What Is Neuromyotonia?

Neuromuscular rigidity refers to spontaneous, continuous, and muscle-active diseases caused by peripheral neuropathy. It is a rare chronic, progressive, neuromuscular disease, also known as Isaacs syndrome, continuous muscle fiber activity, and muscle Relaxation of muscle twitches, etc. Common in adolescents, both men and women, and some patients have a family genetic history. The onset of the disease is slow and progressive, with clinical features characterized by involuntary continuous vibrations of the shoulder, thigh, and calf muscles, which can be reduced or disappeared after light sleep, and can still occur in severe sleep.

Basic Information

nickname: Isaacs syndrome, continuous muscle fiber activity, muscle twitches with muscle relaxation disorders, etc.
English name: neuromyotonia
Visiting department: Neurology

Multiple groups: Common in adolescents, both men and women
Common locations: muscle
Common causes: Caused by peripheral neuropathy
Common symptoms: Muscle stiffness, cramps, twitching, weakness, and delayed muscle relaxation

Causes of neuromuscular rigidity

The cause of neuromuscular rigidity can be divided into congenital and acquired, the latter is more common. Congenital neuromuscular tonicity is associated with abnormalities in the voltage-gated test potassium channel encoded by the KCNA1 gene. Acquired neuromuscular rigidity is related to the production of Anti-VGKCb autoantibodies against their own neuromuscular junctions, and it also affects the normal function of potassium channels. There are reports of this disease associated with right renal hilar clear cell carcinoma with cystic changes. In addition, some patients have thymoma, bronchial cancer, and nasopharyngeal carcinoma. Therefore, the disease may be related to paraneoplastic syndromes and autoimmune disorders.

The electromyogram showed that the fibrillation potential, normal phase potential, and motor and sensory conduction speed were slowed down. The application of botulinum toxin to block peripheral nerves could make myoelectric activity disappear.

Muscle and sural nerve biopsies were normal in most patients. In some patients, muscle fiber biopsy showed uneven muscle fiber size, horn fiber and muscle fiber hypertrophy, small group muscle fiber atrophy, and increased muscle nucleus. ATPase staining showed type muscle fiber homogenization and type muscle fiber atrophy, indicating neurogenic damage. Surgical nerve biopsy showed changes in myelin fibers, segmental myelination, axonal mutation and budding, and Schwann cell proliferation.

Clinical manifestations of neuromuscular rigidity

The main clinical manifestations are muscle stiffness, spasms, twitching, weakness and delayed muscle relaxation in affected muscles, and spontaneous and continuous motor unit discharge activity is detected on the electromyogram. Motor neuron potentials that remain active in the resting state are commonly seen in neuromuscular rigidity and stiff-man syndrome.

The lesions of neuromuscular rigidity can be local or whole body, often affecting the face and limbs. Sleep, nerve block, anesthesia and other means can not prevent muscle stiffness. Electromyography is a more important test method.

The onset of the disease is slow and progressive, and it is characterized by the involuntary continuous tremor of the shoulder, thigh, and calf muscles. Sometimes the tremor is slow and wavy, which is called twitching. The above-mentioned muscles can continuously tremble for several minutes to several hours, occasionally involving the mouth, pharynx, face and respiratory muscles. Lighter people can alleviate or disappear after sleeping, and severe people can still appear in sleep. Secondly, after the affected limb is exercised or after repeated exercise, the muscles become stiff and muscle spasm pain occurs. It can relax for several minutes to several hours. It is similar to muscle rigidity, and muscle percussion does not appear. It is called pseudomuscular rigidity. A few years later, due to the continuous contraction of the wrist and hand muscles, the claws and the foot muscles spasm, so that when walking, the toes land first and the posture is abnormal. In addition, there is sweating and sweating. The electromyogram showed that the beam tremor potential was double wave, triple wave, or multiple wave, and the stiff muscles showed continuous and irregular movement potentials, with large changes in amplitude and shape. With exercise, they can induce strong release and continue to relax muscles. During the process, motor and sensory conduction slow down.

Neuromuscular rigidity

Serum muscle enzyme tests and serum electrolyte tests can help differentiate diagnosis. The electromyogram shows a double wave, triple wave, or multiple wave of the tremor potential. Muscle and sural nerve biopsies were normal in most patients. Muscle biopsy of some patients showed uneven muscle fiber size, hypertrophy of horn fibers and muscle fibers, atrophy of small group muscle fibers, and increased nucleus. ATPase staining showed homotypic muscle group type muscle fibers and type muscle fiber atrophy. Surgical nerve biopsy showed secondary Demyelination and axonal degeneration, muscle pathology showed neurogenic damage.

Diagnosis of neuromuscular rigidity

According to the majority of patients are adolescents or adults, clinical characteristics are involuntary muscle tremor, muscle stiffness and pain after exercise, with sweating should be considered in this disease. Electromyographic examination shows continuous electrical activity for diagnosis. Muscle and gastrocnemius nerve biopsy can help differentiate diagnosis and understand the cause. A small number of patients can be accompanied by visceral cancer, so patients should be carefully and comprehensively examined.

Differential diagnosis of neuromuscular rigidity

Should be distinguished from glycogen storage myopathy, stiff-man syndrome and spinal myoclonus. Glycogen storage myopathy is characterized by muscle biopsy showing a large accumulation of glycogen in muscle fibers, stiff-man syndrome manifested by persistent muscle rigidity and spasm, and spinal myoclonus is often a regular distribution of spinal segmental muscles. Tics.

Neuromuscular rigidity complications

Involving the mouth, pharynx, face, and respiratory muscles can cause difficulty swallowing and suffocation.

Neuromuscular Tonic

At present, there is no treatment for the etiology of this disease, and the treatment is mainly to relieve symptoms. Among them, antiepileptic drugs have a better effect, and diazepam is ineffective for the treatment of this disease. Taking carbamazepine (amide imidazine) or phenytoin can often control the symptoms. It should be taken for a long time to avoid recurrence.

Prognosis of neuromuscular rigidity

The general course of disease is months to years. For patients with malignant tumors, the prognosis is poor.

This disease may be related to paraneoplastic syndromes and autoimmune disorders. It may be caused by peripheral neuropathy in the proximal part of the neuromuscular junction caused by different causes. Therefore, patients should be carefully and comprehensively examined and early diagnosed and treated related diseases.