Neurosonography of tuberous sclerosis with MRI correlation.

A neonate with known antenatal history of multiple cardiac rhabdomyomas detected on fetal echo was born full-term with unremarkable birth history. Physical exam showed multiple hypopigmented macules. No abnormal family history was of note.  Referral for ultrasound brain and kidneys was made at one months of age for underlying suspected phakomatosis.

Ultrasound of the brain (at 1 month age) showed multiple iso- and hyperechoic nodular lesions of less than 1cm in size seen along the walls of the lateral ventricle, with some protruding into the ventricles, including at the caudothalamic groove and near the region of foramen of Monro. Multiple vague hyperechoic lesions are also seen in bilateral subcortical white matter regions, especially at the frontal lobes. Ventricles are otherwise not dilated. Corpus callosum was intact.

Ultrasound of the kidneys was unremarkable with no discrete renal lesions detected (not shown).

Magnetic resonance imaging (at 5 months age) showed corresponding multiple small (<1cm) T1W hyperintense T2W isointense nodules along the ventricular surfaces, suggestive of subependymal nodules (SEN). No definite larger heterogeneous lesion is seen near foramen of Monro to suggest subependymal giant cell astrocytoma (SEGA). Multiple T1W hyperintense T2W isointense lesions are seen in bilateral gray-white junctions involving overlying cortex and subcortical white matter, in keeping with cortical and subcortical tubers. Linear T1W hyperintense foci are seen radiating from periventricular to subcortical white matter is suggestive of radial migration lines. No abnormal white matter cystic lesions.

Tuberous sclerosis complex (TSC) is a rare autosomal dominant neurocutaneous syndrome characterised by benign congenital tumours affecting multiple organs, most frequently the brain, eyes, kidneys, heart and skin. [1] The classical Vogt’s triad of mental retardation, epilepsy and adenoma sebaceum is only seen in less than half of TSC patients, therefore radiological assessment plays an important role in early diagnosis and management.  Earlier studies reported mean age of diagnosis at 5 years of age [2], but more recent studies proved earlier mean age of diagnosis at 6 months old [3], likely due to an increasing antenatal diagnosis of cardiac rhabdomyoma.

Revised diagnostic criteria for tuberous sclerosis by 2012 International Tuberous Sclerosis Complex Consensus Conference include both genetic and clinical criteria [4]. The clinical criteria for definitive TSC include either 2 major features or 1 major and 2 or more minor features. Major features include hypomelanotic macules (≥3, at least 5mm diameter), angiofibromatas (≥3) or fibrous cephalic plaque, ungual fibromas (≥2), shagreen patch, multiple retinal hamartomas, cortical dysplasia (tubers and white matter radial migration lines), subependymal nodules, subependymal giant cell astrocytoma, cardiac rhabdomyoma, lymphangioleiomyomatosis (LAM), angiomyolipomas (≥2). Minor features include “Confetti” skin lesions, dental enamel pits (>3), intraoral fibromas (≥2), retinal achromic patch, multiple renal cysts and non-renal hamartomas.

Detection of subependymal nodules and cortical tubers on neonatal ultrasound brain are relatively uncommon [5], although reported to be common findings in infants receiving a TSC diagnosis of 93% and 88% respectively [6]. Regardless, the findings of multiple subependymal nodules along with cortical and subcortical echogenic lesions on ultrasound should raise high suspicion for diagnosis of TSC with early referral for genetic testing. Care is taken not to mistaken subependymal nodules as haemorrhage or calcifications especially if there was a history of fetal distress and prematurity. 

This case also nicely illustrates the atypical MRI appearance of tubers and white matter lesions which are predominately T1W hyperintense in the background of the hypointense unmyelinated white matter. This has been well described to have benefits of easier detection for young infants [7].

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