Intracranial epidermoid cyst
Citation, DOI, disclosures and article data
At the time the article was created Frank Gaillard had no recorded disclosures.View Frank Gaillard's current disclosures
At the time the article was last revised Craig Hacking had the following disclosures:
- Philips Australia, Paid speaker at Philips Spectral CT events (ongoing)
These were assessed during peer review and were determined to not be relevant to the changes that were made.View Craig Hacking's current disclosures
Intracranial epidermoid cysts are uncommon congenital lesions which account for about 1% of all intracranial tumors. They result from inclusion of ectodermal elements during neural tube closure, and typically present in middle age due to mass effect on adjacent structures. Their content, derived from desquamated epithelial cells, mimics CSF on CT and MRI, with the exception of DWI which demonstrates restricted diffusion. Management is surgical and prognosis is good.
Although predominantly congenital, epidermoid cysts are usually very slow growing and as such take many years to present. Typically patients are between 20 and 40 years of age 6. There may be increased prevalence in males, although this is not found in all series 5,6.
Epidermoid cysts account for ~1% of all intracranial tumors 2,8.
An uncommon association exists with anorectal anomalies, sacral anomalies and presacral mass, and is known as the Currarino triad 5.
Signs and symptoms of epidermoid cysts are due to gradual mass effect, with presentation including 4:
headaches: most common
cranial nerve deficits
raised intracranial pressure
Recurrent aseptic meningitis is uncommon but recognized, similar to the less common dermoid cyst 4.
Epidermoid cysts may be congenital (most common, arising from ectodermal inclusion during neural tube closure 8) or acquired (post-surgical or post-traumatic implantation). Pathologically, intracranial epidermoid cysts are identical to the petrous apex and middle ear congenital cholesteatomas. They differ from dermoid cysts which have both epidermal and skin appendages such as hair and sebaceous cysts and mature teratomas which have all three layers.
They have a thin capsule which is made of a thin layer of squamous epithelium, which macroscopically is white and pearly, and may be smooth, lobulated, or nodular. Internal cystic components are often filled with desquamated epithelial keratin and cholesterol crystals; grossly appearing as a creamy, waxy material. It should be noted that some authors contest that epidermoid cysts are along a spectrum which includes cystic (adamantinomatous) craniopharyngiomas, which have some histological similarities 7. Cholesterol and keratin components account for their distinct imaging characteristics 2.
cerebellopontine angle: 40-50% 2,8
suprasellar cistern: 10-15% 8
fourth ventricle: ~17% 8
interhemispheric: < 5% 9,10
extradural: 10% 8
most within skull: see intradiploic epidermoid cyst
Intracranial epidermoid cysts appear as lobulated lesions that fill and expand CSF spaces and exert a gradual mass effect, insinuating between structures and encasing adjacent nerves and vessels. A common feature of posterior fossa cysts is displacement of the basilar artery away from the pons.
The combination of cellular debris along with a high cholesterol content lower the density of epidermoids to approximately 0 HU, and can thus be identical in density to CSF, and look the same as an arachnoid cyst.
Calcification is seen in a minority of cases (10-25% 8), and rarely an epidermoid cyst may be hyperdense due to hemorrhage, saponification or high protein content ("white epidermoids"). The interhemispheric epidermoids are reported to have peripheral calcification.
They do not enhance and only very rarely demonstrate any enhancement of the wall.
Similar to CT, epidermoids are often indistinguishable from arachnoid cysts or dilated CSF spaces on many MR sequences, except for DWI/ADC which helps to differentiate them.
usually isointense to CSF
higher signal compared to CSF around the periphery of the lesion is frequently seen
rarely they can be of high signal and are known as white epidermoids
rare intralesional hemorrhage can also result in intrinsic high signal
T1 C+ (Gd)
thin enhancement around the periphery may sometimes be seen
in the rare cases of malignant degeneration, enhancement becomes more pronounced
usually isointense to CSF (65%)
slightly hyperintense (35%) to grey matter
rarely hypointense to grey matter, usually in the setting of the so-called white epidermoid (the term refers to the T1 appearance) 2
often heterogeneous/dirty signal; higher than CSF
beware of flow artifact from CSF pulsation which can mimic this appearance
very bright on DWI
similar ADC values compared to adjacent brain parenchyma
useful for differentiation from arachnoid cysts due to increased signal (due to a combination of abnormal restricted diffusion and T2 shine through), which is not seen with arachnoid cysts
Treatment and prognosis
Surgical excision is the treatment of choice if symptomatic. However, complete resection is difficult as not all tissue can be removed, especially from around cranial nerves and vessels. Recurrence is therefore not uncommon, although growth is typically slow and many years can elapse without new symptoms.
The differential for an epidermoid cyst include:
follows CSF on all sequences, including FLAIR and DWI
often fat density due to sebum
typically located along the midline
inflammatory cyst, e.g. neurocysticercosis
smaller, but can be multiple
may enhance peripherally
may have associated edema
usually no restricted diffusion
a solid enhancing component is usually identifiable
- 1. Grossman RI, Yousem DM. Neuroradiology, the requisites. Mosby Inc. (2003) ISBN:032300508X. Read it at Google Books - Find it at Amazon
- 2. Chen CY, Wong JS, Hsieh SC et-al. Intracranial epidermoid cyst with hemorrhage: MR imaging findings. AJNR Am J Neuroradiol. 2006;27 (2): 427-9. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Swartz JD, Harnsberger HR. Imaging of the temporal bone. George Thieme Verlag. (1998) ISBN:0865777004. Read it at Google Books - Find it at Amazon
- 4. deSouza CE, deSouza R, da Costa S et-al. Cerebellopontine angle epidermoid cysts: a report on 30 cases. J. Neurol. Neurosurg. Psychiatr. 1989;52 (8): 986-90. doi:10.1136/jnnp.52.8.986 - Free text at pubmed - Pubmed citation
- 5. Albright AL, Adelson PD, Pollack IF. Principles and practice of pediatric neurosurgery. Thieme Medical Pub. (2007) ISBN:1588903958. Read it at Google Books - Find it at Amazon
- 6. DeMonte F, Gilbert MR, Mahajan A. Tumors of the Brain and Spine. Springer Verlag. (2007) ISBN:0387292012. Read it at Google Books - Find it at Amazon
- 7. Miller NR, Walsh FB, Hoyt WF. Walsh and Hoyt's Clinical Neuro-Ophthalmology. Philadelphia : Lippincott Williams & Wilkins, c2005. (2005) ISBN:0781748127. Read it at Google Books - Find it at Amazon
- 8. Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology. 2006;239 (3): 650-64. Radiology (full text) - doi:10.1148/radiol.2393050823 - Pubmed citation
- 9. Dhananjaya I Bhat, B Indira Devi, A Raghunath, Sampath Somanna, BA Chandramouli. Interhemispheric epidermoids - An uncommon lesion in an uncommon location: A report of 15 cases. Neurology India. 59 (1): 82. doi:10.4103/0028-3886.76874 - Pubmed
- 10. Agarwal V, Vijayan A, Velho V, Mally R. Pearl in interhemispheric fissure: A rare phenomenon. Asian journal of neurosurgery. 7 (4): 229-32. doi:10.4103/1793-5482.106663 - Pubmed