Benign Paroxysmal Positional Vertigo (BPPV): This condition is characterized by brief, episodic vertigo triggered by specific head movements. It is the most common cause of vertigo and often presents with disequilibrium, making it the single most likely diagnosis.

Vestibular Migraine: A condition that involves vertigo, often accompanied by headache and sensitivity to light and sound. It's a common cause of episodic disequilibrium.
Labyrinthitis: An inner ear disorder characterized by inflammation of the labyrinth, leading to vertigo, hearing loss, and sometimes disequilibrium.
Meniere's Disease: A disorder of the inner ear that affects balance and hearing, causing episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear.

Stroke or Transient Ischemic Attack (TIA): Although less common, a stroke or TIA can present with sudden onset of vertigo or disequilibrium, often accompanied by other neurological deficits. Missing this diagnosis could be catastrophic.
Posterior Circulation Infarct: Similar to stroke, an infarct in the posterior circulation can cause vertigo, disequilibrium, and other symptoms like double vision or weakness.
Multiple Sclerosis: An autoimmune disease that can affect the brain and spinal cord, leading to a wide range of symptoms, including disequilibrium, especially if the cerebellum or its connections are involved.

Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain, which can cause vertigo, hearing loss, and disequilibrium due to its location and pressure effects.
Mal de Debarquement Syndrome: A rare condition that occurs after a period of exposure to motion, such as a boat ride, leading to a persistent feeling of swaying or disequilibrium.
Superior Canal Dehiscence: A rare condition where there is an abnormal opening in the bone overlying the superior canal of the inner ear, leading to vertigo and disequilibrium in response to sound or pressure changes.