It is important to understand the developmental trajectories in children with ASD specifically in the following two domains; social communication domain and restricted and repetitive patterns of behaviors and interest domain may vary over time. This will help in understanding the clinical presentation of CP + ASD profile in early childhood as compared to the ASD only profile.

In children at risk for ASD, four developmental trajectories have been described. Firstly the “non-spectrum profile” which consists of children with an identifiable delay in development at 18 months of age who do not meet criteria for ASD by 36 months of age. Secondly, the “severe persistent profile” which consists of children with clear deficits in social affect and repetitive behaviors, which persists over time. Thirdly, “the worsening profile” which consists of children with increasing repetitive behaviors and social affect deficits over time. The fourth group are children who show clear improvement in social affect and significant improvement in verbal skills; “the improving profile” (Lord, Luyster, Guthrie, & Pickles, 2012). Evaluating the developmental trajectories of RRB and interests has also been explored. Using the Autism Diagnostic Interview-Revised (ADI-R), in children diagnosed with ASD their RSM scores remained high over time (2 years through to 9 years of age) indicating consistent severity. Whereas the IS scores started low and increased over time, indicating gradual worsening of these behaviors. A higher nonverbal IQ at age 2 years is associated with milder RSM (Richler et al., 2010). The variability in presentation of ASD in early childhood justifies and mandates close monitoring and repeated assessment to determine the stability of the diagnosis when given in the first 2 years of life.

CP is usually diagnosed within the first 2–3 years of life. Motor challenges are usually the initial presenting challenge; however, challenges in language and social skills may coexist. Consequently the presentation of CP has the ability to mask the initial presenting symptomatology of ASD. The clinician assessing the child often relies on clinical judgement and expertise in addition to assessment instruments to differentiate between the two disorders.

The aim of screening instruments are to facilitate early diagnosis and initiation of appropriate interventions to target the core features of the particular disorder. Screening instruments have limitations; they may indicate when a child has not met an expected developmental milestone but cannot be definitive in its interpretation as there is much variability in “time to achieve” a skill. Results of a screening instrument are also dependent on the observer or caregiver completing the questionnaire which may vary in reliability over time. The results from a screening instrument represent a snapshot in a child’s development and symptoms may be inconsistent over time. If there are abnormalities found on a screening instrument this should prompt the clinician to complete a detailed developmental assessment. The American Academy of Paediatrics recommends screening for ASD at the 18 to 24 months age well baby visit (C. P. Johnson & Myers, 2007). In this section we briefly review screening instruments that are specific for identifying symptoms of ASD, focusing on early childhood. The psychometric properties of these screening tools has been documented extensively in other chapters of this book.

The CHAT is the first screening instrument developed to identify ASD in toddlers (Baron-Cohen, Allen, & Gillberg, 1992). There are five items that are key indicators of ASD, inclusive of; gaze monitoring, pointing to request and pretend play. Low sensitivity, limits the CHAT as a primary instrument for identifying ASD in toddlerhood. This instrument was also tested on children with developmental delays but not with motor impairments. In the presence of a CP presentation especially with upper extremity involvement, critical items identified on the CHAT will be affected. This will negatively impact the specificity, sensitivity, and utility of this instrument.

The M-CHAT is a 23-item questionnaire which is a modified version of CHAT (Robins, Fein, Barton, & Green, 2001). There are six critical items which are key indicators of ASD, inclusive of; interest in other children, pointing to direct interests, showing objects, imitating, response to name and the ability to follow a point. This questionnaire has been used to identify children at risk of ASD in a population of very low birth weight infants who were born preterm (Limperopoulos et al., 2008). Of the 91 children in this study, 23 (25 %) had positive M-CHAT scores. However, only one of these children (who was 18 months of age at testing) was not climbing on objects or stairs, indicating motor delays. This finding suggests that children with social communication deficits as screened by the M-CHAT are unlikely to have coexisting motor impairments.

This is surprising as theoretically a child with CP especially with bilateral upper extremity involvement could score positive on this instrument regardless if ASD is present. This is because three of the five critical items requires coordinated motor function. Regardless of the cause, a positive result on this screening instrument should be followed by a detailed developmental assessment.

The STAT is a 20-min play based interaction between with a child who displays symptoms suggestive of ASD and another person (Stone, Coonrod, & Ousley, 2000). Attention is focused on the child’s ability to play, directs another persons’ attention and motor imitation. This instrument is aimed at screening toddlers between the ages of 14–36 months. These results are important, if validated in larger samples this tool can be used as early as 14 months as a screener for ASD. In the context of a child with CP, play and motor imitation function domains will be mostly impacted. However, evaluating the child’s ability to direct another person’s attention using vocalizations or eye contact might reveal information that may be useful in differentiating between the two disorders.

The SCQ is a 40-item questionnaire which uses questions from the more intensive Autism Diagnostic Interview-Revised (ADI-R) instrument (Rutter, Bailey, & Lord 2003). These questions evaluate the ASD symptomatology in the social, communication domain and the presence of restricted and repetitive behaviors. Psychometric properties of SCQ was only evaluated in psychiatric disorders, intellectual disability, and language delay. A recent study used the SCQ to screen for ASD in an extremely preterm population which included children with neuromotor impairments (Johnson et al., 2011). Using the established cut-off (scores ≥15), the SCQ had an 82 % sensitivity and 88 % specificity for identifying ASD in this population. However, it should be noted that the positive predictive value was relatively low with only 31 % of children with positive screens having received a diagnosis of ASD. Children with functional disabilities, including those with motor impairments, were more likely to screen positive on the SCQ. This may in part be due to parents rating SCQ items positive based on behaviors associated with other neurodevelopmental sequelae. In addition, parents of children with physical and neurosensory impairments were less likely to complete all of the items on the SCQ. This may be due to the fact that some SCQ items are not applicable or are difficult to answer when isolating autistic features from other neurodevelopmental sequelae.

