Hereditary Ataxia : Exploring the Genetic Condition | Plexus
Hereditary ataxia is a group of neurological disorders marked by progressive degeneration of the cerebellum, and eventually leads to problems with voluntary muscle movement, balance, and coordination. Let’s look at the condition in detail, and understand the various types, symptoms, causes, as well as available treatment options.
What is Hereditary Ataxia?
Hereditary ataxia is
essentially an umbrella term for a group of genetically heterogeneous disorders
that affect the nervous system, specifically the cerebellum. This part of the
brain is responsible for coordinating voluntary movements, maintaining balance,
and controlling muscle tone. Since ataxia is degenerative, the functions of the
cerebellum also progressively deteriorate with time.
Types of Hereditary Ataxia
Hereditary Ataxia is
divided according to the mode of inheritance gene - autosomal dominant,
autosomal recessive, X-linked, and mitochondrial. Certain types of ataxia are
indicative of the presence of a mutated gene that secretes irregular proteins.
These proteins then go on to disrupt the regular functioning of nerve cells,
especially those in the cerebellum and spinal cord.
Autosomal Dominant Ataxias
In these types of ataxia,
the individual can inherit the mutated gene from either parent. They are
usually slowly progressive, and typically result in cerebellar atrophy. For the
purpose of this blog, we’ll look at two types of autosomal dominant ataxias:
Spinocerebellar Ataxia (SCA)
Spinocerebellar ataxia, spinocerebellar atrophy, or
spinocerebellar degeneration is a genetic disease caused by either a recessive
or dominant gene. SCA may result in non-coordinated gait, impaired hand-eye
coordination, and abnormal speech. Cerebellar degeneration and cerebellar
ataxia are common symptoms of all types of SCA, with other symptoms being:
● Slurred
speech
● Poor
coordination of movement
● Inability
to perform basic fine motor movements
● Dysphagia
(difficulty in swallowing)
● Unsteady
gait
● Tendency
to trip
● Rapid
back-and-forth eye movements
There are 40 types of SCA
discovered so far. Each type is named SCA1, SCA2, and so on, to indicate the
order in which they were discovered.
SCA3 is the most
common type of Spinocerebellar Ataxia. It is also known as Machado-Joseph Disease.
Read more about Plexus’
Regenerative Rehabilitation for SCA here.
Episodic Ataxia (EA)
EA1 to EA7 along with late-onset
episodic ataxia are like their name suggests, episodic and not progressive. EA1
and EA2 are the most common, with the former involving short ataxic episodes
which can last from seconds to over two minutes. Stress, sudden movement, or
even getting startled are considered triggers to such episodes. EA1 also
manifests as muscle twitching. EA2 can have much longer episodes - 30 minutes
to 6 hours. Also triggered by stress, EA2 can result in dizziness, muscle
weakness, and fatigue. Since EA is not progressive, it does not shorten life
span.
Autosomal Recessive Ataxias
In these types of ataxia,
the mutated gene is inherited from both parents. With both parents as carriers,
1 in 4 children can inherit two copies of the mutated gene and develop ataxia.
Friedreich’s Ataxia
The most common type of
hereditary ataxia, Friedreich’s Ataxia, is caused by the mutated FXN gene, and
is characterized by damage to the cerebellum, spinal cord, and peripheral
nerves which carry signals to the brain and spinal cord from the arms and legs.
The earliest signs of this type of ataxia manifests before 25 years of age at
least, with the first symptom being difficulty in walking. Gradually this
difficulty of movement progresses to the arms and trunk. Some people also
develop high arches (feet deformity) and scoliosis.
Friedreich’s Ataxia also
shares some common symptoms with SCA, including:
● Slurred speech
● Rapid
back-and-forth eye movements
● fatigue
Additionally, Friedreich’s Ataxia can also result in hearing loss, diabetes,
cardiomyopathy, and heart failure.
RFC1 Associated Ataxia
RFC1 is a gene that encodes one of the subunits of Replication
Factor C Complex. This is a five-subunit protein that is critical for DNA
replication and repair. Any changes or mutations in these genes can have
serious consequences, such as neurological disorders.
Mutations in the RFC1 gene (inherited from both parents) can result
in late-onset ataxia, in fact this is one of the latter’s most common causes.
The symptoms typically include dizziness, tingling sensation or numbness in the
body, erratic bouts of coughing.
