Cognitive and Behaviour Change in MND and MND/FTD

Cognitive and behaviour change in MND: the half nobody mentions

For most of the twentieth century, motor neurone disease was described as a condition that destroys the body and leaves the mind entirely intact. That description is still in circulation. It is still what families are told. And it is wrong.

MND Australia’s own figures: over 50 per cent of people with MND may experience changes in thinking and behaviour. About 35 per cent have mild changes. Up to 15 per cent show more significant changes including signs of frontotemporal dementia, and may be diagnosed with MND/FTD.

And this sentence, which matters more than any of the percentages: the changes often appear before motor symptoms, sometimes by several years.

Which means a family may have spent two or three years living with an unexplained personality change — a husband who became apathetic and inflexible, a wife who started saying inappropriate things at family gatherings, somebody who stopped caring about things they had cared about all their life — before any weakness appeared to explain it. By the time MND is diagnosed, the relationship damage has already been done, and nobody has told them the two things are connected.

This guide covers what the changes actually look like, what causes them and what else might, how they are assessed, the specific and urgent implications for legal and care decisions, and what helps. The frontotemporal dementia picture from the dementia side is covered in frontotemporal dementia, and behavioural change in dementia generally in changed behaviour and dementia. This guide is about the MND-specific version.

Why it happens

The short explanation is that MND is not only a disease of motor neurones.

The same protein pathology — most often involving TDP-43 — turns up in both MND and frontotemporal dementia, and the two conditions are now understood as sitting on a single disease spectrum rather than being separate illnesses that occasionally co-occur. MND can affect the frontal and temporal lobes directly.

The genetic evidence makes the link concrete. The C9orf72 repeat expansion, the commonest single genetic cause of familial MND, also causes frontotemporal dementia, and families carrying it can have members with pure MND, members with pure FTD, and members with both. Which means that in some families, what looks like two unrelated illnesses is one.

This is also why the proportion matters more than it appears to. Fifteen per cent sounds like an unusual complication. It is not — it is roughly one person in seven, and when you add the 35 per cent with mild changes, the majority of people with MND are affected to some degree.

What the changes look like

MND Australia’s factsheet groups them, and it is worth knowing the grouping because the behavioural ones are the ones that get misread as character.

Thinking. Reduced focus and slower processing. Difficulty learning new things and recalling information. Impaired reasoning, problem-solving and decision-making. Trouble planning and organising. Reduced awareness of symptoms — which is its own serious problem, discussed below.

Behaviour. Apathy. Rigidity — an inability to tolerate change in routine or plan. Impulsivity. Irritability. Disinhibition, which in practice means saying the wrong thing in social settings, tactlessness, or crossing lines the person never used to cross.

Language. Unusual speech, writing or spelling. Word-finding difficulty. Slower responses. Comprehension problems. Unusual word choices. Repetition. This is a separate problem from the dysarthria MND causes, and distinguishing them matters: dysarthria is a motor problem with intact language, whereas this is language itself being affected. See communication and voice banking with MND.

Emotional lability, also called pseudobulbar affect. Emotional responses that do not match how the person actually feels — uncontrolled laughing or crying, sometimes triggered by very little, sometimes switching between the two. It is more common alongside cognitive change but occurs on its own as well.

Three of these deserve more attention than they get.

Apathy is not depression and is not laziness. This is the most frequently misread change in the whole condition. Apathy is loss of initiation — the person is not sad, not hopeless, and not refusing; the mechanism that converts an intention into an action has been damaged. They will do something if it is started for them. They will not start it. Families read this as giving up, or as depression, or as not trying, and it generates an enormous amount of resentment on both sides. It is a neurological symptom.

Rigidity turns everything into a fight. Somebody who cannot tolerate a change of plan, who insists on a routine being followed exactly, who cannot be reasoned out of a position, is not being difficult on purpose. Cognitive flexibility is a frontal lobe function and it has gone. The management is to minimise unnecessary change, to give advance warning, and to stop trying to win arguments that cannot be won.

