What are the signs and symptoms of central nervous system (CNS) pathology in a 10-month-old infant?

Signs and Symptoms of CNS Pathology in a 10-Month-Old Infant

In a 10-month-old infant, CNS pathology typically presents with seizures, altered consciousness, abnormal tone or movements, developmental regression, persistent vomiting with headache signs, and abnormal eye movements—with seizures being the most common neurological manifestation in this age group. 1

Core Clinical Manifestations by Category

Neurological Signs

• Seizures are the most frequent CNS symptom in infants, ranging from overt convulsive activity to subtle motor status epilepticus 1, 2
• Altered consciousness including lethargy, obtundation, irritability, or difficulty maintaining an alert state 1, 3
• Abnormal muscle tone: hypotonia (floppiness) or hypertonia (increased stiffness), with profound hypotonia suggesting either CNS or neuromuscular pathology 1, 4
• Movement abnormalities including tremors, jitteriness, hyperreflexia, or abnormal posturing 1
• Developmental regression or failure to meet milestones, particularly motor delays 1

Cranial Nerve and Sensory Signs

• Abnormal eye movements including strabismus, squint, or paralysis of upward gaze 1, 5
• Visual impairment or reduced visual acuity 1, 5
• Cranial nerve palsies affecting facial movement, swallowing, or other functions 5
• Papilledema on fundoscopic examination, indicating raised intracranial pressure 1, 5

Signs of Raised Intracranial Pressure

• Macrocephaly (enlarged head circumference) is particularly important in infants under 4 years with intracranial pathology 5
• Persistent vomiting especially when accompanied by headache behaviors (irritability, head holding, inconsolable crying) 1, 5
• Bulging fontanelle in infants with open anterior fontanelle 5
• High-pitched or shrill cry suggesting meningeal irritation or increased pressure 1

Motor and Coordination Abnormalities

• Abnormalities of gait and coordination when the infant attempts supported standing or crawling 5
• Focal weakness or asymmetric movement patterns 1, 5
• Pyramidal signs including increased reflexes and extensor plantar responses 5

Systemic and Behavioral Signs

• Feeding difficulties including poor suck, uncoordinated feeding, or refusal to feed 1, 3
• Failure to thrive or poor weight gain 5, 3
• Excessive irritability or inconsolable crying beyond normal infant fussiness 1
• Fever when accompanied by neurological signs, raising concern for CNS infection 1, 6
• Apnea or periodic breathing particularly concerning in the context of other neurological signs 3

Critical Diagnostic Considerations

Differential Diagnosis Approach

When evaluating a 10-month-old with suspected CNS pathology, clinicians must systematically exclude infectious, metabolic, structural, and genetic etiologies. 1, 6

• CNS infections (meningitis, encephalitis) present with fever, altered consciousness, seizures, and meningeal signs—though fever may be absent in bacterial meningitis 1, 6, 7
• Acute bilirubin encephalopathy manifests as lethargy, hypotonia, poor feeding progressing to irritability, hypertonia, high-pitched cry, and opisthotonus 1
• Structural lesions (tumors, hydrocephalus) typically show progressive symptoms with signs of raised intracranial pressure 1, 5
• Metabolic disorders may present with hypotonia, seizures, and developmental regression 4

Red Flags Requiring Immediate Neuroimaging

The following presentations mandate urgent neuroimaging with MRI (preferred) or CT if immediate evaluation needed: 1, 8, 6

• Seizures with focal neurological deficits 8, 6
• Progressive worsening of symptoms over days to weeks 8
• Papilledema or other signs of raised intracranial pressure 8, 6
• Altered consciousness with nuchal rigidity (meningeal signs) 6, 7
• Abnormal neurological examination findings that cannot be explained by benign causes 8

Common Clinical Pitfalls

Misattribution of Symptoms

• Do not dismiss irritability and poor feeding as simple colic or gastroesophageal reflux when accompanied by neurological signs like altered tone or abnormal movements 1
• Do not assume hypotonia alone indicates neuromuscular disease—early CNS pathology can present with profound hypotonia before other signs emerge 4
• Do not rely on absence of fever to exclude CNS infection, as bacterial meningitis can present without fever in infants 6

Delayed Recognition

• Subtle motor status epilepticus may be missed without EEG monitoring—consider EEG in any infant with unexplained encephalopathy 1
• Non-convulsive status epilepticus presents as encephalopathy without overt seizure activity and requires EEG for diagnosis 1
• Early signs of raised intracranial pressure (irritability, vomiting, lethargy) may precede obvious findings like papilledema or bulging fontanelle 5

Treatment Delays

• Never delay antibiotics for imaging or lumbar puncture when bacterial meningitis is suspected—empiric treatment should begin within 1 hour 6, 7
• Do not perform lumbar puncture before neuroimaging in infants with altered consciousness, focal deficits, or signs of raised intracranial pressure due to herniation risk 6, 7

Age-Specific Considerations for 10-Month-Olds

At 10 months, infants are typically achieving motor milestones including sitting independently, crawling, and pulling to stand. Loss of previously acquired skills or failure to progress developmentally should raise immediate concern for CNS pathology. 1

• Regression of motor skills is particularly concerning and may indicate neurodegenerative conditions or structural lesions 1
• Persistent head lag beyond 6 months or loss of head control suggests significant CNS dysfunction 4
• Asymmetric movements or consistent hand preference before 12 months may indicate contralateral CNS pathology 5