Motor neuron disease Flashcards
What is Motor Neuron Disease?
The motor neuron diseases are a group of progressive neurological disorders that destroy motor neurons; it’s progressive and leads to death, usually as a result of respiratory failure or aspiration
When does motor neuron disease usually present?
50-75
Below age 70 men are affected more often than women
What causes motor neuron disease?
Most cases are sporadic and their causes are usually not known. It is thought that environmental, toxic, viral, or genetic factors may be involved
What are the 4 main clinical patterns of motor neuron disease?
These different presentations usually merge as MND progresses
- Amyotrophic lateral sclerosis (ALS)
- Progressive muscular atrophy
- Progressive bulbar and pseudobulbar palsy (20%)
- Primary lateral sclerosis (1-2%)
How does Amyotrophic lateral sclerosis (ALS) present?
Early symptoms of ALS usually include muscle weakness or stiffness in a limb or muscles of the mouth or throat
Gradually almost all the muscles under voluntary control are affected, and individuals lose their strength and the ability to speak, eat, move, and even breathe
Most people with ALS die from respiratory failure, usually within 3 to 5 years from the onset of symptoms
How does Progressive bulbar and pseudobulbar palsy present?
Dysarthria, dysphagia, nasal regurgitation of fluids and choking
A fasciculating tongue with slow, stiff tongue movements is the classic finding in a mixed bulbar palsy
Pathological laughter and crying may occur in pseudobulbar palsy
What are key facts about the pathophysiology of motor neuron disease?
When the muscles cannot receive signals from the lower motor neurons, they begin to weaken and shrink in size (muscle atrophy or wasting). The muscles may also start to spontaneously twitch. These twitches (fasciculations) can be seen and felt below the surface of the skin.
When the lower motor neurons cannot receive signals from the upper motor neurons, it can cause muscle stiffness (spasticity) and overactive reflexes. This can make voluntary movements slow and difficult. Over time, individuals with MNDs may lose the ability to walk or control other movements.
How would you diagnose motor neuron disease?
A physical exam should be followed by an extensive neurological exam. The exam assesses motor and sensory skills, nerve function, hearing and speech, vision, coordination and balance, mental status, and changes in mood or behavior.
Also:
- Electromyography (EMG) is used to diagnose disorders of lower motor neurons, as well as disorders of muscle and peripheral nerves
- A nerve conduction study
How is motor neuron disease managed?
No treatment has been shown to influence outcome substantially.
Riluzole, a sodium-channel blocker that inhibits glutamate release, slows progression slightly, increasing life expectancy by 3–4 months on average.
Non-invasive ventilatory support and feeding via a gastrostomy help prolong survival. Patients should be supported by a specialist multi-disciplinary team with access to palliative care and a clinical nurse specialist.
