Editing Ataxia (section)

=== Cerebellar ===
{{See also|Cerebellar ataxia}}
The term [[cerebellar ataxia]] is used to indicate ataxia due to dysfunction of the cerebellum.<ref>{{cite web | title = Ataxia - Symptoms & Causes | publisher = Mayo Clinic | date = 3 June 2020 | url = https://www.mayoclinic.org/diseases-conditions/ataxia/symptoms-causes/syc-20355652 | access-date = 10 August 2020}}</ref> The cerebellum is responsible for integrating a significant amount of neural information that is used to coordinate smoothly ongoing movements and to participate in [[motor planning]]. Although ataxia is not present with all cerebellar [[lesion]]s, many conditions affecting the cerebellum do produce ataxia.<ref name="Schmahmann">{{cite journal | vauthors = Schmahmann JD | title = Disorders of the cerebellum: ataxia, dysmetria of thought, and the cerebellar cognitive affective syndrome | journal = The Journal of Neuropsychiatry and Clinical Neurosciences | volume = 16 | issue = 3 | pages = 367–378 | year = 2004 | pmid = 15377747 | doi = 10.1176/jnp.16.3.367 | doi-access =  }}</ref> People with cerebellar ataxia may have trouble regulating the force, range, direction, velocity, and rhythm of muscle contractions.<ref name="isbn0-8036-0093-3">{{cite book | vauthors = Fredericks CM | chapter = Disorders of the Cerebellum and Its Connections | veditors = Saladin LK, Fredericks CM | title = Pathophysiology of the motor systems: principles and clinical presentations | publisher = F.A. Davis | location = Philadelphia | year = 1996 | isbn = 0-8036-0093-3 | chapter-url = http://www.hy-q.com/cooper/pdf/NCS%20Exam/208%20Disorders%20of%20the%20Cerebellum%20and%20its%20Connections.pdf | access-date = 6 May 2012 | url-access = registration | url = https://archive.org/details/pathophysiologyo0000unse_a1k6 }}</ref> This results in a characteristic type of irregular, uncoordinated movement that can manifest itself in many possible ways, such as [[asthenia]], [[asynergy]], delayed reaction time, and [[dyschronometria]].<ref>{{cite journal | vauthors = Tada M, Nishizawa M, Onodera O | title = Redefining cerebellar ataxia in degenerative ataxias: lessons from recent research on cerebellar systems | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 86 | issue = 8 | pages = 922–928 | date = August 2015 | pmid = 25637456 | doi = 10.1136/jnnp-2013-307225 | s2cid = 20887739 }}</ref> Individuals with cerebellar ataxia could also display instability of gait, difficulty with eye movements, [[dysarthria]], [[dysphagia]], [[hypotonia]], [[dysmetria]], and [[dysdiadochokinesia]].<ref name="Schmahmann" /> These deficits can vary depending on which cerebellar structures have been damaged, and whether the lesion is bi- or unilateral.{{citation needed|date=August 2021}}

People with cerebellar ataxia may initially present with poor balance, which could be demonstrated as an inability to stand on one leg or perform [[tandem gait]]. As the condition progresses, walking is characterized by a widened base and high stepping, as well as staggering and lurching from side to side.<ref name ="Schmahmann" /> Turning is also problematic and could result in falls. As cerebellar ataxia becomes severe, great assistance and effort are needed to stand and walk.<ref name ="Schmahmann" /> [[Dysarthria]], an impairment with articulation, may also be present and is characterized by "scanning" speech that consists of slower rate, irregular rhythm, and variable volume.<ref name ="Schmahmann" /> Also, slurring of speech, tremor of the voice, and [[ataxic respiration]] may occur. Cerebellar ataxia could result with incoordination of movement, particularly in the extremities. Overshooting (or hypermetria) occurs with finger-to-nose testing and heel to shin testing; thus, [[dysmetria]] is evident.<ref name ="Schmahmann" /><ref>{{cite journal | vauthors = Manto M, Godaux E, Jacquy J | title = Cerebellar hypermetria is larger when the inertial load is artificially increased | journal = Annals of Neurology | volume = 35 | issue = 1 | pages = 45–52 | date = January 1994 | pmid = 8285591 | doi = 10.1002/ana.410350108 | s2cid = 19328973 }}</ref> Impairments with alternating movements (dysdiadochokinesia), as well as [[Cardiac dysrhythmia|dysrhythmia]], may also be displayed. Tremor of the head and trunk ([[titubation]]) may be seen in individuals with cerebellar ataxia.<ref name ="Schmahmann" />

