Diagnosis

Pineal Epidermoid

Findings

A well circumscribed mass in the pineal body which is heterogeneous to hyperintense on T-1 and hyperintense on T-2 and FLARE images with little or no enhancement post contrast. This mass is obstructing the Sylvian aqueduct, and has no surrounding edema.

Discussion

Intra cranial epidermoids comprise less than 1% of intra cranial neoplasms, although as many as 4% have been reported as incidental finding on MR or autopsies. Most are asymptomatic, although some cause symptoms which are mainly secondary to compression of adjacent structures, hydrocephalus, or aseptic menigitis when these rupture secondary to leakage of their contents. These are slow growing tumors, and usually encase rather than displace adjacent structures.

Epidermoids develop from defects in neural tube closure at 3-5 weeks gestation with inclusion of ectoderm as opposed to other developmental lesions such as dermoids and teratomas, which are made of mesodermal elements as well for the former, and all three germ layers for the latter. These, however, are much less common.

The composition of epidermoids is desquamated epithelium in the form of debris, mainly keratin and cholesterol. This composition gives them a semisolid consistency, and depending on the ratio of keratin to cholesterol, its signal intensity on MR. This variation makes its appearance nonspecific. Its imaging characteristics are low signal intensity on T-1 and high on T-2 with heterogeneity, although as stated previously, this appearance may vary depending on the amount and ratio of their components. There is lack of peritumoral edema, reflecting their slow growing nature, and usually there is no enhancement post contrast injection. Rim enhancement is sometimes seen, however. Differential diagnoses include arachnoid cysts and gliomas.

The clinical presentation seen in this patient is known as "Parinaud's Syndrome". It is secondary to compression of the superior colliculi resulting in paralysis of upward gaze. Other clinical manifestations are mainly from compression of cranial nerves, hydrocephalus, or as previously stated, chemical meningitis.

Treatment is excision via micro surgical technique.

References

1. Brant, Helms: Fundamentals of Diagnostic Radiology (141, 149).
2. Goulianos, et al: "CT and MR of Pineal Region Tumors," MRI, Vol 12 #1, 1994 (17-24).
3. Taveras, Ferruci: Radiology, Diagnosis, Imaging, Intervention. Vol. 3, Ch 73(4).

- J. Esteva, M.D.

Last Update: 3/22/00