Hemimegalencephaly and linear nevus sebaceous syndrome

Nervous System Malformations

PURPOSE OF REVIEW

This article provides an overview of the most common nervous system malformations and serves as a reference for the latest advances in diagnosis and treatment.

RECENT FINDINGS

Major advances have occurred in recognizing the genetic basis of nervous system malformations. Environmental causes of nervous system malformations, such as perinatal infections including Zika virus, are also reviewed. Treatment for nervous system malformations begins prior to birth with prevention. Folic acid supplementation reduces the risk of neural tube defects and is an important part of health maintenance for pregnant women. Fetal surgery is now available for prenatal repair of myelomeningocele and has been demonstrated to improve outcomes.

SUMMARY

Each type of nervous system malformation is relatively uncommon, but, collectively, they constitute a large population of neurologic patients. The diagnosis of nervous system malformations begins with radiographic characterization. Genetic studies, including chromosomal microarray, targeted gene sequencing, and next-generation sequencing, are increasingly important aspects of the assessment. A genetic diagnosis may identify an associated medical condition and is necessary for family planning. Treatment consists primarily of supportive therapies for developmental delays and epilepsy, but prenatal surgery for myelomeningocele offers a glimpse of future possibilities. Prognosis depends on multiple clinical factors, including the examination findings, imaging characteristics, and genetic results. Treatment is best conducted in a multidisciplinary setting with neurology, neurosurgery, developmental pediatrics, and genetics working together as a comprehensive team.

Schimmelpenning Syndrome: An Association with Vascular Anomalies

Objective:

Schimmelpenning syndrome is a rare neurocutaneous disorder characterized by craniofacial nevus sebaceus in association with seizures, developmental delay, and ocular or skeletal pathology. Vascular anomalies also have been described in this condition, and some authors have suggested that the two entities are associated. The purpose of this study was to determine the prevalence of vascular anomalies in Schimmelpenning syndrome.

Methods:

We reviewed the medical records of patients with Schimmelpenning syndrome who were evaluated or were managed at Children's Hospital Boston between 1980 and 2005. In addition, all published cases purported to be Schimmelpenning syndrome were analyzed to determine whether the primary diagnosis was accurate and whether or not there were concurrent vascular anomalies.

Results:

Three of nine patients (33.3%) in our series had a vascular malformation. One patient had coarctation, aortic aneurysm, renal artery, and carotid stenosis; another had a thoracic lymphatic anomaly with chylothorax; and the third had lymphedema of the lower extremities and lymphatic malformation of the neck/chest with chylothorax. Additional findings were seizures (78%), ocular pathology (78%), developmental delay (56%), and skeletal abnormalities (67%). Of 119 cases of authenticated Schimmelpenning syndrome in the literature, 18 vascular malformations were documented in 15 patients (12.6%): venous (n = 7); arterial (n = 5); lymphatic (n = 3); capillary (n = 2); and arteriovenous (n = 1).

Conclusions:

Vascular malformations occur with a higher frequency (12.6 to 33%) in patients with Schimmelpenning syndrome compared with the general population (<1%). Therefore, we conclude that there is an association between vascular anomalies and Schimmelpenning syndrome.

Somatic KRAS mutation in an infant with linear nevus sebaceous syndrome associated with lymphatic malformations: A case report and literature review

RATIONALE

Linear nevus sebaceous syndrome (LNSS) is a rare neurocutaneous syndrome, characterized by nevus sebaceous,central nervous system (CNS), ocular and skeletal abnormalities. The present study describes KRAS somatic mosaic mutation in a case of LNSS with lymphatic malformations (LMs).

PATIENT CONCERNS

A 4-month-old female with a clinical diagnosis of LNSS presented with infantile spasms, mental retardation, skull dysplasia, ocular abnormalities, congenital atrial septal defect, and LMs.

