Motor neuron disease

Motor neuron diseases (MNDs) refer to a spectrum of rare neurodegenerative disorders that selectively impact motor neurons, the nerve cells responsible for controlling voluntary muscle activity. This family of diseases includes conditions such as amyotrophic lateral sclerosis (ALS), progressive bulbar palsy (PBP), pseudobulbar palsy, progressive muscular atrophy (PMA), primary lateral sclerosis (PLS), monomelic amyotrophy (MMA), among others.

Overview of Motor Neuron Diseases

Motor neuron diseases can manifest in both children and adults, with each specific disease affecting patients differently. The common denominator among these conditions is that they all cause movement-related symptoms, predominantly muscle weakness. The majority of these diseases occur sporadically without identified causes, although some forms can be inherited. Studies into these inherited forms have led to the discovery of several genes, such as SOD1, that are thought to provide insights into the pathogenesis of the disease.

Clinical Presentation

Symptoms of motor neuron diseases may be evident at birth or develop gradually later in life. Generally, these diseases worsen over time. Some, like ALS, significantly reduce life expectancy, while others do not. Signs and symptoms are contingent on the specific disease, but commonly include various patterns of muscle weakness, muscle cramps and spasms, difficulty in breathing, and issues with speaking and swallowing. Sensory functions typically remain unaffected. Some patients may also exhibit emotional disturbances, cognitive and behavioural changes.

Diagnosis and Management

The diagnosis of MNDs typically involves neurologic examination that reveals signs of both upper and lower motor neuron damage. Management primarily focuses on alleviating symptoms and enhancing the quality of life as, currently, there are no approved treatments for the majority of motor neuron disorders.

Specific Types of MNDs

Amyotrophic Lateral Sclerosis (ALS)

ALS is the most common type of MND and involves both the upper and lower motor neurons. It is characterized by muscle atrophy, spasticity, and rapidly progressive weakness due to muscle wasting. This results in difficulty speaking, swallowing, and breathing.

Progressive Bulbar Palsy (PBP)

In PBP, the lower motor neurons of the cranial nerves are affected. This results in weakness of the muscles of the face, throat, and tongue, leading to difficulties in speaking, chewing, and swallowing.

Primary Lateral Sclerosis (PLS)

PLS affects the upper motor neurons and leads to spasticity and difficulty with balance, though it does not affect life expectancy.

See also

• Spinal muscular atrophies
• Hereditary motor and sensory neuropathies

Motor neuron disease Resources
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