Hemimegalencephaly with tuberous sclerosis: a longitudinal imaging study

Hemispherectomy for hemimegalencephaly in a 6.5-week-old infant with tuberous sclerosis complex

The aim of this report is to present a unique case of hemimegalencephaly and concomitant tuberous sclerosis complex (TSC1 mutation) with severe neonatal-onset epilepsy, which successfully underwent an anatomical hemispherectomy at 6.5 weeks of age for refractory seizures. Genetic testing confirmed a rare pathogenic, sporadic, heterozygous c.2041 + 1G > A gene mutation in intron 16 of the TSC1 gene, diagnostic for tuberous sclerosis. Post-operatively, the infant remained seizure free for at least 1 year. Following recurrence of her seizures, she has continued on multiple anti-seizure medications and everolimus therapy. We review the pathological and molecular features of this condition and highlight the ethics of intervention and steps taken toward safe neurosurgical intervention in this very young infant.

Synaptic Alterations in a Transgenic Model of Tuberous Sclerosis Complex: Relevance to Autism Spectrum Disorders

Tuberous sclerosis complex (TSC) is a rare, multi-system genetic disease with serious neurological and mental symptoms, including autism. Mutations in the TSC1/TSC2 genes lead to the overactivation of mTOR signalling, which is also linked to nonsyndromic autism. Our aim was to analyse synaptic pathology in a transgenic model of TSC: two-month-old male B6;129S4-Tsc2^tm1Djk/J mice with Tsc2 haploinsufficiency. Significant brain-region-dependent alterations in the expression of several synaptic proteins were identified. The most prominent changes were observed in the immunoreactivity of presynaptic VAMP1/2 (ca. 50% increase) and phospho-synapsin-1 (Ser62/67) (ca. 80% increase). Transmission electron microscopy demonstrated serious ultrastructural abnormalities in synapses such as a blurred structure of synaptic density and a significantly increased number of synaptic vesicles. The impairment of synaptic mitochondrial ultrastructure was represented by excessive elongation, swelling, and blurred crista contours. Polyribosomes in the cytoplasm and swollen Golgi apparatus suggest possible impairment of protein metabolism. Moreover, the delamination of myelin and the presence of vacuolar structures in the cell nucleus were observed. We also report that Tsc2^+/- mice displayed increased brain weights and sizes. The behavioural analysis demonstrated the impairment of memory function, as established in the novel object recognition test. To summarise, our data indicate serious synaptic impairment in the brains of male Tsc2^+/- mice.

Hemimegalencephaly and tuberous sclerosis complex: A rare yet challenging association

Hemimegalencephaly is a rare malformation of cortical development characterised by enlargement of one cerebral hemisphere. The association between hemimegalencephaly and tuberous sclerosis complex, an autosomal dominant genetic disorder, is uncommon and has so far been reported only in a few cases. Intractable epilepsy and severe developmental delay are typical clinical manifestations. Aberrant activation of the mTOR signalling pathway is considered to be the hallmark of the pathogenesis of these two disorders. Thus, mTOR inhibitors such as everolimus represent a promising therapeutic approach to mTOR-associated manifestations. We present a thorough literature review of the association between hemimegaloencephaly and tuberous sclerosis complex.

Cross-sectional Imaging Review of Tuberous Sclerosis

Tuberous sclerosis complex (TSC) is a multisystem, genetic disorder characterized by development of hamartomas in the brain, abdomen, and thorax. It results from a mutation in one of 2 tumor suppressor genes that activates the mammalian target of rapamycin pathway. This article discusses the origins of the disorder, the recently updated criteria for the diagnosis of TSC, and the cross-sectional imaging findings and recommendations for surveillance. Familiarity with the diverse radiological features facilitates diagnosis and helps in treatment planning and monitoring response to treatment of this multisystem disorder.

Hemispherectomy for Hemimegalencephaly Due to Tuberous Sclerosis and a Review of the Literature

BACKGROUND

Hemimegalencephaly with tuberous sclerosis complex is an uncommon association, usually associated with intractable seizures that begin in the neonatal period or early infancy. Typically, the seizures are managed with medications until the patient is older when surgical treatment is considered safe.