DIAGNOSIS

Cervical ultrasonography revealed a 4.6 × 4.6 × 2.2cm no echo packet with clear boundary in the subcutaneous tissues of the right neck. The neck MRI indicated a cyst in the subcutaneous tissues of the right neck. Whole-exome sequencing revealed a low-level heterozygous mutation of the KRAS gene (c.35C > T; p.G12D, 19%) in the skin lesion sample. This mutation was not present in the blood samples of the patient and her parents.

INTERVENTIONS

The patient received sclerotherapy with paicibanil (OK-432) injection for the cyst.

OUTCOMES

Following 1 year of treatment, the patient exhibited fewer seizures. The mental and motor development was significantly improved. The patient can currently walk with assistance and speak simple words.

LESSONS

LNSS is a rare, congenital neurocutaneous syndrome consisting of a spectrum of abnormalities involving the skin, central nervous system, eyes, LMs and other systems. LNSS can be caused by postzygotic somatic mutation in the RAS family of genes. Multidisciplinary evaluation and treatment is needed.

Dyke-Davidoff-Masson syndrome in a Nigerian

Dyke–Davidoff–Masson syndrome (DDMS) is a rare, but important cause of drug-resistant seizures. Dyke–Davidoff–Masson syndrome is a constellation of clinical features that consists of hemiparesis, seizure, facial asymmetry, and intellectual disability with distinct neuroimaging features. A 27-year-old lady presented to us with drug-resistant epilepsy, hemiparesis, and intellectual disability that necessitated her withdrawal from school. Her brain magnetic resonance imaging (MRI) showed cerebral hemiatrophy, calvarial thickening, and hyperpneumatization of the frontal sinuses consistent with DDMS. We discuss the diagnostic and therapeutic implications of DDMS and advocate early referral and evaluation of people with epilepsy in sub-Saharan African settings.

KRAS G12D mosaic mutation in a Chinese linear nevus sebaceous syndrome infant

BACKGROUND

Linear nevus sebaceous syndrome (LNSS) is a multisystem disorder that includes nevus sebaceous and central nervous system, ocular and skeletal anomalies. We report the first case of a KRAS G12D mosaic mutation in a patient diagnosed with LNSS.

CASE PRESENTATION

A 3-month-old female with a clinical diagnosis of LNSS presented with intermittent epilepsy. Her mother carefully collected a skin lesion sample from scratched-off scurf obtained from the patient's nails. DNA was extracted, and long-range PCR was performed to amplify the KRAS gene, which was then analyzed by next-generation sequencing. The results revealed the presence of a low-level heterozygous mutation in the KRAS gene (c.35C>T; p.G12D, 5 %).

CONCLUSIONS

These findings suggest that the KRAS somatic mosaic mutation in this patient may have caused her skin and eye lesions and epilepsy. With this correct diagnosis, the infant can be effectively treated.

Spinal arteriovenous malformation associated with Schimmelpenning syndrome

The authors report the presentation and management of a 13-year-old girl with Schimmelpenning syndrome, a rare neurocutaneous syndrome; this patient suffered hemorrhage of a spinal arteriovenous malformation. This is the first case of a spinal arteriovenous malformation reported in association with Schimmelpenning syndrome. Neurosurgeons should be aware of this rare phacomatosis as well as of the various neurological disorders associated with this diagnosis. The threshold for imaging the neuraxis in these patients should be low.

Diffusion tensor imaging and fiber tractography in brain malformations

Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.

