Anatomy And Physiology

Voluntary conjugate horizontal eye movements begin in the posterior inferior part of the frontal lobe cortex.
The pathway runs downwards to the pontine tegmentum.
These cortical fibers terminate in the contralateral paramedian pontine reticular formation (PPRF).
The PPRF connects to the ipsilateral sixth cranial nerve nucleus.
The medial longitudinal fasciculus (MLF) connects the PPRF to the third and sixth nerve nuclei to coordinate simultaneous abduction and adduction.
Therefore, the right frontal lobe center mediates lateral gaze to the left side, and vice versa.

PPRF&MLF.png

Pathways for vertical eye movements arise diffusely from the parieto-temporal and occipital cortices.
These fibers project to the midbrain reticular formation.
The pathway governing upward eye movements runs dorsal to the pathway for downward eye movements.

Assessment From History

Elicit a history of double vision (diplopia).
Ask about difficulty tracking or following fast-moving objects.
Inquire if the child's eyes seem stuck or deviated to one particular side.
Elicit a history of abnormal head posturing or head tilting, which may indicate compensation for a gaze palsy.
Ask about any recent infections, trauma, or signs of raised intracranial pressure.

Observe the spontaneous resting position of the eyeballs.
Look for conjugate lateral deviation of the eyes.
Observe if the eyes roll upward continuously or have downward conjugate deviation (ocular bobbing).
Look for spontaneous nystagmus and note its direction.

Fix the position of the child's head.
Ask the child not to move the head while moving the eyes.
Ask the child to follow a target (like a bright toy or your finger).
Move the finger to form an English letter 'H' to test all extraocular muscles and conjugate gaze in horizontal and vertical planes.
Note any restriction of movement, failure of both eyes to move together, or nystagmus.

Instruct the child to keep their head still or have the parents hold the head.
Keep your hands wide apart and flicker your fingers on one side, then the other.
Instruct the child to look immediately at the flickering fingers.
Observe for saccadic movements.
In oculomotor apraxia, the child will lack saccadic pursuit and instead thrust the head to follow the object, while the eyes lag behind.

Interruption of the cortical efferent pathway above the decussation results in eye deviation.
A destructive frontal lobe lesion causes the eyes to deviate towards the same side as the lesion.
An irritative frontal lesion (like a focal seizure) causes tonic deviation of the eyes to the opposite side.

A destructive pontine lesion (involving the PPRF) leads to gaze deviation towards the opposite side.
Lateral gaze palsy can signify central herniation with compression.
Tonic upward gaze indicates bilateral hemispheric damage.
Ocular bobbing (rapid downward jerk followed by a slow return) indicates a pontine lesion.

Results from interruption of the medial longitudinal fasciculus (MLF).
During horizontal gaze, the child cannot adduct the eye on the ipsilateral side of the lesion.
The contralateral abducting eye will develop nystagmus.

Results from interruption of both the MLF and PPRF on one side.
Causes complete gaze palsy on the affected side.
Also causes loss of adduction of the ipsilateral eye when looking to the opposite side.
The only horizontal movement remaining is abduction of the contralateral eye.

Use the Doll's eye maneuver (oculocephalic reflex) to test brainstem integrity.
Ensure there is no cervical spine injury before performing the maneuver.
Turn the head rapidly side-to-side or vertically.
A normal response (positive) is conjugate deviation of the eyes in the direction opposite to the head movement.
Absent response indicates structural brainstem abnormalities or metabolic-toxic encephalopathy.

Gaze Assessment:

Inspection: Eyes are centrally placed in the primary position of gaze. No resting tonic deviation of eyes noted. No spontaneous nystagmus or ocular bobbing observed.
Conjugate Movements: Full range of conjugate horizontal and vertical eye movements is present. The child is able to smoothly track objects in all cardinal directions without breaking conjugate alignment.
Saccades: Saccadic pursuit movements are intact and brisk bilaterally. No compensatory head thrusting required (oculomotor apraxia negative).
Specific Maneuvers: No adduction deficit or abducting nystagmus noted on lateral gaze (Internuclear ophthalmoplegia negative).
Interpretation: Supranuclear, nuclear, and internuclear pathways for horizontal and vertical conjugate gaze are intact and functioning normally.