Fetal MRI evaluation of an intracranial mass: in utero evolution of hemorrhage

Imaging of fetal brain tumors

Congenital brain tumors, defined as those diagnosed prenatally or within the first 2 months of age, represent less than 2% of pediatric brain tumors. Their location, prevalence and pathophysiology differ from those of tumors that develop later in life. Imaging plays a crucial role in diagnosis, tumor characterization and treatment planning. The most common lesions diagnosed in utero are teratomas, followed by gliomas, choroid plexus papillomas and craniopharyngiomas. In this review, we summarize the pathogenesis, diagnosis, management and prognosis of the most frequent fetal brain tumors.

Fetal stroke and cerebrovascular disease: Advances in understanding from lenticulostriate and venous imaging, alloimmune thrombocytopaenia and monochorionic twins

Fetal stroke is an important cause of cerebral palsy but is difficult to diagnose unless imaging is undertaken in pregnancies at risk because of known maternal or fetal disorders. Fetal ultrasound or magnetic resonance imaging may show haemorrhage or ischaemic lesions including multicystic encephalomalacia and focal porencephaly. Serial imaging has shown the development of malformations including schizencephaly and polymicrogyra after ischaemic and haemorrhagic stroke. Recognised causes of haemorrhagic fetal stroke include alloimmune and autoimmune thrombocytopaenia, maternal and fetal clotting disorders and trauma but these are relatively rare. It is likely that a significant proportion of periventricular and intraventricular haemorrhages are of venous origin. Recent evidence highlights the importance of arterial endothelial dysfunction, rather than thrombocytopaenia, in the intraparenchymal haemorrhage of alloimmune thrombocytopaenia. In the context of placental anastomoses, monochorionic diamniotic twins are at risk of twin twin transfusion syndrome (TTTS), or partial forms including Twin Oligohydramnios Polyhydramnios Sequence (TOPS), differences in estimated weight (selective Intrauterine growth Retardation; sIUGR), or in fetal haemoglobin (Twin Anaemia Polycythaemia Sequence; TAPS). There is a very wide range of ischaemic and haemorrhagic injury in a focal as well as a global distribution. Acute twin twin transfusion may account for intraventricular haemorrhage in recipients and periventricular leukomalacia in donors but there are additional risk factors for focal embolism and cerebrovascular disease. The recipient has circulatory overload, with effects on systemic and pulmonary circulations which probably lead to systemic and pulmonary hypertension and even right ventricular outflow tract obstruction as well as the polycythaemia which is a risk factor for thrombosis and vasculopathy. The donor is hypovolaemic and has a reticulocytosis in response to the anaemia while maternal hypertension and diabetes may influence stroke risk. Understanding of the mechanisms, including the role of vasculopathy, in well studied conditions such as alloimmune thrombocytopaenia and monochorionic diamniotic twinning may lead to reduction of the burden of antenatally sustained cerebral palsy.

Management of midline dural sinus malformations and review of the literature

PURPOSE

Dural sinus malformations (DSMs) are rare pediatric vascular lesions that have variable presentations and outcomes. We present three cases of midline DSMs and discuss the treatment strategy employed for each lesion. A review of the literature was completed to summarize current literature and treatment practices.

METHODS

A retrospective review of the electronic medical record and all available imaging studies was performed for each of our patients.

RESULTS

Patient 1 had a prenatally diagnosed DSM which decreased in size despite no intervention. She was born without complication and continues to do well at 15 months of age. Patient 2 presented 2 weeks after birth with cardiac failure, intracranial hemorrhage, and seizures and imaging showed a large midline DSM with multiple high-flow shunts. She required multiple endovascular embolizations with complete occlusion of the lesion. At her 3-year follow-up, she was neurologically normal. The third patient was diagnosed prenatally with an enlarging DSM. Multiple endovascular embolizations, surgical decompression, cranial expansion, and CSF diversion were required for treatment. At her 2.5-year follow-up, she was meeting developmental milestones, with some motor delay.

CONCLUSION

Early diagnosis and treatment, if necessary, of DSMs are critical to prevent cardiac failure or parenchymal injury from chronic venous hypertension. Management should be decided on individual case basis depending on the angioarchitecture and progression of the lesion and can involve observation, endovascular embolization, surgical interventions, or a combination of treatments. A personalized approach to treating these variable lesions can be associated with good outcomes.

