Headshaking in 5 horses after paranasal sinus surgery.

To report headshaking and presumptive trigeminal neuritis as a potential complication after paranasal sinus surgery in horses.Retrospective case series.Horses (n = 5) that developed headshaking within 45 days of paranasal sinus surgery.Medical records (2007-2010) of horses that had been evaluated for headshaking after paranasal sinus surgery were reviewed.Of 5 horses that developed headshaking within 45 days of paranasal sinus surgery, resolution occurred after treatment in 2 horses. One horse was euthanatized because clinical signs associated with headshaking could not be controlled. Headshaking persisted in the other 2 horses but was either adequately controlled with analgesics or was considered infrequent and transient enough to not warrant therapeutic intervention. Only 2 of 5 horses returned to full work after development of headshaking.Headshaking because of presumptive trigeminal neuritis is a possible career-ending or fatal complication of paranasal sinus surgery in horses.