This is a case of bilateral thalamic infarction can be caused by an occlusion of the artery of Percheron. This uncommon anatomical variant describes a single dominant artery, arising from the P1 artery, supplying both the medial thalami instead of bilateral blood supply.  

This patient did not have associated midbrain infarction, however, if associated with midbrain infarction, the prognosis is worse.

Other possible causes of bilateral thalamic infarction are cerebral venous thrombosis and top of the basilar syndrome, which need to be excluded as a cause.