Movement disorders among individuals with an Autism Spectrum Disorder (ASD) have been gaining greater attention over recent years. Historically, movement disorders have been considered from two diagnostic perspectives. Primarily, forms of unusual movement have been characterized as one of the fundamental characteristics of ASD as a “narrow range of actions or interests” [Diagnostic and Statistical Manual of the American Psychiatric Association, 4th Edition—Revised, (DSM-4-R, 2000
)]. Secondarily, “odd” movements have been described as an “associated feature” of ASD or in more extreme presentations a diagnosis of catatonia has been rendered (Wing and Shah, 2000
). In either instance, little has been understood or studied in relation to why
individuals diagnosed with ASD present with a wide array of differences in their movement and what relation these movement patterns may have to understanding the underlying etiology of the disorders.
The presentation of aberrant movements in ASD has been apparent from the first inception of the diagnosis (Kanner, 1943
). Movement disorders have included a wide range of differences such as greater clumsiness, motor coordination abnormalities, postural control impairments and instability, hypotonia, muscle rigidity, akinesia, and bradykinesia, and more (Damasio and Maurer, 1978
; Jones and Prior, 1985
; Bauman, 1992
; Kohen-Raz et al., 1992
; Leary and Hill, 1996
; Rogers et al., 1996
; Rapin, 1997
; Ghaziuddin and Butler, 1998
; Molloy et al., 2003
; Minshew et al., 2004
; Donnellan et al., 2006
). However, there is a growing number of researchers who have characterized disorders of movement as fundamental aspects of ASD (Leary and Hill, 1996
; Donnellan et al., 2010
; Fournier et al., 2010
). This is a non-trivial distinction implying that differences in movement may offer clues to the underlying etiology of ASD, rather than simply being “associated” with the diagnosis.
The study of gait has been one domain of movement that has drawn interest for a number of years in this population. However, the relatively small numbers of empirical studies of gait that have been reported have varied in the methodologies and technologies used, participant ages, sample sizes, and ASD subtypes that have been studied (Vilensky et al., 1981
; Hallett et al., 1993
; Vernazza-Martin et al., 2005
; Rinehart et al., 2006a
; Calhoun et al., 2011
; Esposito et al., 2011
). Hence, it is not surprising that these reports have offered mixed findings in the extent and types of movement differences that have been found across these different individuals.
In considering some of the differing accounts of gait in this population, we are struck by two trends. First, every group of individuals diagnosed with an ASD who have participated in studies of gait show some form of movement differences as compared to typically developing control participants. This is consistent with Leary and Hill's (1996
); Fournier et al.'s (2010
) and Donnellan et al.'s (2010
) similar conclusions that movement differences are pervasive among the entire population and as such should be thought of as a core deficit or difference in ASD.
Second, preliminary considerations indicate possible trends regarding the types of differences found in gait patterns correlating with the type of ASD that participants present with. Fournier et al. (2010
) concluded that the pervasive differences in motor functions are not related to intelligence, to which we agree. However, there may be a correlation between the extent or type of differences found in gait as a function of the form or severity of the ASD diagnosis. By “severity” we are referring to the extent of difficulties in the so called “core deficits” of Autism—disorders or differences in communication, social interactions and range of actions and interests. Bear in mind that cognitive status has never been considered a “core deficit,” though ability to perform on any standardized cognitive test will co-vary with communication, social interaction and range of action skills (Zelazo et al., 1989
; Zelazo and Weiss, 1990
). Hence, we should be considering relations between the criteria of ASD such as the type of communication disorders a person presents with and movement patterns, rather than cognition, per se
The few studies of gait that have been reported to date raise a question of whether a relation exists between types of movement differences shown by differing sub-groups of individuals on the Autism Spectrum and the extent of communication impairments. Vilensky et al. (1981
) reported significant differences in a number of spatial and temporal parameters of gait between ASD and control participants. ASD participants in this study were described as having profound disorders of communication and social relatedness. Alternatively, Vernazza-Martin et al. (2005
), whose participants' also presented with significant communication differences, found only relatively minor differences in spatiotemporal parameters of gait, per se
. However, they found significant and meaningful variations or “oscillations” of the head, shoulders and trunk causing less stability and greater variability in posture as they walked. A series of other studies of individuals diagnosed with “High Functioning” Autism and/or Asperger Syndrome reported only minor variations in spatiotemporal parameters of gait, but reported significant variations in coordination, smoothness, consistency, and posture of the arms, head and trunk (Rinehart et al., 2006a
), other parameters of posture and hypotonia associated with gait (Calhoun et al., 2011
), or a generalized “clumsiness” among ASD participants as they walked (Hallett et al., 1993
It is indeed likely that we will learn much from differentiating the gait patterns associated with differences among subtypes of ASD. Hence, it would be useful to segregate more precise descriptors of participants in the study of movement differences in those aspects of development associated with the diagnosis, such as specific descriptors of their social and language skills, or the types of narrow or repetitive range of actions and interests that these individuals show. Terms such as “high functioning” are routinely used in reference to cognitive status, which does not characterize the ASD diagnosis, per se. Similarly, the inclusion of an array of participants who share an ASD diagnosis, but have widely varied measures of communication, social or intellectual functions, needs to be differentiated if we are to tease out precise correlations with movement functions.
It is parenthetically interesting that Kern et al. (2010
) demonstrated that the degree of “severity” in the ASD diagnosis has been shown to correlate with muscle strength. Similarly, Travers et al. (2012
) found a correlation between ASD symptom severity and postural stability. These reports, coupled with the variations in reports of gait described above, indicate a need to differentiate the movement patterns of individuals who differ in their specific forms of ASD. Clearly, there is a need to unpack both the different aspects of movement that can be characterized, as well as clarifying the developmental presentations across the range of individuals who have an ASD diagnosis.
The intention of our current study was to evaluate gait patterns among a group of individuals diagnosed with ASD using narrowly defined a priori selection criteria of “severe” presentations of ASD in general and severe impairments in Verbal Communication specifically, among a group of older teenagers and young adults. We singled out the criteria of severe Verbal Communication impairments precisely because it is fundamental to the ASD diagnosis and because we wanted to look at the most extreme form of that criterion. We hypothesized that individuals with severe forms of Verbal Communication disorders would show widespread quantitative and qualitative aberrations in gait and other movement patterns reflected in CARS “body use” ratings, as compared to control participants of similar age- and gender.