Episode 160. Motor Neuron Disease (MND) with Associate Professor Ernie Butler (Part 2)
Motor neuron disease (MND) refers to a group of relatively rare neurodegenerative diseases in which motor nerves in the spine and brain lose function over time. It affects about 2000 Australians which equates 1 in 11 000 Australians. There are 2 new diagnoses per day with a 1: 300 lifetime risk. About 60% of cases are male and 40% are female and the highest prevalence rate is reported in males aged between 75 and 84 years. In 10% of cases a hereditary basis is at hand although the genetic fault is only determined about 60% of the time.
There are several forms of MND which are classified according to their hereditary basis and which neurons are affected. These include:
Amyotrophic lateral sclerosis-ALS: This is the most common type of MND. It affects both the upper and lower motor neurons — the neurons in the brain and spinal cord — which then affects the muscles of the arms, legs, mouth, and respiratory system. On average, people with ALS live for 3-5 years after receiving the diagnosis, but with supportive care, some people live for 10 years or longer. The renowned English physicist Stephen Hawking lived with ALS for many decades until his death in March 2018 (he had the disease for 55 years - the longest recorded existence with the condition). The American baseball player, Lou Gehrig, also had ALS. This resulted in people calling it Lou Gehrig’s disease. Neale Daniher’s very public diagnosis in Australia in 2013 has significantly raised awareness for this diagnosis. 10-15 % of cases are associated with the development of frontotemporal dementia.
Primary lateral sclerosis: This rare form of MND affects the neurons in the brain and advances more slowly than ALS. It is not fatal but may affect the quality of life. A juvenile form is also described.
Progressive bulbar palsy (PBP): Involves the brain stem. Patients with ALS often have PBP also. PBP causes frequent choking spells and difficulty speaking, eating, and swallowing.
Progressive muscular atrophy: This type of MND is rare. It affects the lower motor neurons in the spinal cord and causes slow but progressive muscle wasting, especially in the arms, legs, and mouth.
Spinal muscular atrophy (SMA): This inherited MND develops in children. There are three types, all caused by a genetic change known as SMA1. It tends to affect the trunk, legs, and arms. The long-term outlook depends on the type.
Kennedy’s disease is also inherited, only affects males (females may be unaware carriers) and presents with shaking hands, muscle cramps and twitches with weakness in the face, arms and legs. Affected males may have trouble swallowing and speaking and develop gynaecomastia and azoospermia.
Causes:
Experts believe that around 10 % of MNDs are hereditary. The other 90% develop randomly.
The exact causes are unclear, but the National Institute of Neurological Diseases and stroke reports that genetic, toxic, viral and other environmental factors may play a role.
Symptoms:
It can be difficult to diagnose MND in the early stages as it may resemble other conditions such as multiple sclerosis or even a small cerebrovascular accident, however muscle fasciculation, weakness and slurred speech should trigger suspicion.
In the diagnosis of MND it is noteworthy that there are no identifiable biomarkers and whilst brain and spinal cord imaging by MRI or CT is useful in excluding other conditions there are no specific identifiable features for MND.
Drugs appear to be effective at slowing the progression of some types of MND. For example, Riluzole-50mg reduces the presynaptic release of glutamate and increases short term survival in ALS. Edaravone is a free radical scavenger and slows disease progression in mild disease.
Botox injections can block the signals from the brain to the stiff muscles for about 3 months at a time and Baclofen (Lioresal) may be a useful muscle relaxant. Physical therapy can assist in alleviating cramps and stiffness and NSAIDS may be helpful with mild to moderate pain from muscle cramping and spasms. Physiotherapists and speech pathologists are an integral part of the management team.
In this episode we have the privilege of exploring this subject further with Associate Professor Ernie Butler a consultant neurologist and founding member of Frankston Neurology Group. He has major clinical expertise is in the management of multiple sclerosis, myasthenia gravis and Parkinson’s disease. He has appointments as the head of neurology at Peninsula Health, as a senior neurologist at Monash Health and as the head of the Monash MS clinic. We have had the honour of working with Ernie previously in episode 88 on MS and episode 89 on Myasthenia Gravis and Guillain Barre syndrome. Please welcome him back to the podcast.
References:
Frankston Neurologyhttps://www.frankstonneurology.com.au › ...Our Neurologists
Amyotrophic lateral sclerosis (ALS): Symptoms, causes and diagnosis
Motor Neurone Disease Association of Western Australiahttps://www.mndawa.asn.auMNDAWA - Home
National Institutes of Health (.gov)www.ncbi.nlm.nih.govMotor Neuron Disease - StatPearls