Transient Ischemic Attack (TIA): Given the history of carotid stenosis, a TIA is a highly plausible cause of dizziness. Carotid stenosis increases the risk of transient ischemic attacks due to the potential for emboli or reduced blood flow to the brain.

Vertebrobasilar Insufficiency: This condition, which affects the posterior circulation of the brain, can cause dizziness and is a concern in patients with a history of carotid stenosis, as they may have more widespread vascular disease.
Orthostatic Hypotension: This is a common cause of dizziness and can be exacerbated by medications, dehydration, or autonomic dysfunction, which might be seen in patients with vascular disease.
Benign Paroxysmal Positional Vertigo (BPPV): Although not directly related to carotid stenosis, BPPV is a common cause of vertigo and can be considered in the differential diagnosis of dizziness.

Stroke: While a TIA is the single most likely diagnosis, an actual stroke (ischemic or hemorrhagic) must be ruled out, as it is a medical emergency requiring immediate intervention.
Cardiac Arrhythmias: Conditions like atrial fibrillation can cause embolic strokes and may present with dizziness. Given the association between carotid disease and cardiac disease, arrhythmias are an important consideration.
Hypoglycemia: Especially in diabetic patients, hypoglycemia can cause dizziness and is easily treatable but potentially fatal if missed.

Vestibular Migraine: Although not as common as other causes of dizziness, vestibular migraine can cause significant vertigo and should be considered, especially if other symptoms like headache or visual auras are present.
Multiple System Atrophy (MSA): A rare neurodegenerative disorder that can cause orthostatic hypotension and dizziness, among other symptoms. It's less likely but should be considered in patients with progressive symptoms not explained by other diagnoses.