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.

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.

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.

Usually the cerebellum and brain stem are formed normally, although in some cases the cerebellum may also be absent. An infant with hydranencephaly may appear normal at birth or may have some distortion of the skull and upper facial features due to fluid pressure inside the skull. The infant's head size and spontaneous reflexes such as sucking, swallowing, crying, and moving the arms and legs may all seem normal, depending on the severity of the condition. However, after a few weeks the infant sometimes becomes irritable and has increased muscle tone (hypertonia). After several months of life, seizures and hydrocephalus may develop, if they did not exist at birth. Other symptoms may include visual impairment, lack of growth, deafness, blindness, spastic quadriparesis (paralysis), and intellectual deficits.

Some infants may have additional abnormalities at birth including seizures, myoclonus (involuntary sudden, rapid jerks), limited thermoregulation abilities, and respiratory problems.

Still other infants display no obvious symptoms at birth, going many months without a confirmed diagnosis of hydranencephaly. In some cases a severe hydrocephalus, or other cephalic condition, is misdiagnosed.

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.

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."

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.

Hydranencephaly or hydrancephaly is a condition in which the brain's cerebral hemispheres are absent to varying degrees and the remaining cranial cavity is filled with cerebrospinal fluid.

Hydranencephaly (or hydrancephaly) is a type of cephalic disorder.

These disorders are congenital conditions that derive from either damage to, or abnormal development of, the fetal nervous system in the earliest stages of development in utero. Cephalic is the medical term for “head” or “head end of body.” These conditions do not have any definitive identifiable cause factor; instead generally attributed to a variety of hereditary or genetic conditions, but also by environmental factors such as maternal infection, pharmaceutical intake, or even exposure to high levels of radiation.

This should not be confused with hydrocephalus, which is an accumulation of excess cerebrospinal fluid in the ventricles of the brain.

In hemihydranencephaly, only half of the cranial cavity is filled with fluid.

Neuronal migration disorder (NMD) refers to a heterogenous group of disorders that, it is supposed, share the same etiopathological mechanism: a variable degree of disruption in the migration of neuroblasts during neurogenesis. The neuronal migration disorders are cerebral dysgenesis, brain malformations caused by primary alterations during neurogenesis; on the other hand, brain malformations are highly diverse and refer to any insult to the brain during its formation and maturation due to intrinsic or extrinsic causes that ultimately will alter the normal brain anatomy. However, there is some controversy in the terminology because virtually any malformation will involve neuroblast migration, either primarily or secondarily.

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)

Different people are affected very differently by this disease. The main manifestation is fluid-filled cysts that grow on the brain and can cause damage that varies depending on their location and severity. Symptoms may manifest early in infancy, or may manifest as late as adulthood. Symptoms associated with autosomal dominant porencephaly type I include migraines, hemiplegia or hemiparesis, seizures, cognitive impairment, strokes, dystonia, speech disorders, involuntary muscle spasms, visual field defects, and hydrocephalus.

Autosomal dominant porencephaly type I is a rare type of porencephaly that causes cysts to grow on the brain and damage to small blood vessels, which can lead to cognitive impairment, migraines, seizures, and hemiplegia or hemiparesis.

Developmental regression is when a child loses an acquired function or fails to progress beyond a prolonged plateau after a period of relatively normal development. Developmental regression could be due to metabolic disorders, progressive hydrocephalus, worsening of seizures, increased spasticity, worsening of movement disorders or parental misconception of acquired milestones. The timing of onset of developmental regression can be established by repeated medical evaluations, prior photographs and home movies. Whether the neurologic decline is predominantly affecting the gray matter or the white matter of the brain needs to be ascertained. Seizures or EEG changes, movement disorders, blindness with retinal changes, personality changes and dementia are features suggestive of grey matter involvement.

