Affected newborns generally have striking neurological defects and seizures. Severely impaired development is common, but disturbances in motor functions may not appear until later in life.

Infants with microcephaly are born with either a normal or reduced head size. Subsequently, the head fails to grow, while the face continues to develop at a normal rate, producing a child with a small head and a receding forehead, and a loose, often wrinkled scalp. As the child grows older, the smallness of the skull becomes more obvious, although the entire body also is often underweight and dwarfed. Development of motor functions and speech may be delayed. Hyperactivity and intellectual disability are common occurrences, although the degree of each varies. Convulsions may also occur. Motor ability varies, ranging from in some to spastic quadriplegia in others.

Microcephaly is a type of cephalic disorder. It has been classified in two types based on the onset:

Microlissencephaly Type B or Barth microlissencephaly syndrome: is a microlissencephaly with thick cortex, severe cerebellar and brainstem hypoplasia. The Barth-type of MLIS is the most severe of all the known lissencephaly syndromes.

This phenotype consists of polyhydramnios (probably due to poor fetal swallowing), severe congenital microcephaly, weak respiratory effort, and survival for only a few hours or days. Barth described two siblings with this type as having a very low brainweight, wide ventricles, a very thin neopallium, absent corpus callosum and absent olfactory nerve.

Microlissencephaly Type A or Norman-Roberts syndrome (NRS): a microlissencephaly with thick cortex without infratentorial anomalies.

Other clinical features may include: a bitemporal narrowing, a broad nasal root. There is postnatal growth retardation, severe mental retardation associated with pyramidal spasticity and epilepsy. This entity could be identical to "lissencephaly with cerebellar hypoplasia type B" (LCHb), and therefore linked to mutations in "RELN" gene.

Hemimegalencephaly is an extremely rare form of macrocephaly and is characterized by uneven development of brain hemispheres (one-half of brain is larger than other). The syndrome can be presented by itself or in association with phakomatosis or hemigigantism. Additionally, hemimegalencephaly will frequently cause severe epilepsy, focal neuro-logical deficits, macrocrania, and mild to severe mental retardation.

Megalencephaly-capillary (MCAP) is one of the two major syndromes of megalencephaly. Typically, MCAP and MPPH can be distinguished by somatic features. MCAP includes many characteristics that are observed at birth including: cutaneous vascular malformations, especially capillary malformations of the face and cutis marmorata, polydactyly, connective tissue dysplasia, and focal or segmental body overgrowth. Furthermore, MCAP can occasionally be linked with asymmetric brain overgrowth (hemimegalencephaly) as well as segmental overgrowth of the body (hemihypertrophy).

There are various symptoms of colpocephaly and patients can experience effects ranging from mild to severe. Some patients do not show most of the symptoms related to colpocephaly, such as psychomotor abnormalilities and agenesis of the corpus callosum. In some cases, signs appear later on in life and a significant number of children suffer only from minor disabilities.

The following list includes common symptoms of colpocephaly.

- partial or complete agenesis of the corpus callosum

- intellectual disability

- motor abnormalities

- visual defects such as, crossing of the eyes, missing visual fields, and optic nerve hypoplasia

- spasticity

- seizures

- cerebral palsy

Intracranial abnormalities include:

- Microcephaly

- Agenesis of the corpus callosum

- Meningomyelocele

- Lissencephaly

- Periventricular leukomalacia (PVL)

- Enlargement of the cisterna magna

- Cerebellar hypoplasia

Cephalic disorders (from the Greek word "κεφάλι", meaning "head") are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system. Cephalic means "head" or "head end of the body."

Cephalic disorders are not necessarily caused by a single factor, but may be influenced by hereditary or genetic conditions, nutritional deficiencies, or by environmental exposures during pregnancy, such as medication taken by the mother, maternal infection, or exposure to radiation. Some cephalic disorders occur when the cranial sutures (the fibrous joints that connect the bones of the skull) join prematurely. Most cephalic disorders are caused by a disturbance that occurs very early in the development of the fetal nervous system.

The human nervous system develops from a small, specialized plate of cells on the surface of the embryo. Early in development, this plate of cells forms the neural tube, a narrow sheath that closes between the third and fourth weeks of pregnancy to form the brain and spinal cord of the embryo. Four main processes are responsible for the development of the nervous system: cell proliferation, the process in which nerve cells divide to form new generations of cells; cell migration, the process in which nerve cells move from their place of origin to the place where they will remain for life; cell differentiation, the process during which cells acquire individual characteristics; and cell death, a natural process in which cells die.

Damage to the developing nervous system is a major cause of chronic, disabling disorders and, sometimes, death in infants, children, and even adults. The degree to which damage to the developing nervous system harms the mind and body varies enormously. Many disabilities are mild enough to allow those afflicted to eventually function independently in society. Others are not. Some infants, children, and adults die, others remain totally disabled, and an even larger population is partially disabled, functioning well below normal capacity throughout life.

