Nasal gliomas present as a solid frontonasal mass on prenatal ultrasound and as an intermediate T1, intermediate to high T2 frontonasal mass on MRI without direct fluid connection to the subarachnoid space.

From the manuscript

Prenatal Diagnosis of Nasal Glioma Associated with Metopic Craniosynostosis: Case Report and Review of the Literature

Abstract
Nasal gliomas (nasal glial heterotopia) are rare benign congenital frontonasal lesions occurring in approximately 1: 20.000 - 40,000 live births. The diagnosis is rarely reported prenatally. Nasal gliomas are typically isolated lesions, with syndromic association being exceedingly rare. Metopic craniosynostosis can occur as an isolated abnormality or in association with multiple syndromes. This case is the first reported case of nasal glioma in association with craniosynostosis in the published literature.