Over 50% of people with MND will experience cognitive and behavioural changes. Most will experience relatively mild changes. For around 10-15% changes will be more severe.
When the changes are more severe, the person may receive a diagnosis of Motor Neurone Disease with Frontotemporal Dementia, also known as MND/FTD. Often the symptoms of dementia precede the motor symptoms, somtimes by a number of years.
Your GP, neurologist or MND Clinic can help with diagnosing changes in cognition and behaviour. A neuropsychologist can also assist with diagnosis and implementing strategies to manage symptoms.
Source
Cognitive and behaviour change in MND (c) MND Australia - Last updated November 2020