Symptoms vary according to the abnormality, but often feature poor muscle tone and motor function, seizures, developmental delays, mental retardation, failure to grow and thrive, difficulties with feeding, swelling in the extremities, and a smaller than normal head. Most infants with an NMD appear normal, but some disorders have characteristic facial or skull features that can be recognized by a neurologist.

Patients diagnosed with porencephaly display a variety of symptoms, from mild to severe effects on the patient. Patients with severe cases of porencephaly suffer epileptic seizures and developmental delays, whereas patients with a mild case of porencephaly display little to no seizures and healthy neurodevelopment. Infants with extensive defects show symptoms of the disorder shortly after birth, and the diagnosis is usually made before the age of 1.

The following text lists out common signs and symptoms of porencephaly in affected individuals along with a short description of certain terminologies.

The prognosis for children with NMDs varies depending on the specific disorder and the degree of brain abnormality and subsequent neurological signs and symptoms.

There are two problems that may occur during development that cause acrania.

Acrania is a rare congenital disorder that occurs in the human fetus in which the flat bones in the cranial vault are either completely or partially absent. The cerebral hemispheres develop completely but abnormally. The condition is frequently, though not always, associated with anencephaly. The fetus is said to suffer from acrania if it meets the following criteria: the fetus should have a perfectly normal facial bone, a normal cervical column but without the fetal skull and a volume of brain tissue equivalent to at least one third of the normal brain size.

Porencephaly is a rare disorder. The exact prevalence of porencephaly is not known; however, it has been reported that 6.8% of patients with cerebral palsy or 68% of patients with epilepsy and congenital vascular hemiparesis have porencephaly. Porencephaly has a number of different, often unknown, causes including absence of brain development and destruction of brain tissue. With limited research, the most commonly regarded cause of porencephaly is disturbances in blood circulation, ultimately leading to brain damage. However, a number of different and multiple factors such as abnormal brain development or damage to the brain tissue can also affect the development of porencephaly.

The following text lists out potential risk factors of developing porencephaly and porencephalic cysts and cavities along with brief description of certain terminologies.

Cysts or cavities can occur anywhere within the brain and the locations of these cysts depend highly on the patient. Cysts can develop in the frontal lobe, parietal lobe, forebrain, hindbrain, temporal lobe, or virtually anywhere in the cerebral hemisphere.

Occurrence of seizures is often reported in children with PVL. In an Israel-based study of infants born between 1995 and 2002, seizures occurred in 102 of 541, or 18.7%, of PVL patients. Seizures are typically seen in more severe cases of PVL, affecting patients with greater amounts of lesions and those born at lower gestational ages and birth weights.

Delayed motor development of infants affected by PVL has been demonstrated in multiple studies. One of the earliest markers of developmental delays can be seen in the leg movements of affected infants, as early as one month of age. Those with white matter injury often exhibit "tight coupling" of leg joints (all extending or all flexing) much longer than other infants (premature and full-term). Additionally, infants with PVL may not be able to assume the same positions for sleeping, playing, and feeding as premature or full-term children of the same age. These developmental delays can continue throughout infancy, childhood, and adulthood.

Choroid plexus cysts (CPCs) are cysts that occur within choroid plexus of the brain. The brain contains pockets or spaces called ventricles with a spongy layer of cells and blood vessels called the choroid plexus. This is in the middle of the fetal brain. The choroid plexus has the important function of producing cerebrospinal fluid. The fluid produced by the cells of the choroid plexus fills the ventricles and then flows around the brain and the spinal cord to provide a cushion of fluid around these structures.

CPCs can form within this structure and come from fluid trapped within this spongy layer of cells, much like a soap bubble or a blister. CPCs are often called "soft signs" or fetal ultrasound "markers" because some studies have found a weak association between CPCs and fetal chromosome abnormalities.

It is believed that many adults have one or more tiny CPCs. The fetal brain may create these cysts as a normal part of development. They are temporary and usually are gone by the 32nd week of pregnancy.

CPCs are a rare cause of intermittent hydrocephalus. This is caused by a blockage of foramina within the ventricular drainage system of the central nervous system (CNS), which can lead to expansion of the ventricles, compressing the brain (the cranial cavity cannot expand to accommodate the increase in fluid volume) and possibly causing damage.

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).

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.

The key features of this syndrome are an enlargement of the fourth ventricle; complete absence of the cerebellar vermis, the posterior midline area of cerebellar cortex responsible for coordination of the axial musculature; and cyst formation near the internal base of the skull. An increase in the size of the fluid spaces surrounding the brain as well as an increase in pressure may also be present. The syndrome can appear dramatically or develop unnoticed.

