1 - Neuroradiology Department, Hospital Dona Estefânia, Centro Hospitalar Universitário de Lisboa Central, Lisboa
2 - Neurosurgery Departement, Hospital Dona Estefânia, Centro Hospitalar Universitário de Lisboa Central, Lisboa
3 - Pathology Departement, Hospital São José, Centro Hospitalar Universitário de Lisboa Central, Lisboa
- Publicação em versão integral: Einstein (São Paulo). 2021;19:1-2. DOI: 10.31744/einstein_journal/2021AI6347
A 15-year old women presented with a 6-month history of progressive right-hand tremor with functional impairment, aggravated by a 1-month history of episodic confusion. The patient underwent a computed tomography scan, which revealed a posterior fossa expansive lesion with cerebrospinal fluid-like density and a midline bone discontinuity (Figures 1A and 1B; soft tissue window not shown). A magnetic resonance imaging (MRI) scan (Figures 1C to 1G) was performed after hospital admission, revealing a posterior fossa expansile lesion with predominant T2 hyperintensity, T1 hypointensity, linear and irregular areas of faint enhancement after gadolinium injection, and a large area with reduced water diffusion. Supratentorial images revealed signs of chronic hydrocephalus. The patient underwent surgery revealing a whitish extraaxial capsulated lesion containing dermal appendages, and histology confirmed the diagnosis of a dermoid cyst (Figures 1H and 1I).
Intracranial dermoid cysts are rare lesions, representing less than 0.5% of primary intracranial tumors.(1) They are congenital ectodermal inclusion cysts and tend to occur in the midline.(1) In rarer occasions in which they develop in the posterior fossa, they tend to locate in the vermis or within the fourth ventricle.(1) Dermoid cysts may be asymptomatic for a long time and present with a long history of vague symptoms, most commonly headache.(2,3) Depending on location, they may be associated with focal neurologic deficits, seizures, and also recurrent aseptic meningitis.(3) Dermoid cysts are classically described as T1-hyperintense lesions, and some authors claim that “all” lesions present that MRI signal.(1) These intracranial cysts are also described as lesions without gadolinium enhancement and with apparent diffusion coefficient values similar to brain parenchyma.(1-4) Some reports describe uncommon imaging features, such as T1-hypointensity, reduced water diffusion or gadoliniumenhancing regions.(2-4) A dermal sinus may present as a clinical/imaging clue to the correct diagnosis.(2)
Keywords: Dermoid cyst; Imaging; T1 hypointense; Signal; MRI