From the Guidelines
Distal muscle weakness is primarily caused by peripheral neuropathies, neuromuscular junction disorders, and certain myopathies, with the most recent and highest quality evidence supporting this multifactorial etiology 1.
Causes of Distal Muscle Weakness
The causes of distal muscle weakness can be broadly categorized into:
- Peripheral neuropathies, such as diabetic neuropathy, Guillain-Barré syndrome, and chronic inflammatory demyelinating polyneuropathy (CIDP) 1
- Neuromuscular junction disorders, including myasthenia gravis and Lambert-Eaton myasthenic syndrome, which affect signal transmission between nerves and muscles 1
- Myopathies, such as inclusion body myositis, distal muscular dystrophies, and myotonic dystrophy, that directly affect muscle strength and function 1
Evaluation and Diagnosis
Evaluation of distal muscle weakness typically involves a thorough neurological examination, electromyography, nerve conduction studies, blood tests, and sometimes genetic testing or muscle biopsy 1.
Treatment
Treatment depends on the underlying cause and may include managing primary conditions, immunosuppressive therapy, physical therapy, or supportive care to maintain function and prevent complications 1.
Additional Considerations
It is essential to consider other potential causes of muscle symptoms, such as statin-associated muscle symptoms, and to evaluate patients for predisposing factors and non-statin etiologies 1. In summary, the management of distal muscle weakness requires a comprehensive approach, considering the various potential causes and underlying conditions, with a focus on maintaining function and preventing complications, as supported by the most recent and highest quality evidence 1.
From the FDA Drug Label
Neurological Increased intracranial pressure with papilledema (pseudo-tumor cerebri) usually after treatment Convulsions Vertigo Headache
The FDA drug label does not answer the question.
From the Research
Causes of Distal Muscle Weakness (Myasthenia)
The causes of distal muscle weakness, also known as myasthenia, can be attributed to various myopathic and genetic conditions. Some of the common causes include:
- Facioscapulohumeral muscular dystrophy (FSHD) 2
- Myotonic dystrophy 2
- Inclusion body myositis 2
- Myofibrillar myopathy (MFM) 2
- Distal muscular dystrophies 2, 3
- Metabolic myopathies 2
- Congenital myopathies 2
Inherited and Acquired Causes
Distal muscle weakness can be caused by both inherited and acquired conditions. Inherited causes are mostly due to mutations in genes coding for myopathic or neurogenic diseases, while acquired causes occur due to inflammatory, endocrine, or toxic etiologies 4.
Genetic Aspects
Advances in molecular genetics have led to the identification of gene lesions responsible for several distal myopathies, and have expanded our understanding of the genetic relationships of distal myopathies to other inherited disorders of muscle 5, 3.
Clinical Features
The clinical features of distal myopathies can be challenging to diagnose due to the unusual phenotype and significant overlap in clinical features of many of these entities. However, characteristic clinical and histological features can aid in their identification 5, 6.