The neurobiology of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a multiorgan genetic disease caused by inactivation of either the TSC1 or TSC2 genes. The disorder typically has profound neurologic involvement and often presents early in life with epilepsy, developmental delay, mental retardation, and autism. These features are generally accepted to result from structural brain abnormalities that are found in patients with TSC. Although much progress has recently been made in discerning the function(s) of the TSC genes, many questions remain as to the role of these genes in brain development and homeostasis. This review will summarize recent progress and suggest future avenues of basic science research.     

伴有癫痫发作的结节性硬化症患者的临床特点

目的分析伴有癫痫发作的结节性硬化症(tuberous sclerosis complex,TSC)患者的临床特点。方法采用回顾性分析方法,总结了85例伴有癫痫发作的TSC患者的资料进行分析。结果伴有癫痫发作的TSC患者男∶女接近2∶1,有TSC家族史14人(17%)。癫痫的发病年龄从10d～22岁不等,25%TSC患者在1岁以内发病,66%在3岁以内发病。53%的患者首次发作表现为全身强直阵挛发作(GTCS),40%为部分性发作,5例(6%)患者有癫痫性痉挛发作。在所有入选患者中,38例(45%)患者有明确的智能障碍,在发病年龄小于1岁的患者中,71%有明确的智能障碍,临床发作仅有GTCS患者中,50%有明确的智能障碍,有癫痫性痉挛发作的患者80%有明确的智能障碍。家族性TSC及散发性TSC患者在临床表现上无明显差异。63/65例患者行头部CT发现室管膜下或/和脑叶钙化灶,75/78例患者行头部MRI检查发现大脑半球皮层下及室管膜下均见多发性结节影,6例合并室管膜下巨细胞型星形细胞瘤(7%)。54/80例患者脑电图提示痫样波局限于一侧。结论发病年龄小于1岁、临床仅有GTCS发作及既往有癫痫性痉挛发作的患者更容易出现智能障碍,大脑半球皮层下及室管膜下多发结节或钙化有助于TSC的诊断。     

The diverse clinical manifestations of tuberous sclerosis complex: a review

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem neurocutaneous disorder. TSC results in hamartomatous lesions primarily involving the skin, central nervous system, kidneys, eyes, heart, and lungs. The clinical findings and severity of TSC are highly variable. Recent advances in our understanding of the complexities of the TSC1 and TSC2 genes are making genotype-phenotype correlations possible. While managing seizures, cognitive dysfunction, and behavioral abnormalities are the primary responsibility of the neurologist, familiarity with all aspects of this disease helps provide better comprehensive care for affected individuals.     

The ominous sequence in patients with tuberous sclerosis complex

Background: The clinical phenotypes and their severity in patients with tuberous sclerosis complex can be quite variable and are sometimes never determined simply by the primary mutation. These make clinically selecting appropriate treatments and predicting disease outcome difficult. In this report, the prognostic ominous sequence was evaluated in association with clinical manifestations and gene mutations. Methods: The patients were classified by each renal lesion of angiomyolipomas and polycystic disease. The other clinical manifestations and outcomes of epilepsy, mental retardation, facial angiofibromas, subependymal giant cell astrocytoma, cortical tubers were reviewed and each gene mutations were analyzed in seven unrelated patients. Results: Two patients with multiple and large proliferative renal angiomyolipoma showed poor clinical outcome than the patients with other renal lesions. These patients presented with progressively proliferative facial angiofibroma, West syndrome, Lennox–Gastaut syndrome, severe mental retardation, subependymal giant cell astrocytoma and they were affected by TSC2 gene mutations. Conclusion: The sequence of progressively proliferative renal angiomyolipoma, facial angiofibroma, West syndrome and TSC2 gene mutations might be prognostic ominous factors.     

The neurobiology of the tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a multisystem disorder that affects numerous organ systems. Brain lesions that form during development, known as tubers, are highly associated with epilepsy, cognitive disability, and autism. Following the identification of two genes and their encoded proteins, TSC1 (hamartin) and TSC2 (tuberin), responsible for TSC, identification of several downstream protein cascades that might be affected in TSC have been discovered. Of primary importance is the mammalian target of rapamycin pathway that controls cell growth and protein synthesis. The mechanisms governing brain lesion growth have not been fully identified but likely altered regulation of the mammalian target of rapamycin cascade by hamartin and tuberin during development leads to aberrant cell growth. Secondary effects of TSC gene mutations might disrupt normal neuronal migration and cerebral cortical lamination. Numerous studies have identified changes in gene and protein expression in animal models of TSC and in human TSC brain specimens that contribute to altered brain cytoarchitecture. This review will provide an overview of the neurobiological aspects of TSC. Author to whom all correspondence and reprint requests should be addressed.     

