As the name suggests, upper motor neuron hypotonia is a condition in which there is a deficiency of the cranial nerves that control movement of muscles and movement of the arms and legs. It can present as stiffness in one or both arms or legs.
The muscles of the arms and legs depend on the motor neurons that connect the brain to the muscles in the spinal cord. The motor neurons can be affected by several diseases and disorders that cause paralysis, including amyotrophic lateral sclerosis (ALS) or Lou Gehrig’s disease.
Lower motor neuron hypotonia
In this condition, the lower motor neurons in the brain’s motor cortex that control the muscles of the legs and pelvis are affected. As with upper motor neuron hypotonia, this can result in stiffness in one or both legs.
A lesion in the cerebellum is responsible for most cases of lower motor neuron hypotonia. In this case, a lesion occurs on the lower surface of the cerebellum, which is responsible for coordinating the muscles of the arms, legs, and pelvis.
This can result in one or more of the following:
- Stiffness in one or more of the limbs
- Difficulty moving the arms and legs
- Difficulty bending over
Cerebellar lesions may also be the result of:
- A stroke
- Huntington’s disease
- Multiple sclerosis
- Traumatic brain injury
Brain tumors can also cause lower motor neuron hypotonia. As the name suggests, they cause a lesion in the cerebellum.
The condition can also be caused by:
- Hydrocephalus (fluid buildup)
Neurodegenerative disorders, which are also called “nerve diseases,” can cause lower motor neuron hypotonia. These disorders affect nerves that can be damaged or degenerate over time.
The most common neurodegenerative disorders that can cause lower motor neuron hypotonia are:
- Amyotrophic lateral sclerosis (ALS)
- Parkinson’s disease
- Spinal muscular atrophy (SMA)
Other conditions that can cause lower motor neuron hypotonia include:
- Guillain-Barr syndrome
- Peripheral neuropathy
- Muscular dystrophy
Tumors that develop in the brain or spinal cord can also cause lower motor neuron hypotonia.
It is thought that neurodegenerative disorders, like ALS, are the main cause of lower motor neuron hypotonia. However, for some people, it may also be due to injuries that affect the brain or spinal cord.
Muscular dystrophy is another condition that can cause lower motor neuron hypotonia. However, it is less common than neurodegenerative disorders.
Tumors that can cause lower motor neuron hypotonia include:
- Brain tumors
- Hemangioblastoma (benign tumor)
What causes lower motor neuron hypotonia?
Lower motor neuron hypotonia can be the result of a number of different conditions that affect the brain, spinal cord, or peripheral nerves of the body.
The brain is the central part of the nervous system and is responsible for coordinating the body’s movement. Damage or lesions to the brain can affect the motor neurons, which are the nerves that send messages to the muscles.
With lower motor neuron hypotonia, the damage or lesions occur in the motor cortex, the part of the brain that controls the muscles.
The following sections will explain what causes lower motor neuron hypotonia and what may be the best way to treat it.
Amyotrophic lateral sclerosis (ALS)
Amyotrophic lateral sclerosis (ALS) is a progressive disease that affects nerve cells in the brain and spinal cord. It causes the body to gradually lose the ability to control voluntary muscles.
Some people with ALS will experience weakness in their muscles, which is what is known as ALS-associated muscle wasting. This muscle wasting can be the result of:
- Muscle breakdown
- Muscle stiffness
- Muscle stiffness and spasticity
- Muscle cramps and spasms
Other symptoms of ALS include:
- Changes in speech
- Changes in swallowing
- Problems with breathing
- Numbness and tingling in the hands and feet
ALS is a rare and fatal condition that affects individuals from both genders and all races.
Most people with ALS will die from respiratory failure within 3 to 5 years of developing it. However, researchers are actively working to uncover new treatments.
Parkinson’s disease, or Parkinson’s disease, is a neurodegenerative disorder that affects nerve cells in the brain.
It is a progressive condition that can cause a number of symptoms to develop. These symptoms include:
- A tremor that causes the hands and feet to shake
- Muscle cramping
- Muscle twitching
- Problems with balance and coordination
Parkinson’s disease is not fully understood. It is often the result of genetic factors and can be caused by a variety of other factors.
It is likely that the damage to the brain or spinal cord’s nerve cells is the cause of lower motor neuron hypotonia.
Spinal muscular atrophy (SMA)
Spinal muscular atrophy (SMA) is a muscular disorder that causes progressive muscle weakness and muscle loss, typically in the thigh and shoulder muscles.
This can cause a person to experience symptoms such as:
- Difficulty walking
- Difficulty lifting objects
- Difficulty with balance and coordination
- Difficulty with swallowing
SMA is an autosomal dominant disease and is passed down through families.
There is no cure for SMA, but it can be managed with medication.
Spinal cord injuries
Injuries to the brain and spinal cord can cause lower motor neuron hypotonia.
Spinal cord injuries can also be caused by:
- Traumatic brain injuries
- Severe spinal cord injuries
Other spinal cord conditions that can cause lower motor neuron hypotonia include:
- Myasthenia gravis
What are the symptoms of lower motor neuron hypotonia?
A person with lower motor neuron hypotonia will typically experience a wide range of symptoms. These symptoms can affect the following areas of the body:
- Nose and sinuses
- Upper extremities
- Lower extremities
Some of the symptoms of lower motor neuron hypotonia can be vague and hard to pinpoint. For example, a person may experience symptoms that do not always correlate with one another.
These symptoms include:
- Slurred speech
- Difficulty chewing
- Difficulty swallowing
- Trouble sleeping
- Muscle weakness
- Muscle soreness
- Trouble with balance
Things to keep in mind
Some conditions that cause lower motor neuron hypotonia, such as ALS, can be life threatening. Be sure to discuss your concerns with your healthcare provider.
Symptoms of lower motor neuron hypotonia may resemble other health conditions. Always talk with your healthcare provider for a diagnosis.
See your healthcare provider if you have any of the following:
- A fever
- Muscle pain or cramps
- Extreme fatigue
- Trouble breathing
- Weakness in the limbs or trunk
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