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Show Journal of Neuro- Ophthalmology 18( 1): 40^ 12, 1998. © 1998 Lippincott- Raven Publishers, Philadelphia Ocular Tilt Reaction with Vertical Eye Movement Palsy Caused by Localized Unilateral Midbrain Lesion Tsutomu Ohashi, M. D., Kikuro Fukushima, M. D., Shinki Chin, M. D., Takayuki Harada, M. D., Kazuhiko Yoshida, M. D., Minoru Akino, M. D., and Hidehiko Matsuda, M. D. A 60- year- old man developed diplopia and experienced difficulty moving his eyes. Vertical movement of each eye, including vestibulo- ocular reflex and smooth pursuit, was extremely limited. Horizontal eye movements were normal. His head position was tilted toward his left. There was 10 prism diopters of exotropia and 10 prism diopters of right hypertropia. Fundus photographs revealed a clockwise torsion of both eyes. These signs indicate leftward ocular tilt reaction. Magnetic resonance imaging showed a small area of an increased signal intensity Manuscript accepted 7/ 24/ 97. From the Departments of Ophthalmology ( T. O., S. C., T. H., K. Y., H. M.) and Physiology ( K. F.), Hokkaido University School of Medicine, Sapporo; and Azabu Neurosurgical Hospital ( M. A.), Azabu, Japan. Address correspondence and reprint requests to Dr. T. Ohashi, Department of Ophthalmology, Hokkaido University School of Medicine, N15 W7, Kita- ku, Sapporo, 060 Japan. localized in the midbrain dorsomedial to the red nucleus on the right side. Based on recent experimental evidence, it may be assumed that the unilateral lesion involving the right interstitial nucleus of Cajal most probably caused leftward ocular tilt reaction in our patient. Key Words: Ocular tilt reaction- Interstitial nucleus of Cajal- Magnetic resonance imaging. The ocular tilt reaction ( OTR), as defined by Westhe-imer and Blair ( 1), is an oculocephalic synkinesis consisting of head tilt, conjugate eye torsion, and hypotropia, all toward the same side ( 2,3). The direction of OTR is described by the side of the lower ear ( 2,3). In contrast to the clear evidence obtained from experimental research on animals regarding meso- diencephalic lateralization of OTR, the evidence from human studies is confusing ( 2) because the direction of OTR is not in A FIG. 1. Note the severe restriction of vertical gaze without limitation of horizontal gaze ( A). Leftward head tilt ( B) and leftward torsion of the eye ( C) as shown in the fundus photographs. C: Intorsion is present when the fovea is above the dashed lines extending horizontally from the optic nerve head center, and extorsion is present when the fovea is below the line extending from the lower edge of the optic nerve head ( 10). OCULAR TILT REACTION 41 accord with lateralization of the lesions ( 4- 6). In addition, the lesions in most of these cases were relatively large, making it difficult to determine the responsible region ( 5). We present the case of a patient with OTR and vertical gaze paralysis in which a small causative lesion was located in the unilateral rostral midbrain dorsomedial to the red nucleus as seen by magnetic resonance imaging. The direction of his OTR coincides exactly with the direction predicted from experimental lesion studies of the interstitial nucleus of Cajal ( 7,8). CASE REPORT On November 24, 1995, this 60- year- old man suddenly noticed weakness of his left arm and leg, as well as diplopia, and was admitted to a neurosurgery hospital. On December 11, he was referred to us for evaluation of his eye movement. Initial examination revealed his best- corrected visual acuity to be 20/ 60 in both eyes. No abnormalities were found in the fundi. Slit examination revealed a moderate nuclear cataract. His right eye exhibited a slight reduced pupillary response to light. The pupil diameters of both eyes were equal. Horizontal movement of each eye was normal ( Fig. 1A), including the vestibulo- ocular reflex and smooth pursuit with a slight abnormality of convergence. Vertical movement of each eye was absent ( Fig. 1A), with severe limitation of the vestibulo- ocular reflex and smooth pursuit. He was unaware that his head tilted 7° toward the left ( Fig. IB) and was unable to correct