BASICS
DESCRIPTION
- Epidermoid tumors are benign, congenital cysts that occur intradurally and extradurally. They are slow-growing and produce symptoms gradually.
- Also called epidermoid cysts, primary cholesteatomas, and epidermoid inclusion cysts
- Third most common tumors of the cerebellopontine angle (CPA)
EPIDEMIOLOGY
Prevalence
Rare intracranial growths constituting 1.8-2.2% of all intracranial tumors �
- Presentation can be at any age but most commonly between the 3rd and 5th decades of life.
- Equal incidence in men and women
- There is a wide ethnic distribution, and there is no known preponderance in any region.
ETIOLOGY AND PATHOPHYSIOLOGY
- Considered a benign lesion; malignant transformation is rare.
- Growth is secondary to accumulation of desquamated epithelial cells; follows a linear growth rate
- Symptoms are due to mass effect and displacement of local structures. Depending on tumor location, it may result in cranial nerve, blood vessel, and brainstem compression.
- Derived from squamous epithelium that is included during neural tube closure
- Epidermoid tumors grow slowly from the buildup of keratin and cholesterol from the continual shedding of the epithelium lining the cyst.
- Formed at the time of neural tube closure between the 3rd and 5th weeks of embryonic life
- Common locations include CPA, parapontine, parapituitary, middle cranial fossa, and dipole of the fontanel.
- Multiple lumbar punctures have been known to be a rare cause.
DIAGNOSIS
HISTORY
- History typically reveals several months to several years of progressive neurologic symptoms.
- Nonspecific symptoms can be due to mass effect: headache (most common), seizure, paresthesias, vision changes, and cranial nerve deficits.
- Symptoms vary widely based on the location of the tumor.
- Parasellar tumor: visual disturbance, hypothalamic dysfunction, cranial nerve palsy, headache, and seizure
- CPA tumor: neurologic defects secondary to impingement on the cranial nerves (V, VII, VIII), headaches, hearing loss, vertigo, facial pain
- 4th ventricle tumor: presents with headache, dementia, psychiatric disorders, and hydrocephalus
PHYSICAL EXAM
- Should consist of a focused general medical exam and a complete neurologic exam
- Neurologic exam should help with localization. Exam may reveal cranial nerve deficit or signs of brainstem or cerebellar involvement.
DIFFERENTIAL DIAGNOSIS
- Differential diagnosis based on radiographic appearance:
- Arachnoid cyst
- Dermoid tumor
- Teratoma
- Schwannoma
- Glioma
- Craniopharyngioma
- Cavernous angioma
- Differential diagnosis of a CPA mass:
- Schwannoma
- Meningioma
- Epidermoid tumor
- Aneurysm
DIAGNOSTIC TESTS & INTERPRETATION
- MRI of brain, with and without contrast, helps differentiate epidermoid tumors from dermoid and arachnoid cysts (1)[B].
- MRI appearance of epidermoids: hypointense on T1, isointense approaching hyperintensity on T2, and no enhancement with gadolinium; hyperintense on diffusion-weighted imaging
- Differentiated from dermoid tumors, which are hyperintense on T1 and T2
- Usual locations: basal surface of the brain, CPA, and parasellar region
- Unusual locations: 4th ventricle, cerebellum, cerebral hemispheres, brainstem, and lateral ventricles
- CT can also identify epidermoid tumors, which show hypoattenuation and have characteristic-lobulated margin.
- No reaction of adjacent bone structures should be noted, this is in contrast to arachnoid cyst and is key to differentiating between them.
- Slight marginal calcifications or enhancement after contrast administration are rare.
Diagnostic Procedures/Other
Surgical resection or biopsy �
- Test interpretation
- Gross appearance: sharply defined mass with irregular lobulated surface that glistens like "mother of pearl,"� white in color, described as "pearly tumors,"� can have spotty calcifications along the surface, and generally solid but can have liquid center
- Histology: thin capsule of stratified squamous keratinized epithelium supported by an outer collagenous layer. Cyst is typically full of proteinaceous debris or rich in cholesterol.
- Epidermoids lack the dermal elements (hair, sebaceous glands, sweat glands) that are found in dermoid tumors.
TREATMENT
No specific medical treatment; may require symptomatic treatment for headache or seizure �
ADDITIONAL THERAPIES
Generally not indicated except in rare instances of malignant transformation. Combination therapies in addition to surgical resection have been shown to be effective at increasing survival (2)[B]. �
SURGERY/OTHER PROCEDURES
Surgery is considered the mainstay of treatment for epidermoid tumors (3)[B]. �
- Indications for surgery: neurologic symptoms secondary to mass effect or local compression
- Complete surgical resection with microsurgical techniques is considered curative to prevent recurrence, however, may not be possible due to adherence of the tumor to neurovascular structures. Partial resection is acceptable due to slow linear growth and rate of recurrence.
