What is the approach to evaluating an infant with delayed motor skill development?

Evaluation of Delayed Motor Skill Development in Infants

The evaluation of an infant with delayed motor skills should follow a systematic approach beginning with developmental surveillance at every well-child visit, administration of standardized screening tools when concerns arise, followed by a focused neuromotor history and physical examination, with selective laboratory testing (creatine phosphokinase and thyroid-stimulating hormone) and subspecialist referral based on specific examination findings. 1

Initial Assessment: Developmental Surveillance and Screening

Elicit and Document Parental Concerns

• Directly ask parents four key questions to identify motor concerns: 1

  • "Is there anything your child is not doing that you think he or she should be able to do?" (delayed acquisition) 1
  • "Is there anything your child is doing that you are concerned about?" (involuntary movements/coordination) 1
  • "Is there anything your child used to be able to do that he or she can no longer do?" (regression) 1
  • "Is there anything other children your child's age can do that are difficult for your child?" (strength/endurance issues) 1

• Parent concern alone is a valid trigger for formal diagnostic investigations, even when clinical observations seem reassuring 2

• Inquire about concerns from extended family members, educators, or childcare providers who know the child well 1

Administer Standardized Screening Tools

• Use brief standardized developmental screening tools that can be completed by parents and scored by nonphysician personnel, with interpretation by the pediatric provider 1
• The Ages and Stages Questionnaire (ASQ-III) is an appropriate validated tool for this purpose 3

Correct for Prematurity

• For infants born before 36 weeks' gestation, correct for prematurity for at least the first 24 months of life to avoid overestimating developmental delays 1, 3

Expanded History When Concerns Identified

Prenatal and Perinatal History

• Review prenatal exposures, maternal infections, complications during pregnancy 1
• Document gestational age, birth weight, Apgar scores, and neonatal complications 1
• Assess for hypoxic-ischemic events (10% of etiologic diagnoses in delayed children) 4

Developmental History

• Watch for aberrant milestone patterns suggesting increased tone or cerebral palsy: 1
  • Rolling supine to prone before prone to supine 1
  • Asymmetric propping with sitting 1
  • Asymmetric grasp or development of handedness before 18 months 1
  • Standing before sitting 1
  • Sitting before rolling (atypical sequence suggesting neuromuscular risk) 2

Family History

• Screen for X-linked disorders, particularly Duchenne muscular dystrophy affecting male relatives on the maternal side 1
• Assess for genetic syndromes, metabolic disorders, and consanguinity 1

Social History

• Identify environmental risk factors and protective factors 1
• Document access to early intervention resources 1

Physical and Neurologic Examination

General Observation

• Observe spontaneous motor function, posture, and play without the stress of deliberate performance testing 1, 3
• This is particularly important when children are tired or stressed 1

Cranial Nerve Examination

• Assess eye movements, confrontation visual fields, and pupillary reactivity 1, 3
• Check for symmetric red reflexes 1, 3
• Observe facial expression quality, including smile and cry 1
• Evaluate oromotor movement, palate and tongue movement 1
• Look for tongue fasciculations (suggesting lower motor neuron disease) 1

Motor Strength Assessment

• Assess strength primarily through functional observation rather than formal testing: 1

  • Antigravity movement in infants 1
  • Sequential transitions from tripod sitting to walking, running, climbing, hopping, and skipping in older children 1
  • Note any Gower maneuver (inability to rise from floor without pushing up with arms, suggesting proximal weakness) 1

• Observe muscle bulk, texture, and presence of atrophy 1

• Note calf hypertrophy (classic for Duchenne muscular dystrophy) 1

Tone Assessment

• In infants, assess postural tone by: 1

  • Ventral suspension in younger infants 1
  • Truncal positioning when sitting and standing in older infants 1

• Assess extremity tone by: 1

  • Scarf sign in infants 1
  • Popliteal angles after the first year 1

• Hypotonia with weakness suggests lower motor neuron or muscle disease 1

• Increased tone may result in early, asymmetric, or "out of order" milestone attainment 1

Reflex Examination

• Check for persistence of primitive reflexes (abnormal) 1
• Assess for asymmetry or absence of protective reflexes 1
• Deep tendon reflexes provide critical localization: 1
  • Diminished or absent reflexes suggest lower motor neuron disorders 1
  • Increased reflexes with abnormal plantar response suggest upper motor neuron dysfunction 1

