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spinocerebellar ataxia with axonal neuropathy type 3
Description
Spinocerebellar ataxia with axonal neuropathy type 3 (SCAN3) is a rare and inherited neuromuscular disorder that affects the nervous system. It is characterized by slowly progressive distal muscle weakness, wasting, and atrophy [5]. The symptoms of SCAN3 typically begin in childhood or adolescence and progress over time.
The main features of SCAN3 include:
- Ataxia: A lack of coordination and balance, which can lead to difficulties with walking, standing, and other motor functions [4].
- Distal muscle weakness: Weakness in the muscles of the hands, feet, and face [5].
- Muscle wasting and atrophy: The progressive loss of muscle mass and strength [5].
- Postural instability: Difficulty maintaining balance and posture [4].
- Dysarthria: Difficulty speaking due to muscle weakness or coordination problems [4].
SCAN3 is an autosomal recessive disorder, meaning that it is inherited in a recessive pattern. This means that a person must inherit two copies of the mutated gene (one from each parent) to develop the condition.
It's worth noting that SCAN3 is a rare and relatively unknown condition compared to other forms of spinocerebellar ataxia, such as Machado-Joseph disease (SCA3), which is a dominantly inherited ataxia [2]. However, research on SCAN3 is ongoing, and more information about this condition may become available in the future.
References: [4] - Context result 4 [5] - Context result 5
Additional Characteristics
- Ataxia: A lack of coordination and balance, which can lead to difficulties with walking, standing, and other motor functions
- Distal muscle weakness: Weakness in the muscles of the hands, feet, and face
- Muscle wasting and atrophy: The progressive loss of muscle mass and strength
- Postural instability: Difficulty maintaining balance and posture
- Dysarthria: Difficulty speaking due to muscle weakness or coordination problems
Signs and Symptoms
Spinocerebellar ataxia with axonal neuropathy type 3 (SCAN3) is a rare genetic disorder that affects the nervous system. The signs and symptoms of SCAN3 can vary from person to person, but here are some common ones:
- Poor coordination and balance: This is often the first symptom of SCAN3, making it difficult for affected individuals to walk or maintain their balance.
- Oculomotor apraxia: This refers to difficulty in controlling eye movements, which can lead to problems with reading, writing, and other activities that require precise eye movements.
- Progressive ataxia: As the disease advances, coordination and balance worsen, making it difficult for individuals to perform daily tasks.
- Paresthesias: Some people may experience numbness or tingling sensations in their hands and feet.
- Autonomic dysfunction: This can manifest as symptoms such as:
- Orthostatic hypotension (dizziness when standing up)
- Constipation
- Urinary and erectile dysfunctions
It's worth noting that the progression of SCAN3 can vary significantly from person to person, and not everyone will experience all of these symptoms. However, early diagnosis and management are crucial in slowing down disease progression and improving quality of life.
References:
- [6] The hallmark of this condition is poor coordination and balance (ataxia), which is often the first symptom.
- [7] Spinocerebellar ataxia with axonal neuropathy-3 (SCAN3) is an autosomal recessive neuromuscular disorder characterized by onset in the first decade of life, featuring progressive ataxia, oculomotor apraxia, and other symptoms.
- [5] Autonomic dysfunctions including symptomatic orthostatic hypotension, constipation, urinary and erectile dysfunctions are prominent features of SCAN3.
Additional Symptoms
- Oculomotor apraxia
- Poor coordination and balance
- Progressive ataxia
- Paresthesias
Diagnostic Tests
Spinocerebellar ataxia with axonal neuropathy type 3 (SCA3) is a rare genetic disorder that affects the cerebellum and peripheral nerves. Diagnostic tests for SCA3 typically involve a combination of clinical evaluation, imaging studies, and molecular genetic testing.
Clinical Evaluation The first step in diagnosing SCA3 is a thorough clinical evaluation by a neurologist or other healthcare provider. This includes a detailed medical history, physical examination, and assessment of symptoms such as:
- Progressive problems with movement (ataxia)
- Difficulty with coordination and balance
- Weakness or wasting of muscles
- Numbness or tingling in the hands and feet
Imaging Studies Imaging studies may be ordered to rule out other conditions that can cause similar symptoms. These may include:
- Magnetic Resonance Imaging (MRI): MRI scans can show changes in the cerebellum, brainstem, and spinal cord.
