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At the recent tuberous sclerosis complex consensus conference, the clinical diagnostic criteria for tuberous sclerosis complex were simplified and revised to reflect both new clinical information about tuberous sclerosis complex and an improved understanding of the disorder derived from molecular genetic studies. Based on this new information, some clinical signs once regarded as pathognomonic for tuberous sclerosis complex are now known to be less specific. No single sign is present in all affected patients, and there is no proof that any single clinical or radiographic sign is absolutely specific for tuberous sclerosis complex. Accordingly, the clinical and radiographic features of tuberous sclerosis complex have now been divided into major and minor categories based on the apparent degree of specificity for tuberous sclerosis complex of each feature. A definitive diagnosis of tuberous sclerosis complex now requires two or more distinct types of lesions, rather than multiple lesions of the same type in the same organ system. Although diagnosis on purely clinical grounds can continue to be difficult in a few patients, there should be little doubt about the diagnosis for those individuals who fulfill these strict criteria. Couples with more than one child with tuberous sclerosis complex, no extended family history, and no clinical features of tuberous sclerosis complex are more likely to have germline mosaicism for tuberous sclerosis than nonexpression of the mutation. Germline mosaicism, while fortunately rare, will not be suspected from either diagnostic criteria or molecular testing until a couple has multiple affected children. Genetic counseling for families with one affected child should include a small (1% to 2%) possibility of recurrence, even for parents who have no evidence of tuberous sclerosis complex after a thorough diagnostic evaluation.
The Tuberous Sclerosis Complex 1998 Consensus Conference clinical criteria represent an important advance in the diagnosis of tuberous sclerosis complex. Since many findings regarded as highly specific for tuberous sclerosis complex are not apparent until late childhood or adulthood, refinements by age may prove of value. We have stratified 106 children into five age groups (0 to 2 years of age, above 2 to 5 years, above 5 to 9 years, above 9 to 14 years, and above 14 to 18 years). Physicians should be alerted as to the frequency of the criteria in different stages of children.
Subependymal giant cell astrocytomas (SEGAs) are relatively rare tumors but occur commonly in the setting of the familial syndrome of tuberous sclerosis complex (TSC). In view of its varied morphology, i.e. resemblance to astrocytic and ganglion cells, its histogenesis remains controversial. We studied 23 cases of SEGA, 19 from our own institute and 4 from NIMHANS, Bangalore. These 19 cases of SEGAs were collected over a period of 23 years (1979 to 2001), and accounted for 0.16% of intracranial tumors and 0.51% of all gliomas reported at our center. The majority of patients presented with visual disturbances (19/23, 82.6%) in the form of decreased vision (60.8%) and blindness (21.7%), generalized tonic clonic seizures (43.4%) and focal motor seizures (4.37%). Age ranged from 4 to 37 years (mean 13.2 years) with male predominance (M:F 2.2:1), and the duration of symptoms varied from 1 month to 96 months (mean 17.2 months). Lateral ventricular involvement was the most common site (91.3%), followed by the third ventricle (8.6%). Nine patients (39.1%) had stigmata of tuberous sclerosis (6 at the time of diagnosis and 3 in the follow-up period). Two patients died due to surgical complications, while the rest were alive and well in the follow-up period ranging from 3 to 264 months (mean 37.1 months). Two patients experienced recurrences, one two years and another 22 years after surgery. Microscopic examination showed varied histology consisting of sweeping bundles of spindle cells, gemistocyte and ganglion-like cells with interspersed inflammatory cell component. The inflammatory cell component on special staining turned out to be an admixture of mast cells and T lymphocytes. Six cases showed areas of necrosis and/or mitosis, but were not indicative of aggressive nature of this tumor. Immunoreactivity for GFAP, NF, S-100, NSE and synaptophysin indicates that this is a hybrid tumor with glial and neuronal differentiation. None of the tumors was immunopositive for HMB-45. The significance of the presence of T lymphocytes and mast cells is not clear. It could be related to tumor immunology and may indicate a favorable prognosis.