1. Horizontal eye movement Generated from horizontal gaze center in PPRF which is connected to ipsilateral 6 th nerve nucleus. From 6 th CN nucleus internuclear neurons cross midline and pass to contralateral MLF to innervate medial rectus in the 3 rd nerve complex Stimulation of PPRF on one side causes a conjugate movement of the eyes to the same side.

2. Vertical eye movements Generated from vertical gaze center ( rostral interstitial nucleus of the MLF ) which lies in midbrain. rostral interstitial nucleus of medial longitudinal fasciculus (riMLF) is a portion of the medial longitudinal fasciculus which controls vertical gaze.medial longitudinal fasciculusgaze

3. medial longitudinal fasciculus (MLF) It yokes the CN nuclei IIIand VI together, and integrates movements directed by the gaze centers (frontal eye field) and information about head movement.IIIVI t is an integral component of saccadic eye movements as well as vestibulo-ocular and optokinetic reflexes.vestibulo-ocularoptokinetic reflexes Lesions of the MLF produce internuclear ophthalmoplegia. Lesions to the MLF are very common manifestations of the disease Multiple sclerosis,where it presents as nystagmus and occasionally diplopia.internuclear ophthalmoplegiaMultiple sclerosisnystagmusdiplopia

4. PPRF lesion gives rise to ipsilateral horizontal gaze palsy with inability to look in the direction of lesion. MLF lesion gives rise to INO

5. Left INO Straight eyes in primary position. Defective left adduction. Ataxic nystagmus of the right eye in right gaze. Convergence is intact Vertical nystagmus on attempted upgaze.

6. SUPRANUCLEAR DISORDERS OF EYE MOVEMENT 1. Horizontal gaze palsies 2. Vertical gaze palsies Internuclear ophthalmoplegia Combined internuclear and PPRF (‘one-and-a-half syndrome’) Parinaud dorsal midbrain syndrome Progressive supranuclear palsy MLF

7. Internuclear ophthalmoplegia Demylination - usually bilateral Vascular disease Important causes Tumours of brainstem Defective left adduction and ataxic nystagmus of right eye Normal left gaze Convergence intact if lesion discrete Lesion involving left MLF

8. ‘One-and-a-half syndrome ’ Ipsilateral (left) gaze palsy Defective left adduction Normal right abduction with ataxic nystagmus Combined lesion of left MLF and PPRF

9. Parinaud dorsal midbrain syndrome In young adults: demylination, trauma and a-v malformations In children: aqueduct stenosis, meningitis and pinealoma Supranuclear upgaze palsy Large pupils with light-near dissociation Lid retracton (Collier sign) Important causes Normal downgaze Convergence weakness Convergence-retraction nystagmus In elderly: vascular accidents and posterior fossa aneurysms

10. Progressive supranuclear palsy Affects elderly Initially involves downgaze Subsequent defective up and horizontal gaze Pseudobulbar palsy Extrapyramidal rigidity ( Steele-Richardson-Olszewski syndrome ) Gait ataxia Dementia