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Case study: intracranial epidermoid cyst causing unilateral proptosis
Epidermoid and dermoid cysts account for less than 1% of all intracranial tumors.
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---Patient with 5 mm of left proptosis and a fullness in superior nasal orbit. Fig.1 Intracranial epidermoid and dermoid cysts are uncommon, accounting for less than 1% of all intracranial tumors. Although congenital in origin, they typically do not present until later in life. The following case describes the unusual presentation of an intracranial epidermoid cyst, presenting as unilateral proptosis. To the best of our knowledge, this has not been previously described in the medical literature.
Case report
---CT scan of the intracranial epidermoid cyst in the left frontal region showing an area of hypodensity compatible with fat (white arrow) and areas of calcification (black arrow). There is erosion of the left lateral wall of the calvarium and the posterior table of the left frontal sinus. Fig.2
A 57-year-old male presented with a chief complaint of a swollen left upper eyelid of 2 months’ duration (Figure 1). During this period, the patient experienced no other symptoms or visual loss.
Examination revealed best corrected visual acuity to be 20/20 bilaterally. Exophthalmometry revealed 5 mm of proptosis in the left eye (base 105; 21 mm in the right eye and 26 mm in the left eye). The left eye was displaced inferiorly and laterally, as well. On palpation, there was a fullness of the left superior nasal orbit with the suggestion of a mass. Anterior and posterior segment examination was unremarkable. The patient had no neurological symptoms. Our initial impression based upon the symptoms and findings was a mucocele involving the frontal sinus.
Computerized tomography (CT) demonstrated an intracranial mass with an area of hypodensity compatible with fat and areas of calcification. There was erosion of the floor of the anterior cranial fossa with breakthrough of the left orbital roof, as well as erosion of the left lateral wall of the calvarium and the posterior table of the left frontal sinus (Figure 2). Magnetic resonance imaging (MRI) confirmed the CT scan findings. T1-weighted images revealed a 6.5-cm nonhomogeneous mass with well-defined margins and nominal surrounding edema, predominantly composed of hyperintense areas consistent with fat (Figures 3, 4). The mass was located in an extra-axial location extending from the floor of the anterior cranial fossa superiorly to compress the left frontal lobe. Inferiorly, the tumor extended into the superior portion of the orbital cone and was inseparable from the anterior portion of the superior oblique muscle with resultant orbital proptosis (Figures 3, 4).
The patient underwent a left frontotemporal pterional craniotomy. The tumor was evacuated by suctioning and curettage. All loose capsule was removed, but those portions firmly adherent to the aura were left in place. These findings were consistent with an epidermoid cyst. Currently, the patient has followed a benign course with no evidence of recurrence.
Discussion
---T1-weighted corneal MRI scan without contrast showing intracranial cyst extending from the left anterior cranial fossa to compress the left orbit, the frontal lobe, the corpus callosum and the frontal horn of both lateral ventricles. Black arrow shows hyperintense area of fat. Fig.3
Intracranial dermoid and epidermoid cysts are rare tumors of congential origin. They are the result of displaced ectodermal tissue caused by faulty closure of the neural tube during the third to fifth week of gestation. Intracranial epidermoids are much more common than dermoids, occurring at a 4:1 ratio. Dermoids typically present within the first three decades of life, whereas epidermoids have a peak incidence in the fourth or fifth decade. Both lesions exhibit a slow growth pattern, which results in a long duration from onset of symptoms to diagnosis. The most common locations are the cerebellopontine angle, suprasellar, cerebellum and temporal fossa, in decreasing order of frequency.
Symptomatology is believed to be related to the location and size of the lesion. Typical symptoms include headache, seizure and dementia. Ruptured intracranial cysts have been shown to cause recurrent aseptic meningitis and transient ischemia attacks. There have been several ophthalmologic presentations reported for these lesions. These include optic atrophy with loss of visual acuity and visual field defects (suprasellar location); papilledema secondary to hydrocephalous (ventricular system); syndrome of Parinaud; upward gaze palsy; retraction-convergence nystagmus; bilateral upper lid retraction (pineal region); and hemifacial spasm (cerebellopontine angle).
On CT scan, intracranial epidermoid and dermoid cysts appear as hypodense, nonhomogeneous masses with attenuation values slightly above cerebrospinal fluid (CSF). This is secondary to their high cholesterol and fatty acid content. Calcifications are an inconsistent feature of epidermoids and are more prevalent in the dermoid cyst.
MRI is the best modality to delineate the extent of the lesion, which is crucial for surgical planning. On T1-weighted images, these cysts appear hyperintense and are well demarcated. They may exhibit a nonhomogeneous appearance, especially when hair and other debris are predominant with signal intensity between those of CSF and brain tissues.
Goal of management
---T1-weighted sagittal scan without contrast showing a circumscribed heterogenous lesion with hyperintense areas of fat (black arrow). Fig.4
The goal of management is complete surgical removal of the tumor. This is difficult secondary to their firm adherence to meninges and normal cerebral tissue. Because of this, complete removal rarely is possible, and intracapsular curettage and irrigation of the cyst cavity is the preferred mode of surgical treatment.
Most of the tumors are incompletely excised, leaving remnants of capsule lined with epithelial cells, which continue the process of keratinization and desquamation causing frequent recurrence of the tumor.
For Your Information:Reference:
- Mark R. Levine, MD, can be reached at Mt. Sinai Medical Building, 26900 Cedar Road, Ste. 311, Beachwood, OH 44122; (216) 464-1484; fax: (216) 464-9398. Dr. Levine has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
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