- Interruption of sympathetic innervation
- First order neuron lesion: brainstem stroke
- Second order neuron lesion: apical lung tumor, neck trauma, other
- Third order neuron lesion: ortbital trauma or inflammation, carotid dissection, other
- Drooping eye lid and small pupil
- Other sx may be related to primary problem, e.g. apical lung tumor→ cough, sob
- Findings depend on location where sympathetics disrupted
- Lid covers more iris on affected side
- Pupils constrict normally to light
- Dilation phase of affected eye is abnl
- Unaffected eye nl