Correct diagnosis
Case 155
【Progress】
Serving unable to supply a major surgery in our hospital our neurosurgeon referred the patient to the medical university hospital where he was scheduled to undergo surgical resection.
【Discussion】
To find the origin of epidermoid cyst is to go back to the time of embryo. Embryo has three germ layers: ectoderm, mesoderm and endoderm. Ectoderm composes of neural plate, neural border plate and epidermis plate. It is documented that at the third or the fourth week of gestation, neural tube is formed from neural groove with convergence of neural layer (1, 2). Neural tube becomes brain and spinal cord and the lumen of neural tube becomes ventricle and central canal. Epidermis layer is also formed outside the neural tube by convergence of epidermis fold coming from epidermis plate. It is believed that epidermoid cyst comes from the pouch of epidermis layer adjacent to the neural tube (1, 2). Namely, it arises when epidermis cells become trapped during neural tube closure.
Epidermoid cyst is composed of epithelium layer of squamous cells, sometimes keratinized, and fluid content. Dermoid cyst includes epithelium organ such as sweat gland, sebaceous gland and hair. Epidermoid cyst and dermoid cyst generate in the development stage of neural tube and epidermis layer. Teratoma includes not only skin organs but also fat tissue, muscle, teeth and bone which come from two or three germ layers. Then, teratoma is believed to be a neoplasm arising from germ cells in the time of embryo (2, 3).
Intracranial epidermoid cyst commonly arises along the surface of cerebrum and cerebellum, namely arising in cerebellopontine angle, para-pontine area and para-sellar area. The patients exhibit symptoms after 20ies to 40ies when the slow growing tumor make pressure to the adjacent central nervous system (3-5). The symptoms are dependent on the tumor sites. The various symptoms are listed such as headaches, vision problems, loss of sensation and/or motion in the upper and lower extremities, dizziness or difficulty with balance and walking, swallowing or speech difficulty and so on (4, 5). Our case presented in our hospital suffering from swallowing disturbance, eating disorder, walking disturbance, dizziness, hoarseness and lowering vision. These symptoms are based on the pressure to the brain stem.
As imaging diagnosis, epidermoid cyst mimics arachnoid cyst on CT and MRI with T1WI and T2WI. However, MRI with diffusion weighted imaging (DWI) is useful to differentiate them because the fluid content in epidermoid cyst is full of cholesterol and/or rich protein, indicative of markedly restricted diffusion, while the fluid content in arachnoid cyst is serous, like cerebral spinal fluid, indicative of diffusion potency (4, 5).
【Summary】
We present a fifty one year-old male suffering from swallowing disturbance, eating disorder, walking disturbance, dizziness, hoarseness and lowering vision. Brain CT and MRI showed infratentorial lesion, compressing brain stem and cerebellum. MRI with DWI was definitive for the diagnosis of epidermoid cyst because it showed high signal intensity corresponded to the content of the epidermoid cyst, differentiating from arachnoid cyst. It is borne in mind that neural tube becomes brain and spinal cord and neural cavity becomes ventricle and central canal, and that epidermoid cyst arises when epidermis cells become trapped during neural tube closure. Epidermoid cyst composes of squamous cell epithelium and cholesterol and/or protein-rich fluid, indicative of MRI with DWI showing high signal intensity. Dermoid cysts include skin organ such as hair, sebaceous gland and sweat gland. Epidermoid cyst and dermoid cyst grow from remnant of ectodermal layer. Meanwhile, teratoma includes components from two or three germ layers, indicative of neoplasm from germ cells. Epidermoid cyst arises along the surface of cerebrum and cerebellum, namely arising in cerebellopontine angle, para-pontine area and para-sellar area. The symptoms appear after the age of 20ies or greater when the slow growing tumor make pressure to the adjacent central nervous system.
【References】
1.Abramson RC, Morawetz RB, Schlitt M. Multiple complications from an intracranial epidermoid cyst: Case report and literature review. Neurosurgery 1989;24:574-8.
2.Burger PC, et al. Tumors of the central nervous system. Armed Forces Institute of Pathology - Atlas of Tumor Pathology. v. 7. Washington, DC: ARP Press, 2007. p. 471-90.
3.Smirniotopoulos JG, et al. Teratomas, dermoids, and epidermoids of the head and neck. Radiographics. 1995 Nov;15(6):1437-55.
4.Chen, S. et al. Quantitative MR evaluation of intracranial epidermoid tumors by fast fluid-attenuated inversion recovery imaging and echo-planar diffusion weighted imaging. Am J Neuroradiol, 2001;. 22: 1089-96, 2001.
5.Patibandla, MR, et al. Brainstem epidermoid cyst: An update. Asian J Neurosurg. 2016; 11: 194–200
2019.7.31