MR imaging of the fetal brain at 1.5T and 3.0T field strengths: comparing specific absorption rate (SAR) and image quality

OBJECTIVES

Our two objectives were to evaluate the feasibility of fetal brain magnetic resonance imaging (MRI) using a fast spin echo sequence at 3.0T field strength with low radio frequency (rf) energy deposition (as measured by specific absorption rate: SAR) and to compare image quality, tissue contrast and conspicuity between 1.5T and 3.0T MRI.

METHODS

T2 weighted images of the fetal brain at 1.5T were compared to similar data obtained in the same fetus using a modified sequence at 3.0T. Quantitative whole-body SAR and normalized image signal to noise ratio (SNR), a nominal scoring scheme based evaluation of diagnostic image quality, and tissue contrast and conspicuity for specific anatomical structures in the brain were compared between 1.5T and 3.0T.

RESULTS

Twelve pregnant women underwent both 1.5T and 3.0T MRI examinations. The image SNR was significantly higher (P=0.03) and whole-body SAR was significantly lower (P<0.0001) for images obtained at 3.0T compared to 1.5T. All cases at both field strengths were scored as having diagnostic image quality. Images from 3.0T MRI (compared to 1.5T) were equal (57%; 21/37) or superior (35%; 13/37) for tissue contrast and equal (61%; 20/33) or superior (33%, 11/33) for conspicuity.

CONCLUSIONS

It is possible to obtain fetal brain images with higher resolution and better SNR at 3.0T with simultaneous reduction in SAR compared to 1.5T. Images of the fetal brain obtained at 3.0T demonstrated superior tissue contrast and conspicuity compared to 1.5T.

In utero magnetic resonance imaging for diagnosis of dural venous sinus ectasia with thrombosis in the fetus

BACKGROUND

Dural venous sinus ectasia with thrombosis (DVSET) in the fetus is a rare condition that can be diagnosed prenatally with the use of fetal MR imaging, yet with limited indication of long-term clinical significance.

OBJECTIVE

To describe and evaluate the diagnostic value of fetal MR imaging in the prenatal diagnosis of dural venous sinus ectasia with thrombosis and its clinical significance.

MATERIALS AND METHODS

We report a series of nine fetuses with dural venous sinus ectasia with thrombosis. The mothers, located in four feto-maternal centres, were referred for fetal MR imaging due to space occupying lesions identified on second-trimester antenatal ultrasound.

RESULTS

In all but one case the dural venous sinus ectasia with thrombosis was in the vicinity of the venous confluence (VC) with various extension in the posterior dural sinuses. Antenatal follow-up imaging was performed in seven cases and showed progression in one, stable appearances in one and regression in five cases. Three pregnancies were terminated. In the remaining six cases there was no reported neurological deficit at up to 44 months of clinical follow-up.

CONCLUSION

This is among the largest series of postnatal clinical follow-up in cases of prenatal diagnosis of dural venous sinus ectasia with thrombosis in the literature. Clinical follow-up suggests a good prognosis when antenatal follow-up shows partial or complete thrombus resolution.

Fetal MR imaging of posterior intracranial dural sinus thrombosis: a report of three cases with variable outcomes

BACKGROUND

Thrombosis of fetal intracranial dural sinuses is a rare entity. A specific type of midline dural sinus thrombosis (DST) at the torcular Herophili with extension into the superior sagittal sinus (SSS) was initially seen on fetal US and was referred to fetal MRI for definite diagnosis and better delineation.

OBJECTIVE

Retrospective comparison to medical literature of three cases, diagnosed at our institution, of midline fetal DST with MR imaging findings and clinical outcomes.

MATERIALS AND METHODS

We reviewed MRI findings on T2-weighted images of our three cases of fetal midline DST and clinical outcomes of these fetuses and compared our findings to medical literature. The MR imaging and clinical findings of our cases extend over 6 years. They consist of three pregnant women, 31-39 years of age each with a single fetus, with fetal MR imaging performed at different gestational ages (GA). Case 1 the MR imaging was performed at 21 5/7 weeks' GA, case 2 at 24 and 33 4/7 weeks' GA, and case 3 at 22 and 25 weeks' GA. Postnatal MRI was performed in case 2 at 6 months of life and case 3 at 1 day of life. Clinical follow-up occurred during the last 6 years.

RESULTS

In all of our cases, T2-W MR imaging demonstrated ballooned midline torcular Herophili with iso- to hypointense mass with or without focal eccentric area of greater hypointensity occupying the torcular Herophili with extension into the SSS. Case 3 had associated leptomeningeal dural vascular malformation overlying the left cerebral hemisphere with development of migrational disorder in the left cerebral hemisphere. Clinical outcome consisted of fetal demise in case 1, normal postnatal outcome in case 2 and severe brain damage with poor postnatal outcome in case 3.

