What are the symptoms of a blood clot in the neck?

Pain and swelling.: A clot in the neck most likely would occur in a major vessel. No hx as to why you ask. The vessesls are large and the blood clot in a major vessel is catastrophic, It could be a stroke in an arterial vessel or venous congestion in the vein. If you think you have one see the doc as soon as possible.

Stroke: Blood clots in the carotid artery usually come from atrial fibrillation in the heart and can move to the brain. See your doctor to check for a carotid bruit, and order an ultrasound (sonogram). If you are at risk stop smoking, avoid hormones, and see your doctor about taking a blood thinner (aspirin, etc). Otherwise discuss your anxiety with your doctor and how to manage it.