions affecting the centres responsible for the generation of vertical saccades. In any case of vertical or acquired OMA a neurological lesion or metabolic cause should be sought. A 10-month-old boy was referred to the Paediatric Ophthalmology clinic with a six-month history of vertical head nodding and suspected hypotonia. He had been noted to drop his chin rapidly, at which time his eyes elevated, and the suspicion was that he had failed to develop good head control. He had been born at term after a normal pregnancy but foetal distress had required a forceps delivery. His Agpar scores were 5 and 9 but despite initial concerns about developmental delay, he was subsequently felt to show normal developmental progress. At the time of presentation he achieved a binocular visual acuity of approximately 6.5 cycles per cm with Teller cards ( ¼ 0.67 Logmar). Ocular examination was normal and there was no significant refractive error. His horizontal eye movements, both pursuit and saccades, were entirely normal, as was up gaze. However, on attempted down gaze he thrust his head downward, a movement which was accompanied by elevation of his *Correspondence: H.E. Willshaw, Consultant Paediatric Ophthalmologist, Birmingham Children’s Hospital, Steel House Lane, Birmingham, UK. Tel.: þ44-121-333-9464; fax: þ44-121333-9461. E-mail address: hwillshaw@aol.com 1090-3798/03/$ - see front matter Q 2003 European Paediatric Neurology Society. Published by Elsevier Science Ltd. All rights reserved. doi:10.1016/S1090-3798(03)00055-2 174 eyes. Downward saccades were absent but down gaze could be elicited with the doll’s head movement. An initial ultrasound examination of the brain suggested an abnormality of the ventricles, but a subsequent MRI scan was reported as showing no abnormality. A diagnosis of vertical OMA was made, and, despite his good general health and development, he was investigated for Niemann Pick (Type C) disease. Marrow aspirate was normal. He was presumed to have a primary vertical OMA, and was referred for further investigation to an eye movement laboratory. The vertical and horizontal optokinetic nystagmus (OKN) projector revealed normal horizontal and downward OKN, but an absent upward OKN, indicating a failure of downward directed saccades. The diagnosis of a form of vertical OMA was confirmed. Re-evaluation of the MRI scan found no abnormality of the basal ganglia but did reveal an old cerebellar infarct and an ischaemic lesion in the thalamus (Fig. 1). These changes, which may have been related to his birth trauma, were located in the area of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), the area responsible for the control of vertical saccades. Follow-up over the ensuing 6 years has shown no change in his eye movements. Visual acuity was 6/6 and N5 unaided in either eye. A number of traits developed notably extreme shyness, reluctance to mix with other children, and obsessive traits. He received help from a clinical psychologist, which has enabled him to integrate much better. He attends main stream school, though he performs in the lower third of the class. Figure 1 MRI scan to show ischaemic lesion (arrow) involving the thalamus. H. Brown, H.E. Willshaw Discussion OMA, first documented by Cogan in 1952, is a condition characterised by the inability to execute voluntary saccades.1 A saccade is a rapid eye movement (250 –7008 sec21) which is used to place an image on the fovea quickly. The stimulus for reflex saccadic movements is most commonly a target eccentric to fixation, but they can occur in response to a sound. They may also be voluntary or may arise as the fast phase of nystagmus (including OKN, which provides a valuable modality for clinical testing in the very young). Neural control for saccadic eye movements is located in the high midbrain and pons. The immediate premotor command for the saccadic pulse is generated by excitatory burst neurones, and abnormalities of burst neurones cause abnormal saccadic initiation or slow saccades. Excitatory burst neurones for horizontal saccades are situated within the paramedian pontine reticular formation (PPRF) and project directly to the VI nucleus. The excitatory burst neurones for vertical saccades are probably in the riMLF and project to the vertical components of the III nerve nuclei.2 The vertical burst neurones are intermingled on each side of the mid-line, and seem to require input from the caudal pons to function normally. Inhibitory burst