Epidermal nevus syndrome

Epidermal nevus syndrome (ENS) is an inclusive term for a heterogeneous group of congenital disorders characterized by the presence of epidermal nevi associated with systemic involvement. These disorders, as are all primary neurocutaneous syndromes, are neurocristopathies. The epidermal nevi that follow the lines of Blaschko and most systemic anomalies in skeletal, ocular, cardiovascular, endocrine, and orodental tissues, as well as lipomas, are due to defective neural crest. The most important and frequent anomaly in the brain in all forms of epidermal nevus syndromes (ENSs) is hemimegalencephaly (HME). This malformation often is not recognized, despite being the principal cause of neurological manifestations in ENSs. They consist mainly of epilepsy and developmental delay or intellectual disability. The onset of epilepsy in ENS usually is in early infancy, often as infantile spasms. Several syndromic forms have been delineated. I propose the term "Heide's syndrome" for those distinctive cases with the typical triad of hemifacial epidermal nevus, ipsilateral facial lipoma, and hemimegalencephaly. Most ENSs are sporadic. The mechanism is thought to be genetic mosaicism with a lethal autosomal dominant gene. Specific genetic mutations (PTEN, FGFR3, PIK3CA, and AKT1) have been documented in some patients. The large number of contributors for over more than a century and a half to the description of these disorders precludes the use of new author eponyms.

A severe form of epidermal nevus syndrome associated with brainstem and cerebellar malformations and neonatal medulloblastoma

Here we report a boy with epidermal nevus syndrome associated with brainstem and cerebellar malformations and neonatal medulloblastoma. The patient had epidermal nevi and complicated brain malformations including macrocephaly with polymicrogyria, dysmorphic and enlarged midbrain tectum, enlarged cerebellar hemispheres with small and maloriented folia. The patient died after surgical resection of medulloblastoma which was newly recognized on MRI at 51 days of age. Postmortem pathological examinations showed very unique and bizarre malformation of the midbrain and hindbrain. The cerebellar cortex exhibited a coarse, irregular and bumpy surface, blurred border between the Purkinje cell layer and internal granule cell layer, and many foci of heterotopia in the cerebellar white matter. The brainstem showed multiple anomalies, including enlargement of superior colliculi, hypoplasia of pyramidal tracts and dysplasia of inferior olivary nuclei. The unusual constellation of brain malformations of our patient will widen the spectrum of epidermal nevus syndrome.

Hemispherectomy in a premature neonate with linear sebaceous nevus syndrome

A male neonate with seizures, linear sebaceous nevus syndrome and hemimegalencephaly underwent hemispherectomy at 36 weeks' gestational age. He has had no clinical seizures in the 13 months since surgery but continues to have sharp wave activity over some parts of the intact hemisphere. He has moderate developmental delay and a mild hemiparesis but is making developmental progress.

A neuropathological study of two autopsy cases of syndromic hemimegalencephaly

Hemimegalencephaly (HMEG) is a malformation of cortical development characterized by unilateral enlargement of the cerebral hemisphere, severe architectural and cellular abnormalities and association with intractable epilepsy. HMEG may represent an isolated lesion of the central nervous system, but may also be associated with several neurocutaneous syndromes. In the present study we discuss the neuropathological findings of two autopsy cases of HMEG associated with linear naevus sebaceous syndrome. Both cases showed the presence of linear naevus sebaceous on extensive areas of the face. The neurochemical profile of the glial and neuronal components in the affected hemisphere was determined using immunocytochemical markers and was compared with the unaffected contralateral hemisphere and normal control tissue. The observed cytomegalic neurones expressed receptors for distinct neurotransmitters, neuropeptides and growth factors. Analysis of components of the phosphoinositide 3-kinase pathway revealed expression of phospho-S6 ribosomal protein in cytomegalic neurones. Autopsy findings confirm the complexity of the histologic phenotypic manifestations in HMEG and proved useful in determining the spectrum of cytoarchitectural and neurochemical abnormalities, underlying the molecular pathogenesis and epileptogenesis of this brain malformation.