Symptoms, which often occur in early infancy, include slower motor development and progressive enlargement of the skull. In older children, symptoms of increased intracranial pressure such as irritability, vomiting, and convulsions and signs of cerebellar dysfunction such as unsteadiness and lack of muscle coordination or jerky movements of the eyes may occur. Other symptoms include increased head circumference, bulging at the back of the skull, problems with the nerves that control the eyes, face and neck, and abnormal breathing patterns.

Dandy–Walker syndrome is frequently associated with disorders of other areas of the central nervous system including absence of the corpus callosum, the bundle of axons connecting the two cerebral hemispheres, and malformations of the heart, face, limbs, fingers and toes.

The Dandy–Walker complex is a genetically sporadic disorder that occurs one in every 30,000 live births. Prenatal diagnosis and prognosis of outcomes associated with Dandy–Walker can be difficult. Prenatal diagnosis is possible with ultrasound. Because the syndrome is associated with an increased risk for fetal karyotype abnormalities, amniocentesis can be offered after prenatal diagnosis. There is a relative contraindication of taking Warfarin during pregnancy, as it is associated with an increased risk of Dandy–Walker syndrome if taken during the first trimester.

Dandy–Walker syndrome (DWS) is a rare group of congenital human brain malformations. There are three subtypes which affect multiple organs to varying degrees, but the fundamental abnormalities involve the cerebellum which controls muscle coordination. The adjacent fourth ventricle is often affected, which can alter the flow of cerebrospinal fluid, increase intracranial pressure, and lead to multiple other brain function problems. The degree of disability varies but is typically lifelong. Treatment may involve physical therapy, special education, or surgical placement of a cerebral shunt. It is named for Walter Dandy and Arthur Earl Walker. In the majority of individuals with Dandy–Walker malformation, signs and symptoms caused by abnormal brain development are present at birth or develop within the first year of life. Some children have a buildup of fluid in the brain (hydrocephalus) that may cause increased head size (macrocephaly). Up to half of affected individuals have intellectual disability that ranges from mild to severe, and those with normal intelligence may have learning disabilities. Children with Dandy–Walker malformation often have delayed development, particularly a delay in motor skills such as crawling, walking, and coordinating movements. People with Dandy–Walker malformation may experience muscle stiffness and partial paralysis of the lower limbs (spastic paraplegia), and they may also have seizures. While rare, hearing and vision problems can be features of this condition.

Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS) and twin oligohydramnios-polyhydramnios sequence (TOPS) is a complication of disproportionate blood supply, resulting in high morbidity and mortality. It can affect monochorionic multiples, that is, multiple pregnancies where two or more fetuses share a chorion and hence a single placenta. Severe TTTS has a 60–100% mortality rate.

In neonates born at or beyond 35 weeks, neonatal encephalopathy may present itself as the following symptoms:

- Reduced level of consciousness

- Seizures (which peak at 48 hours)

- Difficulty initiating and maintaining respiration

- Depression of tone and reflexes

Neonatal encephalopathy (NE), also known as neonatal hypoxic-ischemic encephalopathy (neonatal HIE or NHIE), is defined by signs and symptoms of abnormal neurological function in the first few days of life in an infant born at term. In this condition there is difficulty initiating and maintaining respirations, a subnormal level of consciousness, and associated depression of tone, reflexes, and possibly seizures. Encephalopathy is a nonspecific response of the brain to injury which may occur via multiple methods, but is commonly caused by birth asphyxia.

Callosal disorders can be diagnosed through brain imaging studies or during autopsy. They may be diagnosed through an MRI, CT scan, Sonography, prenatal ultrasound, or prenatal MRI.

This syndrome consists a number of typical features. These include

- Agenesis of the corpus callosum (80-99% patients)

- Hypopigmentation of the eyes and hair (80-99% patients)

- Cardiomyopathy (80-99% patients)

- Combined immunodeficiency (80-99% patients)

- Muscular hypotonia (80-99% patients)

- Abnormality of retinal pigmentation (80-99% patients)

- Recurrent chest infections (80-99% patients)

- Abnormal EEG (80-99% patients)

- Intellectual disability (80-99% patients)

- Cataracts (75%)

- Seizures (65%)

- Renal abnormalities (15%)

Infections of the gastrointestinal and urinary tracts are common. Swallowing and feeding difficulties early on may result in a failure to thrive. Optic nerve hypoplasia, nystagmus and photophobia may occur. Facial dysmorphism (cleft lip/palate and micrognathia) and syndactyly may be present. Sensorineural hearing loss may also be present.

