Shruti K. Nair1, L. Subha 2, K. Mohan Raj3

PRESENTATION OF CASE It is characterised by gaze palsy in ipsilateral side and internuclear ophthalmoplegia on gaze to contralateral side. This case is reported for its rarity. A 65-year-old male reported to our hospital with complaints of double vision for 5 days. He is a known case of diabetes and hypertension for 10 years. On clinical examination, anterior segment was normal. Fundus was normal in both eyes. Vertical eye movements were normal. He had exotropia in right eye. Left eye horizontal movements were absent. Only abduction with nystagmus was present in right eye. MRI showed an exophytic haemorrhagic lesion measuring 2.4 x 1.7 cm size involving pons. In this case, left horizontal gaze palsy is due to parapontine reticular formation lesion and restriction of adduction in left eye was due to internuclear ophthalmoplegia from lesion in medial longitudinal fasciculus. Apart from vertical movements, only abduction was possible in right eye. Hence, this case was diagnosed as one-and-a-half syndrome (OAHS). Parapontine Reticular Formation (PPRF) and Medial Longitudinal Fasciculus (MLF) combined lesions on the same side characterised by- ??? Ipsilateral gaze palsy. ??? Ipsilateral restriction of adduction (internuclear ophthalmoplegia (INO)). ??? Presence of abduction in contralateral eye with nystagmus. ??? Normal vertical movements. Main causes of this rare syndrome are stroke and multiple sclerosis. Other causes include tumours, AV malformations, basilar artery aneurysms and rarely vasculitis, brainstem tuberculoma and neurocysticercosis. A 65-year-old male came to our outpatient department. He was apparently alright when he developed binocular diplopia since 5 days. He denied any history of weakness of any part of the body, paraesthesias or numbness of limbs or face, urinary incontinence, deafness, tinnitus or any slurring of speech. He was a nonsmoker, diabetic and hypertensive for past 10 years. On admission, his pulse was regular, his blood pressure was 130/80 mmHg. The ocular position of left eye on forward gaze was fixed at the midline, while the right eye was abducted. For horizontal ocular movements, only the right eye could abduct with monocular horizontal nystagmus. Also, there was conjugate gaze palsy to left indicating horizontal left One And a Half Syndrome (OAHS), i.e. on leftward gaze, neither eye could pass the midline and on rightward gaze, horizontal jerky nystagmus in the abducting right eye was noticed. Vertical and rotatory nystagmus was absent. Vertical eye movements were preserved. Visual acuity was 6/24 with pin hole 6/12. Pupils 3 mm and normally acting. Fundus was within normal limits. MRI of the brain was taken, which revealed an exophytic haemorrhagic lesion measuring 2.4 x 1.7 cm noted involving the pons.