Is a 1-month-old infant with a soft, open anterior fontanel that responds to external stimuli, normal response to arm lift from supine position, jerky movements upon release when lifting the head, and bilateral plantar flexion upon stimulation of the soles, indicative of a neurological abnormality?

Assessment of a 1-Month-Old Infant with Neurological Examination Findings

The bilateral plantar flexion response (downgoing toes) in this 1-month-old infant is completely normal, as the Babinski reflex (extensor plantar response with upgoing toes) is expected and physiologic at this age. 1 The jerky movements upon head release and other described findings require further evaluation to determine if they represent normal developmental variation or early signs of neurological dysfunction.

Normal vs. Abnormal Findings at 1 Month

Normal Findings Present

• Soft, open anterior fontanel is expected and normal at 1 month of age 2, 3
• Bilateral plantar flexion (downgoing toes) is within normal limits for this age, as extensor plantar responses (Babinski sign) are the expected normal finding in infants and only become abnormal when they persist beyond 12-24 months 1
• Response to external stimuli indicates appropriate arousal and sensory processing 2

Concerning Findings Requiring Assessment

• Jerky movements upon head release may represent normal immature motor control or could indicate abnormal motor patterns that warrant standardized assessment 4
• The quality and pattern of these movements must be evaluated using validated tools rather than subjective observation alone 4

Recommended Diagnostic Approach

Immediate Standardized Assessment

Perform the Hammersmith Infant Neurological Examination (HINE) immediately, as scores <57 at 3 months have 96% predictive value for cerebral palsy, and this tool can identify motor dysfunction even at 1 month. 4, 5

• The HINE specifically evaluates quality of movement, tone, reflexes, and posture in a standardized manner 4
• This assessment distinguishes normal developmental variation from pathological motor patterns 4

General Movements Assessment

If available, the Prechtl Qualitative Assessment of General Movements should be performed before 5 months corrected age, as it has 98% sensitivity for detecting cerebral palsy risk. 4

• Absent fidgety movements or consistently abnormal movement patterns are highly predictive of neurological dysfunction 4
• This assessment is more sensitive than clinical observation alone for detecting subtle motor abnormalities 4

Clinical History Documentation

Obtain detailed pregnancy, birth, and neonatal history focusing on specific risk factors for cerebral palsy. 4, 5

Critical risk factors to document include:

• Prematurity or low birth weight 4
• Birth asphyxia or neonatal encephalopathy 5
• Neonatal seizures 4
• Intrauterine growth restriction 4
• Maternal infections or complications 4

Neuroimaging Considerations

If HINE scores are abnormal (<57) or general movements are consistently abnormal, obtain brain MRI without sedation if feasible at this age. 4, 5

• MRI has 86-89% sensitivity for detecting cerebral palsy-related brain abnormalities 4
• Key patterns to identify include white matter injury, basal ganglia lesions, or brain maldevelopments 4, 5
• Normal MRI does not exclude cerebral palsy risk, as clinical assessment remains paramount 4

Critical Red Flags Requiring Urgent Evaluation

Any of the following findings mandate immediate comprehensive neurological assessment: 4

• Hand asymmetry or early preference for one hand 4
• Persistent head lag beyond what is expected for age 4
• Abnormal tone (either increased or decreased) in trunk or limbs 5
• Absent or asymmetric primitive reflexes 2, 3
• Poor visual fixation or tracking 1

Common Pitfalls to Avoid

Misinterpretation of Normal Age-Appropriate Findings

• Do not interpret extensor plantar responses (upgoing toes/Babinski) as abnormal in infants - this is the expected normal response until 12-24 months 1
• Jerky or tremulous movements can be normal in newborns but must be distinguished from pathological patterns using standardized tools 2, 6

Delayed Assessment

• Cerebral palsy can be accurately diagnosed before 6 months corrected age using appropriate tools - the concept of a "silent period" where diagnosis is impossible is outdated 4
• Early detection enables access to cerebral palsy-specific interventions that optimize neuroplasticity 5

Over-reliance on Single Assessment

• Combination of assessments (HINE + MRI + clinical history) is more accurate than any single tool in isolation 4
• Serial assessments over time provide trajectory information that improves diagnostic accuracy 4

Interim Diagnosis and Management

If motor dysfunction is present on HINE but diagnosis is uncertain, assign the interim diagnosis of "high risk of cerebral palsy" and initiate cerebral palsy-specific early intervention immediately. 4

Essential criterion for this interim diagnosis:

• Motor dysfunction with reduced quality of movement or neurologically abnormal patterns 4

Plus at least one additional criterion:

• Abnormal neuroimaging findings 4
• Clinical history indicating cerebral palsy risk 4

Early Intervention Referral

Refer immediately to cerebral palsy-specific early intervention programs focusing on postural control, movement training, and parent education, as intervention before 6 months corrected age optimizes outcomes. 5

• Do not wait for definitive diagnosis to initiate intervention 4
• Regular monitoring every 4-6 weeks to track developmental trajectory 4

Follow-Up Schedule

Schedule reassessment at 3 months with repeat HINE scoring, as scores at this age have high predictive validity. 4

• Continue monitoring developmental milestones, particularly sitting ability by 9 months 4
• Inability to sit independently by 9 months is a strong indicator requiring comprehensive cerebral palsy evaluation 4