Hypertonia: Difference between revisions

'''Hypertonia''' is a term sometimes used synonymously with '''[[spasticity]]'' and [[Rigidity (neurology)|rigidity]]''rigidity'']] in the literature surrounding damage to the [[central nervous system]], namely [[upper motor neuron lesion]]s.<ref>{{Cite web |url=http://www.ninds.nih.gov/disorders/hypertonia/hmypertonia.htm |title=Archived copyhmypertonia |access-date=2012-12-17 |archive-date=2013-06-18 |archive-url=https://web.archive.org/web/20130618092049/http://www.ninds.nih.gov/disorders/hypertonia/hmypertonia.htm }}{{Full citation needed|date=June 2016}}{{dead link|date=February 2024}}</ref> Impaired ability of damaged [[motor neurons]] to regulate descending pathways gives rise to disordered [[Reflexes|spinal reflexes]], increased excitability of [[muscle spindles]], and decreased [[Synapsis|synaptic]] inhibition.<ref name="O'Sullivan 2007 234">{{cite book|last=O'Sullivan|first=Susan|title=Physical Rehabilitation|url=https://archive.org/details/physicalrehabili00osul|url-access=limited|date=2007|publisher=F.A Davis Company|location=Philadelphia, Pennsylvania |page=[https://archive.org/details/physicalrehabili00osul/page/n240 234]|isbn=9780803612471 }}</ref> These consequences result in abnormally increased [[muscle tone]] of symptomatic muscles.<ref name=pmid19769916>{{cite journal |last1=Sheean |first1=Geoffrey |last2=McGuire |first2=John R. |title=Spastic Hypertonia and Movement Disorders: Pathophysiology, Clinical Presentation, and Quantification |journal=PM&R |volume=1 |issue=9 |pages=827–33 |date=2009 |pmid=19769916 |doi=10.1016/j.pmrj.2009.08.002 |s2cid=30715890 }}</ref> Some authors suggest that the current definition for spasticity, the velocity-dependent over-activity of the [[stretch reflex]], is not sufficient as it fails to take into account patients exhibiting increased muscle tone in the absence of stretch reflex over-activity. They instead suggest that "'''reversible hypertonia'''" is more appropriate and represents a treatable condition that is responsive to various therapy modalities like drug or physical therapy.<ref>{{cite journal |last1=Bakheit |first1=A.M. |last2=Fheodoroff |first2=K. |last3=Molteni |first3=F. |title=Spasticity or Reversible Muscle Hypertonia? |journal=Journal of Rehabilitation Medicine |volume=43 |issue=6 |pages=556–7 |date=2011 |pmid=21491075 |doi=10.2340/16501977-0817 |doi-access=free }}</ref>

Symptoms associated with central nervous systems disorders are classified into positive and negative categories. Positive symptoms include those that increase muscle activity through hyper-excitability of the stretch reflex (i.e., rigidity and spasticity) where negative symptoms include those of insufficient muscle activity (i.e. [[muscle weakness|weakness]]) and reduced motor function.<ref>{{cite journal |last1=Sanger |first1=T. D. |last2=Chen |first2=D. |last3=Delgado |first3=M. R. |last4=Gaebler-Spira |first4=D. |last5=Hallett |first5=M. |last6=Mink |first6=J. W. |s2cid=1974796 |title=Definition and Classification of Negative Motor Signs in Childhood |journal=Pediatrics |volume=118 |issue=5 |pages=2159–67 |year=2006 |pmid=17079590 |doi=10.1542/peds.2005-3016 }}</ref> Often the two classifications are thought to be separate entities of a disorder; however, some authors propose that they may be closely related.<ref>{{cite journal|last1=Damiano|first1=Diane L|author-link=Diane Damiano|last2=Dodd|first2=Karen|year=2002|title=Should we be testing and training muscle strength in cerebral palsy?|journal=Developmental Medicine & Child Neurology|volume=44|issue=1|pages=68–72|doi=10.1111/j.1469-8749.2002.tb00262.x|pmid=11811654|doi-access=free}}</ref>

