63 Epidermoid of the Sella

Case 63 Epidermoid of the Sella

Abdulrahman J. Sabbagh and Jean-Pierre Farmer

Clinical Presentation

An 8-year-old girl presents to the emergency room with sudden painless loss of vision in the left eye.
She has no history of significant fever, systemic symptoms or trauma, and no symptoms of increased intracranial pressure. Her mother reports some behavioral changes.
On examination, visual acuity:
- Right eye: 20/25
- Left eye: no light perception
Pupils
- Left: dilated nonreactive with relative afferent pupillary defect (RAPD)
Funduscopic examination shows optic atrophy on the right side without papilledema.
Extraocular movements are full; there is no diplopia, no pain on movement, and no nystagmus.
Other cranial nerves are normal and the rest of the exam is normal.

Questions

Describe the available imaging studies (Fig. 63.1).
Give three differential diagnoses that would be compatible with the history and images, knowing that this lesion does not enhance on gadolinium infusion.
What other imaging modality would you want to see to get a more accurate diagnosis?
What is RAPD?
What are the available surgical approaches to treat this sellar-suprasellar tumor?
What are contraindications of the transsphenoidal approach?
Describe epidermoid tumors from a gross and microscopic aspect.
What is the difference between epidermoid and dermoid tumors?

Answers

Describe the available imaging studies (Fig. 63.1).
- Lateral skull radiography (Fig. 63.1A), plain computed tomography (CT) (Fig. 63.1B), and magnetic resonance imaging (MRI) (Fig. 63.1C and Fig. 63.1D)
  - Skull x-ray shows flattened sella turcica.
  - CT: Plain axial CT shows a hypodense area in the suprasellar region.
  - MRI: This suprasellar lesion is hypointense on T1-weighted axial MRI and hyperintense on T2. It is displacing the optic chiasm posteriorly. Sagittal MRI showed that this lesion is occupying both the sellar and suprasellar regions.
Give three differential diagnoses that would be compatible with the history and images, knowing that this lesion does not enhance on gadolinium infusion.
- Differential diagnosis includes
  - Arachnoid cyst of the sella
  - Epidermoid of the sella
  - Rathke’s pouch cyst¹
What other imaging modality would you want to see to get a more accurate diagnosis?
- Diffusion-weighted MRI. In this case, it shows restricted diffusion signal, indicating that this is more likely to be an epidermoid cyst (Fig. 63.2A)
- Contrast-enhanced MRI. In this case, it shows no uptake of gadolinium by the tumor (Fig. 63.2B)
- Magnetic resonance angiography. It this case, it shows no evidence of aneurysm or arteriovenous malformation (Fig. 63.2C).¹
What is RAPD?
- Relative afferent pupillary defect (RAPD) is also known as Marcus-Gunn pupil.
- When the pupillary reflex is tested, there is a delay in the reflex on the affected side due to damage or compression of the optic pathway causing reduction in the number of fibers subserving the light reflex on the affected side.²
What are the available surgical approaches to treat this sellar-suprasellar tumor?
- Subfrontal, pterional, supraorbital (cranio-orbital),³ or transsphenoidal approaches^4,5
What are contraindications of the transsphenoidal approach?
- Sphenoid sinus is not pneumatized.
- Sella is too small to reach the suprasellar extension of the tumor.
- Significant suprasellar extension of the tumor that cannot be reached by the transsphenoidal approach. ⁴
Describe epidermoid tumors from a gross and microscopic aspect.
- Gross: Epidermoid tumors envelop and take the shape of their surrounding structures, yet they are separable from them. Pearly in appearance, they can be whitish to grayish with a glistening surface (Fig. 63.3). When opened, they contain flaky waxy material.
- Microscopic: The cyst lining is comprised of stratified squamous epithelium. The contents of the cyst are composed of degenerated keratinocytes. This material is of eosinophilic appearance. ⁶
What is the difference between epidermoid and dermoid tumors?
- Dermoids are usually well demarcated and contain greasy material that may contain hair and adnexal appendages such as sebaceous glands.⁶
- Epidermoids typically do not contain such appendages.