Motor neurone disease

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It is extremely hard to recognise in the early stages, because it shares symptoms with many illnesses - but motor neurone disease is incurable and debilitating, writes Steven Hislop

Motor neurones are nerve cells that carry messages from the brain to the muscles through electrical impulses. They control all our voluntary movements.

There are two types of motor neurones - upper motor neurones and lower motor neurones. Upper motor neurones run from the brain into the spinal cord. The lower motor neurones run from the spinal cord into the muscles.

Motor neurone disease (MND) is an umbrella term used to describe a group of disorders that cause motor neurones to degenerate and die, resulting in muscle weakness and wasting.

There are four main types of MND. The first, and the most common, is amyotrophic lateral sclerosis (ALS), a disease in which upper and lower neurones are affected.

ALS accounts for up to 85% of all MND patients. Progressive bulbar palsy (PBP) is a more aggressive form of ALS. It affects the lower motor neurones and in particular those muscles controlling speech, chewing and swallowing.

Progressive muscular atrophy (PMA) is a rare strain of MND in which mainly the lower motor neurones are affected initially. Primary lateral sclerosis (PLS) is another rare form of MND and is also a relatively mild form in which only the upper motor neurones are affected.

PLS sufferers can have a normal life span if the disease remains confined to upper motor neurones but lower motor neurones often become affected, resulting in progression and degeneration similar to that experienced in the other forms of MND.

Classification into one of these strains depends on the symptoms the patient is suffering from and which group of motor neurones are being affected.

When upper motor neurones are affected the patient will experience muscle weakness and stiffness (spasticity). Where lower motor neurones are affected the muscles become weak and floppy.

In practice, classification into one of these categories is difficult as there is a massive overlap of symptoms between the strains. MNDs are often rapidly progressive and ultimately fatal conditions and it is not uncommon to find both upper and lower neurones to be affected at the advanced stage of the disease regardless of which form of the disease was originally diagnosed.

Initial symptoms

The initial symptoms of MND can be very subtle and may seem somewhat unimportant. It may first be present as a weakened grip, joint stiffness, muscle pains or cramps or even just a feeling of excessive tiredness.

Other symptoms include, but are not limited to, muscle twitches (fasciculation), slurred speech, a general feeling of clumsiness, weakness in a limb or a tendency to trip over things.

Sensory functions (sight, smell, hearing, feeling and taste), personality, memory and intellect are not affected. MND affects men almost twice as often as women and is usually diagnosed between the ages of 50 and 70 - diagnosis under the age of 40 is rare.

Each patient will experience different symptoms and rates of progress until the disease reaches the advanced stages, by which time both upper and lower motor neurone involvement will usually be present and severe incapacity and immobility will be evident. The eventual cause of death in MND is usually respiratory failure as the muscles of the chest fail.

Diagnosis is very difficult as none of the presenting symptoms is unique to MND, and many of the symptoms are common to a number of neurological complaints.

Such symptoms are sometimes referred to as non-specific neurological symptoms. Furthermore, many of the symptoms mentioned above are of no significance if they are present in isolation and patients may not even visit their doctor until some time after they first experience symptoms, depending on how quickly the disease progresses and causes other symptoms to occur.

Even then it may take a long time and a number of tests before a definite diagnosis can be made.

In fact MND is often diagnosed by exclusion of other neurological conditions such as multiple sclerosis via brain imaging, lumbar puncture and blood tests.

A neurologist will confirm the eventual diagnosis after investigations such as an electromyograph - a test that measures the electrical activity of muscles, muscle biopsy and in some instances spinal imaging to exclude a spinal tumour or lesion.

Unknown

As yet the cause remains unknown - though genetics have been found to play a part in some cases. In 5-10% of MND cases there is a family history of the disease. Of these cases, a mutation in the SOD1 gene - a gene responsible for the production of an enzyme to neutralise the harmful effects of the by-products of normal cell processes - has been identified in 20%.

The remaining 90-95% of cases occur without any warning and remain unexplained. Many theories exist attributing the cause to excess production of glutamate (an amino acid which aids the transportation of messages across the motor neurones) or under-nourishment of the neurones themselves but these claims are still unfounded.

There is currently no cure for MND. Riluzole, a medicine that inhibits the production of glutamate, has been shown to slow the progression of the disease in approximately 20% of cases. Even in cases where Riluzole has proven effective it has only slowed the progression of the disease by a few months. Treatment is primarily aimed at relieving the symptoms and making the patient more comfortable.

The number of new cases of MND per year is around two out of every 100,000 people. The vast majority of these MND cases are so rapidly progressive that it is estimated that the amount of people living with MND at any one time is just seven per 100,000 (approximately 5,000 in the UK). Average life expectancy is two to five years from diagnosis.

Some 70% die within three to five years of diagnosis, 20% will survive for more than five years and 10% will survive for more than 10 years. Professor Stephen Hawking is a notable example of someone who has managed to beat the odds, having so far lived for 43 years since his diagnosis in 1963 aged just 21.

Steven Hislop is an underwriter at Scottish Equitable Protect

Underwriting implications

For an applicant with motor neurone disease, life cover will only be available in exceptional cases, for example where the diagnosis was made over five years ago, with very little progression and the applicant remains able to perform all activities of daily life independently.

Critical illness (CI) and disability benefits will be declined. Evidence will be obtained to assess the type of MND, the presenting symptoms and details of the progression of the disease.

A consultant medical officer specialising in neurology will guide assessment. Where terms are available they are likely to be for a short term only and subjected to a significant extra premium.

Family history will also be considered where the applicant has seen a first-degree relative (parent or sibling) affected by MND before the age of 50. These cases will again be discussed with a neurology consultant medical officer to assess whether there is an additional risk.

It may be necessary to obtain evidence to check for any medical history of neurological symptoms that may provide clues to the risk of the applicant developing MND in the future.

On receipt of any such evidence the case will again be referred to the neurology consultant medical officer for further assessment. If there is a perceived extra risk life cover will probably be subject to a small rating. For CI and disability benefits, MND will be excluded where possible, or even declined.

Any presentation with vague neurological symptoms, such as those mentioned previously, and with no apparent cause will have to be treated with extreme caution. The underwriter will be anxious to ascertain that these symptoms are not the first sign of a neurological disease such as MND.

When an applicant has had recent symptoms, a deferred decision may be prudent to ensure that there is a recovery from rather than progression of symptoms.

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