Spastic hypertonia involves uncontrollable [[muscle spasms]], stiffening or straightening out of muscles, shock-like contractions of all or part of a group of muscles, and abnormal [[muscle tone]]. It is seen in disorders such as [[cerebral palsy]], [[stroke]], and [[spinal cord injury]]. Rigidity is a severe state of hypertonia where muscle resistance occurs throughout the entire range of motion of the affected joint independent of velocity. It is frequently associated with lesions of the [[basal ganglia]]. Individuals with rigidity present with stiffness, decreased range of motion and loss of motor control. Rigidity is a nonselective increase in the tone of agonist and antagonist without velocity dependence, and the increased tone remains uniform throughout the range of movement. On the contrary, spasticity is a velocity-dependent increase in tone resulting from the hyper excitability of stretch reflexes.<ref>{{Citation |last=Rushton |first=David N. |title=Intrathecal baclofen for the control of spinal and supraspinal spasticity |date=2008-04-24 |url=http://dx.doi.org/10.1017/cbo9780511544866.011 |work=Upper Motor Neurone Syndrome and Spasticity |pages=181–192 |access-date=2023-07-31 |publisher=Cambridge University Press|doi=10.1017/cbo9780511544866.011 |isbn=9780521689786 }}</ref> It primarily involves the antigravity muscles – flexors of the upper limb and extensors of the lower limb. During the passive stretch, a brief “free interval” is appreciated in spasticity but not in rigidity because the resting muscle is electromyographically silent in spasticity. In contrast, in rigidity, the resting muscle shows firing.<ref>{{Cite journal |last1=Ramanathan |first1=Venkateswaran |last2=Baskar |first2=Dipti |last3=Pari |first3=Hariswar |date=2022 |title='Seatbelt Effect' of spasticity: Contrasting velocity dependence from the clasp knife phenomenon |url=http://www.annalsofian.org/text.asp?2022/25/3/517/338853 |journal=Annals of Indian Academy of Neurology |language=en |volume=25 |issue=3 |pages=517–519 |doi=10.4103/aian.aian_817_21 |pmid=35936584 |issn=0972-2327|pmc=9350785 |doi-access=free }}</ref> [[Dystonia|Dystonic]] hypertonia refers to muscle resistance to passive stretching (in which a therapist gently stretches the inactive contracted muscle to a comfortable length at very low speeds of movement) and a tendency of a limb to return to a fixed involuntary (and sometimes abnormal) posture following movement.{{citation needed|date=June 2016}}

Icing and other [[topical anesthetic]]s may decrease the reflexive activity for short period of time in order to facilitate motor function. Inhibitory pressure (applying firm pressure over muscle tendon) and promoting body heat retention and rhythmic rotation (slow repeated rotation of affected body part to stimulate relaxation)<ref name=text497>{{cite book |last1=O'Sullivan |first1=Susan |year=2007 |title=Physical Rehabilitation |url=https://archive.org/details/physicalrehabili00osul |url-access=limited |location=Philadelphia, PA |publisher=F.A Davis Company |page=[https://archive.org/details/physicalrehabili00osul/page/n507 497] |isbn=9780803612471 }}</ref> have also been proposed as potential methods to decrease hypertonia. Aside from static stretch casting, splinting techniques are extremely valuable to extend joint range of motion lost to hypertonicity.<ref name="Katz, R. 1988">{{cite journal |last1=Katz |first1=Richard T. |title=Management of spasticity |journal=American Journal of Physical Medicine & Rehabilitation |volume=67 |issue=3 |pages=108–16 |year=1988 |pmid=3288246 |doi=10.1097/00002060-198806000-00004|s2cid=45292155 }}</ref> A more unconventional method for limiting tone is to deploy quick repeated passive movements to an involved joint in cyclical fashion; this has also been demonstrated to show results on persons without physical disabilities.<ref name=chang/> For a more permanent state of improvement, exercise and patient education is imperative.