The Landau–Kleffner syndrome is characterized by the sudden or gradual development of aphasia (the inability to understand or express language) and an abnormal electroencephalogram (EEG). LKS affects the parts of the brain that control comprehension and speech (Broca's area and Wernicke's area). The disorder usually occurs in children between the ages of 3 and 7 years. There appears to be a male dominance in the diagnosis of the syndrome (ratio of 1.7:1, men to women).

Typically, children with LKS develop normally, but then lose their language skills. While many affected individuals have clinical seizures, some only have electrographic seizures, including electrographic status epilepticus of sleep (ESES). The first indication of the language problem is usually auditory verbal agnosia. This is demonstrated in patients in multiple ways including the inability to recognize familiar noises and the impairment of the ability to lateralize or localize sound. In addition, receptive language is often critically impaired, however in some patients, impairment in expressive language is the most profound. In a study of 77 cases of Landau–Kleffner syndrome, 6 were found to have this type of aphasia. Because this syndrome appears during such a critical period of language acquisition in a child's life, speech production may be affected just as severely as language comprehension. The onset of LKS is typically between 18 months and 13 years, the most predominant time of emergence being between 3 and 7 years.

Generally, earlier manifestation of the disease correlates with poorer language recovery, and with the appearance of night seizures that last for longer than 36 months. LKS has a wide range of symptom differences and lacks a uniformity in diagnostic criteria between cases, and many studies don't include follow-ups on the patients, so no other relationships between symptoms and recovery have been made known.

Language deterioration in patients typically occurs over a period of weeks or months. However, acute onset of the condition has also been reported as well as episodic aphasia.

Seizures, especially during the night, are a heavily weighted indicator of LKS. The prevalence of clinical seizures in acquired epileptic aphasia (LKS) is 70-85%. In one third of patients, only a single episode of a seizure was recorded. The seizures typically appear between the ages of 4 and 10 and disappear before adulthood (around the age of 15).

Often, behavioral and neuropsychologic disturbances accompany the progression of LKS. Behavioral issues are seen in as many as 78% of all cases. Hyperactivity and a decreased attention span are observed in as many as 80% of patients as well as rage, aggression, and anxiety. These behavior patterns are considered secondary to the language impairment in LKS. Impaired short-term memory is a feature recorded in long-standing cases of acquired epileptic aphasia.

Landau–Kleffner syndrome (LKS)—also called infantile acquired aphasia, acquired epileptic aphasia or aphasia with convulsive disorder—is a rare childhood neurological syndrome.

It is named after William Landau and Frank Kleffner, who characterized it in 1957 with a diagnosis of six children.

There are a variety of medical conditions affecting cognitive ability. This is a broad concept encompassing various intellectual or cognitive deficits, including intellectual disability, deficits too mild to properly qualify as intellectual disability, various specific conditions (such as specific learning disability), and problems acquired later in life through acquired brain injuries or neurodegenerative diseases like dementia. These disabilities may appear at any age.

The most common symptoms of acquired and transient cortical blindness include:

- A complete loss of visual sensation and of vision

- Preservation/sparing of the abilities to perceive light and/or moving, but not static objects (Riddoch syndrome)

- A lack of visual fixation and tracking

- Denial of visual loss (Anton–Babinski syndrome)

- Visual hallucinations

- Macular sparing, in which vision in the fovea is spared from the blindness.

An acquired brain injury (ABI) is brain damage caused by events after birth, rather than as part of a genetic or congenital disorder. It usually affects cognitive, physical, emotional, social or independent functioning and can result from either traumatic brain injury or nontraumatic injury such as stroke, infection or substance abuse. Most definitions of ABI exclude neurodegenerative disorders.

People with a brain injury may have difficulty controlling, coordinating and communicating their thoughts and actions. They may or may not retain their intellectual abilities, depending on the type and extent of the injury. However, the intellectual abilities of a person with a brain injury are likely to be interfered with by the resulting thought coordination and communication difficulties, which can make it difficult for them to express themselves in a manner intelligible to others. This may give the impression of a damaged intelligence even in people with normal intellectual capacity.