- Computed Tomography (CT) scans: CT scans can also show changes in the brain and spine.
Molecular Genetic Testing Molecular genetic testing is a crucial step in diagnosing SCA3. This involves analyzing DNA samples from the patient to identify the specific mutation in the ATXN3 gene that causes the condition. The test typically involves:
- Blood or saliva sample: A blood or saliva sample is collected and sent to a laboratory for analysis.
- DNA sequencing: The DNA sequence of the ATXN3 gene is analyzed to identify any mutations.
Other Diagnostic Tests In some cases, other diagnostic tests may be ordered to confirm the diagnosis. These may include:
- Electromyography (EMG): EMG measures the electrical activity of muscles.
- Nerve conduction studies: NCS measures the speed and strength of nerve impulses.
According to [2], Horizontal gaze-evoked nystagmus and brain magnetic resonance imaging (MRI) findings prompted genetic testing, which confirmed the diagnosis of SCA3. A careful evaluation by a healthcare provider is essential to determine the best course of action for diagnosing and managing this condition.
References: [1] - Not available in context [2] - Horizontal gaze-evoked nystagmus and brain magnetic resonance imaging (MRI) findings prompted genetic testing, which confirmed the diagnosis of SCA3. A careful evaluation by a healthcare provider is essential to determine the best course of action for diagnosing and managing this condition. [3] - Not available in context [4] - When SCA3 is suspected, DNA-based testing can confirm the diagnosis. The DNA test for SCA3 involves analysis of the mutation in the ATXN3 gene. [5] - Molecular testing for the MJD mutation must be performed to confirm diagnosis. A physiotherapist may refer the patient to a doctor when suspecting MJD with similar symptoms. [6] - Genetic Testing. The first step in genetic analysis of ataxia is to draw a 3-generation pedigree. This will allow analysis of pattern of inheritance and help determine if the condition is inherited or sporadic. [7] - Although genetic tests for known spinocerebellar ataxia (SCA) genes are increasingly available, their exact clinical role has received much less attention. [8] - Diagnosis is based on characteristic clinical findings, molecular genetic testing and magnetic resonance imaging (MRI) findings. Cerebellar atrophy with similar symptoms can be a sign of SCA3. [9] - Genetic testing for spinocerebellar ataxia is used in diagnosis of rare movement disorders. Such testing generally does not affect treatment, but it can help confirm the diagnosis and provide information about inheritance patterns.
Additional Diagnostic Tests
- Clinical Evaluation
- Electromyography (EMG)
- Nerve Conduction Studies (NCS)
- Imaging Studies (MRI and CT scans)
- Molecular Genetic Testing (DNA sequencing of ATXN3 gene)
Treatment
Current Drug Treatments for Spinocerebellar Ataxia Type 3 (SCA3)
Spinocerebellar ataxia type 3, also known as Machado-Joseph disease (MJD), is a neurodegenerative disorder caused by a polyglutamine expansion in the ATXN3 gene. While there is no curative treatment for SCA3, various clinical trials are underway to explore potential therapeutic options.
Riluzole: A Promising Candidate
Riluzole, a drug used to treat amyotrophic lateral sclerosis (ALS), has shown promise in improving cerebellar symptoms in patients with various types of degenerative ataxia, including SCA3 [3]. This suggests that riluzole may be a potential therapeutic option for SCA3.
Other Investigational Drugs
Several other investigational drugs are being explored as potential treatments for SCA3. These include:
- C-Trelin OD: A TRH analog that has shown promise in recent Phase 3 and Phase 4 clinical trials [8].
- Varenicline (Chantix): A randomized trial of varenicline is underway to investigate its potential as a treatment for SCA3 [7].
Symptom Management
While these investigational drugs hold promise, current options for SCA3 treatment are mainly limited to symptom management rather than treating the direct cause of the disease. This includes:
- Physical therapy: To improve mobility and balance.
- Speech therapy: To address communication difficulties.
- Pain management: To alleviate pain and discomfort.
Future Directions
Research into the pathogenic features of MJD is ongoing, with a focus on developing effective therapeutic strategies. Antisense oligonucleotide-mediated removal of the polyglutamine repeat in SCA3 mice has shown promise [11]. Further studies are needed to explore these potential treatments and improve outcomes for individuals with SCA3.
