Congenital Bilateral Perisylvian syndrome
The term congenital bilateral perisylvian syndrome (CBPS) describes a structural malformation of the brain. The underlying abnormality is known as ‘polymicrogyria’, which is a malformation of the cerebral cortex (outer layer of the brain). The term polymicrogyria designates an excessive number of small and prominent convolutions (folds) 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.
Polymicrogyria may affect the whole or part of the cortex. Perisylvian polymicrogyria affects the Sylvian fissure, which contains the areas that control movements of the face, tongue and throat. It has become clear that this condition and the bulbar form of cerebral palsy or Worster-Drought syndrome are very closely related or part of a spectrum of the same condition. However, many children with Worster-Drought syndrome have normal MRI scans.
Last updated October 2015 by Professor B Neville, Emeritus Professor of Paediatric Neurology, UCL Institute of Child Health and Great Ormond Street Hospital, London, UK.
CBPS patients have weakness of the face, throat, tongue and the chewing process, with lack of speech or slurred speech and drooling. Most have learning impairments (see entry Learning Disability), behaviour problems and epilepsy. Arthrogryposis (fixed deformity of the ankle joints) has been described in some patients. Seizures usually begin between the ages of four to 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, sometimes occurring as Lennox-Gastaut syndrome. A minority of patients have partial seizures.
Consistent familial recurrence has been reported only for bilateral perisylvian polymicrogyria, which is sporadic in the great majority of patients. In some families, children with similar problems with and without MRI abnormalities have been observed. 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 that were complicated by twin-twin transfusion syndrome.
This is primarily an MRI diagnosis by may need careful examination to be sure if polymicrogyria are present.
Seizures are treated in the usual fashion but there are often difficulties in their management. In addition these children very commonly have cognitive delay, attention deficit hyperactive disorder, autism spectrum condition, depression and anxiety and should be screened and treated for these.
Several families with multiple affected members have been reported with possible autosomal recessive, dominant and X-linked recessive inheritance. These families have been linked to the Xq28 chromosomal region but the causative gene is not known at present.
Prenatal diagnosis using fetal ultrasound or magnetic resonance imaging may be particularly difficult as the regions of the brain that are involved in this malformation may not have reached their final folding until birth.
Information and support in the UK for congenital bilateral perisylvian syndrome is provided by the Worster-Drought Syndrome Support Group (see entry Worster-Drought syndrome).