NORD gratefully acknowledges Phillip L. Pearl, MD, Chief of Epilepsy and Clinical Neurophysiology, Boston Children’s Hospital, Harvard Medical School, for assistance in the preparation of this report.
Congenital bilateral perisylvian syndrome (CBPS) 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 intellectual disability 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).
CBPS is characterized by partial paralysis of the muscles on both sides of the face (facial diplegia), seizures, and intellectual disability.
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 frequently generalized. (Epileptic seizures may be broadly categorized into generalized and focal-onset seizures. Generalized seizures appear to arise over a wide area or both sides or hemispheres of the cerebral cortex, while focal 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). (For more information on these seizure types, use “Epilepsy” 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 intellectual disability is usually present.
The exact cause of CBPS is not completely understood. Associated symptoms and findings are believed to be due to improper development of the outer surface of the brain (cerebral cortex) during embryonic growth. The cerebral cortex, which is responsible for conscious movement and thought, normally consists of several deep folds (gyri) and grooves (sulci). However, in cases of CBPS, newly developed embryonic cells (neuroblasts) fail to migrate to their destined locations in the outer portion of the brain (neuronal dysmigration). As a result, the cerebral cortex does not develop the normal number of cellular layers, and the deep grooves (sulci) that normally develop on the sides (lateral) of both cerebral hemispheres (sylvian fissures or sulcus lateralis cerebri) may form improperly, resulting in an abnormally increased number of folds (gyri) that are unusually small (bilateral perisylvian polymicrogyria). In some cases, the groove separating the front (frontal) and side (parietal) portions (lobes) of the brain (fissure of Rolando or sulcus centralis cerebri) may also be malformed.
In most cases, CBPS appears to occur randomly for unknown reasons (sporadically) in the absence of a family history. However, a few families have been reported in which more than one member has been affected. In such cases, researchers suggest that the condition may potentially be due to an underlying genetic abnormality that may have autosomal recessive inheritance. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In recessive disorders, the condition does not appear unless a person inherits a defective, or mutated, gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
CBPS is a rare neurological disorder that was first recognized as a distinct syndrome in the early 1990s. The disorder is usually apparent at birth (congenital) or early in life, based upon characteristic physical findings and specialized imaging tests. In affected individuals who exhibit infantile spasms, onset of these sudden, involuntary contractions tends to occur within the first six months of life. Onset of other forms of epilepsy potentially associated with CBPS (e.g., atypical absence seizures, atonic-tonic seizures, and/or tonic-clonic seizures) may occur between two to 12 years of life. CBPS appears to affect males and females in equal numbers. Various subtypes have been described based on radiological features as seen on MRI; the prevalence is now known. In a recent review of 35 new cases of polymicrogyria, 22 had bilateral perisylvian distribution (Flotats-Bastardas et al 2012).
CBPS may be diagnosed at birth or early in life, based upon a thorough clinical evaluation, a detailed patient history, and a complete neurological evaluation including advanced imaging techniques such as electroencephalography (EEG), computerized tomography (CT) scanning, or magnetic resonance imaging (MRI).
During an EEG, the brain’s electrical impulses are recorded; such studies may reveal brain wave patterns that are characteristic of certain types of epilepsy. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of the brain’s tissue structure. During MRI, a magnetic field and radio waves are used to create cross-sectional images of the brain.
CT and MRI images may confirm malformations of certain areas of the cerebral cortex (perisylvian and/or perirolandic malformations) and abnormalities of the brain’s deep folds and grooves. In addition, analysis of speech abnormalities due to impaired muscle control (dysarthria) may reveal characteristic patterns among individuals with CBPS, such as difficulty with certain vowels or noise ranges.
The treatment of CBPS is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians, neurologists, surgeons, physical therapists, and others may need to systematically and comprehensively plan an affected child’s treatment.
Treatment with anticonvulsant drugs may help prevent, reduce, or control various types of epilepsy associated with CBPS. In affected infants who exhibit sudden, involuntary contractions of the head, neck, and trunk and/or uncontrolled extension of the legs and/or arms in the first six months of life (infantile spasms or West Syndrome), treatment with adrenocorticotropic hormone (ACTH or corticotropin) has resolved the seizures in some cases. In cases when drug therapy is ineffective in preventing or controlling seizures (intractable epilepsy), surgical removal of tissue in certain areas of the brain (focal corticectomy) or surgical division (callosotomy) of the fibers joining the two cerebral hemispheres (corpus callosum) may result in seizure improvement.
Early intervention is important in ensuring that children with CBPS reach their potential. Special services that may be beneficial to affected children may include physical therapy, special remedial education, speech therapy, and other medical, social, and/or vocational services.
Genetic counseling will be of benefit for affected children and their families. Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:
[Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder (e.g., epilepsy or mental retardation).]
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