CONCLUSION

Our findings of large iso-hypointense thrombus with or without a focal eccentric area more hypointense to thrombus in a dilated torcular Herophili with extension into the SSS on T2-W images corresponds to the majority of cases of this rare type of DST in the medical literature.

Prenatal diagnosis of thrombosis of the dural sinuses: report of six cases, review of the literature and suggested management

OBJECTIVES

To describe and assess the sonographic findings, evolution and clinical implications of thrombosis of the fetal dural sinuses.

METHODS

We compiled a multicenter report of the outcomes of five cases with a prenatal diagnosis of thrombosis of the dural sinuses, and one case in which thrombosis of the dural sinus was diagnosed at necroscopy after termination of pregnancy. Prognostic factors are discussed, and suggestions made for prenatal and postnatal management.

RESULTS

The mean (range) gestational age at diagnosis of thrombosis of the dural sinuses in the five cases in which it was made prenatally was 25.2 (22-31) weeks. In these five cases, diagnosis was made by sonography and confirmed by magnetic resonance imaging (MRI), which showed a blood clot in the region of the torcular herophili. Three of the six cases delivered vaginally with favorable sonographic findings, and normal clinical neurological development. Two pregnancies were terminated at the request of the parents. In one of these cases the prognosis was poor, with signs of fetal decompensation or cardiac failure; the pregnancy was terminated and necropsy revealed thrombosis of the occipital dural sinuses associated with a hemangioma. One infant, in whom the thrombosis developed in conjunction with a dural sinus malformation, died at 4 months of age.

CONCLUSIONS

Thrombosis of the cerebral venous circulation can occur antenatally and is detectable by fetal real-time and color Doppler ultrasound examination. A review of the literature supports targeted evaluation of the fetus by serial ultrasound imaging and MRI to help guide the diagnosis, and to improve the counseling and management of such cases. Partial or total regression, isolated abnormality, absence of fetal decompensation or signs of cardiac failure and favorable clinical evolution are suggestive of favorable prognosis. In such cases, non-interventional neonatal management is recommended.

Fetal Extradural Hematoma: Prenatal Diagnosis and Postmortem Examination

We report the 1st confirmed case of an extradural hematoma diagnosed in utero by ultrasonography and magnetic resonance imaging at 31 weeks' gestation. No signs of intracranial hemorrhage were found. During pregnancy, the expecting mother suffered from sustained cough, and a blood sample test revealed acute pertussis. The presence of fetal hydrocephaly, brain parenchymal deviation, and other abnormalities suggested a poor outcome, and based on these findings pregnancy termination was recommended and carried out. Postmortem examination confirmed the diagnosis of an extradural hematoma in the posterior fossa.

Prenatal Diagnosis of a Trauma-Related Fetal Epidural Hematoma

BACKGROUND

Prenatal diagnosis of fetal intracranial hemorrhage has important etiologic, management, and prognostic implications. Ultrasonography and magnetic resonance imaging (MRI) have been used to identify and evaluate this condition. We present the first reported case of epidural hematoma diagnosed prenatally.

CASE

A 25-year-old para 3 was referred for evaluation of a suspected fetal intracranial abnormality following an alleged assault. Ultrasonography and MRI were used to diagnose an epidural hematoma prenatally. The fetus subsequently died in utero. Autopsy confirmed the presence of an epidural hematoma.

CONCLUSION

Ultrasonography and MRI were useful in diagnosing a fetal epidural hematoma. Unfortunately, no known effective in utero therapy exists for this rare problem.

Prenatal ultrasound detection of bilateral focal polymicrogyria

OBJECTIVES

Prenatal diagnosis by ultrasound of fetal polymicrogyria has been reported only once.

METHODS

We describe an additional case of polymicrogyria in a fetus from a monozygotic twin pair, probably the consequence of twin-to-twin transfusion syndrome.

RESULTS

On ultrasound, there were bilateral cortical hyperechogenic spots, and prenatal magnetic resonance imaging demonstrated the typical features of bilateral focal polymicrogyria.

CONCLUSION

Polymicrogyria can be considered in the differential diagnosis of hyperechogenic brain lesions on fetal ultrasound. We also confirm the risk of brain damage in monochorionic twins pregnancies and the likely hypoxic-ischemic etiology of polymicrogyria.