What Is an Epidermoid Tumor?
These lesions are lined with keratinizing squamous epithelium and contain accumulated keratin, cholesterol crystals, and lipid debris, giving them a pearly, waxy appearance—hence the nickname “pearly tumors.” Epidermoid tumors expand slowly, often over decades, and tend to grow along the subarachnoid spaces, enveloping cranial nerves and major blood vessels. Although benign, their location within neurosurgically sensitive regions can make complete surgical removal difficult, especially without causing neurological damage.Common Locations of Epidermoid Tumors
Epidermoid tumors are most frequently found in cerebrospinal fluid–rich spaces and regions of embryological complexity. Common anatomical locations include the cerebellopontine angle (CPA), the temporal lobe region, and the parasellar cisterns. Less commonly, they may be found in the fourth ventricle, prepontine cistern, or even the spinal canal.Symptoms of Epidermoid Tumor
Since epidermoid tumors grow very slowly, symptoms often go unnoticed for years and become apparent only when adjacent neural structures are compressed. Typical symptoms include:Hearing Loss and Tinnitus: Frequently due to compression of the vestibulocochlear nerve (cranial nerve VIII), especially in CPA tumors.
Facial Weakness or Numbness: Involvement of cranial nerves V and VII may cause altered facial sensation or facial muscle weakness.
Dizziness, Vertigo, or Imbalance: Resulting from cerebellar or vestibular nerve compression.
Persistent Headaches and Nausea: Often related to increased intracranial pressure or hydrocephalus.
Visual Disturbances: Such as double vision or visual field loss, especially when tumors are located near the parasellar cisterns.
Seizures: More common in supratentorial epidermoids that irritate the cerebral cortex.
Diagnostic Evaluation
Magnetic Resonance Imaging (MRI): MRI is the imaging modality of choice. Key features include:
T1-weighted: Typically hypointense
T2-weighted: Hyperintense
Diffusion-Weighted Imaging (DWI): Marked hyperintensity, which is diagnostically specific
Computed Tomography (CT): May reveal a hypodense, non-enhancing lesion; occasionally shows calcification.
Neurological Examination: To assess cranial nerve function, motor strength, coordination, and reflexes depending on tumor location.
Treatment Strategies
1. Microsurgical Resection
Microsurgical excision is the primary and most effective treatment.
The aim is maximal safe resection, which may be subtotal due to the tumor’s adherence to delicate neurovascular structures.
Tools like neuronavigation, intraoperative neuromonitoring, and microsurgical techniques help minimize functional damage.
Total removal often offers long-term relief, but subtotal resection carries a risk of recurrence.
2. Stereotactic Radiosurgery (SRS)
Considered for residual or recurrent lesions not amenable to re-operation.
While epidermoid tumors are generally radioresistant, SRS might help control tumor growth in select cases.
3. Postoperative Monitoring
MRI follow-up is recommended to detect recurrence, especially after partial removal.
Clinical reassessment for cranial nerve recovery or emerging symptoms is also essential.