Reduced awareness of symptoms is dangerous. A person who does not perceive that their swallowing is unsafe will eat the thing that chokes them. A person who does not perceive that their legs are weak will try to walk to the bathroom at 3am. This is not denial and arguing with it does not work, because there is no belief that evidence could change. The approach is to change the environment and the routine rather than to persuade.

Emotional lability is treatable, and it is worth saying to any family dealing with it, because it is distressing and commonly mistaken for emotional breakdown. Raise it with the neurologist specifically.

What else it might be

Before concluding that cognitive change is MND affecting the frontal lobes, several treatable things should be checked, and MND Australia’s guidance lists them for exactly this reason.

Nocturnal hypoventilation. This is the big one and it is routinely missed. A weak diaphragm means carbon dioxide rises overnight, which fragments sleep and causes morning headaches, daytime sleepiness and — critically — impaired concentration, slowed thinking and poor memory. Somebody with untreated respiratory weakness can look cognitively impaired and be substantially restored by non-invasive ventilation. Anybody with new cognitive symptoms in MND should have overnight oximetry and respiratory function tested before any conclusion is drawn. See breathing and MND.

Fatigue, which MND causes independently and which degrades thinking.

Pain, which consumes attention.

Medication side effects — anticholinergics for saliva, benzodiazepines, opioids, muscle relaxants, antidepressants. All can slow cognition. A medication review is cheap and sometimes decisive.

Depression and anxiety, which are common, treatable, and produce poor concentration and apparent memory failure.

Difficulty managing strong emotions, in a situation that would overwhelm anybody.

Dehydration, constipation, infection and sleep deprivation, all of which cause delirium-like cognitive change and all of which are fixable.

The point of this list is not to minimise genuine frontotemporal involvement. It is that the reversible causes are common, several of them are easy to test for, and a label of cognitive impairment tends to stick and stop people looking.

Assessment

Who does it. A GP, neurologist or specialist MND clinic can screen for cognitive and behaviour change. A clinical neuropsychologist provides detailed assessment and can advise on management strategies.

What is used. Screening tools designed for MND exist and matter, because general cognitive screens are poorly suited to this population — a test requiring speech, writing or hand movement will record motor impairment as cognitive impairment. Ask whether the screening instrument used is validated for MND specifically, and whether it covers behavioural change and not only thinking, since behaviour is where most of the change shows up.

Who to ask. Family. The behavioural changes are frequently invisible to the person experiencing them and obvious to everybody around them, and some assessments include a carer-report component for exactly this reason. If nobody has asked you, volunteer it.

What to bring. Specific, dated examples. “He has become apathetic” is less useful than “In March he was still doing the crossword and ringing his brother weekly. Since about June he has not initiated either, and will do the crossword if I put it in front of him.” That contrast is diagnostic information.

Screen early, and screen again. A baseline at diagnosis means a change can be identified later. Without a baseline, every subsequent assessment is a guess about what has altered.

Why this is urgent: capacity and the closing window

Here is the practical consequence that makes this guide something other than background information.

Every piece of advice about MND — including most of the other guides in this library — tells people to plan early. Appoint an enduring power of attorney. Appoint an enduring guardian. Write an advance care directive. Decide about ventilation, gastrostomy, resuscitation, where you want to be cared for, and what you want to happen in a crisis. Sort out superannuation and insurance.

All of that requires decision-making capacity. And if cognitive change is part of the picture — which, at some level, it is for the majority — then the window for those decisions is narrower than the physical progression suggests.

The ordinary mental model of MND is a person whose mind stays sharp while their body fails, with plenty of time to make decisions because the thinking is unaffected. For a substantial minority, that model is wrong, and the timing assumption built on it is wrong too.

MND Australia’s guidance on this is direct: changes can affect the ability to make care and treatment decisions, so advance planning is important, and legal advice is worth getting to make sure plans and wishes are documented.

Translated into instructions:

Do the legal documents in the first weeks after diagnosis, not after the wheelchair, not after the NDIS plan, not once things have settled down. Enduring power of attorney for financial matters and enduring guardianship or its state equivalent for health and personal decisions. See planning ahead with MND.

