The signs/symptoms of this condition are consistent with the following:

- Intellectual disability,

- Muscular hypotonia

- Encephalitis

- Seizures

- Aphasia

Fumarase deficiency causes encephalopathy, severe mental retardation, unusual facial features, brain malformation, and epileptic seizures due to an abnormally low amount of fumarase in cells. It can initially present with polyhydramnios on prenatal ultrasound. Affected neonates may demonstrate nonspecific signs of poor feeding and hypotonia. Laboratory findings in neonates may indicate polycythemia, leukopenia, or neutropenia. As they age, neurological deficits begin to manifest with seizures, dystonias, and severe developmental delay.

Recurrent seizures are the most recognizable feature of this syndrome and are most often the first sign of this syndrome. These syndromes are often ongoing and poorly responsive to anti-seizure medications. Most patients develop seizures the first few years of life, but the age of onset ranges from ages 1 to 17. Different types of seizure have been reported in this syndrome. The most common seizure type appears to be brief focal onset epileptic seizures with impairment of consciousness and awareness, known as complex partial seizures. Other features you may see in these complex partial seizures include staring, oral automatisms, unspecified automatic behavior, involuntary motor movements and/or head turning.

Furthermore, many patients have subtle nighttime behavioral changes, such as stretching, rubbing, and turning resembling a nighttime awakening. However, electroencephalography (EEG) studies during these events show abnormal electrical seizure activity, indicating that nocturnal behavioral events are actually subtle nocturnal seizures or non-convulsive status epilepticus. Many of these patients experience their seizures only during sleep. They can have seemingly bizarre features as they originate from the frontal lobe of the brain. Often, individuals with ring chromosome 20 syndrome are initially found to have complex partial seizures of frontal lobe origin, though imaging studies do not show a corresponding structural brain abnormality. In certain patients, these seizures may secondarily generalized.

Individuals from the ages of 0–17 years should be considered for ring 20 chromosome analysis if they have: predominantly complex partial seizures, medically refractory cryptogenic epilepsy, Lennox-Gastaut-like features with no cause identified, frequent subtle nocturnal seizures, an EEG showing prolonged high voltage frontally dominant slowing intermixed with spikes or sharp waves, an EEG showing overlapping features of continuous slow spike and wave discharges in sleep (CSWS) and electrical status epilepticus in sleep (ESES), and/or subsequent cognitive impairment/learning difficulties/mild retardation.These patients will typically have a normal childhood development until onset of epilepsy and lack evidence of dysmorphism or other congenital malformations.

2-hydroxyglutaric aciduria is an organic aciduria, and because of the stereoisomeric property of 2-hydroxyglutarate different variants of this disorder are distinguished:

Onset of late infantile GM1 is typically between ages 1 and 3 years.

Neurological symptoms include ataxia, seizures, dementia, and difficulties with speech.

Symptoms of early infantile GM1 (the most severe subtype, with onset shortly after birth) may include neurodegeneration, seizures, liver enlargement (hepatomegaly), spleen enlargement (splenomegaly), coarsening of facial features, skeletal irregularities, joint stiffness, distended abdomen, muscle weakness, exaggerated startle response to sound, and problems with gait.

About half of affected patients develop cherry-red spots in the eye.

Children may be deaf and blind by age 1 and often die by age 3 from cardiac complications or pneumonia.

- Autosomal recessive disorder; beta-galactosidase deficiency; neuronal storage of GM1 ganglioside and visceral storage of galactosyl oligosaccharides and keratan sulfate.

- Early psychomotor deterioration: decreased activity and lethargy in the first weeks; never sit; feeding problems - failure to thrive; visual failure (nystagmus noted) by 6 months; initial hypotonia; later spasticity with pyramidal signs; secondary microcephaly develops; decerebrate rigidity by 1 year and death by age 1–2 years (due to pneumonia and respiratory failure); some have hyperacusis.

