In Watson's case, he had sustained critical gunshot wounds to his brain which had resulted in injury to the left sigmoid sinus.
From the sciencedaily.com
The internal jugular vein is formed by the anastomosis of blood from the sigmoid sinus of the dura mater and the common facial vein.
From the en.wikipedia.org
The Duplex scan indicated that the sigmoid sinus was damaged, and a CAT scan of the patient's head showed that he had alson suffered a stroke in the cerebellum.