Horizontal eye movement• Generated from horizontal gaze center in PPRF

which is connected to ipsilateral 6th nerve nucleus.

• From 6th CN nucleus internuclear neurons cross midline and pass to contralateral MLF to innervate medial rectus in the 3rd nerve complex

• Stimulation of PPRF on one side causes a conjugate movement of the eyes to the same side.

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 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.

• t is an integral component of saccadic eye movements as well as vestibulo-ocular and optokinetic 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.

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

• MLF lesion gives rise to INO

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.

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

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

‘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

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

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