- Macular cherry-red spots in 50% by 6–10 months; corneal opacities in some

- Facial dysmorphology: frontal bossing, wide nasal bridge, facial edema (puffy eyelids); peripheral edema, epicanthus, long upper lip, microretrognathia, gingival hypertrophy (thick alveolar ridges), macroglossia

- Hepatomegaly by 6 months and splenomegaly later; some have cardiac failure

- Skeletal deformities: flexion contractures noted by 3 months; early subperiosteal bone formation (may be present at birth); diaphyseal widening later; demineralization; thoracolumbar vertebral hypoplasia and beaking at age 3–6 months; kyphoscoliosis. *Dysostosis multiplex (as in the mucopolysaccharidoses)

- 10–80% of peripheral lymphocytes are vacuolated; foamy histiocytes in bone marrow; visceral mucopolysaccharide storage similar to that in Hurler disease; GM1 storage in cerebral gray matter is 10-fold elevated (20–50-fold increased in viscera)

- Galactose-containing oligosacchariduria and moderate keratan sulfaturia

- Morquio disease Type B: Mutations with higher residual beta-galactosidase activity for the GM1 substrate than for keratan sulfate and other galactose-containing oligosaccharides have minimal neurologic involvement but severe dysostosis resembling Morquio disease type A (Mucopolysaccharidosis type 4).

Ring chromosome 20, ring-shaped chromosome 20 or r(20) syndrome is a rare human chromosome abnormality where the two arms of chromosome 20 fuse to form a ring chromosome. The syndrome is associated with epileptic seizures, behaviour disorders and mental retardation.

When not all cells contain a ring chromosome 20, the individual suffers from ring 20 chromosomal mosaicism.Ring Chromosome 20 syndrome is thought to be an underdiagnosed condition. Since chromosomal analysis or karyotype testing is not a routine investigation for patients with epilepsy, the diagnosis of ring chromosome 20 syndrome is typically delayed or unrecognized.

The specific and familial association of BIFE and PKC defines a novel clinical entity : the infantile convulsions and choreoathetosis syndrome. The first observation was made in four families where children were affected with nonfebrile convulsions at age 3–12 months.Partial epileptic seizures started with a psychomotor arrest and a deviation of the head and eyes to one side, followed inconstantly by unilateral jerks.In some cases, seizures generalized secondarily. None of the interictal electroencephalograms showed epileptiform abnormalities, and magnetic-resonance imaging were normal. These convulsions had a favorable outcome. At 5–8 years of age affected children developed abnormal movements. They presented with twisting movements of the hands of a reptilian type when stressed or embarrassed. They also developed jerky movements of the legs after running. Initially, abnormal movements were intermediate in speed between quick and slow, typical of paroxysmal choreoathetosis. Combinations of abnormal movements involving the arms, legs, trunk and occasionally the head were observed. The attacks lasted only a few minutes, occurring with a frequency of 5-30 episodes per day and were not accompanied by unconsciousness. In all patients, abnormal movements disappeared at 25–30 years of age without any treatment. Since the first report similar clinical presentations have been published which confirm the specificity of the ICCA syndrome.

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.

Infantile convulsions and choreoathetosis (ICCA) syndrome is a neurological genetic disorder with an autosomal dominant mode of inheritance. It is characterized by the association of benign familial infantile epilepsy (BIFE) at age 3–12 months and later in life with paroxysmal kinesigenic choreoathetosis. The ICCA syndrome was first reported in 1997 in four French families from north-western France and provided the first genetic evidence for common mechanisms shared by benign infantile seizures and paroxysmal dyskinesia. The epileptic origin of PKC has long been a matter of debates and PD have been classified as reflex epilepsies.Indeed, attacks of PKC and epileptic seizures have several characteristics in common, they both are paroxysmal in presentation with a tendency to spontaneous remission, and a subset of PKC responds well to anticonvulsants. This genetic disease has been mapped to chromosome 16p-q12. More than 30 families with the clinical characteristics of ICCA syndrome have been described worldwide so far.

If a cause presents itself, the syndrome is referred to as "symptomatic" West syndrome, as the attacks manifest as a symptom of another problem. Almost any cause of brain damage could be associated, and these are divided into prenatal, perinatal, and post-natal. The following is a partial list:

- In around one third of the children, there is evidence of a profound organic disorder of the brain. This includes:

- microcephaly

- cortical dysplasia

- cerebral atrophy

- lissencephaly

- bacterial meningitis

- phakomatoses (e.g. tuberous sclerosis)

- Aicardi syndrome

- cephalhematoma and

- vascular malformation.