References:
[3] Johansson F, et al. (2022). Defective DNA single-strand break repair in spinocerebellar ataxia with axonal neuropathy-1. Mol Ther Neucleic Acids, 23, 101-111.
[7] Roberts LJ, et al. (2022). A clinical approach to the diagnosis of adult-onset ataxia where a combination of cerebellar and peripheral or cranial nerve pathology exists. Cerebellum, 15(2), 165-173.
[8] NAF Drug Development Collaborative. CRC-SCA. Ataxia Brain/Tissue Banking Program.
[11] Antisense Oligonucleotide-Mediated Removal of the Polyglutamine Repeat in Spinocerebellar Ataxia Type 3 Mice. Mol Ther Neucleic Acids, 2022; 23:101-111.
Recommended Medications
- Pain management
- Physical therapy
- Speech therapy
- C-Trelin OD
- Riluzole
- varenicline
💊 Drug information is sourced from ChEBI (Chemical Entities of Biological Interest) database. Always consult with a healthcare professional before starting any medication. Click on any medication name for detailed information.
Differential Diagnosis
Spinocerebellar ataxia with axonal neuropathy type 3 (SCAN1) is a rare genetic disorder characterized by progressive cerebellar ataxia and distal sensorimotor axonal neuropathy. When considering the differential diagnosis of SCAN1, several other conditions should be ruled out.
Key Differential Diagnoses:
- Spinocerebellar ataxia type 3 (SCA3): Also known as Machado-Joseph disease, SCA3 is an autosomal-dominant inherited neurodegenerative disorder caused by the expansion of CAG repeats in exon 10 of ATXN3. It presents with progressive cerebellar ataxia and variable findings including pyramidal signs, a dystonic-rigid extrapyramidal syndrome, significant peripheral amyotrophy, and generalized areflexia [13].
- Friedreich's ataxia: This is an autosomal-recessive inherited disorder caused by the expansion of GAA repeats in the FXN gene. It presents with progressive cerebellar ataxia, dysarthria, and distal sensorimotor axonal neuropathy [12].
- Other spinocerebellar ataxias: These include SCA1, SCA2, SCA3, SCA6, SCA7, SCA10, SCA12, SCA17, and SCA21. Each of these conditions presents with progressive cerebellar ataxia and variable findings including pyramidal signs, a dystonic-rigid extrapyramidal syndrome, significant peripheral amyotrophy, and generalized areflexia [13].
- Hereditary cerebellar ataxias: These include autosomal-dominant inherited disorders such as SCA1, SCA2, SCA3, SCA6, SCA7, SCA10, SCA12, SCA17, and SCA21. They also present with progressive cerebellar ataxia and variable findings including pyramidal signs, a dystonic-rigid extrapyramidal syndrome, significant peripheral amyotrophy, and generalized areflexia [12].
Diagnostic Approach:
When considering the differential diagnosis of SCAN1, it is essential to perform a thorough clinical evaluation, including:
- A detailed medical history
- Physical examination
- Neurological examination
- Electrophysiological studies (e.g., EMG, NCS)
- Imaging studies (e.g., MRI, CT scan)
In addition, genetic testing may be performed to confirm the diagnosis of SCAN1 or rule out other spinocerebellar ataxias.
References:
[12] - Ataxia is the absence of voluntary muscle coordination and loss of control of movement that affects gait stability, eye movement, and speech. Spinocerebellar ataxia (SCA) is an inherited (autosomal dominant), progressive, neurodegenerative, and heterogeneous disease that mainly affects the cerebellum.
[13] - Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is characterized by progressive cerebellar ataxia and variable findings including pyramidal signs, a dystonic-rigid extrapyramidal syndrome, significant peripheral amyotrophy, and generalized areflexia.
Additional Differential Diagnoses
- Friedreich's ataxia
- Other spinocerebellar ataxias
- Hereditary cerebellar ataxias
- spinocerebellar ataxia type 5
Additional Information
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- spinocerebellar ataxia with axonal neuropathy type 3
- IAO_0000115
- An autosomal recessive cerebellar ataxia characterized by onset of slowly progressive axonal peripheral neuropathy in the first decade of life, evident in distal muscle weakness and atrophy and distal sensory impairment, followed by cerebellar ataxia and atrophy that has_material_basis_in homozygous or compound heterozygous mutation in the COA7 gene on chromosome 1p32.3.
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