PATIENT DESCRIPTION

We describe a 7-week-old infant with tuberous sclerosis (TSC1 mutation) and hemimegalencephaly who underwent a functional hemispherectomy for status epilepticus. No clinical seizures have occurred since surgery nearly 5 years ago and subsequent weaning of antiepileptic drugs 3 years ago. This is one of the youngest patients with tuberous sclerosis complex treated with a hemispherectomy and one of seven patients described in the literature.

CONCLUSIONS

Our patient, along with previously reported cases, suggests that a hemispherectomy is a viable option in the very young. With evolution of this surgical process since its inception nearly 6 decades ago, it may now be performed safely in early infancy, engendering the possibility of seizure freedom in most and thus optimizing neurodevelopmental outcome.

Hemispheric dysplasia and hemimegalencephaly: imaging definitions

BACKGROUND AND PURPOSE

Hemispheric dysplasia (HD) and hemimegalencephaly (HME) are both brain malformations with early clinical manifestation including developmental delay and intractable epilepsy. Sometimes the differentiation of these conditions is not simple. HME is an anomaly of cortical development caused by a combination of neural proliferation and cell migration dysfunction, showing lobar or hemispheric enlargement. On the other hand, HD shows no brain hypertrophy, and even brain atrophy, eventually.

PATIENTS AND METHODS

To compare both conditions, we reviewed clinical, MRI, and histopathology of 23 patients with developmental delay and refractory epilepsy treated with hemispheric surgery.

RESULTS

Histologically, both groups presented polymicrogyria, focal cortical dysplasia, gray matter (GM) heterotopia, pachygyria, and agyria. The white matter (WM) showed different degrees of gliosis and myelin impairment. Even though with no specificity in histopathology, the degree of lesion was more impressive on HME. The combination of WM dysmyelination and hypertrophy leads to the so called hamartomatous appearing. Although not all HME showed brain enlargement and some HD might show no size changes or atrophy, the size of affected hemisphere and the hamartomatous appearance of the WM were the more relevant signs to differentiate both conditions.

CONCLUSION

Brain MRI was the best diagnostic tolls because it allowed together high contrast resolution, whole brain coverage and spatial distribution analysis. HD and HMD showed brain asymmetry tendency, but in opposite directions. The size of affected hemisphere and the hamartomatous appearance of the WM were the more relevant signs to differentiate both conditions.

A developmental and genetic classification for malformations of cortical development: update 2012

Malformations of cerebral cortical development include a wide range of developmental disorders that are common causes of neurodevelopmental delay and epilepsy. In addition, study of these disorders contributes greatly to the understanding of normal brain development and its perturbations. The rapid recent evolution of molecular biology, genetics and imaging has resulted in an explosive increase in our knowledge of cerebral cortex development and in the number and types of malformations of cortical development that have been reported. These advances continue to modify our perception of these malformations. This review addresses recent changes in our perception of these disorders and proposes a modified classification based upon updates in our knowledge of cerebral cortical development.

Progressive hemispheric shrinking in hemimegalencephaly: a possible role for seizure-related neuronal loss

Hemimegalencephaly (HME) is a developmental brain lesion consisting of a unilateral enlarged, dysplastic, and often highly epileptogenic cerebral hemisphere. Most patients exhibit early onset intractable seizures, status epilepticus, hemiplegia, hemianopsia, and developmental delay. Major surgical procedures are advocated for limiting the devastating consequences of epilepsy. We studied a female with HME, early onset intractable seizures and recurrent status epilepticus, in whom progressive hemiatrophy of the enlarged hemisphere and normal growth of the contralateral hemisphere, exceeding the size of the dysplastic hemisphere, was demonstrated by magnetic resonance imaging. Histopathology, following functional hemispherectomy at the age of 7 years, demonstrated severe neuronal loss with an elevated number of cells exhibiting the morphological and biochemical features of apoptosis. Eighteen months after surgery the patient was seizure-free (Engel class I) and exhibited improved motor and language skills, alertness and social behaviour. We hypothesize that nearly continuous seizure activity might sustain seizure-induced brain injury in the dysplastic hemisphere but causal heterogeneity and associated anatomical factors may influence differently the individual predisposition to atrophic changes.

