In March last year it was reported veteran Hollywood actor Bruce Willis had lost the ability to communicate.

At that time he was diagnosed with aphasia – where sufferers speak in sentences that don’t make sense, use unrecognisable words and don’t understand other people’s conversation.

While Willis was struggling with cognitive issues, there was some hope his problems may not be permanent: Aphasia doesn’t necessarily stem from neuro-degeneration.

This week, however, the once witty superstar has been diagnosed with  a relatively uncommon form of neuro-degeneration called fronto-temporal dementia.  There is no cure or treatment. His symptoms will progressively worsen.

Why the mistaken diagnosis?

Fronto-temporal dementia is an umbrella term for a group of brain disorders that primarily affect the frontal and temporal lobes of the brain. These areas of the brain are associated with personality, behaviour and language.

The difficulty is, it’s not uncommon for people with fronto-temporal dementia to be misdiagnosed with a psychiatric condition or Alzheimer’s disease. Unlike in Alzheimer’s disease, memory loss isn’t an early symptom.

Types of  fronto-temporal dementia

There are two main types of fronto-temporal dementia:

Behavioural variant fronto-temporal dementia manifests as personality and behavioural changes.

Primary progressive aphasia disrupts the patient’s ability to communicate. This is where the temporal lobes, those behind the ear, are affected first.

Areas C,D and F marked in red indicate damage to the brain associated with primary progressive aphasia.

Primary progressive aphasia is presumably the type that has afflicted Willis, although that hasn’t been publicly confirmed.

In the early stages of this variant, thinking, perception and behaviour aren’t, as yet, affected.

Either way, as Dr Bruce Miller, a professor of neurology at the University of California, San Francisco, told The New York Times, fronto-temporal dementia “hits the parts of the brain that make us the most human”.

Who is affected by this disease?

Fronto-temporal dementia tends to occur at a younger age than Alzheimer’s disease.

It often begins between the ages of 40 and 65, but occurs later in life as well.

Fronto-temporal dementia makes up approximately 10 to 20 per cent of dementia cases.

According to the Mayo Clinic, there are genetic mutations that have been linked to fronto-temporal dementia. But more than half of the people who develop fronto-temporal dementia have no family history of dementia.

Risk factors specifically for primary progressive aphasia include:

• Learning disabilities. If you had a childhood learning disability, particularly developmental dyslexia, you might be at somewhat higher risk of primary progressive aphasia.
• Certain gene mutations. Rare gene mutations have been linked to the disorder. If other members of your family have had primary progressive aphasia, you might be more likely to develop it.

How does the disease progress?

It begins with mild cognitive changes, where most people, even those close to them, do not recognise any particular symptoms they would be worried about.

When changes in behaviour and mental sharpness first become apparent, they tend to be written off as a consequence of ageing. Stumbling over words or being momentarily confused in putting together a phrase isn’t seen as a problem.

But as these problems become more consistent, and severe, it’s apparent that something serious is occurring. This was the case for Willis a year ago.

Abilities don’t merely decline, they collapse

People with primary progressive aphasia will progress from jumbled and confused speech to eventually losing the ability to speak and write, and to comprehend written and spoken language.

Some people develop ‘apraxia of speech’, where they have difficulties in forming sounds for speaking – and this can occur while they retain the ability to write and comprehend, for a time at least.

Eventually, memory and other cognitive abilities are impaired.

Some develop problems with movement, demonstrating tics and difficulties found in people with Parkinson’s disease.

Eventually, the person cannot care for themselves

As it goes with different forms of dementia, patients tend to develop depression, or behavioural or social problems as the disease progresses.

These might present as “blunted emotions such as unconcern, poor judgment or inappropriate social behaviour”.

For more detail on the stages of decline, see here.