The SRS-2 is a 65 item questionnaire which evaluates ASD symptomatology in the social, communication domain and the presence of restricted and repetitive behaviors (Constantino & Gruber, 2012). There are five treatment subscales: Social Awareness; Social Cognition; Social Communication; Social Motivation; and Restricted Interests and Repetitive Behavior. The Social Communication and Behavioral subscales map unto the DSM 5 diagnostic symptom criteria for ASD. This instrument is sensitive to identify behavioral difficulties among children. There is limited specificity in discriminating oppositional type behaviors and ASD. Higher total scores indicate greater severity of social impairment. This is a good instrument to monitor change in severity of ASD symptomatology over time.

Interestingly both the CHAT and M-CHAT identifies the absence of pointing as a significant indicator for ASD. In the face of CP these instruments may be limited in their utility as a discriminator of ASD. The STAT instrument has a strong motoric component (pointing, motoric imitation) thus the clinician must be cautious in interpretation of the results in the face of CP. We have to recognize that a child with upper extremity involvement may not be able to point or show an object to another or may do so in an atypical manner. These instruments do not rely on the presence of language comprehension or speech. The CHAT, M-CHAT, and STAT instrument have not been validated in toddlers with a motor impairment, thus extrapolating its psychometric properties to the CP population should be done with caution.

When reviewing the CP ASD literature there is one screening instrument that has been mentioned frequently, the Baby and Infant Screen for Children with aUtIsm Traits-Part 1 (BISCUIT-Part 1) (Matson, Wilkins, Sevin, Knight, Boisjoli, & Sharp 2009). This instrument was developed using a sample of 276 children including children who were neurotypical or had a diagnosis of a neurodevelopmental disorder including neuromotor disorders such as CP. This instrument is the only instrument to date that has been tested on children with neuromotor disorders. However, given the new DSM 5 diagnostic classification of ASD and the removal of the PDD-NOS profile, when using this tool one has to take this into consideration, in interpreting scores.

There are two instruments which are considered ‘gold standard’ in the assessment of a child with social communication deficits and atypical behaviors. This includes; Autism Diagnostic Interview-Revised (ADI-R) and Autism Diagnostic Observation Schedule-2 (ADOS-2) . One limitation of the ADI-R tool is that its discriminatory ability decreases in children with mental ages below 20 months. This instrument is not recommended in children with a mental age less than 18 months (Cox et al., 1999). The algorithm scores generated is able to discriminate ASD from language impairment (Mildenberger, Sitter, Noterdaeme, & Amorosa, 2001) and developmental delays (Cox et al., 1999; Lord, Rutter, & Le Couteur, 1994).

Understanding the child’s level of cognitive function is important in interpreting results of diagnostic tests. The use of standardized assessment of cognitive skills and adaptive skills should be considered as part of the battery of tests administered. The Mullen Scales of Early Learning is an instrument that characterizes the cognitive and developmental profile of a child from birth to 68 months. This instrument is commonly used in the evaluation of children with neurodevelopmental challenges. A preliminary study identified that this tool lacks the ability to differentiate between a CP and ASD profile (Burns, King, & Spencer, 2013). In a child with a dual diagnosis of CP + ASD, the use of a single diagnostic instrument to differentiate between the two diagnostic profiles is nonexistent.

There has been limited studies which evaluate the co-occurrence of ASD in the presence of CP. Studies focus on the prevalence of the dual diagnosis, presentation of symptomatology, age of diagnosis of the CP + ASD subtype.

The current best practice for diagnosing ASD in a child with CP is completing a thorough clinical assessment and combining this with the clinician’s judgement. The assessment of ASD in the face of CP should entail a detailed history, examination and structured observation of the child’s social and communication skills , complemented with standardized diagnostic instruments which are validated for children with motor difficulties. Diagnostic instruments used to identify a diagnosis of ASD in the presence of significant motor impairments must be interpreted with caution. Given current limitations of ASD diagnostic instruments as outlined in the previous section, it is important that the clinician utilize a multidisciplinary approach in evaluating social communication skills in a child diagnosed with CP. This approach is preferred given the significant overlap of presenting symptomatology in the SCD in both disorders. The presence of intellectual disability can further complicate the identification of ASD in a child with CP. A clinician who is familiar with the developmental presentation and variability of both disorders should take the lead in the assessment. This team may comprise a pediatrician/developmental pediatrician, psychologist, speech and language pathologist, occupational therapist, and physiotherapist as indicated.

The clinical manifestation of CP usually occurs in early childhood and a diagnosis is usually apparent by 2–3 years of age. There is much heterogeneity in the clinical presentation of ASD. The core features of ASD manifests in early childhood; however, cases where the severity of symptomatology is milder may not demonstrate impairments until later; during the school age years. We have proposed a stepwise approach in evaluating a child who presents with CP and impairments in social and communication domain suggestive of ASD.

A holistic approach is required when evaluating a child who demonstrates impairments in social communication skills in the presence of motor impairment. We propose a five-step approach in the assessment of such a child. Establishing continuity of care with the patient to be able to appreciate subtle changes in the social affect development and behavior domains over time is strongly recommended.

The first step of assessment includes a detailed developmental and behavioral history. We outline key points for each section of the history that should raise the clinician’s index of suspicion regarding an possible diagnosis of ASD. Risk factors, associations, and distinguishing factors for ASD in each section are noted below: