Prenatal diagnosis of lissencephaly : A case report Prenatalna dijagnoza lizencefalije

Introduction. Lissencephaly (“smooth brain”) forms a major group of brain malformations due to abnormal neuronal migration. It can cause severe intellectual and motor disability and epilepsy in children. The prenatal diagnosis of this malformation is rare. Case report. We presented a case of the prenatal diagnosis of lissencephaly. A 30-year old pregnant woman was reffered to the hospital at the week 35 of gestation for magnetic resonance imaging (MRI) after an ultrasound examination demonstrated fetal cerebral ventriculomegaly. Fetal MRI of the brain showed “smooth”, agyrya cortex. The female infant was born at term with birth weight of 2,500 g and Apgar score 8, showing global developmental delay. Postnatal ultrasound and MRI confirmed classical lissencephaly. She is now 8 years old and has spastic quadriparesis, mental retardation and epilepsy. Conclusion. Confirmation of the ultrasound diagnosis with MRI is desirable for the prenatal diagnosis of lissencephaly.


Introduction
Malformations of cortical development are significant causes of delay in psychomotor development and epilepsy in children [1][2][3] .Lyssencephaly ("smooth brain") forms a major group of brain malformations due to widespread abnormal migration 1,2,4 .Other two major categories of malformations are cobblestone complex malformations (also known as type 2 lissencephaly) and all types of heterotopia.With magnetic resonance imaging (MRI), these disorders can be identified in life 5 .
Classical lissencephaly (OMIM # 607432), formely designed as type 1, is a severe neurological malformation charac-terized by a lack of sulcation of the cortical plate, that produces a smooth brain surface, cortical thickening with four primitive layers and ventriculomegaly 3,6,7 .The brain has no gyri (agyria) or very low gyri (pachygyria) or there is a related disorder known as subcortical band heterotopia (SBH) 3,7,8 .Due to contribution of computed tomography (CT) and MRI, this spectrum of gyral abnormalities was graded in the following way: grade 1, complete agyria; grade 2, diffuse agyria with few sulci in anterior regions; grade 3, anterior pachygyria (few, broad gyri) and posterior agyria; grade 4, pachygyria more prominent in the posterior brain regions than in anterior; grade 5, pachygyria posteriorly with SBH and grade 6, SBH only 9  mutations of LIS1 at 17 p.13.3 is highly specific for more severe changes in posterior brain regions ( p > a gradient), while lissencephaly due to mutations of XLIS at X q 22.3-q23 often have more severe gyral abnormalities in the anterior brain regions (a > p gradient) 10 .TUBA1A usually show posteriorpredominant lissencephaly similar to LIS1 11 .
Studies have identified two major genes responsible for classical lissencephaly: LIS1 (named PAFAH1B1) gene at 17 p13.3and the XLIS (DCX) gene at Xq 22.3-q23 [12][13][14] .Both proteins are important for normal neuronal migrational processes.Approximately 76% of patients with classical lissencephaly show mutations in these two genes 15 .Recently, mutations of TUBA1A gene at the 12q12-q14 is detected in several cases with lissencephaly.TUBA1A belongs to the alpha-tubulin protein family which is needed for correct cell movements.Mutation of TUBA1A are responsible for 1-4% of cases 16,17 .Other types of lissencephaly caused by mutation of: RELN, VLDLR and ARX have been decribed 10,18 .These types of lissencephaly are less common and known as "variant lissencephaly".It is important that the morphology of lissencephaly caused by mutations of those three genes differs from that caused by LIS1, DCX and TUBA1A mutations.Lissencephaly with cerebellar hypoplasia (LCH) results from mutations of two genes: the reelin (RELN) gene and very low-density lipoprotein receptor gene (VLDLR).Xlinked lissencephaly with abnormal genitalia and agenesis of the corpus callosum (XLAG) has been associated with ARX gene.
Children with classical lissencephaly usually have hypotonia at birth, but spasticity develop later in infancy.Clinical manifestations include seizures, spastic quadriplegia and profound mental retardation.The onset of seizures is usually between 6-12 months.Infantile spasms followed by hypsarrhytmia are seen in the majority of children and they respond at first to corticotropin or other antiepileptic drugs.Unfortunately, almost all children will go on to have frequent seizures and severe psychomotor retardation.LIS1 gene which cause classical lissencephaly is connected with two clinical disorders.The first one is the isolated lissencephaly sequence (ILS) which is characterized by lacks of typical facial appearance and the second is Miller-Dieker syndrome (MDS) (OMIM #247000), where typical facial features and other congenital defects exist 19,20 .
The prenatal diagnosis of this malformation is rare.MRI imaging should be useful in screening for malformation of cortical development such as lissencephaly.The aim of this case report was to characterise the delivery and postnatal neurodevelopmental outcome of the fetus reffered for MRI following suspicion on ultrasound of ventriculomegaly.

