Conjugate Gaze Palsies
(See also Overview of the Cranial Nerves.)
In conjugate gaze palsies, the two eyes cannot move in one direction (side to side, up, or down) at the same time.
Conjugate gaze palsies affect horizontal gaze (looking to the side) most often. Upward gaze is affected less often, and downward gaze is affected even less often. People may notice that they cannot look in certain directions.
There are no specific treatments.
The most common cause of horizontal gaze palsy is damage to the brain stem, often by a stroke. Often, the palsy is severe. That is, moving the eyes past the midline to the opposite side is very difficult.
Palsies can also be caused by damage to the front part of the cerebrum, usually by a stroke. The resulting palsy may not be as severe as that caused by damage to the brain stem, and symptoms often lessen with time.
Vertical gaze decreases gradually with age, but vertical gaze palsy is more severe than age-related changes. Usually, upward gaze is affected.
The most common cause of vertical gaze palsy is damage to the top part of the brain stem (midbrain), usually by a stroke or tumor.
In upward vertical gaze palsies, the pupils may be dilated. When people with this palsy look up, the eye may make involuntary, repetitive fluttering movements called nystagmus. That is, the eye rapidly moves upward or downward, then slowly drifts in the other direction.
Parinaud syndrome is an upward vertical gaze palsy. It usually results from a pineal tumor that presses on the area of the brain that controls vertical gaze or from a stroke. People with this syndrome tend to look down. Their eyelids are pulled back, and the pupils are dilated.
If downward gaze but not upward gaze is impaired, the cause is usually progressive supranuclear palsy.