Benign Paroxysmal Positional Vertigo (BPPV): This condition is characterized by brief, intense episodes of vertigo triggered by specific head movements. It's a common cause of sudden onset dizziness and is often related to the movement of otolith crystals in the inner ear.

Vestibular Neuritis: An inflammation of the vestibular nerve, which can cause sudden, severe vertigo that lasts for days. It's often associated with viral infections.
Labyrinthitis: An inner ear disorder characterized by inflammation of the part of the inner ear responsible for balance (labyrinth). It can cause sudden onset of vertigo, hearing loss, and tinnitus.
Migraine-associated Vertigo: Some people experience vertigo as part of a migraine episode. This can be accompanied by headache, nausea, and sensitivity to light and sound.

Stroke or Transient Ischemic Attack (TIA): Although less common, sudden onset dizziness can be a symptom of a stroke or TIA, especially if accompanied by other neurological deficits such as weakness, numbness, or difficulty with speech.
Posterior Circulation Stroke: Specifically, a stroke affecting the posterior circulation can present with vertigo, ataxia, and other symptoms without the typical hemiparesis seen in anterior circulation strokes.
Cardiac Causes (e.g., Arrhythmias, Cardiac Arrest): Certain cardiac conditions can lead to reduced blood flow to the brain, resulting in dizziness or vertigo. These conditions are medical emergencies.

Multiple Sclerosis: In rare cases, multiple sclerosis can present with vertigo as an initial symptom due to lesions in the brainstem or cerebellum.
Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain can cause vertigo, hearing loss, and tinnitus, though it typically develops slowly over time.
Meniere's Disease: A disorder of the inner ear that causes episodes of vertigo, ringing in the ears (tinnitus), hearing loss, and a feeling of fullness in the ear. The episodes can be sudden but are often recurrent.