Neurodegenerative diseases (e.g., Dementia with Lewy Bodies, Parkinson's disease): These conditions are known to cause hallucinations due to the degeneration of brain cells and the subsequent disruption of neurotransmitter systems. Hallucinations in these diseases can be visual, auditory, or a combination of both, and they are a common feature, especially in the advanced stages.

Delirium: A state of altered consciousness characterized by confusion, disorganized thinking, and altered perception, which can include hallucinations. It is often caused by medical conditions, medications, or substance withdrawal.
Seizure disorders (e.g., temporal lobe epilepsy): Certain types of seizures, especially those originating from the temporal lobe, can cause complex visual or auditory hallucinations.
Migraines: Some individuals experience aura symptoms during migraines, which can include hallucinations, typically visual.
Infections (e.g., meningitis, encephalitis): Infections affecting the central nervous system can lead to hallucinations due to inflammation and damage to brain tissue.
Endocrine disorders (e.g., hyperthyroidism): Severe endocrine imbalances can lead to psychiatric symptoms, including hallucinations, though this is less common.

Vitamin B12 deficiency: While less common, a severe deficiency in vitamin B12 can lead to neurological and psychiatric symptoms, including hallucinations. Missing this diagnosis could lead to irreversible neurological damage if not treated promptly.
Heavy metal poisoning (e.g., lead, mercury): Exposure to heavy metals can cause a range of neurological symptoms, including hallucinations, and is critical to diagnose due to the potential for treatment and prevention of further exposure.
Autoimmune encephalitis: A group of conditions that occur when the body's immune system mistakenly attacks healthy brain cells, leading to inflammation of the brain. Hallucinations can be a symptom, and early diagnosis is crucial for effective treatment.

Charles Bonnet Syndrome: A condition in which visually impaired individuals experience complex, vivid visual hallucinations. It is considered rare in the general population but more common among those with significant visual impairment.
Peduncular hallucinosis: A rare condition characterized by vivid visual hallucinations, typically resulting from lesions in the peduncles of the midbrain.
Hallucinations associated with prion diseases (e.g., Creutzfeldt-Jakob disease): These are rare, fatal brain disorders that can cause a variety of neurological symptoms, including hallucinations, though this is not the most common presenting feature.