Epidemiology of hemimegalencephaly: a case series and review

Hemimegalencephaly (HME) is a congenital brain malformation characterized by unilateral enlargement of the cerebral hemisphere. Clinically, HME is typically associated with hemiparesis, psychomotor retardation, and intractable seizures usually apparent soon after birth. HME is often an isolated finding, but it has been described as an occasional feature of a large number of syndromes, many of which may not be readily identified at birth. There are a multitude of case series and reports of HME in the English literature; however, there is no comprehensive, unbiased, detailed survey characterizing the proportion of cases of HME that are associated with a syndrome. We performed a retrospective study of all cases of HME seen at our institution from 1990 to 2003. Of the 15 cases of HME identified, 53% (8/15) were non-syndromic and 47% (7/15) of the cases were associated with a known or suspected genetic syndrome. In patients with syndromic HME, many of the syndromic features were not readily discernible at birth or in early infancy. It is, therefore, imperative to continually evaluate any infant with HME for signs and symptoms of these and other syndromes. Knowing the relative differential diagnosis will lead to a more comprehensive evaluation, improvement in expectant management, and appropriate counseling of families before considering radical surgical options such as hemispherectomy.

Sonographic characteristics of linear nevus sebaceous sequence

Linear nevus sebaceous is a hamartomatous lesion most commonly seen on the face and head of infants and diagnosed after birth. We describe a patient with sonographic findings of linear nevus sebaceous seen initially at 30 weeks' gestation. Other associated sonographic findings include macrocephaly and polyhydramnios. When associated with a midline soft tissue mass, these findings are highly suggestive of the presence of congenital linear nevus sebaceous sequence.

Targeted gene expression analysis in hemimegalencephaly: activation of beta-catenin signaling

Hemimegalencephaly (HMEG) is a developmental brain malformation characterized by unilateral hemispheric enlargement, cytoarchitectural abnormalities, and an association with epilepsy. To define the developmental pathogenesis of HMEG, the expression of 200 cell signaling, growth, angiogenic, and transcription factor genes was assayed in HMEG samples (n=8) with targeted cDNA arrays. Differential expression of 31 mRNAs across the 4 gene families was identified in HMEG compared with control cortex. Increases in growth and transcription factor genes included JNK-1, cyclic AMP response element binding protein (CREB), and tuberin mRNAs and decreases included insulin-like growth factor-1 (IGF-1), transforming growth factor beta-3 (TGF-beta3), and NFkB mRNAs. Increased expression of cyclin D1, c-myc, and WISP-1 mRNAs in HMEG suggested activation of the Wnt-1/beta-catenin cascade. Western analysis demonstrated increased levels of non-phosphorylated beta-catenin, which transcriptionally activates cyclin D7 and c-myc genes, but reduced levels of Ser33/Ser37/Thr41 phospho-beta-catenin, which is essential for beta-catenin-inactivation, in HMEG. Altered expression of 31 mRNAs from 4 gene families in human HMEG may lead to aberrant cell growth and hemispheric enlargement during brain development. Enhanced cyclin D1 and c-myc transcription likely reflects increased transcriptionally active beta-catenin due to decreased Ser33/Ser37/Thr41 phospho-beta-catenin and suggests activation of the Wnt-1/beta-catenin cascade in HMEG.

Sleeping position and electrocortical activity in low birthweight infants

OBJECTIVE

To evaluate the effects of prone and supine sleeping positions on electrocortical activity during active (AS) and quiet (QS) sleep in low birthweight infants.

DESIGN

Randomised/crossover study.

SETTING

Infant Physiology Laboratory at Children's Hospital of New York.

PATIENTS

Sixty three healthy, growing, low birthweight (birth weight 795-1600 g) infants, 26-37 weeks gestational age.

INTERVENTIONS

Six hour continuous two channel electrocortical recordings, together with minute by minute behavioural state assignment, were performed. The infants were randomly assigned to prone or supine position during the first three hours, and positions were reversed during the second three hours.

OUTCOME MEASURES AND RESULTS

Fast Fourier transforms of electroencephalograms (EEGs) were performed each minute and the total EEG power (TP), spectral edge frequency (SEF), absolute (AP) and relative (RP) powers in five frequency bands (0.01-1.0 Hz, 1-4 Hz, 4-8 Hz, 8-12 Hz, 12-24 Hz) were computed. Mean values for TP, SEF, AP, and RP in the five frequency bands in the prone and supine positions during AS and QS were then compared. In the prone sleeping position, during AS, infants showed significantly lower TP, decreased AP in frequency bands 0.01-1.0 Hz, 4-8 Hz, 8-12 Hz, 12-24 Hz, increased RP in 1-4 Hz, and a decrease in SEF. Similar trends were observed during QS, although they did not reach statistical significance.

