Apparently novel genetic syndrome of pachygyria, mental retardation, seizure, and arachnoid cysts

Familial and syndromic forms of arachnoid cyst implicate genetic factors in disease pathogenesis

Arachnoid cysts (ACs) are the most common space-occupying lesions in the human brain and present significant challenges for clinical management. While most cases of ACs are sporadic, nearly 40 familial forms have been reported. Moreover, ACs are seen with increased frequency in multiple Mendelian syndromes, including Chudley-McCullough syndrome, acrocallosal syndrome, and autosomal recessive primary ciliary dyskinesia. These findings suggest that genetic factors contribute to AC pathogenesis. However, traditional linkage and segregation approaches have been limited in their ability to identify causative genes for ACs because the disease is genetically heterogeneous and often presents asymptomatically and sporadically. Here, we comprehensively review theories of AC pathogenesis, the genetic evidence for AC formation, and discuss a different approach to AC genomics that could help elucidate this perplexing lesion and shed light on the associated neurodevelopmental phenotypes seen in a significant subset of these patients.

Familial arachnoid cysts: a review of 35 families

INTRODUCTION

Arachnoid cysts are commonly considered congenital lesions, but this has not been proven. With the development of neuroimaging and DNA testing technology, more cases of familial arachnoid cysts have been reported. Herein, we review such cases.

MATERIALS AND METHODS

The PubMed, Embase, and Web of Science databases were searched for case reports of arachnoid cysts published through April 2018. Case reports were included only if two or more related patients were diagnosed with an arachnoid cyst by neuroimaging or intraoperatively. For each report, the following data were extracted: first author name, date of publication, number of families, number of patients, location of the arachnoid cysts, patient age, patient sex, and genetic mutations and associated disease.

RESULTS

Our searches identified 33 case reports involving 35 families and 115 patients. The locations of arachnoid cysts were similar in 25 of the 35 families. Spinal extradural arachnoid cysts were reported most often, followed by arachnoid cysts in the middle fossa and posterior fossa. A left-sided predominance was noticed for arachnoid cysts of the middle fossa. Mutation of the FOXC2 gene was reported most often, and arachnoid cysts may be associated with mutations on chromosome 16.

CONCLUSIONS

Although the origin of arachnoid cysts is believed to have a genetic component by some researchers, the genes associated with arachnoid cysts remain unknown. Unfortunately, the evidence remains insufficient.

Familial intracranial arachnoid cysts with a missense mutation (c.2576C > T) in RERE: A case report

RATIONALE

Arachnoid cysts are relatively common intracranial space-occupying lesions; nevertheless, familial intracranial arachnoid cysts are extremely rare, with only a few cases having been reported.

PATIENT CONCERNS

The proband was a 7-year-old girl who had experienced generalized tonic-clonic seizures 5 times in the 8 days prior to admission. Nine months later, her 6-year-old younger female cousin presented to us with a 3-day history of headache.

DIAGNOSES

Brain magnetic resonance imaging (MRI) confirmed the diagnosis of arachnoid cyst for both of the girls.

INTERVENTIONS

A cyst-peritoneal shunting and cyst fenestration were performed for the 7-year-old girl and her cousin separately. Sanger sequencing revealed a heterozygous missense mutation (c.2576C > T) in the Arginine-Glutamic Acid Dipeptide Repeats gene (RERE).

OUTCOMES

The outcome was favorable and the follow-up was uneventful.

LESSONS

We hypothesize that the mutation in RERE may be associated with the pathogenesis of familial intracranial arachnoid cysts.

Mutations in CRADD Result in Reduced Caspase-2-Mediated Neuronal Apoptosis and Cause Megalencephaly with a Rare Lissencephaly Variant

Lissencephaly is a malformation of cortical development typically caused by deficient neuronal migration resulting in cortical thickening and reduced gyration. Here we describe a “thin” lissencephaly (TLIS) variant characterized by megalencephaly, frontal predominant pachygyria, intellectual disability, and seizures. Trio-based whole-exome sequencing and targeted re-sequencing identified recessive mutations of CRADD in six individuals with TLIS from four unrelated families of diverse ethnic backgrounds. CRADD (also known as RAIDD) is a death-domain-containing adaptor protein that oligomerizes with PIDD and caspase-2 to initiate apoptosis. TLIS variants cluster in the CRADD death domain, a platform for interaction with other death-domain-containing proteins including PIDD. Although caspase-2 is expressed in the developing mammalian brain, little is known about its role in cortical development. CRADD/caspase-2 signaling is implicated in neurotrophic factor withdrawal- and amyloid-β-induced dendritic spine collapse and neuronal apoptosis, suggesting a role in cortical sculpting and plasticity. TLIS-associated CRADD variants do not disrupt interactions with caspase-2 or PIDD in co-immunoprecipitation assays, but still abolish CRADD’s ability to activate caspase-2, resulting in reduced neuronal apoptosis in vitro. Homozygous Cradd knockout mice display megalencephaly and seizures without obvious defects in cortical lamination, supporting a role for CRADD/caspase-2 signaling in mammalian brain development. Megalencephaly and lissencephaly associated with defective programmed cell death from loss of CRADD function in humans implicate reduced apoptosis as an important pathophysiological mechanism of cortical malformation. Our data suggest that CRADD/caspase-2 signaling is critical for normal gyration of the developing human neocortex and for normal cognitive ability.

