Romina Moavero

Neurological and neuropsychiatric aspects of tuberous sclerosis complex

Tuberous sclerosis (also known as tuberous sclerosis complex [TSC]) is a multisystem genetic disorder that affects almost every organ in the body. Mutations in the TSC1 or TSC2 genes lead to disruption of the TSC1-TSC2 intracellular protein complex, causing overactivation of the mammalian target of rapamycin (mTOR) protein complex. The surveillance and management guidelines and clinical criteria for tuberous sclerosis were revised in 2012, and mTOR inhibitors are now recommended as treatment options for subependymal giant cell astrocytomas and renal angiomyolipomas-two common features of the disease. However, most morbidity and mortality caused by tuberous sclerosis is associated with neurological and neuropsychiatric manifestations. Treatment of epilepsy associated with tuberous sclerosis remains a major challenge, with more than 60% of patients having ongoing seizures. Tuberous-sclerosis-associated neuropsychiatric disorders (TAND) are multilevel and occur in most individuals with the disorder, but are rarely assessed and treated. Clinical trials of mTOR inhibitors to treat seizures and TAND are underway. Management of the neurological and neuropsychiatric manifestations of the disorder should be coordinated with treatment of other organ systems. In view of the age-related expression of manifestations from infancy to adulthood, continuity of clinical care and ongoing monitoring is paramount, and particular attention is needed to plan transition of patient care from childhood to adult services.

Genotype/Phenotype Correlations in Tuberous Sclerosis Complex.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the development of widespread hamartomatous lesions in various organs, including brain, skin, kidneys, heart, and eyes. Central nervous system is almost invariably involved, with up to 85% of patients presenting with epilepsy, and at least half of patients having intellectual disability or other neuropsychiatric disorders including autism spectrum disorder. TSC is caused by the mutation in one of the 2 genes TSC1, at 9q34, and TSC2, at 16p13.3. They respectively encode for hamartin and tuberin, which form an intracellular complex inhibiting the mammalian target of rapamycin. Mammalian target of rapamycin overactivation following the genetic defect determines the cell growth and proliferation responsible for TSC-related lesions, as well as the alterations in neuronal excitability and synaptogenesis leading to epilepsy and neuropsychiatric disorders. A causative mutation for the disorder is identified in about 85% of patients with a clinical diagnosis of TSC. Mosaicism and technology limits likely explain most of the no mutation identified cases. This review confirms that patients with TSC2 mutations considered as a group usually present a more severe phenotype, characterized by higher number of tubers, earlier age at seizure onset and higher prevalence of intellectual disability. However, the clinical phenotype of the disease presents a high variability, thus making the prediction of the phenotype on an individual basis still challenging. The increasing application of new molecular techniques to subjects with TSC has the potential to significantly reduce the rate of patients with no mutation demonstrated and to identify an increasing higher number of mutations. This would hopefully allow a better characterization of higher risk mutations, which might help clinicians to plan individualized surveillance plans. Furthermore, the increasing availability of disease registries to collect clinical and genetics data of patients help to define more valid and clinically oriented genotype or phenotype correlations.

The Role of mTOR Inhibitors in the Treatment of Patients with Tuberous Sclerosis Complex: Evidence-based and Expert Opinions.

Tuberous sclerosis complex (TSC) is a genetic disorder arising from mutations in the TSC1 or TSC2 genes. The resulting over-activation of the mammalian target of rapamycin (mTOR) signalling pathway leaves patients with TSC susceptible to the growth of non-malignant tumours in multiple organs. Previously, surgery was the main therapeutic option for TSC. However, pharmacological therapy with mTOR inhibitors such as everolimus and sirolimus is now emerging as an alternate approach. Everolimus and sirolimus have already been shown to be effective in treating subependymal giant cell astrocytoma (SEGA) and renal angiomyolipoma (AML), and everolimus is currently being evaluated in treating TSC-related epilepsy. In November 2013 a group of European experts convened to discuss the current options and practical considerations for treating various manifestations of TSC. This article provides evidence-based recommendations for the treatment of SEGA, TSC-related epilepsy and renal AML, with a focus on where mTOR inhibitor therapy may be considered alongside other treatment options. Safety considerations regarding mTOR inhibitor therapy are also reviewed. With evidence of beneficial effects in neurological and non-neurological TSC manifestations, mTOR inhibitors may represent a systemic treatment for TSC.

