Severe hydrocephalus caused by diffuse leptomeningeal and neurocutaneous melanocytosis of antenatal onset: a clinical, pathologic, and molecular study of 2 cases

The genetic basis of hydrocephalus: genes, pathways, mechanisms, and global impact

Hydrocephalus (HC) is a heterogenous disease characterized by alterations in cerebrospinal fluid (CSF) dynamics that may cause increased intracranial pressure. HC is a component of a wide array of genetic syndromes as well as a secondary consequence of brain injury (intraventricular hemorrhage (IVH), infection, etc.) that can present across the age spectrum, highlighting the phenotypic heterogeneity of the disease. Surgical treatments include ventricular shunting and endoscopic third ventriculostomy with or without choroid plexus cauterization, both of which are prone to failure, and no effective pharmacologic treatments for HC have been developed. Thus, there is an urgent need to understand the genetic architecture and molecular pathogenesis of HC. Without this knowledge, the development of preventive, diagnostic, and therapeutic measures is impeded. However, the genetics of HC is extraordinarily complex, based on studies of varying size, scope, and rigor. This review serves to provide a comprehensive overview of genes, pathways, mechanisms, and global impact of genetics contributing to all etiologies of HC in humans.

An update on congenital melanocytic nevus syndrome: A case report and literature review

Congenital melanocytic nevus syndrome (CMNS) is a rare condition characterized by pigmented skin lesions that are usually present at birth and are associated with an increased risk of neurological abnormalities and malignant melanoma. It mostly results from a post-zygotic NRAS mutation of neural-derived crest cells, leading to uncontrolled cell growth. Because of the increased knowledge of the genetics underlying CMNS, targeted therapy becomes a promising treatment option. We present a case of CMNS in a newborn. Physical examination at birth showed a giant congenital melanocytic nevus, extending from the occipital to the lower lumbar region. A magnetic resonance imaging scan revealed multiple cerebral and cerebellar parenchymal lesions. Genetic analysis of the cutaneous lesions showed the presence of an NRAS Q61R mutation. The patient was treated with dermabrasion to reduce the color intensity of the nevus. However, this was complicated by recurrent wound infections and laborious wound healing. At the age of 1 year, the patient had an age-appropriate psychomotor development, without neurological deficits.

Genes causing congenital hydrocephalus: Their chromosomal characteristics of telomere proximity and DNA compositions

Congenital hydrocephalus (CH) is caused by genetic mutations, but whether factors impacting human genetic mutations are disease-specific remains elusive. Given two factors associated with high mutation rates, we reviewed how many disease-susceptible genes match with (i) proximity to telomeres or (ii) high adenine and thymine (A + T) content in human CH as compared to other disorders of the central nervous system (CNS). We extracted genomic information using a genome data viewer. Importantly, 98 of 108 genes causing CH satisfied (i) or (ii), resulting in >90% matching rate. However, such a high accordance no longer sustained as we checked two factors in Alzheimer's disease (AD) and/or familial Parkinson's disease (fPD), resulting in 84% and 59% matching, respectively. A disease-specific matching of telomere proximity or high A + T content predicts causative genes of CH much better than neurodegenerative diseases and other CNS conditions, likely due to sufficient number of known causative genes (n = 108) and precise determination and classification of the genotype and phenotype. Our analysis suggests a need for identifying genetic basis of both factors before human clinical studies, to prioritize putative genes found in preclinical models into the likely (meeting at least one) and more likely candidate (meeting both), which predisposes human genes to mutations.

CT and MRI findings in leptomeningeal melanocytosis

Leptomeningeal melanocytosis is a rare cause of seizure in the pediatric population. Shown here is a case of this disease in a 9-year-old male who presented with seizures and minor trauma. Imaging showed progression of leptomeningeal enhancement in the setting of increased seizure activity, and biopsy confirmed the diagnosis. The patient received immunotherapy but eventually succumbed to the disease. This case serves as an educational tool to improve awareness of melanocytic proliferation as a differential consideration for leptomeningeal enhancement.

The Rare Neurocutaneous Disorders: Update on Clinical, Molecular, and Neuroimaging Features

Phakomatoses, also known as neurocutaneous disorders, comprise a vast number of entities that predominantly affect structures originated from the ectoderm such as the central nervous system and the skin, but also the mesoderm, particularly the vascular system. Extensive literature exists about the most common phakomatoses, namely neurofibromatosis, tuberous sclerosis, von Hippel-Lindau and Sturge-Weber syndrome. However, recent developments in the understanding of the molecular underpinnings of less common phakomatoses have sparked interest in these disorders. In this article, we review the clinical features, current pathogenesis, and modern neuroimaging findings of melanophakomatoses, vascular phakomatoses, and other rare neurocutaneous syndromes that may also include tissue overgrowth or neoplastic predisposition.

Perineural Pseudoinvasion: An Unusual Phenomenon in Nonmalignancies

Perineural invasion (PNI) is characterized as tumoral or nontumoral cells invading in or around the nerves. The neural invasion is considered as a histopathologic characteristic for malignancy and is considered a mechanism for its spread. Both of these patterns usually portend a poor prognosis and very often are markers to prompt additional treatment. There are also some nonmalignancies representing PNI, including benign neoplasms, mimicking lesions, and disorders, such as chronic pancreatitis and endometriosis. The previously recommended terms are PNI, spread, or infiltration. To distinguish PNI in malignancies from that in nonmalignancies, we propose the term "perineural pseudoinvasion" to convey their nonmalignant behavior. Despite the low prevalence, awareness of this benign pseudoinvasion is necessary to avoid aggressive treatment and its misdiagnosis with malignancies. We conducted a systematic search in PubMed and Scopus databases up to December 2015 to find articles reporting PNI in nonmalignancies. After screening, 63 articles were identified as relevant. There were also 2 review articles discussing PNI in nonmalignancies. We aim to present an overview of the perineural pseudoinvasion and to discuss the previously published review articles.