Benign Paroxysmal Positional Vertigo (BPPV): This condition is characterized by brief, intense episodes of vertigo triggered by specific head movements, often accompanied by nausea and vomiting. The acute onset of dizziness, potentially triggered by movement, makes BPPV a plausible initial consideration.

Vestibular Migraine: A condition that involves vertigo as a primary symptom, often accompanied by headache, sensitivity to light and sound, and sometimes visual auras. The combination of acute dizziness and headache fits well with vestibular migraine.
Labyrinthitis: An inner ear disorder characterized by inflammation of the labyrinth, which can cause severe vertigo, hearing loss, and sometimes headache. The acute onset of symptoms aligns with labyrinthitis.
Inner Ear Infection: Such as viral or bacterial infections affecting the inner ear, leading to symptoms like dizziness, headache, and sometimes fever. The acute presentation could suggest an infectious cause.

Subarachnoid Hemorrhage: Although less common, this is a critical diagnosis to consider due to its high morbidity and mortality. The sudden onset of a severe headache (often described as "the worst headache of my life") accompanied by dizziness could indicate a subarachnoid hemorrhage.
Stroke or Transient Ischemic Attack (TIA): Dizziness and headache can be symptoms of a stroke or TIA, especially if accompanied by other neurological deficits. Early recognition is crucial for timely intervention.
Meniere's Disease: While not immediately life-threatening, missing Meniere's disease could lead to significant morbidity. It's characterized by episodes of vertigo, hearing loss, tinnitus, and ear fullness, which could initially present with dizziness and headache.

Multiple Sclerosis: An autoimmune disease that can present with a wide range of neurological symptoms, including dizziness and headache, due to demyelination in the central nervous system. The onset can be acute, but it's less common as an initial presentation with these specific symptoms.
Acoustic Neuroma: A benign tumor on the nerve connecting the inner ear to the brain, which can cause dizziness, hearing loss, and sometimes headache due to its location and pressure effects. The symptoms can develop gradually, but in some cases, there might be an acute presentation.
Chiari Malformation: A structural defect in the cerebellum that controls balance, which can cause dizziness, headache, and sometimes neck pain. Symptoms can be acute or chronic, depending on the severity of the malformation and its impact on surrounding structures.