<prompt> All are causes of Horners syndrome exceptPancoast tumourLateral Medullary Wallenberg syndromeInternal carotid aery dissectionNeurosyphilis  <response>: Pancoast tumor is a tumor in apex of lung which can compress the sympathetic trunk and leads to horner syndrome. Wallenberg syndrome due to aerial hemorrhage or infarct can damage the sympathetic chain running in lateral aspect of medulla and can leads to horner syndrome. Internal carotid aery dissection can damage the sympathetic trunk running posterior to it and can leads to horner syndrome. Neurosyphillis as such doesnt affect the sympathetic fibres directly. 