Death in infancy is not uncommon and is usually due to cardiac complications or severe infections.

Some syndromes that frequently include ACC are Aicardi syndrome, Andermann syndrome, Shapiro syndrome, acrocallosal syndrome, septo-optic dysplasia (optic nerve hypoplasia), Mowat–Wilson syndrome, John Sayden syndrome, Menkes syndrome, and L1CAM Syndrome. Some conditions that are sometimes associated with ACC include maternal nutritional deficiencies or infections, metabolic disorders, fetal alcohol syndrome, craniofacial abnormalities, and other oral and maxillofacial pathologies.

Many of the physical features associated with the disorder are congenital. Characteristic craniofacial abnormalities typically include a long, narrow head that is disproportionate to the body size, a broad and prominent forehead, and a triangular-shaped face with a hypoplastic midface, pointed chin, prominent mouth, fleshy tipped upturned nose, large ears, and full lips. The teeth may be abnormally crowded together in some affected individuals.

Microcephaly is a characteristic in which the circumference of the head is smaller than normal due to improper development of the brain. It is caused by genetic disorders, infections, radiation, medications or alcohol abuse during pregnancy. Defects in the growth of the cerebral cortex lead to many of the features associated with microcephaly. There is currently no known method of correcting microcephaly. However, there are a variety of symptomatic treatments that help to counter some of its adverse effects, such as speech and occupational therapies, as well as medication to control seizures and hyperactivity. Microcephaly has a vast range of prognoses: some patients experience little to very mental retardation and can reach regular age-appropriate milestones. Others may experience severe mental retardation and neuromuscular side effects.

Individuals with 3-M syndrome suffer from severe prenatal growth retardation due to growth delays during fetal development resulting in a low birth weight. Growth delays continue after birth throughout childhood and adolescence, ultimately leading to a short stature.

The cranium consists of three main sections including the base of the cranium (occipital bone), the face (frontal bone), and the top (parietal bones) and sides (temporal bone) of the head. Most of the bones of the cranium are permanently set into place prior to birth. However, the temporal and parietal bones are separated by sutures, which remain open, allowing the head to slightly change in shape during childbirth. The cranial sutures eventually close within the first couple of years following birth, after the brain has finished growing.

In individuals with SCS, the coronal suture separating the frontal bones from the parietal bones, closes prematurely (craniosynostosis), occasionally even before birth. If the coronal suture closes asymmetrically or unilaterally, then the face and forehead will form unevenly, from side-to-side. People with SCS have pointy, tower-like heads because their brain is growing faster than their skull, resulting in increased intracranial pressure (ICP) and causing the top of the head and/or forehead to bulge out to allow for brain growth. The face appears uneven, particularly in the areas of the eyes and cheeks, and the forehead appears wide and tall.

Because of the abnormal forehead, there is less space for the normal facial features to develop. This results in shallow eye sockets and flat cheekbones. The shallow eye sockets make the eyes more prominent or bulging and cause the eyes to be more separated than normal (hypertelorism). The underdeveloped eye sockets, cheekbones, and lower jaw cause the face to appear flat. Furthermore, the minor downward slant of the eyes along with the drooping eyelids (ptosis) adds to the overall unevenness of the face.

Physical Symptoms

- Heart Defects

- Characteristics of Autism

- Genital defects (in males)

- Childhood hypotonia

- Respiratory infections

- Motor Delay

- Renal defects

Behavioural Symptoms

- Passiveness

- Sociability

- Aggression

- Biting, and/or hitting

- Moodiness

- Disliking routine changes

LFS is clinically distinguished from other X-linked forms of intellectual disability by the accompanying presence of marfanoid habitus. Marfanoid habitus describes a group of physical features common to Marfan syndrome. Including Marfan syndrome and LFS, marfanoid features of this type have also been observed with several other disorders, one of which is multiple endocrine neoplasia type 2.

In LFS, specific features identified as marfanoid include: a long, narrow face; tall, thin stature; long, slender limbs, fingers and toes (not unlike arachnodactyly) with joint hyperextensibility, shortened halluces (the big toes) and long second toes.

The diagnosis of marfanoid habitus in LFS is often delayed because many of the physical features and characteristics associated with it are usually not evident until adolescence.