ABPN NDD key terms

The embryonic precursor of the central nervous system that forms by folding and fusion of the neural plate; failure of closure produces defects such as anencephaly and myelomeningocele.

The embryonic process in which the neural plate folds into a tube; primary neurulation forms the brain and upper spine, while secondary neurulation forms the lower sacral cord.

A neural tube defect in which meninges and spinal cord tissue protrude through an unfused vertebral arch, causing lower-limb weakness, bowel and bladder dysfunction, and hydrocephalus.

A congenital hindbrain anomaly with downward displacement of the cerebellar vermis and medulla through the foramen magnum; strongly associated with myelomeningocele and obstructive hydrocephalus.

Abnormal accumulation of cerebrospinal fluid within the ventricular system, raising intracranial pressure; in children it may cause macrocephaly, vomiting, irritability, or downward gaze.

A disruption of neuronal movement from the ventricular zone to the cortex during fetal development, producing malformations such as lissencephaly, pachygyria, and heterotopia that cause epilepsy and intellectual disability.

A cortical malformation with excessive small, fused gyri and an irregular cortical surface; it may be genetic, ischemic, or infectious in origin and often causes seizures and developmental delay.

A focal malformation of cortical development with disorganized lamination and abnormal neurons or balloon cells; a common cause of medically refractory focal epilepsy in children.

The developmental formation of synaptic connections between neurons; it peaks in early childhood and is followed by activity-dependent pruning that refines neural circuits.

Activity-dependent elimination of excess synapses during childhood and adolescence that refines neural circuits; disrupted pruning is implicated in autism and schizophrenia.

The wrapping of axons by oligodendrocyte processes to form myelin, which speeds conduction; it proceeds from posterior to anterior and continues into adulthood, supporting emerging cognitive skills.

A developmental window during which experience strongly shapes a neural circuit; examples include visual cortex development and language acquisition, with reduced plasticity after closure.

The occipitofrontal circumference measured with a tape; plotted on growth charts, it screens for microcephaly, macrocephaly, and abnormal brain growth in infants and children.

Head circumference more than two standard deviations below the mean for age and sex; causes include genetic syndromes, congenital infection, and teratogen exposure, often with intellectual disability.

Head circumference more than two standard deviations above the mean for age and sex; it may reflect benign familial trait, hydrocephalus, or a metabolic storage disorder.

Involuntary movement patterns present in early infancy, such as the Moro and palmar grasp reflexes, that normally integrate as cortical control matures; persistence suggests neurologic abnormality.

A functional skill, such as sitting, walking, or first words, that most children achieve within an expected age range; delayed or lost milestones prompt developmental evaluation.

Loss of previously acquired skills such as language or motor abilities; it warrants urgent evaluation for epilepsy, metabolic disease, or neurodegenerative disorders such as Rett syndrome.

Significant delay in two or more developmental domains in a child under five years; it is a descriptive diagnosis requiring etiologic evaluation, including genetic testing.

A disorder with onset in the developmental period involving deficits in intellectual functioning and adaptive behavior that limit everyday functioning; severity ranges from mild to profound.

The conceptual, social, and practical skills needed for everyday independent functioning; deficits in these skills, not IQ alone, define intellectual disability.

A neurodevelopmental disorder defined by persistent deficits in social communication and interaction plus restricted, repetitive behaviors or interests, with onset in early development.

The use of verbal and nonverbal behavior, such as gestures, eye contact, and conversational reciprocity, to interact with others; deficits are a core feature of autism spectrum disorder.

The Modified Checklist for Autism in Toddlers, a parent-report screening tool used at 18 and 24 months; positive screens require follow-up interview and diagnostic evaluation.

Attention-deficit/hyperactivity disorder, characterized by developmentally inappropriate inattention and/or hyperactivity-impulsivity present before age twelve and impairing functioning across settings.

A standardized parent and teacher questionnaire that quantifies ADHD symptoms and related problems; it supports diagnosis and treatment monitoring but is not diagnostic alone.

A group of permanent movement and posture disorders due to nonprogressive injury of the developing brain; it is classified by motor type and topography and often includes epilepsy and sensory deficits.

A cerebral palsy pattern with predominant lower-extremity spasticity, often from periventricular leukomalacia in preterm infants; ambulation may be delayed with scissoring gait.

White matter injury near the lateral ventricles, typically from prematurity or hypoxic-ischemic insult; it is a leading cause of spastic diplegic cerebral palsy.

The most common inherited cause of intellectual disability, due to CGG repeat expansion in FMR1; features include macroorchidism, long face, and autism-like behavior.

An X-linked disorder caused by MECP2 mutations, affecting mostly girls, with normal early development followed by regression of hand use and language and stereotypic hand movements.

Trisomy 21, causing intellectual disability, hypotonia, characteristic facies, and increased risk of congenital heart disease, atlantoaxial instability, and early Alzheimer disease.

Reduced resting muscle tone, causing floppiness and delayed motor milestones; it is a sign rather than a diagnosis, seen in Down syndrome, neuromuscular disease, and central disorders.

A group of congenital infections, including toxoplasmosis, rubella, cytomegalovirus, and herpes simplex, that cause microcephaly, hearing loss, and developmental disability.

The range of effects from prenatal alcohol exposure, including characteristic facial features, growth restriction, and neurobehavioral impairment such as ADHD and learning problems.

A condition in which frequent epileptic activity itself contributes to cognitive and behavioral decline, as in infantile spasms or Lennox-Gastaut syndrome; early treatment aims to limit impairment.

An early-onset epilepsy with clusters of flexor or extensor spasms and hypsarrhythmia on EEG; prompt treatment with hormonal therapy or vigabatrin improves developmental outcome.

Electroencephalography records cortical electrical activity; it detects epileptiform discharges, supports seizure classification, and identifies patterns such as hypsarrhythmia or slow spike-wave.

A medication class, including methylphenidate and amphetamines, that increases dopaminergic and noradrenergic activity and is first-line pharmacotherapy for ADHD in children.

Federally supported services for infants and toddlers with developmental delay or risk, providing therapy and family support to improve developmental trajectories before school age.

A legally required school plan for a child with a disability that specifies goals, services, and accommodations under special education law, developed with parents and school staff.

A school accommodation plan under federal disability law that provides modifications so a student with a disability can access the general curriculum, without necessarily requiring special education.