Ataxia Telangiectasia
This is a very rare form of
hereditary ataxia. It is a multisystem ataxia because it impacts different
organs and tissues. It develops in individuals who inherit the
ataxia-telangiectasia mutated from both their parents. Its symptoms include:
● Unsteady gait (ataxia)
● Small dilated blood vessels near surface
of the skin, especially around the eyes and on the earlobes (telangiectasia)
● Red or dilated blood vessels in the eyes
(oculocutaneous telangiectasia)
● Increased susceptibility to infections
because of weakened immune system
● Increased sensitivity to ionizing
radiation
● Elevated risk of certain cancers,
especially leukemia and lymphoma (increased risk in children with ataxia
telangiectasia)
● Progressive neurological degeneration
Congenital Cerebellar Ataxia
Present at birth, this type
of ataxia is a result of damage to the cerebellum. Its symptoms include:
● Unsteady gait
● Hypotonia (low muscle tone)
● Floppy and weak muscles
● Delayed motor development
● Dysphagia
● Speech delays and difficulties
● Cognitive impairment
Wilson’s Disease
This condition is a result
of toxic buildup or accumulation of copper in various tissues, especially in
the liver and brain. This accumulation is caused by the inheritance of two
copies of ATP7B which is responsible for encoding a critical protein that supports
copper transport within the body. Its symptoms include:
● Unsteady gait
● Fatigue
● Abdominal pain
● Jaundice
● Muscle stiffness
● Tremors
● Speech difficulties
● Mood swings
● Depression
● Cognitive impairment
Hereditary Ataxia Diagnosis
In order to accurately
diagnose the type of hereditary ataxia, your doctor may perform a comprehensive
evaluation that includes:
● Clinical assessment: Medical history,
family history, detailed assessment of symptoms
● Genetic testing: Identification of
specific gene mutation to plan treatment and management of condition
● Neurological examination: Testing
coordination, reflexes, muscle strength, etc.
● Imaging studies: MRI (magnetic resonance
imaging) to evaluate structure of cerebellum and check for abnormalities, EMG
(electromyography) to assess nerve and muscle function
Hereditary Ataxia Treatment at
Plexus
At our centers in Bangalore
and Hyderabad, we offer advanced regenerative rehabilitation for ataxia. This customizable
program comprises stem cell therapy, physiotherapy, occupational therapy, as
well as speech and language therapy.
At Plexus, we use mesenchymal stem cells
(MSCs) that possess the ability to transform into different kinds of human
cells. Through suitable application, MSCs can be turned into neurons to replace
the ones lost or damaged in ataxia, thereby restoring neural function to a
point where the patient recovers enough mobility and function to live a more
independent life.
Apart from stem cell therapy,
our rehabilitation program focuses on:
● Coordination
training
● Balance
training
● Trunk
stability training
● Trunk
rehabilitation
● Core
strengthening
● Locomotor
exercises
● Activities
for Daily Living (ADL)
● Handwriting
training
● Hand
function training
● Balance
training
● Swallowing
techniques
● Articulation
techniques
● Pronunciation
exercises
● Assistive
communication devices
● Oral
musculature strengthening exercises
Although, there is little
one can do to avoid inheriting ataxia, timely diagnosis and early intervention
can go a long way in managing the condition. At Plexus, we provide
state-of-the-art therapeutic care to provide you the best chance at living a
life of dignity and purpose.
FAQs
What are the 3 types of ataxia?
The 3 types of ataxia are:
● Sensory Ataxia: Caused by a dysfunction in
the sensory nerve pathways, leading to problems with joint position sense.
● Vestibular Ataxia: Linked to issues with
the inner ear's vestibular system, affecting balance and coordination.
● Cerebellar Ataxia: Associated with damage
to the cerebellum, impacting coordination, balance, and voluntary muscle
movements.
What is the most common type of
hereditary ataxia?
Friedreich's Ataxia is one
of the most common types of hereditary ataxia, caused by mutations in the FXN
gene.
How do you diagnose hereditary
ataxia?
Diagnosing hereditary
ataxia involves genetic testing to identify specific gene mutations, clinical
neurological examinations, MRI to check for abnormalities in the cerebellum, as
well as EMG to evaluate nerve and muscle function.
What is the difference between
ataxia and apraxia?
Ataxia refers to a lack of
coordination in voluntary muscle movements. It affects gait, balance, and fine
motor skills. It is typically a progressive neurological condition that is
caused by damage to the brain, spinal cord, and peripheral nerves.
Apraxia on the other hand
involves a difficulty in planning and executing purposeful movements despite
having the physical ability to perform them.
Is ataxia similar to Parkinson's?
Although ataxia and
Parkinson’s are characterized by impaired movement, ataxia primarily affects
coordination and balance due to cerebellar dysfunction, while Parkinson's
involves tremors, stiffness, and bradykinesia resulting from dopamine
deficiency in the basal ganglia.
They have different causes
and symptoms.
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