- Mortality is <6% and is decreasing using microsurgical techniques.
- In a case series, complete resection was possible in 73% of new tumors and 17% of recurrent cases (3)[B].
- Small incidentally noted tumors can be monitored safely with serial exams and imaging.
- Neuronavigation is routinely used during neurosurgery to avoid damaging sensitive structures (3)[B].
INPATIENT CONSIDERATIONS
Admission Criteria/Initial Stabilization
- Admit to neurosurgery for surgical resection if presenting with acute neurologic symptoms.
- Uncontrolled symptoms from acute hydrocephalus, seizures, headache, or local mass effect may require hospitalization.
- If clinically stable at diagnosis, may be admitted electively for resection of the tumor
Nursing
Requires routine postoperative care as well as frequent assessment of neurologic function, generally every 2 hours after surgery �
Discharge Criteria
Discharge once neurologically stable. �
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
Follow up with neurosurgery after hospital discharge. �
Patient Monitoring
- Radiologic follow-up with MRI (preferred) or CT in intervals of 1 to 2 years after surgical resection
- Close observation and radiologic surveillance every 3 to 12 months if surgery is deferred at diagnosis
DIET
No dietary restrictions �
PATIENT EDUCATION
- The Epidermoid Brain Tumor Community: (www.epidermoidbraintumor.org) patient-based educational Web site
- Patients should be educated about postoperative wound care.
- Patients with seizures should be educated about seizure precautions (i.e., do not swim alone, driving restrictions per state regulations, avoid roofs and ladders, do not operative heavy machinery, carry seizure medications at all times).
PROGNOSIS
- Prognosis is generally good, and complete surgical resection is curative.
- Malignant transformation is exceedingly rare.
- Epidermoid cysts can recur, presumably from residual tumor capsule.
- Regrowth of a tumor is slow. Time period for regrowth is the patient's age at onset of symptoms plus 9 months.
COMPLICATIONS
- Malignant transformation
- Rare complication
- Transformation to squamous cell carcinoma
- Malignant transformation is characterized by rapid onset of symptoms, recurrence, tumor enhancement on CT or MRI, and leptomeningeal carcinomatosis.
- Prognosis is poor.
- Mean survival outcomes for groups treated with palliative management, chemotherapy, stereotactic radiosurgery, and multiple postoperative adjuvant therapies were 5.3 months, 25.7 months, 29.2 months, and 36.3 months, respectively.
- Aseptic meningitis
- Can be a postoperative complication or can occur spontaneously
- May occur in up to 40% of operative cases
- Due to leakage of cyst contents
- Treatment is with corticosteroids (dexamethasone) and, if clinically indicated, empiric antibiotics for viral or bacterial meningitis until CSF cultures are negative.
- Noncommunicating hydrocephalus may be an additional complication of aseptic meningitis.
- Postoperative hemorrhage and delayed postoperative hemorrhage
- Incidence in recent case series was 5.61% and 4.91%, respectively.
- Onset of delayed postoperative hemorrhage ranges from 5 to 23 days after surgery.
- Manifestations include intracranial hypertension, meningeal irritation, brain herniation, seizures, and syncope.
- Mortality rates of delayed postoperative hemorrhage, hematoma, and subarachnoid hemorrhage were 28.6%, 27.3%, and 30%, respectively, in recent case series.
- Cranial nerve deficits from resection or adherence of the capsule
- Cranial nerve deterioration, such as diplopia, facial palsy, or swallowing difficulties, in 55% of patients
REFERENCES
11 Bonneville �F, Sarrazin �JL, Marsot-Dupuch �K, et al. Unusual lesions of the cerebellopontine angle: a segmental approach. Radiographics. 2001;21(2):419-438.22 Nagasawa �DT, Choy �W, Spasic �M, et al. An analysis of intracranial epidermoid tumors with malignant transformation: treatment and outcomes. Clin Neurol Neurosurg. 2013;115(7):1071-1078.33 Aboud �E, Abolfotoh �M, Pravdenkova �S, et al. Giant intracranial epidermoids: is total removal feasible? J Neurosurg. 2015;122(4):743-756.
ADDITIONAL READING
- Samii �M, Tatagiba �M, Piquer �J, et al. Surgical treatment of epidermoid cysts of the cerebellopontine angle. J Neurosurg. 1996;84(1):14-19.
- The Epidermoid Brain Tumor Community. www.epidermoidbraintumor.org
CODES
ICD10
Q04.6 Congenital cerebral cysts �
ICD9
742.4 Other specified congenital anomalies of brain �
SNOMED
- Epidermoid cyst of brain
- congenital cerebral cyst (disorder)
CLINICAL PEARLS
- Epidermoid tumors are rare intracranial cysts that are generally benign and slow-growing.
- Symptoms are due to mass effect and compression of surrounding structures.
- Epidermoid tumors are generally managed surgically, and complete resection is considered curative.