Motor Deficits in Children with Autism and Related Disorders

Joni Daichman, MSPT, Tracy Cueli-Dutil, DPT and Roberto Tuchman, M.D. 

Paper presented at the Geneva Centre Internal Symposium on Autism, Toronto, Canada (October 2002)

There has been an increased interest in the relationship between motor function, cognition, attention, language development and social communication disorders over the last few years.(Gillberg 1998; Landgren, Kjellman et al. 1998; Kadesjo and Gillberg 1999) The purpose of this brief report is to review the sensorimotor system as it applies to autism and related disorders. In addition we will discuss and highlight the motor clinical findings in children with autism and related disorders and provide preliminary data on our own clinical experience. 

The sensorimotor system 

The functional motor system is dependent on an intact sensory system.  Although movement can occur without sensory information, quality of movement requires continuous sensory feedback.  Many children with autism present with over-reactive, under-reactive, or fluctuating reactivity levels to sensory input that significantly impairs their ability to interact with others and with the environment.(O’Neill and Jones 1997)  The senses of vision, hearing, and touch inform us about our surroundings and our own position relative to them.  The proprioceptive and the vestibular systems communicate with the motor systems about the length and tension of muscles, the angles of the joints, and the position of the body in space.  Sensory and motor information are then integrated in order for coordinated movement to occur.  Although children with autism are typically ambulatory and appear to function well within their environment on a gross motor level, the quality of their movement is typically very poor.

Proprioception includes position sense and movement sense and is important for maintaining balance and controlling limb movement.  Proprioceptive information is derived from mechanoreceptors located in joint capsules, muscle spindle receptors, and cutaneous mechanoreceptors.  Its information is relayed to the brain by the dorsal column medial lemniscus tract to the somatic sensory cortex.  It also travels to the cerebellum, various brain stem nuclei, and the motor cortex.  Proprioception is responsible for the body’s knowledge of position in space during static and dynamic activities.  Proprioceptive dysfunction may lead to impaired grading of movement, postural control, motor planning and body awareness.  These are all clinical problems that may be encountered in children with autism and related disorders.

The purpose of the vestibular system is the sense of balance, the coordination of head and body movements, and the ability to maintain eye position while the head moves.  Vestibular information is derived from the movement of hair cells in the inner ear and is relayed to the vestibulocochlear nerve to the vestibular nuclei in the brain stem and to the flocculonodular lobe of the cerebellum.  This system is responsible for antigravity tone, posture and balance.  Vestibular dysfunction may lead to gravitational insecurity, decreased motor planning, decreased bilateral coordination, decreased balance and decreased body awareness. This system has been implicated in many of the sensorimotor problems in autism and related disorders but the research in this area has been controversial and difficult to interpret.

The tactile system informs the brain of crude touch through the anterolateral system and of discriminative touch, such as vibration and two point discrimination, through the dorsal  column medial lemniscus tract. Tactile dysfunction may lead to decreased development of motor control and body awareness secondary to the dysfunctional input and aversion to exploring new tactile experiences. For example, the child with autism or a related disorder may be unsure of where his hands are on the ball in order to initiate, sequence, and execute the movements necessary to place the ball in the basket.

Motor Function: Clinical Findings

Children with autism commonly have difficulty performing motor skills, such as throwing or kicking a ball secondary to decreased balance, bilateral coordination, postural control, gradation of movement, and motor planning. Balance is perceived by the vestibulocochlear system and somatosensory systems, which can be impaired with autism.  Hypotonia affects the ability to perform anti-gravity movements and to establish co-contraction of muscles. A decrease in vestibular output may lead to hypotonia, which makes typical movement patterns more challenging than for children with normal tone. As a result, these children experience decreased pelvic control, hyperextension at the elbows and knees in weightbearing, proximal muscle weakness, fixing patterns and further intake of abnormal sensory information. Avoidance of movements and postures that stress the musculoskeletal system may lead to further weakness in anti-gravity positions.

These factors combined with language disorders and the inability to interpret environmental feedback impact their ability to effectively motor plan activities, both language and motor-based. Therefore, children with oral-motor dyspraxia may also have a likelihood of a motor dyspraxia and should be evaluated for this impairment. The ability to motor plan includes the initiation, timing, sequencing and execution of gross motor tasks. If any of the aforementioned neuroanatomical pathways are disturbed, protective, equilibrium and righting reactions can also be impaired. All of these deficits lead to a decreased ability to safely negotiate and interpret environmental stimuli.