Do them while capacity is unambiguous, so that nobody can later question whether they were validly made. A document signed when cognitive change is already apparent is a document that can be challenged, which is precisely the situation the document was meant to prevent.

Have the treatment conversations now. Ventilation, tracheostomy, gastrostomy, hospital admission, resuscitation, and what the person wants if they develop a chest infection and respiratory failure. Record the answers. A documented decision made in month two governs what happens in month twenty; an undocumented one leaves a family guessing at 3am in an emergency department.

Get a cognitive baseline recorded. It protects the person both ways: it establishes capacity at the time the documents were signed, and it allows genuine change to be identified later.

And if there are children, or a complex estate, or a second marriage, or a business: get proper legal advice rather than a template, and get it early. These are the situations where a capacity dispute does real damage.

What helps

Keep the routine simple and predictable. Rigidity and reduced flexibility make change expensive. Fewer surprises, more warning, same order.

Limit appointments. MND generates an extraordinary number of them, and each one costs attention and energy. Bundle them where possible. Decline the ones that are not doing anything.

Use external aids. A diary, a whiteboard, a shared calendar, lists, written instructions. Externalise anything that relies on initiation or planning.

Keep communication short and clear. One idea at a time. Short sentences. Avoid long explanations and multi-part questions.

Allow extra time for everything, and particularly for responses.

Watch for triggers. Tiredness, pain, hunger, noise, too many people, and late afternoon are the usual ones. Most behavioural incidents are preceded by one of them.

Stay calm and do not argue the unarguable. Where there is no insight, evidence does not help. Change the situation rather than the person’s mind.

Externalise prohibitions. “The doctor says you can’t” works better than “I won’t let you.” It takes the conflict out of the relationship and puts it onto an institution.

Treat the treatable. Ventilate the nocturnal hypoventilation. Review the medications. Address the pain and the depression. Then reassess.

And get support for the family. This is the part of MND families find hardest, harder frequently than the physical care, because it changes who the person is rather than what they can do. The grief for somebody who is still present but altered has no ritual attached to it. Dementia Australia’s National Dementia Helpline on 1800 100 500 supports MND/FTD families, and the state MND association on 1800 777 175 can connect you with counselling. See families and carers.

What this does to the family, and why it is different

Worth a section of its own, because the behavioural changes do more relationship damage than the physical disease and families are rarely warned.

The changes get read as character. This is the central problem. Physical weakness is obviously the illness; nobody blames a person for a weak hand. Apathy, irritability, tactlessness and rigidity look like choices. So the partner experiences it as their husband becoming selfish, or their wife becoming cruel, and they respond as you would respond to selfishness or cruelty — with hurt, then argument, then resentment.

And where the changes came first, the damage predates the diagnosis. In the subset of people whose frontotemporal changes appear years before any weakness, a family may have spent two or three years in marriage counselling, or estranged, or managing what they understood as depression or a midlife collapse. The diagnosis then arrives and reframes those years retrospectively, which is its own kind of grief: the realisation that the arguments were a symptom.

The guilt that follows is predictable and worth naming. Families who were angry at somebody who turned out to be ill carry that badly. The honest answer is that nobody could reasonably have known, that the behaviour was genuinely difficult to live with whatever its cause, and that being angry at it was not a moral failure.

Loss of empathy is the hardest one. Where frontotemporal change reduces the capacity for empathy, a partner can find themselves caring intensively for somebody who shows no apparent concern for what it is costing them. That is not ingratitude. It is a damaged function, and it is extremely painful regardless of knowing that.

What actually helps. Getting the change assessed and named, so it stops being a character question. Treating the reversible contributors, especially nocturnal hypoventilation. Stopping the arguments that cannot be won. Counselling, individually rather than as a couple in the first instance. Other families — the state MND association on 1800 777 175 and Dementia Australia’s National Dementia Helpline on 1800 100 500 can both point to groups where this particular combination is understood.

And lowering the bar. A family dealing with both a terminal motor disease and a personality change is dealing with two illnesses at once, in a timeframe that allows no adjustment. Doing it imperfectly is the only way it gets done.