Supranuclear ocular movements comprise chiefly vertical and horizontal movements; horizontal movements are controlled by the subcortical centres located mainly at the pontine level and vertical movements at the level of the rostral midbrain.1 2 The classic one and a half syndrome is produced by a unilateral pontine tegmental lesion that includes the paramedian pontine reticular formation and medial longitudinal fasciculus on the same side, and has been considered an important ocular sign in neurological diagnosis.1 3 4 Vertical, as distinct from horizontal, one and a half syndrome, has also been documented recently.1 2 5 6 We report on a patient with concurrent vertical and horizontal one and a half syndromes.

A 57 year old man was admitted to hospital with a sudden onset of dysarthria and loss of consciousness while playing golf. He had a history of aortic regurgitation and heart failure 8 years previously, and underwent aortic valve replacement 5 years previously, when he started to take oral antiplatelet and anticoagulant drugs. On admission, he was comatose, and his blood pressure was 140/76 mm Hg. He also had atrial fibrillation, Cheyne-Stokes respiration, bilateral miosis, and a positive Babinski's sign. Brain CT showed lesions suspected of being infarcts in the right medial thalamus and the left upper cerebellum. According to neurological findings on day 4 after onset of disease, he was in a state of hypersomnia. While awake, his head tilted slightly to the left, the right eye was slightly deviated upward, the left eye slightly downward, and there was bilateral miosis. For horizontal ocular movements, only the right eye could abduct with monocular horizontal nystagmus. Also, there was bilateral conjugated leftward palsy, indicating horizontal left one and a half syndrome. On the other hand, for vertical ocular movement, only the left eye could gaze downward. Also, difficulty in downward gaze of the right eye and bilateral conjugated upward palsy, indicating vertical one and a half syndrome, were noted (figure A). Doll's eye test (oculocephalic reflex) was weak but positive, and the eyes were unable to converge. There was also ataxic dysarthria, cerebellar ataxia of the left limbs and trunk, right sided hemisensory disturbance, and bilaterally positive Babinski's sign. Brain MRI showed infarcts in the right medial thalamus, left dorsal portion of the upper midbrain, and left upper cerebellum (figure B). On magnetic resonance angiography performed at the same time, partial obstruction of the left posterior cerebral artery was noted at its origin. Cardiogenic cerebral embolism was suspected in the pathogenesis of the serial episode in this patient.

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(A) Ocular movements of the patient. The right eye was slightly deviated upward, the left eye slightly downward in the primary position (P). For vertical movement, only the downward gaze of the left eye is possible. Downward palsy of the right eye and bilateral conjugated upward palsy were seen. For horizontal movements, the rightward gaze of only the right eye is present. The rightward palsy of the left eye and bilateral conjugated leftward palsy are shown. The eyes are unable to converge (C) and Doll's eye test (D) is weak but positive. (B) Brain MRI. a, b axial FLAIR imaging. c, d coronal T2 weighted imaging. High signal intensity areas are noted in the right medial thalamus, the left dorsal part of the rostral midbrain, and the left upper cerebellum.

At 7 days the patient still tended to become unconscious, accompanied by Cheyne-Stokes respiration, when talking to a familiar person. About 1 month later he talked about occurrences at the onset and began to show an interest in his surroundings. At 2 months, adduction of the left eye, bilateral leftward gaze, downward gaze of the right eye, and bilateral upward gaze showed moderate improvement. The gait disturbance persisted and he is still in a wheelchair.

Classic horizontal one and a half syndrome is commonly caused by a vascular accident occurring in the lower pons involving the paramedian pontine reticular formation and the medial longitudinal fasciculus.1 3 4 In the present patient one and a half syndrome, however, was thought to be due to two concurrent lesions of distinct nerve tracts in the left upper midbrain—that is, descending fibres from the frontal eye fields of the cerebral cortex after decussation at the midbrain level and medial longitudinal fasciculus fibres ascending on the opposite side. Attention has recently focused on the rostral interstitial nucleus of the medial longitudinal fasciculus, interstitial nucleus of Cajal, and posterior commissure, all located in the tegmentum of the mesencephalon, as the brain stem centres for vertical eye movement.1 2 Vertical one and a half syndrome consists of a bilateral conjugate upgaze palsy and a unilateral downward palsy,2 5 or a bilateral conjugate downward palsy and a monocular upgaze palsy.6 It has been reported that the fibres involved in upward gaze from the posterior commissure may explain bilateral upgaze palsy, and the fibres involved in downward gaze may be affected on one side before their decussation in contralateral lesion, or after their decussation in ipsilateral lesion.2 A patient was also reported with bilateral downgaze palsy and bilateral lesions of the rostral interstitial nucleus of the medial longitudinal fasciculus.6Furthermore, it was reported that a unilateral lesion of the interstitial nucleus of Cajal resulted in tilting of the head towards the opposite side.7 Therefore, it can be assumed that the leftward tilting of the head seen in the patient under study was caused by a lesion of the right interstitial nucleus of Cajal.

The present patient thus seems to be a rare case of the coexistence of two distinct syndromes, vertical and horizontal one and a half syndromes, although the lesions responsible for these syndromes are different. Even though the exact anatomical and physiological mechanism underlying vertical gaze still remains obscure in many respects, vertical one and a half syndrome is considered to be one of the important neurological signs suggestive of a lesion affecting the rostral midbrain. The particular pathogenetic mechanism of this interesting syndrome will be elucidated through future elaborate comparative studies of clinical manifestations and diagnostic imaging.