Dysmetria is thought to be caused by a deficit in the control of interaction [[torque]]s in multijoint motion.<ref name="pmid10805697">{{cite journal | vauthors = Bastian AJ, Zackowski KM, Thach WT | title = Cerebellar ataxia: torque deficiency or torque mismatch between joints? | journal = Journal of Neurophysiology | volume = 83 | issue = 5 | pages = 3019–3030 | date = May 2000 | pmid = 10805697 | doi = 10.1152/jn.2000.83.5.3019 | s2cid = 10244619 }}</ref> Interaction torques are created at an associated joint when the primary joint is moved. For example, if a movement required reaching to touch a target in front of the body, [[flexion]] at the [[shoulder]] would create a torque at the [[elbow]], while [[extension (kinesiology)|extension]] of the elbow would create a torque at the [[wrist]]. These torques increase as the speed of movement increases and must be compensated and adjusted for to create coordinated movement. This may, therefore, explain decreased coordination at higher movement velocities and accelerations.
* [[Vestibulocerebellar syndrome|Dysfunction of the vestibulocerebellum]] ([[flocculonodular lobe]]) impairs balance and the control of eye movements. This presents itself with [[postural instability]], in which the person tends to separate his/her feet upon standing, to gain a wider base and to avoid titubation (bodily oscillations tending to be forward-backward ones). The instability is, therefore, worsened when standing with the feet together, regardless of whether the eyes are open or closed. This is a negative [[Romberg's test]], or more accurately, it denotes the individual's inability to carry out the test, because the individual feels unstable even with open eyes. {{Citation needed|date=May 2012}}
* Dysfunction of the [[Anatomy of the cerebellum#Phylogenetic and functional divisions|spinocerebellum]] ([[vermis]] and associated areas near the midline) presents itself with a wide-based "drunken sailor" [[gait]] (called truncal ataxia),<ref name="Blumenfeld">{{cite book | vauthors = Blumenfeld H | title = Neuroanatomy through clinical cases | url = https://archive.org/details/neuroanatomythro00blum | url-access = limited | publisher = Sinauer | location = Sunderland, Mass | year = 2002 | pages = [https://archive.org/details/neuroanatomythro00blum/page/n342 670]–671 | isbn = 0-87893-060-4 }}</ref> characterised by uncertain starts and stops, lateral deviations, and unequal steps. As a result of this gait impairment, [[falling (accident)|falling]] is a concern in patients with ataxia. Studies examining falls in this population show that 74–93% of patients have fallen at least once in the past year and up to 60% admit to fear of falling.<ref name="pmid20157791">{{cite journal | vauthors = Fonteyn EM, Schmitz-Hübsch T, Verstappen CC, Baliko L, Bloem BR, Boesch S, Bunn L, Charles P, Dürr A, Filla A, Giunti P, Globas C, Klockgether T, Melegh B, Pandolfo M, De Rosa A, Schöls L, Timmann D, Munneke M, Kremer BP, van de Warrenburg BP | title = Falls in spinocerebellar ataxias: Results of the EuroSCA Fall Study | journal = Cerebellum | volume = 9 | issue = 2 | pages = 232–239 | date = June 2010 | pmid = 20157791 | doi = 10.1007/s12311-010-0155-z | s2cid = 23247877 }}</ref><ref name="pmid15645525">{{cite journal | vauthors = van de Warrenburg BP, Steijns JA, Munneke M, Kremer BP, Bloem BR | title = Falls in degenerative cerebellar ataxias | journal = Movement Disorders | volume = 20 | issue = 4 | pages = 497–500 | date = April 2005 | pmid = 15645525 | doi = 10.1002/mds.20375 | s2cid = 35160189 }}</ref>
* Dysfunction of the [[Anatomy of the cerebellum#Phylogenetic and functional divisions|cerebrocerebellum]] (lateral hemispheres) presents as disturbances in carrying out voluntary, planned movements by the extremities (called appendicular ataxia).<ref name="Blumenfeld" /> These include:
** [[Intention tremor]] (coarse trembling, accentuated over the execution of voluntary movements, possibly involving the head and eyes, as well as the limbs and torso)
** Peculiar writing abnormalities (large, unequal letters, irregular underlining)
** A peculiar pattern of [[dysarthria]] (slurred speech, sometimes characterised by explosive variations in voice intensity despite a regular rhythm)
** Inability to perform rapidly alternating movements, known as dysdiadochokinesia, occurs, and could involve rapidly switching from [[pronation]] to [[supination]] of the forearm. Movements become more irregular with increases of speed.<ref name="Schmitz">{{cite book | chapter = Examination of Coordination |vauthors=Schmitz TJ, O'Sullivan SB | title = Physical rehabilitation | url = https://archive.org/details/physicalrehabili00osul | url-access = limited | publisher = F.A. Davis | location = Philadelphia | year = 2007 | pages = [https://archive.org/details/physicalrehabili00osul/page/n199 193]–225 | isbn = 978-0-8036-1247-1  }}</ref>
** Inability to judge distances or ranges of movement happens. This dysmetria is often seen as undershooting, [[hypometria]], or overshooting, [[hypermetria]], the required distance or range to reach a target. This is sometimes seen when a patient is asked to reach out and touch someone's finger or touch his or her own nose.<ref name="Schmitz" />
** The rebound phenomenon, also known as the loss of the check reflex, is also sometimes seen in patients with cerebellar ataxia, for example, when patients are flexing their elbows isometrically against a resistance. When the resistance is suddenly removed without warning, the patients' arms may swing up and even strike themselves. With an intact check reflex, the patients check and activate the opposing triceps to slow and stop the movement.<ref name="Schmitz" />
** Patients may exhibit a constellation of subtle to overt cognitive symptoms, which are gathered under the terminology of [[Cerebellar cognitive affective syndrome|Schmahmann's syndrome]].<ref>{{cite journal | vauthors = Manto M, Mariën P | title = Schmahmann's syndrome - identification of the third cornerstone of clinical ataxiology | journal = Cerebellum & Ataxias | volume = 2 | pages = 2 | date = 2015 | pmid = 26331045 | pmc = 4552302 | doi = 10.1186/s40673-015-0023-1 | doi-access = free }}</ref>