Early onset epileptic encephalopathy or genetically determined encephalopathy with early onset epilepsy? Lessons learned from TSC

BACKGROUNDnIn tuberous sclerosis complex (TSC) a relationship has been shown between early and refractory seizures and intellectual disability. However, it is uncertain whether epilepsy in TSC is simply a marker in infants who are destined to develop an encephalopathic process or if seizures play a causal role in developing an encephalopathy.nnnMETHODSnThis paper summarizes the key points discussed during a European TSC workshop held in Rome, and reviews the experimental and clinical evidence in support of the two theories.nnnRESULTS/CONCLUSIONnThere are many factors that influence the appearance of both early seizure onset and the encephalopathy resulting in neurodevelopmental deficits. Experimental studies show that as a consequence of the TSC genes mutation, mammalian target of Rapamycin (mTOR) overactivation determines an alteration in cellular morphology with cytomegalic neurons, altered synaptogenesis and an imbalance between excitation/inhibition, thus providing a likely neuroanatomical substrate for the early appearance of refractory seizures and for the encephalopathic process. At the clinical level, early signs of altered developmental trajectories are often unrecognized before 12 months of age. Evidence from experimental research shows that encephalopathy in TSC might have a genetic cause, and mTOR activation caused by TSC gene mutation can be directly responsible for the early appearance of seizures and encephalopathy.

White matter disruption is associated with persistent seizures in tuberous sclerosis complex

BACKGROUND AND AIMSnWhite matter is diffusely altered in tuberous sclerosis complex (TSC), and these alterations appear to be more evident in subjects with a more severe neurologic phenotype. However, little is known on the correlation between white matter alterations and epilepsy in TSC. The aims of this study were to evaluate the effects of early onset and refractory seizures on white matter by using diffusion tensor imaging (DTI).nnnMETHODSnWe enrolled 20 children with TSC and epilepsy onset in the first 3years of life and grouped them according to seizure persistence or freedom. All patients underwent brain MRI with DTI. Specific ROIs have were placed to generate tracks to calculate fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Statistical analysis was performed by ANOVA.nnnRESULTSnChildren with persistent seizures presented an overall reduced FA, with statistically significant differences on the cingulum (right p=0.003, left p=0.016), the left cerebral peduncle (p=0.020), the superior cerebellar peduncles (right p=0.008, left p=0.002), the posterior limbs of internal capsule (right p=0.037, left p=0.015), the external capsule (right p=0.018, left p=0.031), the inferior frontooccipital fasciculus (right p=0.010, left p=0.026), and the temporal trunk (right p=0.017, left p=0.001).nnnCONCLUSIONSnOur study demonstrated that children with persistent seizures present more significant alterations of brain connectivity in areas crucial for global cognitive maturation, executive functions, and verbal abilities, implying a higher risk of cognitive impairment, attention-deficit hyperactivity disorder, and autism.

mTOR dysregulation and tuberous sclerosis-related epilepsy

ABSTRACT Introduction. The mammalian target of rapamycin (mTOR) pathway has emerged as a key player for proper neural network development, and it is involved in epileptogenesis triggered by both genetic or acquired factors. Areas covered. The robust mTOR signaling deregulation observed in a large spectrum of epileptogenic developmental pathologies, such as focal cortical dysplasias and tuberous sclerosis complex (TSC), has been linked to germline and somatic mutations in mTOR pathway regulatory genes, increasing the spectrum of ‘mTORopathies’. The significant advances in the field of TSC allowed for the validation of emerging hypotheses on the mechanisms of epileptogenesis and the identification of potential new targets of therapy. Recently, a double-blind phase III randomized clinical trial on patients with TSC related epilepsy, demonstrated that adjunctive treatment with mTOR inhibition is effective and safe in reducing focal drug resistant seizures. Expert commentary. mTOR signaling dysregulation represents a common pathogenic mechanism in a subset of malformations of cortical development, sharing histopathological and clinical features, including epilepsy, autism, and intellectual disability. EXIST-3 trial provided the first evaluation of the optimal dosage, conferring a higher chance of reducing seizure frequency and severity, with adverse events being similar to what observed with lower dosages.

Metastatic Group 3 Medulloblastoma in a Patient With Tuberous Sclerosis Complex: Case Description and Molecular Characterization of the Tumor

Medulloblastoma is the most common pediatric brain tumor. We describe a child with tuberous sclerosis complex that developed a Group 3, myc overexpressed, metastatic medulloblastoma (MB). Considering the high risk of treatment‐induced malignancies, a tailored therapy, omitting radiation, was given. Based on the evidence of mammalian target of rapamycin mTORC, mTOR Complex; RAS, Rat sarcoma; RAF, rapidly accelerated fibrosarcoma (mTOR) pathway activation in the tumor, targeted therapy was applied resulting in complete remission of disease. Although the PI3K/AKT/mTOR signaling pathway plays a role in MB, we did not find TSC1/TSC2 (TSC, tuberous sclerosis complex) mutation in our patient. We speculate that a different pathway resulting in mTOR activation is the basis of both TSC and MB in this child; H&E, haematoxilin and eosin; Gd, gadolinium.