Case report
We presented a case of the prenatal diagnosis of the lissencephaly.A 30-year-old pregnant woman was reffered to the hospital at the week 35 of gestation for MRI after an ultrasound examination demonstrated fetal ventriculomegaly, defined as ventricular size (measured at the atrium of the lateral ventricle) more than 10 mm.At the week 35 of gesta-tion, the fetal MRI showed that the gyral pattern was smoother than the expected third-trimester configuration, suggesting lissencephaly (Figure 1).Fetal blood sampling by cordocentesis revealed a normal karyotype of 46, XX and screening for infections (toxoplasma, rubella, cytomegalovirus and herpes simplex virus) confirmed normal results.There was no consanguinity or family history of neurological disorders.The mother had three older sons and no history of spontaneous abortion.She did not have diabetes mellitus and denied any exposure to teratogenic agents or infectious diseases during pregnancy.The pregnancy was normal until 35 weeks gestation when ventriculomegaly was first noted on prenatal ultrasound.Then, the prenatal suspicion of lissencephaly was made, the parents were counseled accordingly, and they elected to continue the pregnancy.The female infant was born at the week 38 of gestation with the body weight of 2,500 g and 5-minutes Apgar score was 8. Abnormal fetal movement had not been noted during fetal ultrasonography.There was no complications during the vaginal vertex delivery which followed.Upon examination, mild generalised hypotonia and poor growth were noted, but apart from that, physical condition was unremarkable.Postnatal ultrasound of the brain showed characteristic findings for lissencephaly.There was the absence of gyration underneath the supperior sagittal sinus and a pseudo-liver pattern of echoreflections in the parenchyma between pia matter and ventricle caused by subcortical heterotopic neurons.The interhemispheric fissure was not flanked by branching sulci and the lateral fissure did not show a horizontal Y, but had been reduced to a slit, the point of which courses caudally downwards.This was a consequence of the absense of opercularization with a widely patient sylvian fossa that points caudally.Discrepant dilatation of the occipital horns, colpocephaly, was present and agenesis of the corpus callosum, too.MRI of the brain showed that the surface of the brain was flat due to the lack of sulcation, and that the sylvian fissures were shallow and vertically oriented; therefore, the brain had a figure-of-eight shape in axial section.The cortex was markedly thickened, and a hyperintense band corresponding to the sparse cell zone was clearly visible with asymmetric and mildly dilated lateral ventricles.There was also marked callosal hypoplasia and the diagnosis of lissencephaly was made.Colpocephaly, the completely "smooth" (agyrya) cortex and the open insula, were seen on axial MR planes (Figures 2 and 3).Cytogenetic analysis of blood lymphocytes revealed a 46, XX karyotype.Mutation analysis of the LIS1 gene was not performed because the parents refused.
First seizures were noted at the age of two months, and the baby was admitted to our hospital.Infantile spasms were continuosly observed and electroencephalography (EEG) showed hypsarrhythmia; thus, the diagnosis of West syndrome was made (Figure 4).Neurological examination was unremarkable except for hypotonia.Facial appearance, cranial nerves, and deep tendon reflexes were normal.Spasms disappeared after adrenocorticotropic hormone (ACTH) and vigabatrin therapy.Focal seizures appeared at the age of two years and were intractable, not responding to various antiepileptic drugs.Hypotonia was replaced by hypertonia and opisthotonic posturing.Deep tendon reflexes were exaggerated, and the Babinski sign and ankle clonus were elicited bilaterally.The growth was poor associated with microcephaly.She was not aware of her surroundings.Visual tracking was not adequate for the age, in the presence of intermittent ocular deviation with nystagmus.Later, focal seizures predominated and interictal EEG showed generalized spike and wave discharges (Figure 5).They were resistant to different medications (lamotrigine, valproate, topiramate, levetiracetam).The weakness progressed to paralysis and intelectual retardation was severe.Fundoduplication was performed at the age of four years due to persistent symptoms of gastroesophageal disease.
The girl is now aged 8 years, and her general condition is relatively stable.She remained with severe psychomotor delay, developing head control at the age of 4 years and not rolling until the age 5 years.She did not show any progression in psychomotor development and displayed spastic quadriplegia, mental retardation, intractable seizures and microcephaly.