The National Institute of Neurological Disorders and Stroke (NINDS) is currently "conducting and supporting research on normal and abnormal brain and nervous system development."

Colpocephaly is characterized by disproportionately large occipital horns of the lateral ventricles (also frontal and temporal ventricles in some cases). MRI and CT scans of patients demonstrate abnormally thick gray matter with thin poorly myelinated white matter. This happens as a result of partial or complete absence of the corpus callosum. Corpus callosum is the band of white matter connecting the two cerebral hemispheres. The corpus callosum plays an extremely important role in interhemispheric communication, thus lack of or absence of these neural fibers results in a number of disabilities.

The lemon sign on CT scans of patients refers to the shape of the fetal skull when the frontal bones lose their normal convex contour and appear flattened or inwardly scalloped. This gives the skull a shape similar to that of a lemon. The sign is seen on transverse sonograms of the fetal cranium obtained at the level of the ventricles.

A special case is found in literature where lissencephaly, colpocephaly, and septal agenesis are all present together. The CT scans of the patient shows the ventricular system having a unique appearance of a crown of a king. This is referred to as the 'CROWN SIGN'.

Where known, the ICD-10 code is listed below.

- Anencephaly (Q00.0)

- Colpocephaly (ICD10 unknown)

- Holoprosencephaly (Q04.2)

- Ethmocephaly (ICD10 unknown)

- Hydranencephaly (Q04.3)

- Iniencephaly (Q00.2)

- Lissencephaly (Q04.3)

- Megalencephaly (Q04.5)

- Microcephaly (Q02)

- Porencephaly (Q04.6)

- Schizencephaly (Q04.6)

Microhydranencephaly (MHAC) is a severe abnormality of brain development characterized by both microcephaly and hydranencephaly. Signs and symptoms may include severe microcephaly, scalp rugae (a series of ridges), and profound developmental delay. Familial occurrence of the condition is very rare but it has been reported in a few families. It has been suggested that MHAC is possibly inherited in an autosomal recessive manner.

Not all cranial abnormalities seen in children with craniosynostosis are solely a consequence of the premature fusion of a cranial suture. This is especially true in the cases with syndromic craniosynostosis. Findings include elevation of the intracranial pressure; obstructive sleep apnoea(OSA); abnormalities in the skull base and neurobehavioral impairment.

Schizencephaly can be distinguished from porencephaly by the fact that in schizencephaly the fluid-filled component, if present, is entirely lined by heterotopic grey matter while a porencephalic cyst is lined mostly by white matter. Individuals with clefts in both hemispheres, or bilateral clefts, are often developmentally delayed and have delayed speech and language skills and corticospinal dysfunction. Individuals with smaller, unilateral clefts (clefts in one hemisphere) may be weak or paralyzed on one side of the body and may have average or near-average intelligence. Patients with schizencephaly may also have varying degrees of microcephaly, Intellectual disability, hemiparesis (weakness or paralysis affecting one side of the body), or quadriparesis (weakness or paralysis affecting all four extremities), and may have reduced muscle tone (hypotonia). Most patients have seizures, and some may have hydrocephalus.

Impaired venous outflow is often caused by a hypoplastic jugular foramen. This causes an increase in the intracranial blood volume, thereby causing an increase in intracranial pressure.

This can be further complicated with a possible Arnold-Chiari malformation, which can partially obstruct the flow of cerebro-spinal fluid from the neurocranium to the spinal cord. The Chiari malformation may be asymptomatic or present with ataxia, spasticity or abnormalities in breathing, swallowing or sleeping.

Due to the impaired venous outflow, which may be further complicated with an Arnold-Chiari malformation, there is often a clinical image of hydrocephalus present. Hydrocephalus is seen in 6.5 to 8% of patients with Apert's syndrome, 25.6% in patients with Crouzon's syndrome and 27.8% of those with Pfeifer's syndrome.

Ventriculomegaly is a usual finding in children with the Apert syndrome.

Macrocephaly is customarily diagnosed if head circumference is greater than two standard deviations (SDs) above the mean. Relative macrocephaly occurs if the measure is less than two SDs above the mean, but is disproportionately above that when ethnicity and stature are considered. In research, cranial height or brain imaging is also used to determine intracranial volume more accurately.

The classic triad for congenital rubella syndrome is:

- Sensorineural deafness (58% of patients)

- Eye abnormalities—especially retinopathy, cataract, and microphthalmia (43% of patients)

- Congenital heart disease—especially pulmonary artery stenosis and patent ductus arteriosus (50% of patients)

Other manifestations of CRS may include:

- Spleen, liver, or bone marrow problems (some of which may disappear shortly after birth)

- Intellectual disability

- Small head size (microcephaly)

- Eye defects

- Low birth weight

- Thrombocytopenic purpura

- Extramedullary hematopoiesis (presents as a characteristic blueberry muffin rash)

- Hepatomegaly

- Micrognathia

Children who have been exposed to rubella in the womb should also be watched closely as they age for any indication of:

