WordNet

convulsion characterized by alternating contractions and relaxations
of or relating to abnormal neuromuscular activity characterized by rapidly alternating muscle contraction and relaxation; "clonic spasm"

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/23 09:38:51」(JST)

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Clonus (from the Greek for "violent, confused motion") is a series of involuntary, rhythmic, muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways, and in many cases is, accompanied by spasticity (another form of hyperexcitability).^[1] Unlike small, spontaneous twitches known as fasciculations (usually caused by lower motor neuron pathology), clonus causes large motions that are usually initiated by a reflex. Studies have shown clonus beat frequency to range from 3–8 Hz on average, and may last a few seconds to several minutes depending on the patient’s condition.^[1]

Signs and symptoms

Clonus is most commonly found at the ankle, specifically with a dorsiflexion/plantarflexion movement (up and down).^[2] Some case studies have also reported clonus in the finger, toe, and laterally in the ankle (as opposed to the typical up and down motion).^[3]^[4]

Ankle (medial gastrocnemius)^[2]
Patella (knee cap)
Triceps surae^[2]^[3]
Biceps brachii^[3]

Cause

Clonus is typically seen in people with stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy.^[2] Clonus has also appeared after ingesting potent serotonergic drugs, where ingestion strongly predicts imminent serotonin toxicity (serotonin syndrome).

Mechanism

Hyperactive stretch reflexes

The self re-excitation of hyperactive stretch reflexes theory involves a repetitive contract-relax cycle in the affected muscle, which creates oscillatory movements in the affected limb.^[1] In order for self re-excitation to exist, both an increase in motor neuron excitability and nerve signal delay are required.^[1] Increased motor neuron excitability is likely accomplished by alterations to the net inhibition of neurons occurring as a result of injury to the CNS (stroke/ spinal cord injury).^[1] This lack of inhibition biases neurons to a net excitatory state, therefore increasing total signal conduction.^[1] Signaling delay is present due to an increased nerve conduction time.^[1] Long delays are primarily due to long reflex pathways, which are common in distal joints and muscles.^[1] This may therefore explain why clonus is typically found in distal structures like the ankle.^[1] Frequency of clonus beats have been found to be directly proportional to the length of the reflex pathway it is found in.^[1]

Central oscillator

Clonus, with respect to the presence of a central oscillator, functions on the theory that when the central oscillator is turned on by a peripheral event, it will continue to rhythmically excite motor neurons; therefore creating clonus.^[1]

Although the two proposed mechanisms are very different in [theory] and are still debated, some studies now propose the potential of both mechanisms co-existing to create clonus.^[1] It is thought that the stretch reflex pathway may be stimulated first, and through its events, cause a decreased synaptic current threshold.^[1] This decreased synaptic current threshold would enhance motor neuron excitability as nerve impulses would be more readily conducted, and thus turn on this central oscillator.^[1] This theory is still being investigated.^[1]

Clonus and spasticity

Clonus tends to co-exist with spasticity in many cases of stroke and spinal cord injury likely due to their common physiological origins.^[1] Some consider clonus as simply an extended outcome of spasticity.^[1] Although closely linked, clonus is not seen in all patients with spasticity.^[1] Clonus tends to not be present with spasticity in patients with significantly increased muscle tone, as the muscles are constantly active and therefore not engaging in the characteristic on/off cycle of clonus.^[1] Clonus results due to an increased motor neuron excitation (decreased action potential threshold) and is common in muscles with long conduction delays, such as the long reflex tracts found in distal muscle groups.^[1] Clonus is commonly seen in the ankle but may exist in other distal structures as well.^[2]

Diagnosis

Clonus at the ankle is tested by rapidly flexing the foot into dorsiflexion (upward), inducing a stretch to the gastrocnemius muscle.^[1] Subsequent beating of the foot will result, however only a sustained clonus (5 beats or more) is considered abnormal. Clonus can also be tested in the knees by rapidly pushing the patella (knee cap), towards the toes.

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u Hilder, Joseph M.; Zev W. Rymer (September 1999). "A Stimulation Study of Reflex Instability in Spasticity: Origins of Clonus". IEEE Transactions on Rehabilitation Engineering 7 (3): 327–340. doi:10.1109/86.788469. Retrieved May 6, 2012.
^ ^a ^b ^c ^d ^e Douglas, Wallace M.; Bruce H Ross; Christine K. Thomas (Aug 25, 2005). "Motor unit behaviour during clonus". Journal of Applied Physiology 99 (6): 2166–2172. doi:10.1152/japplphysiol.00649.2005. PMID 16099891.
^ ^a ^b ^c Weisenburg, Theodore H (November 1903). "Triceps, Biceps and Finger Clonus". Journal of Nervous and Mental Diseases 30 (11): 681–683. doi:10.1097/00005053-190311000-00003. Retrieved May 6, 2012.
^ Mitchell, John K. (May 1902). "Two unusual forms of clonus: toe clonus and lateral ankle clonus". Journal of Nervous and Mental Disease 29 (5): 260–261. doi:10.1097/00005053-190205000-00002. Retrieved May 6, 2012.

