Endolymphatic sac tumors (ELSTs) are a rare type of growth originating within the inner ear’s endolymphatic sac or duct. Though slow-growing, their location within the delicate inner ear structures can cause significant health issues.
What is an Endolymphatic Sac Tumor?
An endolymphatic sac tumor is an uncommon papillary epithelial neoplasm, a growth with finger-like projections arising from the cells lining the endolymphatic sac or duct. This sac, a small fluid-filled pouch on the posterior temporal bone behind the inner ear, regulates endolymph volume and pressure. Endolymph is a fluid bathing inner ear sensory cells, involved in hearing and balance.
A tumor in this sac can disrupt fluid balance and pressure, leading to hearing and balance symptoms. Though considered benign, these tumors are locally aggressive, growing into and damaging the surrounding bone and temporal bone structures. They are also highly vascular.
Recognizing the Symptoms
Symptoms of an endolymphatic sac tumor develop gradually as the tumor expands. Hearing loss is a common symptom, which can be progressive, fluctuating, or sudden, often affecting only one ear. This hearing loss may mimic Ménière’s disease due to tumor-induced fluid buildup in the inner ear.
Patients may also experience tinnitus (ringing or buzzing in the ears), balance issues, or vertigo. As the tumor enlarges and presses on adjacent structures, it can lead to facial nerve weakness or paralysis, and headaches. Less common symptoms include aural fullness or intralabyrinthine hemorrhage.
Diagnosis and its Connection to VHL Disease
Diagnosing an endolymphatic sac tumor involves imaging studies to visualize the growth within the temporal bone. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans are the primary tools, revealing characteristic bone erosion and intense tumor enhancement on contrast-enhanced images. Audiometry, a hearing test, also assesses the extent and type of hearing loss.
ELSTs have a strong association with von Hippel-Lindau (VHL) disease, a genetic disorder. About 10% to 25% of VHL patients develop an ELST; bilateral tumors are almost always seen in VHL patients. VHL disease is an autosomal dominant disorder caused by a mutation in the VHL tumor suppressor gene, predisposing individuals to various tumors and cysts in organs like the brain, spinal cord, kidneys, and pancreas. Therefore, an ELST diagnosis often prompts genetic testing for VHL, emphasizing screening for this broader genetic condition.
Treatment Options
Surgical removal is the primary treatment for an endolymphatic sac tumor, aiming for complete resection. The tumor’s complex location within the inner ear and temporal bone can make complete removal challenging, especially for larger lesions or those extended into structures like the facial nerve or jugular bulb. Early detection and surgical intervention help prevent further hearing loss.
If complete surgical removal is not feasible, or for any remaining tumor, radiation therapy (e.g., stereotactic radiosurgery) may be considered as an alternative or additional treatment. For very small, asymptomatic tumors, a “watch and wait” approach with regular monitoring may be adopted. The optimal treatment strategy depends on tumor size, extent, and the patient’s overall health and symptoms.
Prognosis and Follow-Up
The long-term outlook for individuals with endolymphatic sac tumors is generally good with appropriate management. However, due to their locally aggressive nature and the possibility of incomplete resection, regular follow-up imaging (typically MRI scans) is important to monitor for recurrence or new lesions. This is especially relevant for individuals with von Hippel-Lindau disease, who have a higher predisposition to these and other VHL-related growths.
Patients may experience persistent effects like hearing loss or balance issues even after successful treatment, depending on the initial tumor damage. While recurrence is possible, particularly if the tumor was not completely removed, a good prognosis is associated with early detection and comprehensive management.