- Developmental delay

- Autism

- Schizophrenia

- Growth retardation

- Learning disabilities

- Diabetes mellitus

- Glaucoma

Mild prenatal growth retardation

Moderate postnatal growth retardation

Mild to severe developmental delay

Severely impaired speech

Seizures

Microcephaly

Sparse hair

Progressive skin wrinkling

Thick, anteverted alae nasi

Long and broad philtrum

Large mouth

Thin upper and thick lower vermilion

Progressive prominence of distal phalanges

Progressive prominence of inter-phalangeal joints

Short metacarpals–metatarsals

Neu-Laxova syndrome presents with severe malformations leading to prenatal or neonatal death. Typically, NLS involves characteristic facial features, decreased fetal movements and skin abnormalities.

Fetuses or newborns with Neu–Laxova syndrome have typical facial characteristics which include proptosis (bulging eyes) with eyelid malformations, nose malformations, round and gaping mouth, micrognathia (small jaw) and low set or malformed ears. Additional facial malformations may be present, such as cleft lip or cleft palate. Limb malformations are common and involve the fingers (syndactyly), hands or feet. Additionally, edema and flexion deformities are often present. Other features of NLS are severe intrauterine growth restriction, skin abnormalities (ichthyosis and hyperkeratosis) and decreased movement.

Malformations in the central nervous system are frequent and may include microcephaly, lissencephaly or microgyria, hypoplasia of the cerebellum and agenesis of the corpus callosum. Other malformations may also be present, such as neural tube defects.

The most common symptoms of Nicolaides–Baraitser syndrome are mild to severe developmental delays with absent or limited speech, seizures, short stature, sparse hair, typical facial characteristics, brachydactyly, and prominent finger joints and broad distal phalanges.

Macrocephaly may be pathological, but many people with abnormally large heads or large skulls are healthy. Pathologic macrocephaly may be due to megalencephaly (enlarged brain), hydrocephalus (water on the brain), cranial hyperostosis (bone overgrowth), and other conditions. Pathologic macrocephaly is called "syndromic" when it is associated with any other noteworthy condition, and "nonsyndromic" otherwise. Pathologic macrocephaly can be caused by congenital anatomic abnormalities, genetic conditions, or by environmental events.

Many genetic conditions are associated with macrocephaly, including familial macrocephaly related to the holgate gene, autism, "PTEN" mutations such as Cowden disease, neurofibromatosis type 1, and tuberous sclerosis; overgrowth syndromes such as Sotos syndrome (cerebral gigantism), Weaver syndrome, Simpson-Golabi-Behmel syndrome (bulldog syndrome), and macrocephaly-capillary malformation (M-CMTC) syndrome; neurocardiofacial-cutaneous syndromes such as Noonan syndrome, Costello syndrome, Gorlin Syndrome, (also known as Basal Cell Nevus Syndrome) and cardiofaciocutaneous syndrome; Fragile X syndrome; leukodystrophies (brain white matter degeneration) such as Alexander disease, Canavan disease, and megalencephalic leukoencephalopathy with subcortical cysts; and glutaric aciduria type 1 and D-2-hydroxyglutaric aciduria.

At one end of the genetic spectrum, duplications of chromosomes have been found to be related to autism and macrocephaly; at the other end, deletions of chromosomes have been found to be related to schizophrenia and microcephaly.

Environmental events associated with macrocephaly include infection, neonatal intraventricular hemorrhage (bleeding within the infant brain), subdural hematoma (bleeding beneath the outer lining of the brain), subdural effusion (collection of fluid beneath the outer lining of the brain), and arachnoid cysts (cysts on the brain surface).

Schizencephaly () is a rare birth defect characterized by abnormal clefts lined with grey matter that form the ependyma of the cerebral ventricles to the pia mater. These clefts can occur bilaterally or unilaterally. Common clinical features of this malformation include epilepsy, motor deficits, and psychomotor retardation.

Microcephaly is a disorder in which the circumference of the head is smaller than average for the person's age and gender. Most children with microcephaly also have a smaller than typical brain and intellectual disability. Some of the most common signs and symptoms associated with microcephaly are seizures, poor feeding, high pitched cry, intellectual disability, developmental delay, and increased movement of arms and legs.

The signs and symptoms of Kaufman oculocerebrofacial syndrome are consistent with the following:

- High palate

- Microcephaly

- Constipation

- Intellectual disability

- Muscular hypotonia

- Nystagmus

Aicardi syndrome is a rare genetic malformation syndrome characterized by the partial or complete absence of a key structure in the brain called the corpus callosum, the presence of retinal abnormalities, and seizures in the form of infantile spasms. Aicardi syndrome is theorized to be caused by a defect on the X chromosome as it has thus far only been observed in girls or in boys with Klinefelter syndrome. Confirmation of this theory awaits the discovery of a causative gene. Symptoms typically appear before a baby reaches about 5 months of age.

Vision abnormalities in children with 1p36 have been wide-ranging, including: