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A neuromuscular disease damages the neurons or nerve cells that send messages that control voluntary muscles. This lapse in communication may result in muscle weakness and atrophy, often leading the patient to experience pain, muscle cramps, twitching and mobility problems. Neuromuscular disease can affect the muscles, the central nervous system, and the peripheral nervous system, which includes the arms and legs. There are seven different types of neuromuscular disease — muscular dystrophies, cerebral palsy, motor neuron diseases, disorders of the neuromuscular junction, metabolic diseases of the muscle, peripheral nerve conditions, and various myopathies.
Muscular dystrophies are a group of neuromuscular diseases that are genetically inherited. These diseases are the result of defects in the genes that are responsible for normal muscle function. Muscular dystrophies can be further broken down into nine distinct categories: Duchenne Muscular Dystrophy (DMD); Becker Muscular Dystrophy (BMD); Emery-Dreifuss Muscular Dystrophy (EDMD); Limb-Girdle Muscular Dystrophy (LGMD); Facioscapulohumeral Muscular Dystrophy (FSHD); Myotonic Dystrophy (MMD); Oculopharyngeal Muscular Dystrophy (OPMD); Distal Muscular Dystrophy (DD); and Congenital Muscular Dystrophy (CMD).
Cerebral palsy (CP) is also classified as a neuromuscular disease, as it stems from the brain's difficulty with controlling muscles. CP may be mild or quite severe and sometimes causes problems with speech and hearing, mental retardation and spastic movements. CP is usually diagnosed in childhood.
Motor neuron diseases (MND) are a group of neuromuscular diseases that are caused by degeneration of motor neurons in the spinal cord and brain. These diseases typically lead to weakness and atrophy — first in the arm and leg muscles, and later in the muscles leading to the throat and face. Motor neuron diseases include three types of spinal muscle atrophy (SMA) diseases diagnosed in childhood — SMA Type I, SMA Type II, and SMA Type III. Also included are spinal bulbar muscular atrophy (SBMA), adult spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's Disease.
Diseases of the neuromuscular junction are another classification of neuromuscular disease. These diseases generally result from a malfunctioning of the neuromuscular junction, which is the place where a nerve passes signals to muscles. This group of diseases includes Lambert-Eaton Syndrome (LES), the auto-immune disease Myasthenia Gravis (MG) and Congenital Myasthenic Syndrome (CMS), an inherited condition.
Metabolic diseases of the muscle also fall into the neuromuscular disease category. These illnesses are usually caused by inherited defects that interfere with the body's processing of chemical reactions during normal cellular functioning. Metabolic diseases of the muscle can be diagnosed in infancy, childhood or adulthood. This group includes mitochondrial myopathy (MITO), carnitine deficiency (CD) and lactate dehydrogenase deficiency (LDHA).
Diseases of the peripheral nerve can be classified as neuromuscular diseases as well. These conditions are typically the result of damage to the nerves in the peripheral nervous system, which includes the arms, legs, torso, face and some cranial nerves. Common symptoms of peripheral nerve diseases are numbness and pain in the extremities. Diseases in this category are Charcot-Marie-Tooth Disease (CMT), Dejerine-Sottas Disease (DS) and Friedreich's Ataxia (FA).
Many different kinds of myopathies — diseases affecting the skeletal muscles or muscles that connect to bones — also belong to the neuromuscular disease category. Myopathies usually cause gradual muscle weakness and atrophy closest to the center of the body. These diseases may be caused by genetic defects or metabolic, endocrine or inflammatory conditions. Examples of myopathies include nemaline myopathy (NM), periodic paralysis (PP) and Central Core disease (CCD).