Muscle Cramps and Contractures

Muscle cramps are painful, sudden, involuntary muscle contractions that are typically self-limiting. They are typically part of normal human physiology but can be associated with a wide range of acquired and inherited causes. They are infrequently due to progressive systemic or neuromuscular diseases. Contractures are defined as muscle shortening resulting in an inability of the muscle to relax normally and are generally myogenic in origin. See also Leg Cramps.
Muscle cramps are thought to arise from spontaneous ectopic discharges of motor nerves or the terminal branches of motor axons. Their precise pathophysiology remains unknown. A muscle contracture, on the other hand, is the shortening of the muscle resulting in an inability of the muscle to relax, and usually has a myogenic cause.
== Clinical Features ==
Clinical features of muscle cramp and its mimics. Modified from Dijkstra et al
Phenomenon 	Definition/Description 	Occurrence/Examples 	EMG 	History/Symptoms
Muscle cramp 	Involuntary, painful shortening of a muscle due to a non-physiological supramaximal muscle contraction 	Exercise-induced, idiopathic (often nocturnal), or secondary to an underlying condition or exogenous trigger	Continuous motor unit action potential activity; activity increases in antagonist muscle when patient moves agonist muscle	Tightened muscle; very painful; stretching provides relief
Contracture 	Muscle shortening resulting in an inability to relax normally 	Metabolic myopathies (e.g., McArdle), Brody's disease, hypothyroidism, rippling disease (myoedema mounding) 	Electrically silent; insufficient ATP to break actin-myosin bonds 	Exertional muscle stiffness or cramping; stretching doesn't provide relief; longer duration than muscle cramp
Dystonia 	Simultaneous contraction of agonist and antagonist muscles, causing altered joint position and often repetitive movements and postures 	Cervical dystonia, blepharospasm, writer's cramp, hand or foot dystonia 	Continuous motor unit action potential activity; activity increases in antagonist muscle when patient moves agonist muscle	Pain and rigidity from muscle contractions
Myotonia 	Delayed muscle relaxation after voluntary contraction or sensory stimulation 	Myotonic dystrophy, non-dystrophic myotonias 	Abnormal spontaneous repetitive muscle fibre discharge with waxing and waning of frequency and amplitude 	Muscle stiffness, discomfort, or "stuck" sensation; warm-up phenomenon with repeated movement
Myokymia 	Continuous involuntary rippling movements of the muscle 	Healthy individuals (eyelid myokymia), episodic ataxia type I, neuromyotonia, Morvan syndrome 	Abnormal spontaneous repetitive muscle fibre discharge with waxing and waning of frequency and amplitude 	Wave-like or worm-like rippling; palpable
Restless legs syndrome 	Unpleasant leg sensations with urge to move; resolved by leg movement 	Most frequent during evening and night 	- 	Difficulty distinguishing from muscle cramps; very unpleasant urge to move; no muscle stiffness
Periodic limb movement disorder	Repetitive limb movements (every 20-40 s) during sleep 	Occurs only during sleep 	- 	Unaware of movements; daytime somnolence, poor sleep, or waking multiple times at night
Spasticity 	Increased muscle tone affecting different muscle groups to varying extents; resistance most prominent at start of passive movement, lessens as movement proceeds	Upper motor neurone lesions (e.g., stroke, motor neurone disease) 	- 	Mild stiffness to painful, uncontrollable spasms
Stiff person syndrome 	Stiffness in axial and limb muscles with periods of muscle contractions, precipitated by sudden movements, noise, or emotions; often with anti-GAD antibodies 	Associated with diabetes mellitus type 1, paraneoplastic syndromes, and other autoimmune diseases 	Continuous motor unit action potential activity; ameliorated by intravenous benzodiazepine, sleep, and anesthesia 	Stiffness, muscle pain, and muscle cramps, often starting in the lumbar region
== Resources ==
== References ==
Category:Muscle Disorders