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Related Concept Videos

Alterations in Muscle Tone lll01:11

Alterations in Muscle Tone lll

Rigidity and myotonia are distinct abnormalities of muscle tone that affect resistance and relaxation during movement. Although both involve altered muscle contraction, they arise from different neurological and muscular mechanisms.CharacteristicsRigidity is characterized by uniform resistance to passive movement across the entire range, independent of speed, affecting flexors and extensors equally. It may appear as lead-pipe rigidity (smooth, constant resistance) or cogwheel rigidity...
Alterations in Muscle Tone ll01:12

Alterations in Muscle Tone ll

Alterations in muscle tone are common manifestations of neurological disorders and reflect dysfunction within different nervous system regions. Spasticity, paratonia, and dystonia represent distinct forms of hypertonia, each with unique mechanisms, clinical features, and diagnostic importance.CharacteristicsSpasticity happens from upper motor neuron lesions and is characterized by velocity-dependent resistance to passive movement. Clinical features include:Exaggerated deep tendon reflexesClonus...
Disorders of the Skeletal Muscle01:28

Disorders of the Skeletal Muscle

The clinical conditions affecting the skeletal muscle tissue are broadly categorized as musculoskeletal and neuromuscular disorders.
Musculoskeletal disorders
Musculoskeletal disorders involve injuries and conditions affecting the skeletal muscles and associated connective tissues. These disorders can arise from acute biomechanical stresses or chronic overuse and can occur across different age groups. Common injuries include sprains, fractures, and muscular strains, often resulting from...
Classification of Skeletal Muscle Relaxants01:28

Classification of Skeletal Muscle Relaxants

Skeletal muscle relaxants are a group of drugs that can reduce muscle stiffness and induce temporary paralysis to relieve pain. These agents can act centrally to reduce muscle tone or spasms in painful conditions such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or spinal injuries; they are called antispasmodics or spasmolytics.
Peripherally acting skeletal muscle relaxants interfere with the neurotransmission at the neuromuscular end plate to induce paralysis during...
Skeletal Muscle Relaxants: Adverse Effects01:21

Skeletal Muscle Relaxants: Adverse Effects

Skeletal muscle relaxants are widely used for muscle paralysis and relieving pain following any muscle injury or stiffness. However, depending on the drug type, they can have adverse effects that range from mild to severe. Usually, nondepolarizing neuromuscular blockers have minimal side effects. For example, drugs like d-tubocurarine, cisatracurium, and rocuronium cause hypotension, whereas drugs like baclofen, when stopped abruptly, can lead to the recurrence of spastic conditions.
Unlike...
Muscle Stimulation Frequency01:22

Muscle Stimulation Frequency

The contraction strength of muscles is regulated by motor neurons, which modulate the frequency of action potentials dispatched to the motor units based on the body's requirements. This process of varying the muscle stimulation frequency allows muscles to contract with a force that is precisely tailored to the needs of the moment, whether lifting a feather or a heavy box.
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...

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Updated: May 14, 2026

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation
07:53

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Published on: September 13, 2015

Muscle Stiffness due to Neuromuscular Hyperexcitability.

Bashar Katirji1,2

  • 1Neuromuscular Center & EMG Laboratory, Neurological Institute, University Hospitals, Cleveland Medical Center, Cleveland, Ohio, USA.

Muscle & Nerve
|May 13, 2026
PubMed
Summary

Neuromuscular hyperexcitability disorders cause muscle stiffness and spasms due to nervous system or muscle issues. Early diagnosis and treatment, including immunotherapy for autoimmune causes, are crucial for managing these rare conditions.

Keywords:
hyperexcitabilitymuscle stiffnessmyotoniarippling musclestiff person

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Last Updated: May 14, 2026

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation
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Stimulated Single Fiber Electromyography (SFEMG) for Assessing Neuromuscular Junction Transmission in Rodent Models

Published on: March 8, 2024

Area of Science:

  • Neurology
  • Neuroimmunology
  • Clinical Electrophysiology

Background:

  • Neuromuscular hyperexcitability disorders present with muscle stiffness, spasms, or cramps.
  • These uncommon conditions stem from central or peripheral nervous system dysfunction, with delayed diagnosis being common.
  • Understanding the diverse etiologies is key for effective management.

Purpose of the Study:

  • To review the clinical features, diagnostic methods, and underlying mechanisms of neuromuscular hyperexcitability disorders.
  • To differentiate between central and peripheral nervous system disorders, as well as muscle-specific conditions.
  • To highlight the role of autoantibodies and electrophysiological findings in diagnosis.

Main Methods:

  • Literature review of neuromuscular hyperexcitability disorders.
  • Analysis of diagnostic criteria including autoantibody testing and electromyography (EMG).
  • Categorization based on affected system (central nervous system, peripheral nerve, muscle).

Main Results:

  • Stiff-person syndrome, an immune-mediated central disorder, is associated with glutamic acid decarboxylase antibodies.
  • Peripheral nerve hyperexcitability syndromes (e.g., Isaacs, Morvan) show specific EMG findings and are linked to voltage-gated potassium channel antibodies.
  • Myotonic disorders and rare myopathies like RMD and Brody disease represent distinct muscle-based causes of stiffness.

Conclusions:

  • Neuromuscular hyperexcitability disorders encompass a spectrum of conditions requiring specific diagnostic approaches.
  • Autoimmune mechanisms, particularly involving antibodies against GAD and VGKC-complex proteins, are significant in central and peripheral disorders.
  • Electrophysiological studies (EMG) are essential for diagnosing peripheral nerve and muscle disorders, differentiating them from central causes.