Bilateral Perisylvian Polymicrogyria

(formerly called Congenital Bilateral Perisylvian Syndrome)

(Source: National Organization for Rare Disorders)

General Discussion

Congenital Bilateral Perisylvian Syndrome (CBPS, also called Bilateral Perisylvian Polymicrogyria) is an extremely rare neurological disorder that may be apparent at birth (congenital), infancy, or later during childhood. It is characterized by partial paralysis of muscles on both sides (diplegia) of the face, tongue, jaws, and throat (pseudobulbar palsy); difficulties in speaking (dysarthria), chewing (mastication), and swallowing (dysphagia); and/or sudden episodes of uncontrolled electrical activity in the brain (epilepsy). In most cases, mild to severe mental retardation is also present. Associated symptoms and findings are thought to be due to improper development of the outer surface of the brain (cerebral cortex) during embryonic growth (neuronal dysmigration). In most cases, the disorder appears to occur randomly for unknown reasons (sporadically).

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Symptoms

Congenital Bilateral Perisylvian Syndrome, also known as CBPS, is characterized by partial paralysis of the muscles on both sides of the face (facial diplegia), seizures, and mental retardation.

In those with CBPS, impairment of certain nerves (cranial nerves) that emerge from the brain may result in sudden, involuntary spasms of facial muscles as well as partial paralysis of both sides (diplegia) of the face, jaws, tongue, and throat (pharynx). Impaired control of these muscles may cause difficulty chewing (mastication), swallowing (dysphagia), and/or pronouncing certain sounds and words (dysarthria). In some cases, affected individuals may be unable to speak.

Most individuals with CBPS also experience seizures or sudden recurrent episodes in which uncontrolled electrical discharges from nerve cells (neurons) of the outer region of the brain (cerebral cortex) cause involuntary muscle contractions, sensory disturbances, loss of consciousness, and/or other associated findings (epilepsy). Several different types of seizures may occur in the same affected individual. However, reports indicate that the epileptic seizures are most frequently generalized rather than partial in nature. (Epileptic seizures may be broadly categorized into generalized and partial seizures. Generalized seizures appear to arise over a wide area or both sides or hemispheres of the cerebral cortex, while partial seizures have an onset limited to a part of one hemisphere.)

In some cases, generalized seizures may be characterized by sudden breaks or momentary lapses of awareness or action; fluttering of the eyelids; twitching of facial muscles; and/or other findings (absence or petit mal seizures). In those with CBPS, the beginning and end of such seizure episodes may not be as distinct as often seen in absence seizures or they may be associated with loss of muscle tone or other atypical findings (i.e., atypical absence or petit mal seizures). Additional types of generalized seizures occur in some cases. Some affected individuals may have seizure episodes characterized by sustained muscle contraction or muscle jerks followed by sudden loss of muscle tone (atonic [astatic] seizures), potentially causing falls. In addition, some may have seizures characterized by an abrupt loss of consciousness, generalized stiffening of muscles, rhythmic contraction and relaxation of all muscle groups, and other findings (tonic-clonic or grand-mal seizures). In some cases, affected infants may first experience seizures characterized by sudden, brief, involuntary contractions of the neck, trunk, arms, and legs (infantile spasms or West Syndrome). (For more information on these seizure types, use "Epilepsy" or "West" as your search terms in the Rare Disease Database.)

Children with CBPS may also have delays in the development of certain physical, mental, and behavioral skills that are typically acquired at particular stages (developmental milestones), such as language and speech development and certain motor abilities. In addition, mild to severe mental retardation is usually present.

(Source: Contact a Family)

The term Congenital Bilateral Perisylvian syndrome (CBPS) describes a structural malformation of the brain. The underlying anomaly is Polymicrogyria, a malformation of the cerebral cortex (outer layer of the brain). The term polymicrogyria designates an excessive number of small and prominent convolutions spaced out by shallow and enlarged sulci (grooves), giving the surface of the brain a lumpy aspect. Although it may be difficult to recognise mild forms of polymicrogyria on a magnetic resonance imaging (MRI) scan, infolding of the outer layer of the brain and secondary, irregular, thickening due to packing of microgyri (small folds) represent quite distinctive MRI characteristics.

Patients have paralysis of the face, throat, tongue and the chewing process, with dysarthria (speech difficulties) and drooling. Most have cognitive deficit and epilepsy. Fixed deformity of the ankle joints (arthrogryposis) has been described in some patients. Seizures usually begin between the ages of 4 and 12 years and are poorly controlled in about 60 per cent of patients. The most frequent seizure types are atypical absences, tonic or atonic drop attacks and tonic-clonic seizures, often occurring as Lennox-Gastaut syndrome. A minority of patients (26 per cent) have partial seizures.

Polymicrogyria may have a focal or regional distribution or involve the whole cortical mantle (covering of the brain). There are consequently a wide spectrum of clinical manifestations which include children with severe encephalopathies (brain impairments) and intractable epilepsy, or normal individuals with selective impairment of cognitive functions (mental processes) in whom the mild cortical abnormality is only detected on pathological brain study.

Several malformation syndromes featuring bilateral polymicrogyria have been described, including bilateral perisylvian polymicrogyria (the most frequent form), bilateral parasagittal parietooccipital polymicrogyria, bilateral frontal polymicrogyria and unilateral perisylvian or multilobar polymicrogyria. Several distinct entities might exist with regional distribution in which contiguous, non overlapping areas of the cerebral cortex are involved, possibly under the influence of regionally expressed developmental genes. Consistent familial recurrence has been reported only for bilateral perisylvian polymicrogyria, which is sporadic in the great majority of patients. A genetic basis is also possible for unilateral polymicrogyria, at least in some cases.

Bilateral perisylvian polymicrogyria has been reported in children born from identical twin pregnancies which were complicated by twin-twin transfusion syndrome.

(Source: Christopher A. Walsh Laboratory)

Perisylvian Syndrome refers to a neurological disorder in which a particular area of the brain (called the perisylvian region) develops abnormally. This disorder has also been referred to by other names in the past, including Worster-Drought Syndrome, when it was not clear what the underlying problem was. We now know, however, that most if not all patients with this disorder have a specific developmental abnormality in their perisylvian region called polymicrogyria, which means that the normal pattern of folds on the surface of the brain is replaced with many small abnormal folds. Therefore, we now generally refer to this disorder as perisylvian polymicrogyria.

Perisylvian polymicrogyria can vary significantly in severity. On MRI, it can be seen on both sides of the brain (bilateral) or on just one side (unilateral). Individuals with perisylvian syndrome may have learning difficulties, cerebral palsy, and seizures, as with many developmental brain problems. What is more distinctive about perisylvian polymicrogyria, however, is that individuals often have problems using the muscles of the face, throat, jaws and tongue Ð when this is mild it may lead to just a speech impediment or a tendency to drool but if more severe it can lead to difficulties with feeding as a baby. In addition, some individuals with perisylvian polymicrogyria may be born with joint deformities (arthrogryposis).

There are likely many different causes of perisylvian polymicrogyria. Sometimes it may result from problems during pregnancy. For example, perisylvian polymicrogyria has been seen in children born from identical twin pregnancies complicated by twin-twin transfusion syndrome. It is possible that the affected twin did not receive enough oxygen to the brain during pregnancy, which resulted in the development of the polymicrogyria. In other cases, perisylvian polymicrogyria may be due to a change (mutation) in a gene. Reports from some families with multiple affected members suggest different modes of inheritance including X-linked, autosomal recessive, and autosomal dominant. One study showed that a few families were linked to the Xq28 region but no gene in that location has yet been identified.