Benign Paroxysmal Positional Vertigo (BPPV): This condition is a common cause of dizziness and can be associated with tinnitus. The new onset of dizziness in a patient with chronic tinnitus could be due to the development of BPPV, especially if the patient experiences vertigo triggered by specific head movements.

Meniere's Disease: A disorder of the inner ear that can cause episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. The progression of Meniere's could explain the new dizziness in a patient with pre-existing tinnitus.
Vestibular Migraine: Migraines can cause vertigo and tinnitus, and some patients may experience these symptoms without the typical headache phase. The new onset of dizziness could be a manifestation of vestibular migraine in a patient with chronic tinnitus.
Labyrinthitis: An inner ear disorder characterized by inflammation of the part of the inner ear responsible for balance (labyrinth). It can cause dizziness and tinnitus, among other symptoms.

Stroke or Transient Ischemic Attack (TIA): Although less common, a stroke or TIA can present with sudden onset of dizziness and tinnitus. It is crucial to rule out these conditions due to their high morbidity and mortality.
Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain. It can cause tinnitus, dizziness, and hearing loss. Early detection is important for treatment planning.
Multiple Sclerosis: An autoimmune disease that can affect various parts of the brain and spinal cord, including areas responsible for balance and hearing. It might present with a wide range of symptoms, including dizziness and tinnitus.

Superior Semicircular Canal Dehiscence: A rare condition where there is an abnormal opening in the bone overlying the superior semicircular canal of the inner ear. It can cause a variety of auditory and vestibular symptoms, including sound-induced vertigo and tinnitus.
Cogan Syndrome: A rare disorder characterized by recurrent corneal inflammation and vestibular-auditory symptoms, including tinnitus and dizziness. It can be associated with systemic vasculitis.
Ototoxicity: Certain medications and substances can cause damage to the inner ear, leading to tinnitus and dizziness. This could be a consideration if the patient has been exposed to such substances.