Mammalian Target of Rapamycin Inhibitors and Life-Threatening Conditions in Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a multisystem disease associated with an overall reduction in life expectancy due to the possible occurrence of different life-threatening conditions. Subjects affected by TSC are, in fact, at risk of hydrocephalus secondary to the growth of subependymal giant cell astrocytomas, or of sudden unexpected death in epilepsy. Other nonneurological life-threatening conditions include abdominal bleeding owing to renal angiomyolipomas rupture, renal insufficiency due to progressive parenchymal destruction by multiple cysts, pulmonary complications due to lymphangioleiomyomatosis, and cardiac failure or arrhythmias secondary to rhabdomyomas. In the last decades, there has been a great progress in understanding the pathophysiology of TSC-related manifestations, which are mainly linked to the hyperactivation of the so-called mammalian target of rapamycin (mTOR) pathway, as a consequence of the mutation in 1 of the 2 genes TSC1 or TSC2. This led to the development of new treatment strategies for this disease. In fact, it is now available as a biologically targeted therapy with everolimus, a selective mTOR inhibitor, which has been licensed in Europe and USA for the treatment of subependymal giant cell astrocytomas and angiomyolipomas in subjects with TSC. This drug also proved to benefit other TSC-related manifestations, including pulmonary lymphangioleiomyomatosis, cardiac rhabdomyomas, and presumably epileptic seizures. mTOR inhibitors are thus proving to be a systemic therapy able to simultaneously address different and potentially life-threatening complications, giving the hope of improving life expectation in individuals with TSC.

Reduction in retinal nerve fiber layer thickness in tuberous sclerosis complex

PurposeThe aim of our study was to non-invasively investigate central nervous system axonal integrity in patients with tuberous sclerosis complex (TSC). Diffuse microstructural white matter abnormalities reflecting axonal disorganization, reduced/altered myelination, or gliosis have been described in individuals with TSC. Optical coherence tomography (OCT) is a fast, easy-to-perform, non-invasive, and cost-efficient method to assess retinal morphology in vivo and to measure the thickness of the retinal nerve fiber layer (RNFL).MethodsIn order to assess central nervous system axonal integrity, eight subjects with TSC have been investigated by OCT to evaluate RNFL and they have been compared with matched healthy controls.ResultsWhen comparing mean overall RNFL thicknesses of the TSC group with those of the control group, the TSC group presented with significantly lower RNFL values, compared to the control group, in the temporal quadrant (62.5u2009±u20096.9 vs. 76.9u2009±u20095.4; tu2009=u200914.438; pu2009<u20090.0001).ConclusionsSince a reduced RNFL thickness might be seen as an indicator of chronic axonal degeneration or lack of appropriate neuronal development, our results support the presence of axonal alterations in TSC and also that white matter disorganization could be much more diffuse than originally thought. Since axonal alterations directly derive from mammalian target of rapamycin (mTOR) overactivation, which occurs early during fetus development, the RNFL thinning we observed could represent one of the facets of such early neurodevelopmental abnormalities.

Safety and tolerability profile of new antiepileptic drug treatment in children with epilepsy

ABSTRACT Introduction: Treatment of pediatric epilepsy requires a careful evaluation of the safety and tolerability profile of antiepileptic drugs (AEDs) to avoid or minimize as much as possible adverse events (AEs) on various organs, hematological parameters, and growth, pubertal, motor, cognitive and behavioral development. Areas covered: Treatment-emergent AEs (TEAEs) reported in the literature 2000–2018 regarding second- and third-generation AEDs used in the pediatric age, with exclusion of the neonatal period that exhibits specific peculiarities, have been described on the basis of their frequency, severity/tolerability, and particular association with a given AED. Expert opinion: Somnolence/sedation and behavioral changes, like irritability and nervousness, are among the most commonly observed TEAEs associated with almost all AEDs. Lamotrigine, Gabapentin, Oxcarbazepine, and Levetiracetam appear to be the best-tolerated AEDs with a ≤2% withdrawal rate, while Tiagabine and Everolimus are discontinued in up to >20% of the patients because of intolerable TEAEs. For some AEDs, literature data are scanty to draw a high-level evidence on their safety and tolerability profile. The reasons are: insufficient population size, short duration of treatments, or lack of controlled trials. A future goal is that of identifying clearer, easier, and more homogeneous methodological strategies to facilitate AED testing in pediatric populations.