The value of fetal brain MRI on the diagnostic pathway of tuberous sclerosis complex presenting with cardiac rhabdomyomas

Clinical History

A 27-year-old pregnant woman at 32 weeks of gestation underwent routine obstetric ultrasound on which two hyperechogenic intracardiac mass lesions were found. The diagnosis was intracardiac rhabdomyomas. They are highly associated with Tuberous sclerosis complex (TSC). Although there was no family history of TSC a fetal brain-MRI was performed.

Imaging Findings

Fetal brain MRI performed at a 1.5-Tesla MR-unit, using a sense-body coil, revealed bilateral small subependymal nodules with high signal intensity on T1-weighted images (T1W) and low signal intensity on T2-weighted images (T2W) (Fig. 1).
A postnatal echocardiography depicted the two hyperechogenic intracardiac mass lesions (Fig. 2).
Forty-eight hours after birth a brain ultrasound revealed subependymal, white matter and cortical hyperechogenic lesions in both hemispheres (Fig. 3). The cerebellum did not show any abnormality. Twenty days after birth a brain MRI demonstrated multiple subependymal nodules, cortical tubers and migration lines in both hemispheres. The lesions exhibited high signal intensity on T1W and low signal intensity on T2W images compatible with TSC (Fig. 4).

Discussion

Tuberous sclerosis complex is an autosomal dominant genetic disorder with relatively high spontaneous mutation rate up to 75-80%. Mutation or deletion of TSC1 or TSC2 gene is responsible for the development of this disease. Mental retardation, seizures and adenoma sebaceum is the classic triad of this disease. TSC affects different organs. Subependymal hamartomas, subependymal giant cell astrocytomas (SEGA), cortical tubers and white matter radial migration lines are the most characteristic intracranial findings. Patients having SEGA are at risk to develop obstructive hydrocephalus [1]. Fetal US is mainly able to detect large subependymal tumours but small subependymal lesions are usually not visualized [2].
Other organs that are also often affected are the kidneys (angiomyolipomas), the eyes (hamartomas), the lungs (lymphangioleiomyomatosis), the skin (hypomelanotic macules, café au lait spots , fibromas) [1]. Approximately 80% of children with diagnosed TSC have cardiac rhabdomyomas [3].
In our patient, the presence of cardiac tumours on fetal and postnatal ultrasound led to further examination. Cardiac tumours are very rare at any age. The most common cardiac tumours in children are rhabdomyomas originating from the myocardium [4, 5]. The incidence is 0.02- 0.08% in live-born infants [6]. This non-malignant tumour has at least 50% coincidence with TSC. Rhabdomyoma can affect any part of the heart and is quite often multifocal. The clinical appearance depends on the size and the localization of the tumour. Large tumours in the left ventricle can even lead to heart failure. Another dangerous complication is arrhythmias when the tumour arises near the heart electrical conduction area. The most critical period of possible complications is the 2nd and 3rd trimester because rhabdomyomas grow very fast at this period. Tumour growth stops after birth and may disappear completely afterwards. Multiplicity of rhabdomyomas is predictive of TSC. Fetal echocardiography can detect rhabdomyomas as early as in the 18-20 gestational weeks. The lesions are homogenous and hyperechogenic. Fetuses with cardiac rhabdomyomas and cerebral lesions often develop arrhythmias, heart failure, hydrops and hydrocephalus. Therefore early diagnosis of TSC can help in the appropriate management of these patients.
In conclusion, when cardiac lesions are detected prenatally, there should be a very strong suspicion of TS, and while fetal Brain MR may be of help as in this case, it may not be able to confirm or exclude TS in all patients.

Differential Diagnosis List

Final Diagnosis

TSC associated with cardiac rhabdomyomas.

URL:	https://www.eurorad.org/case/12497
DOI:	10.1594/EURORAD/CASE.12497
ISSN:	1563-4086