this tilt voluntarily. In the primary position, his eye position was about 10 prism diopters exotropic and 10 prism diopters of right hypertropic as detected by prism and cover testing. Fundus photographs taken with his head held in an upright position revealed intorsion of the right eye and extorsion of the left eye ( Fig. 1C). Neurological examination revealed a slight left hemiparesis, hyperreflexia of the left lower extremity, and positive Babinski sign of the right leg. Tl- weighted magnetic resonance imaging revealed a high signal area suggesting a recent hemorrhage in the midbrain on the right side dorsomedial to the red nucleus ( Fig. 2). DISCUSSION Our case is interesting in two ways. First, the unilateral midbrain lesion caused both upward and downward gaze palsy. Unilateral midbrain lesions commonly result in only upgaze paresis, because of lesions of the posterior commissure. On the contrary, bilateral midbrain lesions have been reported to exhibit an isolated palsy of the downward gaze. Recently, Ranalli et al. ( 9) reported that unilateral midbrain lesions caused both upward and downward vertical eye movement disorders. They presented two possible explanations for downward eye movement paresis caused by a unilateral lesion: ( a) downward saccade signals decussate in the ventral posterior commissure of Bucher and Burgi and transverse FIG. 2. T1- weighted magnetic resonance images demonstrate an increased small- signal intensity ( arrows in A and B) located in the right side of the midbrain dorsomedial to the red nucleus ( RN). A: Sagittal section close to the midline. B: Axial section of the midbrain. C: Diagram of the midbrain. The lesion revealed by axial section is hatched. riMLF ( medial longitudinal fasciculus) and INC ( interstitial nucleus of Cajal) indicate the location dorsomedial of the RN close to the aqueduct. SN, substantia nigra. the region of the opposite rostral interstitial medial longitudinal fasciculus ( riMLF) before descending to the oculomotor and trochlear motor neurons; or ( b) inhibitory burst signals that silence antagonist upward- acting muscles are impaired. The second interesting point of this case is that, in addition to complete vertical gaze palsy, leftward OTR was caused by a small, localized lesion in the right midbrain. J Neuro- Ophtlwlmol, Vol. IS, No. I, 1998 42 T. OHASHI ETAL. There are only nine published reports of cases with OTRs caused by meso- diencephalic and medullary lesions. In three of these cases, the lesion was not clearly lateralized ( 5). In two of these, the direction of OTR was opposite to what was expected based on experimental lesions in cats; that is, it was ipsiversive in the two patients ( 4,6). The cases of four patients reported by Hal-magyi et al. ( 2) had unilateral meso- diencephalic lesions that produced a tonic contraversive OTR; however, these lesions were large when compared with the lesion in our case. In animal experiments, the direction of OTR is ipsi-lateral when electrical stimulation is applied to the rostral tegmentum ( 1). On the other hand, lesion studies reveal that the direction of OTR is contralateral to the lesion ( 7,8). In our case with a small unilateral lesion localized in the rostral midbrain, the direction of OTR coincided with the direction of experimental lesion studies applied in the interstitial nucleus of Cajal. REFERENCES 1. Westheimer G, Blair S. The ocular tilt reaction: a brain stem oculomotor routine. Invest Ophthalmol Vis Sci 1975; 14: 833- 9. 2. Halmagyi G, Brandt T, Dieterich M, Curthoys I, Stark R, Hoyt W. Tonic contraversive ocular tilt reaction due to unilateral meso-diencephalic lesion. Neurology 1990; 40: 1503- 9. 3. Zackon D, Sharpe J. The ocular tilt reaction and skew deviation. In: The Vestibulo- Ocular Reflex and Vertigo. New York, NY: Raven Press; 1993: 131- 4. 4. Hedges T, Hoyt W. Ocular tilt reaction due to an upper brainstem lesion: paroxysmal skew deviation, torsion and oscillation of the eyes with head tilt. Ann Neurol 1982; 11: 537- 40. 5. Brandt T, Dieterich M. 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Ophthalmology 1982; 89: 58- 62. ./ Neitiv- Oplithalmol, Vol. 18. No. I, 1998 |