Ghaziuddin and Buttler(Ghaziuddin and Butler 1998) found problems with motor coordination in children with pervasive developmental disorders, with greater coordination difficulties in child with autism as compared to children with pervasive developmental disorder not otherwise specified and Asperger syndrome as measured by the Bruininks-Oseretsky Test of Motor Proficiency. Kohen-Raz , Volkmar & Cohen(Kohen-Raz, Volkmar et al. 1992) studied postural control in children with autism using tetra-ataxiametry which is based on the measurement of changes in vertical force while the subject stands on four footplates with eyes open/closed and standing on/off elastic pads. Results found that children with autism presented with increased stability on more difficult positions, stood with an unusual distribution of weight, and excessively mobilized in the more primary, somatosensory postural control systems when visual cues were fully available. In addition they found that the subjects with autism were about  2-3 standard deviations below normal levels for stability, were a heterogeneous subject pool, and age-related changes were not noted. The postures of the subjects with autism were characterized by a directionally inconsistent and sporadic lateral sway, in contrast to the typical anteroposterior sway. This study suggests that children with autism have a general postural insecurity, which does not appear to improve naturally with age. All of these impairments lead to a decreased ability to safely negotiate obstacles in the environment and decreased age appropriate skills. Without the development of basic gross motor skills, children with autism will have difficulty participating in recreational activities, which further enhance physical activity and social interaction.

Disturbances in the quality of gait have been noted in various studies of children with autism. Typical gait disturbances include toe-walking, ataxia, decreased heel strike and push-off, clumsiness, and upper limb posturing. Ataxic gait may be a result of a cerebellar ataxia or a sensory ataxia caused by under-reactive proprioceptive and vestibular systems. Upper limb posturing, decreased ankle ROM, normal stride time, increased stance time, decreased step length and increased knee flexion in early stance has been found in individuals with autism.(Vilensky, Damasio et al. 1981) Other investigators have indicated that there are minimal statistically significant gait abnormalities, including increased variability, decreased knee flexion in early stance and reduction of dynamic vertical forces in adults with autism.(Hallett, Lebiedowska et al. 1993) This latter group found only minor quantifiable abnormalities in gait, by observation but they reported irregular gait of all participants in their study.

Several studies have investigated toe walking in both typically developing children and children with autism. In a study of the relationship between language and toe-walking (N=799) the frequency of toe-walking increased as the severity of language impairment increased. (Accardo and Whitman 1989) Another study identified children diagnosed with idiopathic toewalking and found no delays in sensory integration function 0/9, moderate negative correlation between age and ankle ROM limitations, delayed gross motor skills in 3/11 children, delays in fine motor skills in 4/12 children, low attention span 4/13 children and language delays 10/10 children.(Shulman, Sala et al. 1997) These studies suggest that children with “idiopathic toewalking” may actually have undiagnosed language difficulties.

Motor findings in children with autism are diverse and in most clinical situations remain under-diagnosed. There is growing evidence that suggests a strong relationship between motor function and cognition, language development and social communication. Future studies on autism and related disorders will need to address these issues both to increase our understanding of this complex relationship and appropriate clinical management. 

References:

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Hallett, M., M.K. Lebiedowska, et al. (1993). “Locomotion of autistic adults.” Arch Neurol 50(12): 1304-8

Kadesjo, B. and C. Gillberg (199). “Developmental coordination disorder in Swedish 7-year old children.” J Am Acad Child Adolesc Psychiatry 38(7): 820-8

Kohen-Raz, R., F. R. Volkmar, et al. (1992). “Postural control in children with autism.” J Autism Dev Disord 22(3): 419-32

Landgren, M.,  B. Kjellman, et al. (1998). “Attention deficit disorder with developmental coordination disorders.” Arch Dis Child 79(3): 207-12.

O’Neill, M. and R. S. Jones (1997). “Sensory-perceptual abnormalities in autism: a case for more research?” J Autism Dev Disord 27(3): 283-93.

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Vilensky, J. A., A. r. Damasio, et al. (1981). “gait disturbances in patients with autistic behavior: a preliminary study.” Arch Neurol 38(10): 646-9