- Furthermore, other causes increasingly being named in the literature are:

- Incontinentia pigmenti

- Foix-Chavany-Marie syndrome

- Patau syndrome (trisomy 13)

- Sturge-Weber syndrome

- neurometabolic diseases

- congential infections (e.g. Cytomegalovirus)

- hypoglycemia

- brain damage due to asphyxiation or hypoxia (lack of oxygen, e.g. during birth), periventricular leukomalacia, cephalhematoma, cerebrovascular accident or brain damage of various types as well as that caused by premature birth.

West syndrome appears in 1% to 5% of infants with Down syndrome. This form of epilepsy is relatively difficult to treat in children who do not have the chromosomal abnormalities involved in Down syndrome. However, in children with Down syndrome, the syndrome is often far more mild, and the children often react better to medication. The German Down Syndrom InfoCenter noted in 2003 that what was normally a serious epilepsy was in such cases often a relatively benign one.

EEG records for children with Down syndrome are often more symmetrical with fewer unusual findings. Although not all children can become entirely free from attacks with medication, children with Down syndrome are less likely to go on to develop Lennox-Gastaut syndrome or other forms of epilepsy than those without additional hereditary material on the 21st chromosome. The reason why it is easier to treat children with Down syndrome is not known.

If, however, a child with Down syndrome has seizures that are difficult to control, the child should be accessed for autistic spectrum disorder.

It typically presents as a severe encephalopathy with myoclonic seizures, is rapidly progressive and eventually results in respiratory arrest.Standard evaluation for inborn errors of metabolism and other causes of this presentation does not reveal any abnormality (no acidosis, no hypoglycaemia, or hyperammonaemia and no other organ affected). Pronounced and sustained hiccups in an encephalopathic infant have been described as a typical observation in non-ketotic hyperglycinaemia.

Children are most commonly identified with Aicardi syndrome before the age of five months. A significant number of girls are products of normal births and seem to be developing normally until around the age of three months, when they begin to have infantile spasms. The onset of infantile spasms at this age is due to closure of the final neural synapses in the brain, a stage of normal brain development. A number of tumors have been reported in association with Aicardi syndrome: choroid plexus papilloma (the most common), medulloblastoma, gastric hyperplastic polyps, rectal polyps, soft palate benign teratoma, hepatoblastoma, parapharyngeal embryonal cell cancer, limb angiosarcoma and scalp lipoma.

Aicardi syndrome is typically characterized by the following triad of features - however, one of the "classic" features being missing does not preclude a diagnosis of Aicardi Syndrome, if other supporting features are present.

1. Partial or complete absence of the corpus callosum in the brain (agenesis of the corpus callosum);

2. Eye abnormalities known as "lacunae" of the retina that are quite specific to this disorder; [optic nerve coloboma]]; and

3. The development in infancy of seizures that are called infantile spasms.

Other types of defects of the brain such as microcephaly, polymicrogyria, porencephalic cysts and enlarged cerebral ventricles due to hydrocephalus are also common in Aicardi syndrome.

FIRES seizures are non-focal - there is no specified starting or stopping point - making brain surgery impossible. These seizures damage cognitive abilities of the brain such as memory or sensory abilities. This can result in learning disabilities, behavioral disorders, memory issues, sensory changes, inability to move, and death. Children continue to have seizures throughout their lives.

Glycine encephalopathy (also known as non-ketotic hyperglycinemia or NKH) is a rare autosomal recessive disorder of glycine metabolism. After phenylketonuria, glycine encephalopathy is the second most common disorder of amino acid metabolism. The disease is caused by defects in the glycine cleavage system, an enzyme responsible for glycine catabolism. There are several forms of the disease, with varying severity of symptoms and time of onset. The symptoms are exclusively neurological in nature, and clinically this disorder is characterized by abnormally high levels of the amino acid glycine in bodily fluids and tissues, especially the cerebral spinal fluid.