Interdependence of clinical factors predicting cognition in children with tuberous sclerosis complex

Cognitive development in patients with tuberous sclerosis complex is highly variable. Predictors in the infant years would be valuable to counsel parents and to support development. The aim of this study was to confirm factors that have been reported to be independently correlated with cognitive development. 102 patients included in this study were treated at the ENCORE-TSC expertise center of the Erasmus Medical Center-Sophia Children’s Hospital. Data from the first 24 months of life were used, including details on epilepsy, motor development and mutation status. Outcome was defined as cognitive development (intellectual equivalent, IE) as measured using tests appropriate to the patients age and cognitive abilities (median age at testing 8.2 years, IQR 4.7–12.0). Univariable and multivariable regression analyses were used. In a univariable analysis, predictors of lower IE were: the presence of infantile spasms (β = ?18.3, p = 0.000), a larger number of antiepileptic drugs used (β = ?6.3, p = 0.000), vigabatrin not used as first drug (β = ?14.6, p = 0.020), corticosteroid treatment (β = ?33.2, p = 0.005), and a later age at which the child could walk independently (β = ?2.1, p = 0.000). An older age at seizure onset predicted higher IE (β = 1.7, p = 0.000). In a multivariable analysis, only age at seizure onset was significantly correlated to IE (β = 1.2, p = 0.005), contributing to 28% of the variation in IE. In our cohort, age at seizure onset was the only variable that independently predicted IE. Factors predicting cognitive development could aid parents and physicians in finding the appropriate support and schooling for these patients.     

Neuroimaging in tuberous sclerosis complex

PURPOSE OF REVIEW: In this review we discuss recent advances in the neuroimaging of patients with tuberous sclerosis complex (TSC), highlighting its application in improving clinical management, particularly in the case of intractable epilepsy. RECENT FINDINGS: Progress in structural and functional imaging has led to further characterization of the brain lesions in TSC. New magnetic resonance imaging techniques that can delineate the extent of structural brain abnormalities in TSC have been developed. Diffusion tensor imaging unveils the microstructural abnormalities of the brain lesions and of the morphologically normal appearing white matter in TSC. It can potentially identify the epileptogenic zone. Positron emission tomography scanning with 2-deoxy-2-[18F]fluoro-D-glucose can assess the full extent of functional brain abnormalities in TSC. The use of alpha [11C] methyl-L-tryptophan positron emission tomography scanning has proven to be a useful tool in the identification of epileptogenic tubers and has improved the outcome of surgery for epilepsy in TSC. SUMMARY: Major advances of neuroimaging in TSC have shown evidence of widespread structural and functional brain abnormalities. In TSC patients with intractable epilepsy, new neuroimaging modalities can now provide an accurate assessment of the epileptogenic zone, thereby permitting improved identification of patients who can have good seizure outcome following surgery for epilepsy.     

Hemimegalencephaly in tuberous sclerosis complex

The purpose of this case report is to describe the computed tomographic and magnetic resonance imaging findings of the brain of a 16-month-old girl with an uncommon association between hemimegalencephaly and tuberous sclerosis complex. When a large calcification is found within a hemimegalencephalic cerebral hemisphere, further investigation of a suspected associated tuberous sclerosis complex or another phakomatosis is required to determine pertinent treatment options and genetic counseling.     

Diagnosis of tuberous sclerosis complex

Tuberous sclerosis complex is a dominantly inherited disorder affecting multiple organs; because of its phenotypic variability, the diagnosis of tuberous sclerosis complex can be difficult in the young or in individuals with subtle findings. Recently revised consensus diagnostic criteria for tuberous sclerosis complex reflect an improved understanding of its clinical manifestations and its genetic and molecular mechanisms. The diagnostic criteria are based on the premise that there are probably no truly pathognomonic clinical signs for tuberous sclerosis complex; signs that were once regarded as specific occur as isolated findings in individuals with no other clinical or genetic evidence of tuberous sclerosis complex. Consequently, the revised criteria require tuberous sclerosis complex-associated lesions of two or more organ systems or at least two dissimilar lesions of the same organ to confirm the diagnosis. The addition of DNA testing complements clinical diagnosis and allows more precise genetic counseling and, in some individuals, prenatal diagnosis. Nevertheless, the 15% false-negative rate for DNA testing and the occurrence of germline mosaicism in about 2% of individuals with tuberous sclerosis complex make it difficult to exclude the diagnosis of tuberous sclerosis complex in family members.     

Psychological profile of adults with tuberous sclerosis complex

The Symptom Checklist-90-Revised, a standardized self-report measure of psychological symptoms, was administered to 42 adults with tuberous sclerosis complex (TSC). Approximately 45% reported high overall psychological distress, most commonly involving interpersonal sensitivity, psychoticism, depression, and obsessive-compulsive symptoms. Symptoms were related to number of organ systems affected by TSC and, in some cases, to seizure history, but not to genotype, IQ, education, severity of epilepsy, or use of anticonvulsant or psychiatric medication.     