CONCLUSIONS

The prone sleeping position promotes a shift in EEG activity towards slower frequencies. These changes in electrocortical activity may be related to mechanisms associated with decreased arousal in the prone position and, in turn, increased risk of sudden infant death syndrome.

Molecular pathogenesis of focal cortical dysplasia and hemimegalencephaly

My laboratory recently demonstrated that there is selective expression of phosphoribosomal S6 protein in balloon cells in focal cortical dysplasia and hemimegalencephaly but no expression of the upstream kinase, phospho-p70S6 kinase. Two proteins activated by phospho-p70S6 kinase, phospho-STAT3 and phospho-4EBP1, were not detected in balloon cells. Using complementary DNA arrays in hemimegalencephaly specimens, we found increased expression of cyclin D1 and c-myc messenger ribonucleic acids (RNAs). Expression of cyclin D1 and c-myc genes is transcriptionally activated by beta-catenin. Western analysis demonstrated increased levels of nonphosphorylated beta-catenin in hemimegalencephalic cortex. Reduced levels of Ser33, Ser37, and Thr41 phospho-beta-catenin, sites known to be phosphorylated by glycogen synthase kinase 3 and to be essential for beta-catenin inactivation, were detected in hemimegalencephaly. Enhanced transcription of cyclin D1 and c-myc messenger RNAs, increased transcriptionally active beta-catenin, and decreased Ser33/Ser37/Thr41 phospho-beta-catenin suggest activation of the Wnt-1/beta-catenin cascade in hemimegalencephaly, which can lead to aberrant cell proliferation and hemispheric enlargement during brain development. Enhanced activation of phospho-S6 and beta-catenin suggests two converging cell pathways that can be pivotal in the pathogenesis of focal cortical dysplasia and hemimegalencephaly.

Altered Expression of Neurotransmitter-receptor Subunit and Uptake Site mRNAs in Hemimegalencephaly

PURPOSE

Hemimegalencephaly (HMEG) is characterized by unilateral hemispheric enlargement and severe cytoarchitectural abnormalities that are highly associated with intractable epilepsy. No studies have defined alterations in neurotransmitter-receptor subunit gene expression in HMEG. We hypothesize that a differential expression of excitatory amino acid and gamma-aminobutyric acid (GABA)A-receptor subunit messenger RNAs (mRNAs) exists in HMEG.

METHODS

The expression of mRNAs encoding 20 neurotransmitter-receptor subunits, synthetic enzymes, and uptake sites as well as select additional candidate genes was defined in HMEG samples (n=8) compared with homotopic control cortex specimens by using targeted complementary DNA (cDNA) arrays. Expression of GLT-1 (a glial glutamate transporter), EAAC-1 (neuronal glutamate transporter), and NMDA2B was corroborated by immunohistochemical, Western, and ligand-binding assays.

RESULTS

Differential expression of 11 neurotransmitter-related mRNAs was demonstrated in HMEG compared with control cortex. For example, expression of GLT-1 and GluR6 mRNAs was enhanced, whereas diminished expression of the neuronal glutamate transporter EAAC-1, GABAAalpha2, GABAAgamma2, GABAAgamma3, NMDA2B, GluR1, GluR2, GluR4, and GluR5 subunits occurred. Reduced NMDA2B subunit mRNA expression in HMEG was confirmed by receptor ligand-binding assays by using the NMDA2B-receptor antagonist ifenprodil, which revealed barely detectable levels of NMDA2B binding compared with that in control cortex.

CONCLUSIONS

Selective alterations occur in distinct neurotransmitter-receptor and -uptake sites in HMEG. Differential expression of neurotransmitter-receptor and -uptake sites in HMEG may contribute to epileptogenesis in HMEG.