horizontal saccadic palsy. Saccades are very quick intermittent eye movements. The paramedian pontine reticular formation(PPRF), also in the pons is responsible for saccadic movement, relaying signals to the abducens nucleus. Lesions in the PPRF cause what would be saccadic horizontal eye movements to be much slower or in the case of very severe lesions, nonexistent. Horizontal gaze palsies are known to be linked to Progressive Scoliosis. This occurs because pathways controlling saccadic movements are disrupted by the lesion and only slow movements controlled by a different motor pathway are unaffected. Lesions in the midbrain can interfere with efferent motor signals before they arrive at the pons. This can also cause slowed horizontal saccadic movements and failure for the eye to reach its target location during saccades. This damage normally happens in the oculomotor nucleus of the midbrain As in horizontal saccadic palsy, the saccades are stopped or slowed from the disrupted pathway, only in this case the signal is disrupted before it reaches the PPRF. One-and-a-half syndrome is associated with damage to the paramedian pontine reticular formation and the medial longitudinal fasciculus. These combined damages cause both a complete gaze impairment on the ipsilateral side and a "half" gaze impairment on the contralateral side. As seen in horizontal saccadic palsy, the impairment of the contralateral side gaze is caused by the disrupted pathways coming from the PPRF, while the "half" impairment is from the signal passing through the medial longitudinal fascicles not being able to reach its target. One-and-a-Half syndrome is normally associated with horizontal gaze. Although more rare than horizontal, one-and-a-half syndrome from damage to the paramedian pontine reticular formation and the medial longitudinal fasciculus can be shown to affect vertical gaze. This can cause impairment of vertical gaze, allowing only one eye to move vertically. Diagnosis A patient may be diagnosed with a conjugate gaze palsy by a physician performing a number of tests to examine the patient's eye movement abilities. In most cases, the gaze palsy can simply be seen by inability to move both eyes in one direction. However, sometimes a patient exhibits an abduction nystagmus in both eyes, indicating evidence of a conjugate gaze palsy. A nystagmus is a back and forth "jerk" of the eye when attempting to hold a gaze in one direction. Classification Conjugate gaze palsies can be classified into palsies affecting horizontal gaze and vertical gaze. Horizontal gaze palsies Horizontal gaze