Intracranial epidermoid cyst accounts for 0.2– 1.8 % of all intracranial neoplasms and approximately 50 % of intracranial epidermoid cyst occurred in the cerebellopontine angle, followed by parasellar region, basal cistern, sylvian, pineal region and ventricle systems [5–7]. Unless rupture taking place, it usually follows a benign clinical course . Preoperational diagnosis relies solely on radiological examination, but sometimes it is difficult to be differentiated from other cystic lesions . In the case presented, the patient resorted to medical help because of a ruptured intracranial epidermoid cyst with rare MRI manifestation. Most interestingly, the serum CA 199 level of this patient was extremely high. MRI and serum CA 199 level were monitored for 38 months after surgery, and special attention was paid to the correlation between them. According to our knowledge, the case reported was the first of this kind.
On CT scans, intracranial epidermoid cyst is hypodense with calcification present in 10– 25 % of cases . On MRI scans, they may display low to high signal on T1WI and usually high signal on T2WI depending on the cystic contents. Fluid attenuated inversion recovery (FLAIR) and diffusion weighted imaging (DWI) can be helpful with differentiation of intracranial epidermoid cyst from other intracranial cysitc lesions. However, the diagnosis is still sometimes confused. Although rare, intracranial epidermoid cyst can rupture spontaneously. In most cases, the cholesterol crystals spread throughout the subarachnoid space and the ventricular system, presented as multiple lesions on MRI, and resulting in chemical or aseptic meningitis. In our case, the intracranial epidermoid cyst was originally situated adjacent to the anterior horn of left ventricle. Once rupture occurred, the lipid content leaked into the ventricle, and meanwhile, the CSF rushed into the cystic lesion. Since lipid did not dissolve in CSF and possessed a lower density, stratification was observed on MRI.
The treatment of ruptured intracranial epidermoid cyst includes the use of steroids and antibiotics to release the symptoms, with combination of surgical resection . Sufficient irrigation with saline and hydrocortisone has been recommended during surgery . The huge lesion in our case communicated with lateral ventricle and disseminated along the CSF pathway, making total resection impossible. Therefore, in addition to the strategies mentioned above, lumbar drainage was administrated to facilitate CSF clearance.
Takeshita attributed the various levels of CA 199 to the amount of secretary glands, thickness of capsule, location of intracranial epidermoid cyst and the existence of a blood brain barrier (BBB) . In our case, the dramatic increase of CA 199 could be explained by the strongly positive staining of CA 199 in capsule and the damage of BBB. We speculated that the aseptic ventriculitis and meningitis secondary to lesion rupture destroyed the BBB, resulted in increased permeability of vascular endothelium. CA 199 dispersed from cystic content into ventricular system and further into the systemic circulation. Serum CA 199 kept out-of-limit 10 days after surgery, which might be attributed to the persistence of ventriculitis and long half-life of CA 199. Serum CA 199 decreased gradually two months after operation, resulting from the evacuation of cystic content and successful control of ventriculitis. 38 months’ follow-up suggested a close relativity between serum CA 199 level and MRI manifestation. However, rupture is not the only reason leading to elevated serum CA 199. The increase of the size of epidermoid cyst, as detected by MRI during last follow-up, could generate more CA 199 bearing glands and result in elevated serum CA 199 level.
The augmentation of the other tumor markers including CEA, CA 125 and CA 242 were also observed. These tumor biomarkers, together with CA 199, were all originated from epithelial tissue. Therefore, it was not strange for CEA and CA 125 to be found positively stained in IHC and elevated in serum. As for the negative finding of CA 242 in IHC study, it may be the result of sampling error, since only subtotal resection of the capsule was achived and part of the capsule was suctioned away during the surgery.
Further study of CA 199 expression in a cohort of 41 intracranial epidermoid cyst cases in our hospital demonstrated a reproducible finding in consistent with this case report (data not reported). There were totally 12 patients with CA 199 higher than the upper limit of 37U/mL. CA 199 were significantly higher in patients with intracranial epidermoid cyst than in healthy controls (48.19 ± 73.88U/mL vs 7.0 ± 4.1U/mL, p < 0.001). To evaluate the diagnostic value more systematically and accurately, prospective study with more cases and longer follow-up are needed. Our interesting findings in this case and the above preliminary results, together with the data from other investigators, indicate a possible role of CA 199 in the diagnosis and follow-up of intracranial epidermoid cyst.