Recently, I have met a lot of elderly Parkinson’s disease (PD) patients with some intellectual decline and mental behavioral abnormalities in the middle and late stages of the disease, most of which are due to Parkinson’s disease dementia (PDD), but some of which are due to improper use of medications. Today, I would like to talk to you about how to recognize Parkinson’s disease dementia early in clinical practice. First, let’s understand the definition of Parkinson’s disease dementia, which is dementia that occurs during the course of a clinically confirmed diagnosis of Parkinson’s. That is, the motor symptoms of Parkinson’s disease (e.g., bradykinesia, tremor, etc.) appear first, and only after a number of years does a decline in intelligence occur. There is another clinical condition, called Lewy body dementia, which has the same pathologic changes as PD, and thus has many similarities in clinical manifestations. Currently, the distinction is made on the basis of 1 year, i.e., if cognitive dysfunction occurs 1 year after the appearance of motor symptoms in PD, it is diagnosed as PDD, and if cognitive dysfunction and motor symptoms appear successively or simultaneously within 1 year, it is diagnosed as dementia with Lewy bodies. Secondly, Parkinson’s disease dementia is mainly characterized by subcortical dementia, which is highlighted by reduced executive function, attention and visuospatial ability, while language function and orientation are relatively preserved (patients can often recognize the door of their home and can have normal conversations with doctors). The fluctuation of the above symptoms is an important feature, with patients experiencing fluctuations in impairment of attention and arousal states primarily, and symptoms are more pronounced in times of stress and anxiety or environmental change. Finally, there are psychiatric symptoms, especially recurrent hallucinations are the most prominent psychiatric symptoms of dementia in Parkinson’s disease, which can appear in the early stages of the disease. And it gradually worsens as the disease progresses. The patient’s hallucinations are characterized by very specific, vivid hallucinations about people or animals (seeing bugs in the bed, mice on the floor), which are recurrent and can last for several minutes per episode. In addition, depression and apathy are common affective disorders in patients and are sometimes easily mistaken for depression by family members. Other psychiatric symptoms may also be manifested, including anxiety, irritability, and agitation. Behavioral disorders during the rapid eye movement sleep period (shouting, punching and kicking at night) occur at night, and the patient seldom experiences hallucinatory symptoms. Through the above clinical manifestations, if Parkinson’s disease dementia is suspected, further refinement of cranial MRI, MMSE, Munkar Scale and other examinations can be further corroborated. However, it is worth noting clinically that a portion of Parkinson’s patients with dementia-like manifestations are due to inappropriate drug use. Almost all anti-Parkinson’s disease drugs may cause psychiatric symptoms, the most common is the anticholinergic drug – Antan (Benzhexol Hydrochloride), for the elderly over 65 years old must be used under the guidance of a doctor, do not add or increase the dose by yourself. In addition, amantadine, dopamine agonists (Senforo, Tysudan), Cotrimoxazole, Sildenafil, and even levodopa-type drugs can cause psychiatric symptoms to occur. Therefore, it is best to consult a doctor who specializes in movement disorders before choosing a medication, especially in elderly patients. Once the family notices that the patient already has cognitive dysfunction, they should seek medical attention and taper off the use as much as possible. If the symptoms are significantly relieved or reversed by discontinuing the medication, it means that the symptoms of mental behavior and cognitive impairment are induced by the medication; otherwise, they are most likely due to the disease itself. The following is some more knowledge for the reference of all Parkinson’s patients, which Parkinson’s patients are prone to Parkinson’s dementia, and which patients are relatively less prone to dementia. (1) Advanced age, for the young type of Parkinson’s patients (onset before the age of 40) is less likely to develop dementia; (2) the longer the course of the disease, the more likely to develop dementia; (3) early that is, poorer intelligence patients, the later development of dementia is more likely; (4) early hallucinations (to exclude the drug-induced); (5) the patient has sleep behavioral disorders (such as sleep involuntary shouting, body movement, etc.) and the daytime (5) Patients with sleep behavior disorder (e.g. involuntary shouting during sleep, etc.) and daytime sleepiness are more likely to develop dementia (6) Atypical PD motor symptoms (especially postural gait abnormality (PIGD/non-tremor dominated) in PD. Treatment of Parkinson’s dementia starts with anti-Parkinson’s disease treatment, and the choice of drugs is based on the preferred choice of levodopa-type preparations, and if other anti-Parkinson’s disease medications are used, they should be followed strictly by the doctor’s guidance, paying attention to the dosage of the medication and its method of use. Clinically, once psychiatric symptoms or intellectual decline occurs, the first thing that should also be considered is to reduce or discontinue the use of Parkinson’s drugs, in order of priority: anticholinergic drugs, amantadine, dopamine agonists, kotanyl, MAO-B inhibitors. Consider appropriate dose reductions of levodopa-based agents if necessary. If drug adjustment is ineffective for severe hallucinations and psychosis, antipsychotic drugs (e.g., clozapine, olanzapine, but there is an increased risk of bradykinesia) can be added.Patients with PDD can choose cholinesterase inhibitors, such as carbadine, donepezil, etc., and excitatory amino acid receptor antagonists (meperidine) can also be chosen, but all of the above drugs need to be gradually increased in dosage, and it is recommended that the patient follow doctor’s instructions.