![]() ![]() These “release signs” were described by Hughlings Jackson in 1931 as “positive signs” ( Jackson et al., 1931), and have been suggested to be enhanced reflexes released by pyramidal lesions ( Landau and Clare, 1959). Hyperreflexia and hypertonia are the classic upper motor neuron (UMN) signs thought to occur from the loss of corticospinal motor tract suppression of the spinal reflex arc. Further, the proposed connectivity can be generalized to help explain other insults including stroke, atonic seizures, and spinal shock. Unlike traditional explanations, this theory more adequately explains the findings of postoperative supplementary motor area syndrome in which hyporeflexia motor deficit is observed acutely in the face of intact primary motor cortex connections to the spinal cord. Further, evidence for the underlying connectivity is presented and implicates the dominant role of supraspinal inhibitory influence originating in the supplementary motor area descending through the corticospinal tracts. This article highlights the common observation of acute hyporeflexia after central nervous system insults and explores the underlying anatomy and physiology. Unfortunately, these simple descriptions consistently fail to adequately explain the pathophysiology and connectivity leading to acute hyporeflexia and delayed hyperreflexia that result from such insult. Historic theories to explain these contradictory findings have implicated a number of potential mechanisms mostly relying on the loss of descending corticospinal input as the underlying etiology. ![]() However, acute hypotonia and areflexia with motor deficit are hallmark findings after many central nervous system insults such as acute stroke and spinal shock. Hypertonia and hyperreflexia are classically described responses to upper motor neuron injury. 3Division of Neurosurgery, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada.2Department of Neurosurgery, Gui de Chauliac Hospital, Montpellier University Medical Center, Montpellier, France.1Neurosciences Institute, Maine Medical Center, Portland, ME, USA.A unanimous understanding of the term hypotonia would favor further research.Ĭhildren Down syndrome Floppy muscle Hypotonia Muscle tone Quantitative evaluation.Ĭopyright © 2022 The Author(s). The most used test in the diagnosis of hypotonia is observation, followed by the pull-to-sit test, and adoption of frog posture. The characteristics associated with hypotonia, more highly debated by authors are muscle strength, hypermobility, or the maintenance of antigravity postures. ![]() Fifty-three characteristics associated with hypotonia and tests used for its evaluation were located, with pull to sit and vertical suspension being the most frequently referenced. The quality of the studies was also assessed, and data were extracted.Ī total of 8778 studies were identified and analyzed, of which 45 met the inclusion criteria. Two reviewers evaluated the articles and collected the data in a table, noting the authors, date of publication, type of study, and characteristics or tests described in relation to hypotonia. Those describing characteristics or tests of hypotonia assessment were included, excluding those that exclusively addressed peripheral hypotonia. A search of databases (Pubmed, Cochrane, Web of Knowledge, among others) was performed in May 2021 to identify relevant studies. Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used to develop the systematic review protocol. It is necessary to perform a systematic review to know which characteristics are described as associated with hypotonia in children and which methods are used for its diagnosis. Hypotonia is considered a determinant factor in multiple developmental disorders and is associated with various characteristics and morbidities. ![]()
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