Praxis Assessment (Older Children)

• Differentiate dyspraxia (inability to formulate, plan, and execute complex movements) from weakness 1
• Test age-appropriate gross motor skills: stair climbing, one-foot standing, hopping, running, skipping, throwing 1
• Test fine motor skills: buttoning, zipping, snapping, tying, cutting, using objects, drawing 1

Sensory Examination

• Test touch and pain sensation, as neuromotor dysfunction can be accompanied by sensory deficits 1

Critical Red Flags Requiring Urgent Evaluation

The following findings mandate immediate comprehensive evaluation and subspecialist referral: 1, 2

• Regression of any previously acquired motor skills (major red flag for progressive neuromuscular disorders) 1, 2
• Absent rolling at 7 months 2
• Inconsistent head control in prone position at 7 months 2
• Failure to achieve sitting without support by 9 months 2
• Asymmetry in hand use or persistent one-handed activities (suggesting unilateral cerebral palsy) 2
• Hypotonia with feeding difficulties or dysmorphic features 2
• Marked asymmetry in movement patterns developing after 9 months 2

Selective Laboratory Testing

When to Measure Creatine Phosphokinase (CK)

• Obtain serum CK in all children with motor delay and low tone, especially with concomitant weakness 1
• CK is significantly elevated in Duchenne muscular dystrophy, usually >1000 U/L 1
• Elevated CK should prompt molecular sequencing of the DMD gene for confirmation 1
• DMD typically presents at 2-4 years but signs may be evident earlier 1
• One-third of DMD cases are new mutations without family history 1

Thyroid-Stimulating Hormone (TSH)

• Measure TSH concentration when low to normal tone is identified 1
• Hypothyroidism can present with hypotonia and developmental delays 1

Additional Testing by Subspecialists

• Other neuromuscular disorders (myotonic dystrophy, spinal muscular atrophy, mitochondrial disorders, congenital myasthenia gravis) require electrodiagnostic or specific genetic testing performed by subspecialists 1
• Comprehensive neurologic evaluation yields an etiologic diagnosis in 63.3% of globally delayed children 4
• Etiologic categories include cerebral dysgenesis (16.7%), hypoxic-ischemic encephalopathy (10%), chromosomal abnormalities (10%), toxins (8.3%), and metabolic disorders (5%) 4

Referral Strategy

Early Intervention Referral

• All children with suspected neuromotor delay should be referred to early intervention or special education resources immediately 1
• Concurrent referrals to physical and/or occupational therapy should be made while diagnostic investigations proceed 1
• Children benefit from educationally and medically based therapies even without a specific diagnosis 1

Subspecialist Referral

• Direct physician-to-physician communication is recommended when red flags are identified 1
• Subspecialists may include neurologists, developmental pediatricians, geneticists, physiatrists, or orthopedists 1
• Sharing digital photographs via secure Internet connection may expedite evaluations 1
• The absence of red flags does not rule out significant neuromotor disease; all children with motor delays require thorough and serial evaluation 1

Ongoing Management

For Children Without Identified Disorder

• Schedule early return visits for further surveillance with particular attention to areas of concern 1
• More frequent visits facilitate prompt referrals when indicated 1
• Instruct parents to return immediately if the child loses any motor skills or develops new concerns about strength, respiration, or swallowing 2

For Children With Identified Disorder

• Identify as a child with special health care needs and initiate chronic condition management 1
• Actively participate in care coordination activities 1
• Make evidence-based decisions regarding therapies in consultation with family, therapists, subspecialists, and educators 1
• Establish management plans with relevant, measurable, valid outcomes that are reviewed and updated regularly 1

Common Pitfalls to Avoid

• Do not delay referral to early intervention while awaiting a specific diagnosis - therapy should begin immediately 1
• Do not dismiss parental concerns even when examination seems normal - parent concern is a valid trigger for investigation 2
• Do not fail to correct for prematurity in infants born before 36 weeks - this leads to overdiagnosis of delays 1, 3
• Do not overlook subtle asymmetries in movement or tone - these may indicate unilateral cerebral palsy 2, 3
• Do not attempt formal examination when the infant is tired or stressed - this yields inaccurate results 1, 3
• Remember that a detailed clinical history is the most critical component - it establishes diagnosis in the majority of cases, with physical examination and investigations influencing management in less than 6% 5