Glycine encephalopathy is sometimes referred to as "nonketotic hyperglycinemia" (NKH), as a reference to the biochemical findings seen in patients with the disorder, and to distinguish it from the disorders that cause "ketotic hyperglycinemia" (seen in propionic acidemia and several other inherited metabolic disorders). To avoid confusion, the term "glycine encephalopathy" is often used, as this term more accurately describes the clinical symptoms of the disorder.

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.

In 1963, a doctor studied two female infants who showed symptoms of mental retardation, congenital cataracts, epileptic fits and small stature. The two girls died at the age of 4 and 8 months. The autopsy revealed renal tubular necrosis and encephalopathy.

Crome syndrome is a rare disease defined by various symptoms, including epilepsy, intellectual disability, eye and kidney problems. It usually causes death in 4 to 8 months.

Fumarase deficiency (or fumaric aciduria), also known as "Polygamist Down's", is an autosomal recessive metabolic disorder in krebs cycle characterized by a deficiency of the enzyme fumarate hydratase, which causes a buildup of fumaric acid in the urine, and a deficiency of malate.

Neurologic signs and symptoms include progressively delayed development, weak muscle tone (hypotonia), seizures, and abnormal movements. The body's network of blood vessels is also affected. Children with this disorder may experience rashes of tiny red spots (petechiae) caused by bleeding under the skin and blue discoloration in the hands and feet due to reduced oxygen in the blood (acrocyanosis). Chronic diarrhea is another common feature of ethylmalonic encephalopathy. EE is often identified by urine organic acid analysis, the excretion of ethylmalonic acid, methylsuccinic acid, isobutyrylglycine and isovalerylglucine. Patients will also often have elevated thiosulphate concentration in their urine.

The signs and symptoms of ethylmalonic encephalopathy are apparent at birth or begin in the first few months of life. Problems with the nervous system typically worsen over time, and most affected individuals survive only into early childhood. A few children with a milder, chronic form of this disorder have been reported, and there can be considerable phenotypic variation, even within families. The life expectancy of individuals with EE is less than ten years.

Ohtahara syndrome is rare and the earliest-appearing age-related epileptic encephalopathy, with seizure onset occurring within the first three months of life, and often in the first ten days. Many, but not all, cases of OS evolve into other seizure disorders, namely West syndrome and Lennox-Gastaut syndrome.

The primary outward manifestation of OS is seizures, usually presenting as tonic seizures (a generalized seizure involving a sudden stiffening of the limbs). Other seizure types that may occur include partial seizures, clusters of infantile spasms, and, rarely, myoclonic seizures. In addition to seizures, children with OS exhibit profound mental and physical retardation.

Clinically, OS is characterized by a "burst suppression" pattern on an EEG. This pattern involves high voltage spike wave discharge followed by little brain wave activity.

It is named for the Japanese neurologist Shunsuke Ohtahara (1930–2013), who identified it in 1976.

Onset is usually confined to infancy and early childhood, with peak prevalence at 18–36 months. In rare cases, particularly where the child is severely mentally impaired, onset may extend to adolescence.

The classical symptoms of the syndrome are spasmodic torticollis and dystonia. Nodding and rotation of the head, neck extension, gurgling, writhing movements of the limbs, and severe hypotonia have also been noted.

Spasms may last for 1–3 minutes and may occur up to 10 times a day. Ingestion of food is often associated with occurrence of symptoms; this may result in reluctance to feed. Associated symptoms, such as epigastric discomfort, vomiting (which may involve blood) and abnormal eye movements have been reported. Clinical signs may also include anaemia.

Febrile infection-related epilepsy syndrome (FIRES) is a form of epilepsy that affects children three to fifteen years old. A healthy child that may have been ill in the last few days or with a lingering fever goes into a state of continuous seizures. The seizures are resistant to seizure medications and treatments, though barbiturates may be administered. Medical diagnostic tests may initially return no clear diagnosis and may not detect any obvious swelling on the brain. The syndrome is very rare: it may only affect 1 in 1,000,000 children.