External links

Dr. Gilman on Serotonin Toxicity
Video about Clonus at the ankle
Video about Clonus at the knee (patella)

UpToDate Contents

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1. 成人における詳細な神経学的検査 the detailed neurologic examination in adults
2. セロトニン症候群 serotonin syndrome
3. 筋萎縮性側索硬化症およびその他の運動ニューロン疾患の臨床的特徴 clinical features of amyotrophic lateral sclerosis and other forms of motor neuron disease
4. 幼児における非てんかん性発作性障害 nonepileptic paroxysmal disorders in infancy
5. ビタミンB12および葉酸欠乏症の病因および臨床症状 etiology and clinical manifestations of vitamin b12 and folate deficiency

English Journal

Hyperthermia-induced seizures alter adenosine A1 and A2A receptors and 5'-nucleotidase activity in rat cerebral cortex.

León-Navarro DA1, Albasanz JL1, Martín M1.
Journal of neurochemistry.J Neurochem.2015 Aug;134(3):395-404. doi: 10.1111/jnc.13130. Epub 2015 May 13.
Febrile seizure is one of the most common convulsive disorders in children. The neuromodulator adenosine exerts anticonvulsant actions through binding adenosine receptors. Here, the impact of hyperthermia-induced seizures on adenosine A1 and A2A receptors and 5'-nucleotidase activity has been studie
PMID 25907806

Preparation and evaluation of floating tablets of pregabalin.

Kanwar N1, Kumar R, Sarwal A, Sinha VR.
Drug development and industrial pharmacy.Drug Dev Ind Pharm.2015 Jul 6:1-7. [Epub ahead of print]
Floating tablets of pregabalin were prepared using different concentrations of the gums (xanthan gum and guar gum), Carbopol 974P NF and HPMC K100. Optimized formulations were studied for physical tests, floating time, swelling behavior, in vitro release studies and stability studies. In vitro drug
PMID 26146770

Tramadol overdose causes seizures and respiratory depression but serotonin toxicity appears unlikely.

Ryan NM1, Isbister GK.
Clinical toxicology (Philadelphia, Pa.).Clin Toxicol (Phila).2015 Jul;53(6):545-50. doi: 10.3109/15563650.2015.1036279. Epub 2015 Apr 22.
CONTEXT: Tramadol is a commonly used centrally acting analgesic associated with seizures and suspected to cause serotonin toxicity in overdose.OBJECTIVE: This study sought to investigate the effects of tramadol overdose, and included evaluation for serotonin toxicity based on the Hunter Serotonin To
PMID 25901965

Japanese Journal

Leg-Robot for Demonstration of Spastic Movements of Brain-Injured Patients with Compact Magnetorheological Fluid Clutch

KIKUCHI Takehito,ODA Kunihiko,FURUSHO Junji
Advanced robotics : the international journal of the Robotics Society of Japan 24(5), 671-686, 2010-04-01
NAID 10028167399

1A2-F08 神経-筋制御系モデルを導入した足クローヌスの再現と足部痙性シミュレータ(Leg-Robot)による評価実験

菊池武士,小田邦彦,河村圭吾
ロボティクス・メカトロニクス講演会講演概要集 2010, "1A2-F08(1)"-"1A2-F08(4)", 2010-00-00
… In the previous report, we proposed a leg-shaped robot (Leg-Robot) with a Compact MR Fluid Clutch (CMRFC) to establish highly safe human-machine co-existent system, and control methods to realize ankle clonus. … Additionally, we have conducted to introduce a neuromuscular model to control clonus-like movement of the Leg-Robot for education of physiology. … In this paper, we describe a trial of reproduction of the ankle clonus by introducing the neuromuscular model in computer simulation. …
NAID 110008741419

コンパクトMR流体クラッチを用いた足部痙性シミュレータの開発

菊池武士,小田邦彦,山口紗代 [他],古荘純次
日本ロボット学会誌 27(8), 933-941, 2009-10-15
… Finally, experimental results of haptic control for ankle clonus are described. …
NAID 10026089500

Related Pictures

★リンクテーブル★

リンク元	「ミオクローヌス」「間代」「clonic」
拡張検索	「nocturnal myoclonus syndrome」「cortical reflex myoclonus」「essential myoclonus」「familial myoclonus」「spinal myoclonus」