Motor Neurone Disease Flashcards
What is motor neurone disease (MND)?
Motor neurone disease is an umbrella term that encompasses a variety of specific diagnoses. Motor neurone disease is a progressive, ultimately fatal condition where the motor neurones stop functioning. There is no effect on the sensory neurones and patients should not experience any sensory symptoms.
Give examples of MND
Amyotrophic lateral sclerosis (ALS) is the most common and well-known specific motor neurone disease. Stephen Hawking had amyotrophic lateral sclerosis.
Progressive bulbar palsy is the second most common form of motor neurone disease. It affects primarily the muscles of talking and swallowing.
Other types of motor neurone disease to be aware of are progressive muscular atrophy and primary lateral sclerosis.
What is the most common MND?
What % does this account for?
Amyotrophic lateral sclerosis (ALS) accounts for 75% of cases of MND.
Briefly differentiate between the types of MND
Notes: amyotrophic lateral sclerosis, primary lateral sclerosis, progressive muscular atrophy and progressive bulbar palsy
Amyotrophic lateral sclerosis
- Typically LMN signs in arms and UMN signs in legs
Primary lateral sclerosis
- UMN signs only
Progressive muscular atrophy
- LMN signs only
- Affects distal muscles before proximal
- Carries best prognosis
Progressive bulbar palsy
- Palsy of the tongue, muscles of chewing/swallowing and facial muscles due to loss of function of brainstem motor nuclei
- carries worst prognosis
Briefly describe the pathophysiology of MND
There is a progressive degeneration of both upper and lower motor neurones. The sensory neurones are spared.
What are the signs of lower MND?
Signs of lower motor neurone disease:
- Muscle wasting
- Hypotonia
- Fasciculations (twitches in the muscles)
- Reduced reflexes
- Weakness
What are the signs of upper MND?
Signs of upper motor neurone disease:
- Increased tone
- Spasticity
- Brisk reflexes
- Upgoing plantar responses
- Weakness
What causes MND?
The exact cause is unclear although several mechanisms have been considered. There is a genetic component and many genes have been linked with an increased risk of developing the condition. Taking a good family history is important as around 5-10% of cases are inherited. There also seems to be an increased risk with smoking, exposure to heavy metals and certain pesticides.
In familial cases, what causes MND?
In familial cases the gene responsible lies on chromosome 21 and codes for superoxide dismutase.
What are the risk factors for MND?
- Genetic predisposition or family history
- >40 years
What are the clinical features of MND?
Note: generally
Classically, there is a combination of upper motor neuron and lower motor neuron signs.
Upper motor neuron signs include spasticity, hyperreflexia and upgoing plantars (though they are often down going in MND).
Lower motor neuron signs include fasciculations, and later atrophy.
Generally, the eye and sphincter muscles are spared until late in the disease course and sensory disturbance is not seen.
If there is sensory disturbance, should MND be considered as a diagnosis?
If sensory disturbance is present this should prompt the consideration of an alternative diagnosis.
What are the clinical features of amyotrophic lateral sclerosis?
- Upper extremity weakness
- Stiffness with poor co-ordination and balance
- Spastic and unsteady gait
- Painful muscle spasms
- Difficulties in arising from chairs and climbing stairs
- Head drop
- Progressive difficutlies in maintaining an erect posture
- Muscle atrophy
- Strained slow speech
- Dysphonic speech
- Cough and choking on liquids and food
How is MND diagnosed?
The diagnosis of motor neuron disease is clinical based on the presence of upper and lower motor neurone signs, disease progressiona and absence of any other explanations for the presentations.
Although NMD is a clinical diagnosis, what investigations can be ordered to confirm NMD?
- Electromyography (EMG)
- Repeptivive nerve stimualtion
- MRI brain and spine
