1 - Neuroradiology Department, Hospital Dona Estefânia, Centro Hospitalar e Universitário Lisboa Central (CHLC), Lisbon, Portugal
2 - Neuroradiology Department, Hospital Central do Funchal, Funchal, Portugal
3 - Neurosurgery Department, Hospital Dona Estefânia, Centro Hospitalar e Universitário Lisboa Central (CHLC), Lisbon, Portugal
- XVIII congresso SPNR, 16 a 18 Novembro 2023, Braga
Introduction and Purpose: An intracranial dermoid cyst (DC) is an inclusion cyst derived from embryonic ectodermal remnants caused by incomplete cleavage of neural tube. DCs arise during the third to fifth gestational week and represent less than 1% of intracranial masses. Most intracranial DCs are almost always extraaxial, usually in the midline, and most common in children/young adults. They have a predilection for the suprasellar cistern, followed by the posterior fossa and frontonasal region. DCs grow very slowly and only a few reaches or exceeds the size of 5 cm, referred to as giant dermoid cysts (GDCs). Symptoms are mainly location dependent. The purpose of this work is to illustrate the findings that can be found in neuroimaging in patients with DCs.
Methods: The authors present two pediatric cases of female patients with GDCs of the midline posterior fossa, with progressive symptoms/signs of intracranial hypertension.
Results and Discussion: Most DCs are hypodense and appear almost identical to fat on CT scans. Calcification may be present and they may rupture (chemical meningitis). MRI is the preferred method of investigation. DCs resemble fat on imaging, but signal intensity varies with fat and dermal appendages content, generally appearing heterogeneously hyperintense on T1 and T2/FLAIR. In the cases presented, the lesions have different signal from that described in the literature, with predominate hyposignal on T1 and diffusion restriction, however they have a typical multi-layered appearance (onion-skin like), which may correspond to the linear/striated lamellae of keratinaceous debris and hair. Another diagnostic clue includes the sinus tract that connects the median occipital cranial vault to the lesion. Both patients underwent surgical resection with histological confirmation.
Conclusions: DCs are uncommon lesions that may present with atypical imaging features. Its onion-skin appearance and the presence of an associated sinus tract can help in its differential diagnosis.
Keywords: intracranial dermoid cyst; posterior fossa; signal; MRI