Discussion
Gene mutations, extrinsic factors, maternal metabolic disturbances and specific syndromes are associated with malformations of cortical development.Apart from genetic factors which are responsible for lissencephaly, different environmental factors can cause lissencephalic-like syndromes, such as teratogens (trauma, hypoxia, toxins, drugs, radiation), infections (fetal cytomegalovirus infection) and maternal diabetes mellitus and phenylketonuria 21,22 .Genetic testing when there is a chromosome abnormality or gene mutations in the affected family, or ultrasound and MRI findings by detecting different structural defects, are diagnostic tools for prenatal diagnosis of lissencephaly [23][24][25] .The diagnosis is not easy when it is an isolated case as the one reported.
We reported the ultrasound and MRI prenatal diagnosis and postnatal confirmation of classical lissencephaly associated with severe intellectual and motor disability and intractable epilepsy.Clinical course of this child was significant for continued seizures and global developmental delay.Seizures were not responding to various antiepileptic drugs, confirming results of other studies about no effective treatment 26 .Many patients require better care because of feeding problems and infectious complications, and in that cases, children do reach early adulthood 27 .It is similar with our reported case.
Gyryfication is perhaps the most important change that occurs in the fetal brain during gestation 28 .In very preterm babies born around the week 22-23 of gestation the brain surface is smooth with very few sulci and gyri.Gyrification is progressing rapidly between 25 and 30 weeks 29 .Only after the 30th gestational week will gyration be developed sufficiently to allow the diagnosis of lissencephaly 30 .Discrepant dilatation of the occipital horns, colpocephaly and the absence of opercularization of insula are nearly always present ultrasound findings which should raise the suspicion on lissencephaly.When the disorder occurs in connection with other malformations such as cardiac defects, genital abnormalities and characteristic facies, the Miller-Dieker syndrome may be present.In many cases there is a deletion of the short arm of chromosome 17 and genetic testing is important to diagnose it 31 .
The important characteristic of classical lissencephaly is the similar pathological and radiological pattern even when different genetic causes are responsible for disease 16 .The new data show that location of the mutation can not predict the severity of the clinical presentation in the LIS1-related lissencephaly directly 32,33 .On the other hand, the severity of the mutation on the LIS1 protein confirm good relationship with radiological phenotype and lissencephaly grading 34,35 .The results suggest that genetic causes of lissencephaly could account for the type of neuroimiging changes.Here, we reported a non-moleculary confirmed case, but we showed the importance of fetal ultrasound and MRI for understanding of normal brain development and providing practical help to families of affected patients in the form of prognosis and counselling.
Depending on the severity, malformation of the cortex can cause a range of outcomes including death in infancy, psychomotor retardation and seizures 36 .Prognosis is usually poor and related to the degree of smoothness, but early diagnosis could allow better care for the patient.The phenotype could be characterised by severe neurological abnormalities, like in the presented case [36][37][38] .
Fetal MRI can depict smooth brain surface, but only in the third trimester of pregnancy 27,28,39,40 .The presented case confirms that fetal MRI may identify additional important finding apart from ventriculomegaly, which could alter patient counselling 41 .Although prenatal diagnosis of ventriculomegaly is now easy and much more frequent finding in routine ultrasound examination, ventriculomegaly could be associated with different neurological outcomes.In the presented case, MRI was helpful to carefully identify lissencephaly in utero.We conclude that the ventriculomegaly detected with ultrasound is important clinical indication for fetal MRI.As the genetics of congenital malformations becomes more complex, MRI in combination with ultrasound can provide important information on specific brain phenotypes.

Conclusion
Confirmation of the ultrasound diagnosis with MRI is desirable for the prenatal diagnosis of lissencephaly.A combination of these two technique in utero is an important diagnostic tool in the combination with genetic testing for lissencephaly.

Fig. 1 -
Fig. 1 -Fetal magnetic resonance imaging of the brain shows that the gyral pattern is smoother than the expected thirdtrimester configuration, suggesting lissencephaly.

Fig. 2 -
Fig. 2 -Axial magnetic resonance images at the age of two months shows colpocephaly, the absence of gyration and an open insula -features typical for lissencephaly.