By Martin D Timchur DC B.App.Sc, Grad. Cert. Eng, M. Chiro, MAppSc (Med Imag) Chiropractic Radiologist
56y/o male presents with deteriorating vision in the right eye. He suffered a head trauma approximately 12 months earlier.
MRI of the Brain was performed with the following images and sequences:
Axial T1 weighted image
Axial T1 + Contrast
Axial T2 PROP (Propeller)
Axial T2 FLAIR
(Fluid Attenuated Inversion Recovery)
Axial DWI (Diffusion Weighted Image)
A well defined lobulated T1 and T2 hyperintense mass is present just superior to the sellar tursica and extends posteriorly, just above the interpeduncular cistern (yellow arrow).
The lesion lies immediately inferior to the optic chiasm, extending posteriorly to the left. The pituitary is of normal appearance. No post-contrast enhancement is seen within the lesion or supratentorial parenchyma, brain stem or cerebellum.
This lesion is consistent with a supra-sellar dermoid cyst.
Dermoid cysts are uncommon lesions seen as lobulated midline masses with low attenuation on CT and increased signal on T1.
MRI without enhancement post-contrast.
They account for approximately 5% of primary intracranial tumours with a slight female predilection.
They most commonly are seen in the first 3 decades of life and are ectodermal in origin. They are lined by stratified squamous epithe- lium and may contain hair, sweat and sebaceous glands. They do not contain fat. Similar lesions which contain adipose tissue would be considered a teratoma.
- Carniopharyngioma (enhance post-gado)
- Intracranial teratoma
- Intracranial lipoma (fat signal intensity on all sequences)
Headache is the most common presenting feature, although they may be asymptomatic and found incidentally, or have vague symptoms over a long period of time.
Mass effect is a common cause of symptomatic presentation, including of the optic chiasm as in this case. However, rupture may also occur resulting in leakage of sebum into the subarach- noid space. This may cause an aseptic meningitis requiring urgent medical management.
In symptomatic cases, the lesion may be excised, although in some cases, complete excision may not be possible due to proximity to surrounding structure. In such cases, recurrence may occur. Malignant transformation to squamous cell carcino- ma is extremely rare.
- Uncommon and usually asymptomatic
- When symptomatic, usually caused by mass-effect against adjacent structures
- Hi T1 signal, variable T2 signal without enhancement
- Symptomatic lesions usually excised without recurrence
- Benign tumour behaviour
A free downloadable version of this case study can be accessed here: Visual_Disturbance.