<ref name=text497/> [[Isokinetic]],<ref>{{cite journal |last1=Giuliani |first1=Carol A. |year=1997 |title=The Relationship of Spasticity to Movement and Considerations for Therapeutic Interventions |journal=Neurology Report |volume=21 |issue=3 |pages=78–84 |doi=10.1097/01253086-199721030-00009|doi-access=free }}</ref><ref>{{cite journal |last1=Light |first1=K E |last2=Giuliani |first2=C A |year=1992 |title=Effect of Isokinetic Exercise Effort on the Arm Coordination of Spastic Hemiparetic Subjects |journal=Neurology Report |volume=16 |issue=4 |pages=19 |doi=10.1097/01253086-199216040-00016|doi-access=free }}</ref><ref>{{cite journal |last1=Giuliani |first1=C A |last2=Light |first2=K E |last3=Rose |first3=D K. |year=1993 |title=The Effect of an Isokinetic Exercise Program on Gait Patterns in Patients with Hemiparesis |journal=Neurology Report |volume=17 |issue=4 |pages=23–4 |doi=10.1097/01253086-199317040-00029|doi-access=free }}</ref><ref>{{cite journal |last1=Brown |first1=D. A. |last2=Kautz |first2=S. A. |title=Increased Workload Enhances Force Output During Pedaling Exercise in Persons With Poststroke Hemiplegia |journal=Stroke |volume=29 |issue=3 |pages=598–606 |year=1998 |pmid=9506599 |doi=10.1161/01.STR.29.3.598 |citeseerx=10.1.1.568.9281 }}</ref> [[Aerobic exercise|aerobic]],<ref>{{cite journal |last1=Hunter |first1=Marque |last2=Tomberlin |first2=JoAnn |last3=Kirkikis |first3=Carol |last4=Kuna |first4=Samuel T |title=Progressive exercise testing in closed head-injured subjects: comparison of exercise apparatus in assessment of a physical conditioning program |journal=Physical Therapy |volume=70 |issue=6 |pages=363–71 |year=1990 |pmid=2345780 |doi=10.1093/ptj/70.6.363 }}</ref><ref>{{cite journal |last1=Jankowski |first1=LW |last2=Sullivan |first2=SJ |title=Aerobic and neuromuscular training: effect on the capacity, efficiency, and fatigability of patients with traumatic brain injuries |journal=Archives of Physical Medicine and Rehabilitation |volume=71 |issue=7 |pages=500–4 |year=1990 |pmid=2350220 }}</ref><ref>{{cite journal |last1=Potempa |first1=K. |last2=Lopez |first2=M. |last3=Braun |first3=L. T. |last4=Szidon |first4=J. P. |last5=Fogg |first5=L. |last6=Tincknell |first6=T. |title=Physiological Outcomes of Aerobic Exercise Training in Hemiparetic Stroke Patients |journal=Stroke |volume=26 |issue=1 |pages=101–5 |year=1995 |pmid=7839377 |doi=10.1161/01.STR.26.1.101 }}</ref> and [[strength training]]<ref>{{cite journal |last1=Damiano |first1=Diane L. |last2=Abel |first2=Mark F. |title=Functional outcomes of strength training in spastic cerebral palsy |journal=Archives of Physical Medicine and Rehabilitation |volume=79 |issue=2 |pages=119–25 |year=1998 |pmid=9473991 |doi=10.1016/S0003-9993(98)90287-8 }}</ref><ref>{{cite journal |last1=Damiano |first1=Diane L. |last2=Vaughan |first2=Christopher L. |last3=Abel |first3=Mark E. |title=Muscle response to heavy resistance exercise in children with spastic cerebral palsy |journal=Developmental Medicine and Child Neurology |volume=37 |issue=8 |pages=731–9 |year=1995 |pmid=7672470 |doi=10.1111/j.1469-8749.1995.tb15019.x |s2cid=33519087 |doi-access=free }}</ref><ref>{{cite journal |last1=Miller |first1=G T |last2=Light |first2=K E |last3=Kellog |first3=R. |year=1996 |title=Comparison of Isometric-Force Control Measures in Spastic Muscle of Poststroke Individuals Before and After Graded Resistive Exercise |journal=Neurology Report |volume=20 |issue=2 |pages=92–3 |doi=10.1097/01253086-199620020-00041|doi-access=free }}</ref><ref>{{cite journal |last1=Hall |first1=C |last2=Light |first2=K |title=Heavy restrictive exercise effect on reciprocal movement coordination of closed-head injured subjects with spasticity |journal=Neurology Report |volume=14 |pages=19 |year=1990 }}</ref> exercises should be performed as prescribed by a physiotherapist, and stressful situations that may cause increased tone should be minimized or avoided.<ref name=text497/>