Popular science summary of the project The purpose of the study is to investigate in a Swedish population how well the investigators' previous ultrasound findings match the final diagnosis (PD, APS or ET) after a particularly long follow-up time, which greatly increases the certainty that the diagnosis does not change more and is thus correct. Furthermore, the investigators want to study whether the initial ultrasound findings have changed during the control interval and whether measurement results regarding the diameter in one of the fluid-filled rooms in the brain (third ventricle) can be correlated with the development of cognitive impairment or dementia later in the course of the disease. For this, this study have got ethical permission to go into the patients' medical records and to call a subgroup back to the clinic to be able to do a new examination and a memory test.

Inclusion Criteria:

• Patients with parkinsonism or essential tremor who came into contact with our clinic before 2017
• Satisfactory transcranial bone window
• Previous TU (clinical indication)

Exclusion Criteria:

• No transcranial bone window

Newly diagnosted patients with parkinsonism between 2013-2017 at our centre