neurones are situated in the rostral medulla. They receive input from the horizontal excitatory burst neurones, and then send information to the contralateral VI nucleus—thus providing the appropriate reciprocal innervation. The burst neurones are normally silent, but discharge at a high frequency just before the saccade. Cogan described OMA as head thrusting to accomplish horizontal ocular refixations. The saccades have increased latency and reduced amplitude, but the velocity is normal. Typically at the start of a horizontal head movement the eyes close and the head moves towards the eccentric new target. The eyes respond to the active vestibular system by rotating conjugately in the opposite direction. The head rotation overshoots the intended target and the deviated eyes take up fixation of the object. While fixation is maintained, the head slowly moves back until realigned with the eyes. This pattern usually develops around 4 – 8 months, but may not occur if there is inadequate head control. It has been suggested that the induced vestibulo-ocular response (VOR) during head thrusting is also pathological, and represents a failure to cancel the VOR in the normal way during head movement. The head thrusting usually decreases with age. A case of disturbed vertical gaze Table 1 Systemic conditions associated with abnormal horizontal saccades. Aids Ataxia-telangiectasia Balint’s syndrome Friedreich’s ataxia Gaucher’s disease Joubert’s syndrome Neurofibromatosis Niemann Pick syndrome Spinocerebellar degeneration Vitamin A and E deficiencies Whipple’s disease The great majority of saccadic initiation failure occurs in childhood and affects horizontal saccades. OMA may be seen as an isolated event (Cogan’s or congenital) or as part of a systemic disorder (Table 1). Vertical OMA has since been described,3,4 but is much less common. Unlike the horizontal disorder there are no cases of idiopathic vertical OMA recorded. A recent study of OKN in children with unusual head/eye movements found those children with abnormal/absent vertical OKN to have normal vertical and horizontal doll head movements. Those that had an abnormal vertical OKN, but normal horizontal OKN were highly likely to have pathology in the rostral midbrain. Those children with absent up and/or down vertical OKN had abnormalities on MRI involving the brainstem and/or cerebellum.5 Table 2 shows the site of lesions, which have been implicated in the production of vertical saccadic abnormalities. Our patient showed a similar, vertically orientated OMA. Review of the earlier MRI scans showed that there was an old cerebellar infarct and a lesion near the thalamus (Fig. 1). The latter was the likely cause of his vertical OMA and may have been related to his traumatic birth. However acquired OMA is commonly accompanied by cerebellar pathology (Joubert’s syndrome, ataxia-telangiectasia etc.) and it may well be that part of the pathology of the observed head and eye 175 Table 2 Causes of vertical saccadic abnormalities. Vertical saccadic abnormality Cause Slow vertical saccades Focal lesion in midbrain Paralysis of all vertical or predominantly downward saccades Vertical saccade obliquely misdirected to contralateral side of lesion Slow horizontal saccades Whipple’s disease Niemann Pick type C Progressive supranuclear palsy Gaucher’s disease (I,II,III) Huntington’s chorea Focal lesion riMLF Bilateral pontine lesions Unilateral pontine lesion movements includes failure to cancel the VOR during head movements. No case of idiopathic/ congenital vertical OMA has been described. Therefore, in any case of vertical or acquired OMA a neurological lesion or metabolic cause should be looked for. References 1. 2. 3. 4. 5. Cogan DG. A type of congenital ocular motor apraxia presenting jerky head movements. Trans Am Acad Ophthalmol Otolaryngol 1952;56:853—62. Buttner-Ennever JA, Buttner U, Cohen B, et al. Vertical gaze paralysis and the rostral interstitial nucleus of the medial longitudinal fasciculus. Brain 1982;105:125—49. Ebner R, Lopez L, Ochoa S, Crovetto L. Vertical ocular motor apraxia. Neurology 1990;40(4):712—3. Kitano K, Hirayama K, Tokumaru Y, Furumoto H, Komatsuzaki A. Selective impairment of downward gaze; report of two cases of midbrain and bilateral paramedian thalamic infarction. Rinsho Shinkeigaku (Clinical Neurology) 1989; 29(5):593—8. Garbutt S, Harris CM. Abnormal vertical optokinetic nystagmus in infants and children. Br J Ophthalmol 2000;84: 451—5.