[Arachnoid cysts: Embriology and pathology]

There is still great controversy surrounding the origin of the arachnoid cyst. The most accepted theory in the case of congenital cysts explains how they are formed from an anomalous development of the arachnoid membrane, which is unfolded allowing the accumulation of cerebrospinal fluid inside and creating a cyst. This theory seems to explain the origin of convexity and sylvian cistern arachnoid cysts, whereas those in other locations might be due to other mechanisms. In the anatomopathological analysis, the arachnoid cyst wall can be seen as having few differences from normal, although thickened due to an increase quantity of collagenous material. A description of the embryological development of the arachnoid layer and cyst formation is presented, describing the main anatomopathological findings.

Dyke-davidoff-masson syndrome associated with epidermoid tumour and arachnoid cyst: a case report

BACKGROUND

Dyke-Davidoff-Masson Syndrome (DDMS) is a rarely seen clinical entity which is characterised by cerebral hemiatrophy, contralateral hemiparesis and epilepsy. Radiological features are typical, such as unilateral atrophy of the cerebral hemisphere and associated compensatory bone changes in the skull, like thickening, enlargement of the paranasal sinuses and mastoid air cells.

CASE REPORT

In this article, we report the first case of DDMS associated with epidermoid tumour and arachnoid cyst, who underwent operation for an epidermoid tumour in the inter-hemispheric region. To our knowledge, this is the first report of DDMS associated with multiple intracranial pathologies and this association has not been previously described in the literature.

CONCLUSION

Any patient who receives DDMS in the light of clinical and radiological findings should be investigated for concomitant pathologies. Different sequences of MRI may be useful in the diagnosis of other intracranial lesions.

Diverse arachnoid cyst morphology indicates different pathophysiological origins

BACKGROUND

There are few, limited, and to some extent contradictory, reports on the cellular and subcellular morphology of arachnoid cysts. In the literature cyst membranes are described as similar to, or as vastly different from, normal arachnoid membranes.

METHODS

This paper reports electron microscopic analyses of symptomatic cysts from 24 patients (12 males and 12 females; age 10-79), that underwent fenestration surgery. Fourteen cysts were located in the middle cranial fossa (temporal), one in the interpeduncular cistern, five in the posterior fossa, and four were overlying the frontal cortex.

RESULTS

Microscopic findings confirmed the diverse nature of this clinical condition. Twelve cyst walls resembled normal arachnoid, four had a conspicuous core of dense fibrous tissue with a simple epithelial lining, and the remaining aberrant cysts exhibited non-arachnoid luminal epithelia with plentiful microvilli and/or cilia, and also nervous tissue components in the wall. The possible identity and origin of various cyst types are discussed. We hypothesize that cysts are formed mostly at an early stage of embryonic development, as a teratological event.

CONCLUSIONS

Cysts with various epithelial linings and extracellular components most likely have different barrier properties and fluid turnover characteristics. Further studies are needed to elucidate relations between cyst morphology, fluid composition, pathogenesis, and clinical behaviour including growth rate and relapse tendency.

Intracranial arachnoid cyst family with autosomal recessive trait mapped to chromosome 6q22.31-23.2

BACKGROUND

Arachnoid cysts are congenital fluid-filled compartments within the cerebrospinal fluid cisterns and cerebral fissures. They most commonly occur sporadically, and familial occurrence has rarely been reported. In this study, we showed the first genetic linkage in the literature in a pure intracranial arachnoid cyst family with autosomal recessive trait.

METHODS

We identified an intracranial arachnoid cyst family in southern Turkey whose six of seven offspring had intracranial arachnoid cysts in different localizations, and collected venous blood from seven offspring of the family. Whole-genome linkage analysis was performed in all offspring.

RESULTS

A theorical maximum logarithm of the odds score of 4.6 was identified at chromosome 6q22.31-23.2. This result shows strong genetic linkage to this locus.

CONCLUSIONS

We present the first genetic linkage analysis result in a pure intracranial arachnoid cyst family in literature. Further investigation of this linkage area can reveal a causative gene causing the intracranial arachnoid cyst phenotype and can illuminate the pathogenesis of this disease.