Teaching Case

A 5 year-old female patient with motor mental retardation referred with autistic behavioural disturbances, and epileptic seizure attacks developing within the last few weeks.

A 5 year-old female patient with motor mental retardation referred with autistic behavioural disturbances, and epileptic seizure attacks developing within the last few weeks. An MRI study of the cranium was performed with a 1.5 T MR scanner, with SE T1, FSE T2, post gadolinium SE T1 weighted sequences on three planes.

Tuberous sclerosis(TS) is a neurocutaneous disorder with an estimated prevalance of 1 per 20,000. It is inherited in an autosomal dominant manner in 20 to 50 % of cases, with the rest resulting from spontaneous mutations. The classical clinical triad of TS includes seizures, mental retardation (in less than 50 % of patients), and adenoma sebaceum(facial nevus). Myoclonic seizures beginning in infancy or early childhood are the presenting symptoms in 80 % of cases . Multiple organ systems are involved in TS and associated findings include central nervous system subependymal and cortical tubers,white matter lesions,giant cell astrocytomas of foramen of Monroe,cutaneus lesions(facial angiofibromas,shagreen patches,ash- leaf spots and subungual fibromas), retinal hamartomas,renal angiomyolipomas and cysts,interstitial lung disease, and cardiac rhabdomyomas. Intracranial manifestations are thought to be secondary to a dysplasia of stem cells extending from subependymal region to the cortex. Cortical hamartomas are small nodular lesions that expand involved gyri. Subependymal nodules are frequently calcifying hamartomas. White matter lesions are composed of heterotopic giant cells (balloon cells) and associated hypomyelination. Subependymal giant cell astrocytomas are located at or near the foramen of Monroe and enlarge over time while remaining histologically benign and seen at 15 % of tuberous sclerosis cases.Anatomically,these tumors differ from the subependymal hamartomas by their size and tendency to enlarge. As these tumors enlarge,usually result in a clinical presentation of hydrocephalus due to their characteristic location. Signal intensity or enhancement pattern are not useful in making the distinction between benign hamartomas and giant cell tumors. Most important criteria is progressive enlargement.MRI findings of hamartomas differs by age.In the neonate subependymal nodules appear hyperintense on T1 and PD weighted images, and relatively hypointense on T2 weighted images. As the white matter myelinization increases,these lesions become more isointense with white matter on T1, and hypointense to white matter on T2 weighted images. These lesions demonstrate variable contrast enhancement following gadolinium administration. Giant cell astrocytomas enhance intensely with gadolinium administration.Treatment of TS includes medical management of seizure activity,surgical resection of dominant seizure foci or giant cell astrocytomas as necessary.Prognosis varies with the severity of expression of the disease.