Epidermoid Cyst Brain: Formation, Symptoms, and Removal

Epidermoid cysts in the brain are rare, slow-growing growths that develop from trapped skin cells during early development. While benign, their location can cause significant neurological effects as they expand. Symptoms may not appear until adulthood when pressure on nearby structures becomes problematic. Early detection and management are key to preventing complications.

Formation In The Brain

Epidermoid cysts originate from ectodermal cells misplaced during embryonic development. These cells, which normally form skin, hair, and nails, become trapped within neural structures. Over time, they create a cyst lined with stratified squamous epithelium, which produces keratin and cholesterol, causing gradual growth. Unlike tumors, these cysts do not proliferate uncontrollably but expand due to cellular debris accumulation.

Their slow growth results from continuous keratin shedding, which combines with cholesterol crystals and desquamated cells, forming a pearly, multilayered interior. Unlike fluid-filled arachnoid cysts, epidermoid cysts have a heterogeneous consistency, appearing as soft, lobulated masses with irregular borders. Lacking intrinsic blood vessels, they differ from tumors or vascular malformations.

The embryological origin explains their deep-seated location. During neural tube closure, ectodermal remnants become trapped in regions where the brain folds and develops. This accounts for their presence near the midline, particularly where embryonic fusion occurs. Common sites include the cerebellopontine angle, suprasellar cistern, and fourth ventricle, where neural tissue folding and compartmentalization take place. These cysts often remain undetected until expansion compresses adjacent structures, leading to symptoms.

Typical Locations

Epidermoid cysts develop in regions where ectodermal remnants are trapped during fetal development, often in areas of complex neural folding. The cerebellopontine angle (CPA) is a frequent site, situated between the cerebellum and pons. This region contains critical neurovascular structures, including cranial nerves responsible for facial movement, hearing, and balance. Cysts here can cause hearing impairment, facial numbness, or imbalance as they grow.

Another common location is the suprasellar cistern, near the pituitary gland and optic chiasm. Cysts in this area may compress optic pathways, leading to gradual vision loss or bitemporal hemianopsia. Compression of the pituitary stalk can cause endocrine disturbances, including diabetes insipidus or hypothalamic dysfunction. Because these cysts grow slowly, they can reach considerable size before symptoms prompt diagnosis.

The fourth ventricle, located in the posterior fossa between the cerebellum and brainstem, is another site where these cysts may form. Given its role in cerebrospinal fluid (CSF) circulation, cysts here can obstruct CSF flow, leading to hydrocephalus. This results in increased intracranial pressure, causing headaches, nausea, vomiting, and, in severe cases, altered consciousness. The confined space of the fourth ventricle means even a modestly sized cyst can significantly affect neurological function.

Neurological Signs And Symptoms

As epidermoid cysts expand, they exert pressure on adjacent neural structures, causing neurological symptoms that vary by location. The slow growth often results in an insidious onset, with mild, intermittent symptoms that worsen over time. Early signs, such as headaches, dizziness, or subtle sensory changes, are frequently mistaken for common conditions like migraines, leading to delayed diagnosis.

As the cyst enlarges, cranial nerve compression can cause more distinctive symptoms. In the cerebellopontine angle, involvement of the vestibulocochlear nerve (cranial nerve VIII) may lead to progressive hearing loss, tinnitus, or balance disturbances. Patients might experience vertigo or persistent unsteadiness, particularly with head movements. If the trigeminal nerve (cranial nerve V) is affected, facial numbness, tingling, or neuropathic pain can occur, resembling trigeminal neuralgia.

Motor impairments arise when the cyst encroaches on the brainstem or cerebellum. Weakness, coordination difficulties, and dysmetria—impaired movement accuracy—may become apparent, particularly in fine motor tasks. In advanced cases, brainstem compression can disrupt autonomic functions like breathing and swallowing, creating life-threatening complications. Cognitive effects, though less common, may include memory disturbances or attention deficits if cortical or subcortical pathways are affected.

Imaging Methods

Detecting an epidermoid cyst requires imaging techniques that differentiate it from other intracranial lesions. Magnetic resonance imaging (MRI) is preferred for its ability to visualize soft tissue structures. On conventional MRI, epidermoid cysts typically appear as non-enhancing lesions with signal characteristics similar to cerebrospinal fluid. However, diffusion-weighted imaging (DWI) helps distinguish them from arachnoid cysts, as epidermoid cysts appear hyperintense on DWI, while arachnoid cysts remain hypointense.

Computed tomography (CT) is useful in detecting calcifications within the cyst or assessing bony erosion. Epidermoid cysts sometimes contain fine calcifications that are more visible on CT scans. Additionally, CT helps evaluate skull remodeling caused by prolonged pressure from the cyst. However, due to its limited soft tissue contrast, CT is secondary to MRI in diagnosing these lesions.

Surgical Removal Methods

When an epidermoid cyst becomes symptomatic, surgical removal is the primary treatment. Due to their slow growth, surgery is typically reserved for cases where neurological function is compromised or further complications are likely. Removing these cysts is challenging because they often adhere to cranial nerves and blood vessels. Unlike well-defined tumors, epidermoid cysts infiltrate subarachnoid spaces, making complete excision difficult.

Microsurgical techniques allow precise dissection while minimizing trauma to surrounding structures. The goal is maximal safe resection—removing as much of the cystic content and epithelial lining as possible while preserving neurological function. Complete removal is not always feasible, especially when the cyst is attached to critical structures like the brainstem or optic pathways. In such cases, subtotal resection alleviates symptoms while reducing the risk of complications. Residual cyst lining can lead to recurrence, necessitating long-term monitoring through periodic imaging.