Cortical blindness is the total or partial loss of vision in a normal-appearing eye caused by damage to the brain's occipital cortex. Cortical blindness can be acquired or congenital, and may also be transient in certain instances. Acquired cortical blindness is most often caused by loss of blood flow to the occipital cortex from either unilateral or bilateral posterior cerebral artery blockage (ischemic stroke) and by cardiac surgery. In most cases, the complete loss of vision is not permanent and the patient may recover some of their vision (Cortical visual impairment). Congenital cortical blindness is most often caused by perinatal ischemic stroke, encephalitis, and meningitis.

Rarely, a patient with acquired cortical blindness may have little or no insight that they have lost vision, a phenomenon known as Anton–Babinski syndrome.

Cortical blindness and cortical visual impairment (CVI), which refers to the partial loss of vision caused by cortical damage, are both classified as subsets of neurological visual impairment (NVI). NVI and its three subtypes—cortical blindness, cortical visual impairment, and delayed visual maturation—must be distinguished from ocular visual impairment in terms of their different causes and structural foci, the brain and the eye respectively. One diagnostic marker of this distinction is that the pupils of individuals with cortical blindness will respond to light whereas those of individuals with ocular visual impairment will not.

Oculocerebrocutaneous syndrome (also known as Delleman–Oorthuys syndrome) is a condition characterized by orbital cysts, microphthalmia, porencephaly, agenesis of the corpus callosum, and facial skin tags.

Sinus pericranii typically present as soft palpable masses along midline skull, which may fluctuate in size depending on body positioning. Classically, these lesions are not associated with color change of the overlying skin, such as with other vascular lesions such as hemangioma.

Sinus pericranii (SP) is a rare disorder characterized by a congenital (or occasionally, acquired) epicranial venous malformation of the scalp. Sinus pericranii is an abnormal communication between the intracranial and extracranial venous drainage pathways. Treatment of this condition has mainly been recommended for aesthetic reasons and prevention of hemorrhage.

Chorea (or choreia, occasionally) is an abnormal involuntary movement disorder, one of a group of neurological disorders called dyskinesias. The term "chorea" is derived from the Greek word "χορεία" (=dance; see choreia), as the quick movements of the feet or hands are comparable to dancing.

The term hemichorea refers to chorea of one side of the body, such as chorea of one arm but not both (analogous to hemiballismus).

Chorea is characterized by brief, semi-directed, irregular movements that are not repetitive or rhythmic, but appear to flow from one muscle to the next.

These 'dance-like' movements of chorea often occur with athetosis, which adds twisting and writhing movements. Walking may become difficult, and include odd postures and leg movements.

Unlike ataxia, which affects the quality of voluntary movements, or Parkinsonism, which is a hindrance of voluntary movements, the movements of chorea and ballism occur on their own, without conscious effort. Thus, chorea is said to be a hyperkinetic movement disorder.

When chorea is serious, slight movements will become thrashing motions; this form of severe chorea is referred to as ballism or ballismus.

AOS and expressive aphasia (also known as Broca's aphasia) are commonly mistaken as the same disorder mainly because they often occur together in patients. Although both disorders present with symptoms such as a difficulty producing sounds due to damage in the language parts of the brain, they are not the same. The main difference between these disorders lies in the ability to comprehend spoken language; patients with apraxia are able to fully comprehend speech, while patients with aphasia are not always fully able to comprehend others' speech.

Conduction aphasia is another speech disorder that is similar to, but not the same as, apraxia of speech. Although patients who suffer from conduction aphasia have full comprehension of speech, as do AOS sufferers, there are differences between the two disorders. Patients with conduction aphasia are typically able to speak fluently, but they do not have the ability to repeat what they hear.

Similarly, dysarthria, another motor speech disorder, is characterized by difficulty articulating sounds. The difficulty in articulation does not occur due in planning the motor movement, as happens with AOS. Instead, dysarthria is caused by inability in or weakness of the muscles in the mouth, face, and respiratory system.