Longitudinal CT and MR appearances of hemimegalencephaly in a patient with tuberous sclerosis

CASE REPORT

A 3-day-old baby was referred to our institution with seizures since birth and a presumptive diagnosis of cerebral tumor detected by prenatal ultrasound. Computed tomography (CT) and Magnetic Resonance (MR) imaging performed immediately after birth revealed the presence of an enhancing mass in the left cerebral hemisphere.

DISCUSSION

The possibility of a congenital malignant brain tumor was considered. Although surgery was advised, the parents opted for conservative medical management. The infant was under treatment for seizures with antiepileptic drugs. At 7-month follow-up, there was a noticeable increase in the seizure activity with signs of developmental delay and increased head circumference. Repeat CT and MR imaging showed features of hemimegalencephaly with a calcified mass involving the left hemisphere. The patient was diagnosed to have tuberous sclerosis. This case report illustrates how an enhancing mass (possibly a tuber) over a period of time diminishes in size and becomes calcified in a patient with tuberous sclerosis and associated hemimegalencephaly.

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.

Intractable epilepsy in hemimegalencephaly and tuberous sclerosis complex

Hemimegalencephaly is a rare brain malformation consisting of the enlargement of 1 hemisphere, often associated with abnormal cortical gyration, thick cortex, large neurons, and increased astrocytes. Cranial asymmetry is the first clinical sign usually present at birth; in the most severe cases, hemimegalencephaly may be evident during pregnancy. Hemiparesis, intractable epilepsy, and developmental delay are the typical clinical manifestations. Tuberous Sclerosis Complex is an autosomal dominant disorder affecting about 1 in 6000 live births; the number of spontaneous mutations is remarkable. It is characterized by the development of hamartias, or nongrowing lesions, and hamartomas, which grow as benign tumors and rarely progress to malignancy. These lesions most frequently involve the brain, skin, kidneys, eyes, and heart. The rare association of hemimegalencephaly and tuberous sclerosis complex has been reported in a few cases. The authors report the case of a 4-year-old boy with left hemimegalencephaly, tuberous sclerosis complex genetically confirmed, and intractable epilepsy originating from the nonhemimegalencephalic hemisphere.

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.

Characteristic brain magnetic resonance imaging (MRI) findings in neonates with tuberous sclerosis complex

We describe the brain magnetic resonance imaging (MRI) findings in eight neonates with tuberous sclerosis complex to further delineate the spectrum of characteristic findings in these patients. In addition to the previously described characteristic brain MRI findings in neonates, which included cortical tuber, transmantle dysplasia, subependymal nodules, cerebral subependymal giant cell astrocytomas, white-matter anomalies, and hemimegalencephaly, we found one neonate with cerebellar subependymal giant cell astrocytomas and one patient who had a normal MRI and computed tomographic scan of the brain at 4 days of age but subsequently was found to have cortical tubers and subependymal nodules by MRI.

Longitudinal MR findings in a patient with hemimegalencephaly associated with tuberous sclerosis

A patient with an unusual association between tuberous sclerosis complex and hemimegalencephaly is reported. At 2 days of age, CT scan disclosed right hemimegalencephaly with periventricular faint calcification. At 1 month of age, magnetic resonance imaging showed right hemimegalencephaly with T1 and T2 shortening. The right frontal and parietal lobes were compatible with transmantle dysplasia. At 6 months of age, the right hemisphere had decreased in size. Atrophic changes continued to progress until 3 years of age. Periventricular calcification in the right hemisphere became marked with age. The patient developed frequent partial motor seizures from 6 weeks of age and infantile spasms from 5 months of age. Electroencephalogram revealed low amplitude of background activities in the right frontal area. The cause of this atrophic change in the hemimegalencephalic hemisphere, which could be a hamartomatous lesion, remains unknown.