Epilepsy surgery for children with tuberous sclerosis complex

Tuberous sclerosis complex is associated with medically refractory seizures and developmental delay in children. These epilepsies are often resistant to antiepileptic drugs, can be quite severe, and usually have a negative impact on the child's neurologic and cognitive development. It is believed that functional outcome is improved if seizures can be controlled at an early age. The surgical treatment of intractable epilepsy in children and adults with tuberous sclerosis complex has gained significant interest in recent years. Previously published studies have shown a potential benefit from resection of single tubers, with most of the results noted in relatively older children. All of these reports support the idea that if a single primary epileptogenic tuber or region can be identified, then a surgical approach is appropriate. However, most children with tuberous sclerosis complex have multiple potentially epileptogenic tubers, rendering localization challenging, and they are therefore rejected as possible surgical candidates. We have used a novel surgical approach using invasive intracranial monitoring, which is typically multistaged and bilateral. This multistage surgical approach has been useful in identifying both primary and secondary epileptogenic zones in patients with tuberous sclerosis complex with multiple tubers. Multiple or bilateral seizure foci are not necessarily a contraindication to surgery in selected patients. Long-term follow-up will determine whether this approach has durable effects. We await better methods for identifying the epileptogenic zone, both noninvasive and invasive.     

Cognitive prognosis of patients with tuberous sclerosis complex

To assess cognitive outcome in patients with tuberous sclerosis complex (TSC) and identify predictive risk factors, we reviewed records of 107 patients who underwent comprehensive neuropsychiatric evaluation. Fifty-seven percent of patients with TSC had normal-range IQ/developmental quotient (DQ). Cognitive outcome was strongly associated with refractory seizures and TSC2 mutation. In TSC, IQ/DQ is bimodally distributed, and more than half of individuals are in the normal range.     

Study of the relationship between tuberous sclerosis complex and autistic disorder

There has been increasing awareness that there are behavioral phenotypes in tuberous sclerosis complex with neuropsychiatric symptom complex such as autistic disorder and attention-deficit hyperactivity disorder (ADHD). However, the neurobiologic basis of autistic disorder in tuberous sclerosis complex is still unknown. We studied two cohorts of children followed up since 1986 until 2003, one cohort with tuberous sclerosis complex and another cohort with autistic disorder, to determine the incidence of autistic disorder in tuberous sclerosis complex and the incidence of tuberous sclerosis complex in autistic disorder respectively. We established a Tuberous Sclerosis Complex Registry in 1985 at the University of Hong Kong. In 2004, 44 index cases (the male to female ratio was 0.75:1) were registered. Three had a positive family history of tuberous sclerosis complex. Thus, the total number of tuberous sclerosis complex cases was 47. We adopted the diagnostic criteria of tuberous sclerosis complex for case ascertainment. The period prevalence rate of tuberous sclerosis complex for children and adolescents aged < 20 years is 3.5 per 10,000 (on Hong Kong island, excluding the eastern region with 125,100 aged < 20 years in 2003). Of 44 cases with tuberous sclerosis complex, 7 had autistic disorder. Thus, the incidence of autistic disorder in tuberous sclerosis complex is 16%. During the 17-year period (1986-2003), we collected a database of 753 children (668 boys and 84 girls; male to female ratio 8:1) with autistic disorder and pervasive developmental disorders. For all children with autistic disorder or pervasive developmental disorders, we routinely examined for any features of tuberous sclerosis complex by looking for neurocutaneous markers such as depigmented spots, which appear in 50% of children with tuberous sclerosis complex by the age of 2 years. For those with infantile spasm or epilepsy, the clinical features of tuberous sclerosis complex were monitored regularly during follow-up. Of these, seven had tuberous sclerosis complex. Thus, the incidence of tuberous sclerosis complex in autistic disorder is 0.9%. All of these children are mentally retarded, with moderate to severe grades in an intellectual assessment conducted by a clinical psychologist. Future studies should be directed toward looking at the various behavioral phenotypes in tuberous sclerosis complex and defining these with standardized criteria to look for any real association with the underlying genetic mutation of TSC1 or TSC2 gene or even the site of tubers in the brain.     

Brain abnormalities in tuberous sclerosis complex

Tuberous sclerosis complex is an autosomal dominant multisystem disorder. Spontaneous mutations occur in up to 60% of patients with gene loci located on chromosomes 9q34 (TSC1) and 16p13 (TSC2). Diagnosis is established with the identification of various neurocutaneous markers and multiple organ system hamartomas. The variable expression of severity, the potential for cognitive dysfunction, and epilepsy compound the clinical picture. The intracranial abnormalities include the identification of migration and hamartomatous brain lesions, such as tubers, subependymal nodules, and subependymal giant cell astrocytomas. A number of other neuroimaging and morphometric abnormalities coexist, which can be identified with current neuroimaging techniques. This review examines the spectrum of brain abnormalities encountered in tuberous sclerosis complex and presents them as not merely a collection of lesions but more cohesively in the context of a global neuronal migration disorder.