Endolymphatic sac tumor
The endolymphatic sac tumor is a rare tumor that is strongly associated with Von Hippel–Lindau disease (VHL). It occurs in the endolymphatic sac, which is an area located deep within the inner ear at the end of the endolymphatic duct. Patients in which this tumor occurs tend to have a good prognosis in the long term due to the tumor's inability to metastasize beyond the initial growth site, although permanent loss of hearing and recurrence of the tumor are common associated outcomes.
Definition & Facts
Within the inner ear lies the endolymphatic duct and its terminal sac, a pouch-like structure. This is the most posterior area of the inner ear, reaching all the way to the dura mater, which is the outermost of the meninges which are the membranes that surround the brain. Rarely, a tumor may develop in the sac and/or duct.
Patients in which this occurs almost always have von Hippel-Lindau syndrome. The tumor can occur in patients without VHL, but this event is quite rare. This endolymphatic sac tumor grows slowly, but will cause problems as its size increases and it begins to irreversibly hinder the function of the inner ear, which is vital to hearing and balance. It is difficult to remove completely once detected, but will not metastasize beyond the inner ear.
Symptoms & Complaints
The tumor can grow undetected over a period of years with the hearing loss worsening as it does so, primarily because of hemorrhage occurring within the inner ear or invasion of nearby structures such as the cochlea. Additionally, as with many kinds of hearing loss, tinnitus, which is an experience of ringing in the ears, can be an accompanying condition.
The other functions of the inner ear may also be impacted with the growth of the tumor as it extends into the spaces of the inner ear. This can include difficulties with balance, vertigo, or even ataxia, which is a condition in which muscle movements fail to coordinate correctly, resulting in a characteristic limp or gait abnormality. The presence of balance issues along with hearing loss are a signal to the provider to test for the presence of an endolymphatic sac tumor.
Most patients who develop an endolymphatic sac tumor also have von Hippel-Lindau syndrome. Approximately 10% to 16% of those with VHL syndrome will develop the tumor, usually at an earlier stage in life than the few patients without VHL syndrome who develop this tumor.
The cause is tied to the hallmark of VHL syndrome, which is a genetic mutation of the VHL gene. This causes an inability on the part of the patient to produce enough VHL protein to suppress the growth of tumors throughout the body, of which an endolymphatic sac tumor may only be one of many.
It is extremely rare, but not impossible, for someone without VHL syndrome to develop this tumor. If progressive hearing loss is detected in someone without VHL, it's important to rule out any other cause of the hearing loss so that in the rare case that an endolymphatic sac tumor is present it may be detected.
Diagnosis & Tests
Since a significant percentage of those patients with VHL syndrome will develop this tumor, the presence of VHL syndrome along with impaired inner ear function is a strong signal that an endolymphatic sac tumor is present.
In order to verify the existence of a developing endolymphatic sac tumor in the patient, a health provider can make use of magnetic resonance imaging (MRI) or computed tomography (CT) scan. The presence of an abnormal mass on these scans centered in the endolymphatic sac, along with the hearing loss and/or balance issues emblematic of the condition, is a good sign that an endolymphatic sac tumor is growing in the inner ear, although it is important to differentiate it from other tumors that can grow in the inner ear or cranium area, such as metastatic renal cell carcinoma or thyroid cancer..
Exploratory surgery is another way to detect an endolymphatic sac tumor that is too small to show up on typical scans, although this is not yet a recommended method of detection.
Treatment & Therapy
The first line of treatment when confronted with an endolymphatic sac tumor is to undertake a surgical removal of the tumor from the inner ear. The tumor should be completely and thoroughly removed, although a surgeon may opt to attempt to preserve the hearing of the patient as much as possible. However, preference should be given to complete removal of the tumor over preservation of hearing ability of the patient.
The location of this tumor, especially for a late stage tumor that has grown large, will normally make it difficult for a surgeon to completely remove. For this reason, recurrence or persistence of the tumor is likely in this situation.
Radiotherapy is another way to treat an endolymphatic sac tumor, usually in conjunction with surgery. In the case of a tumor being too large to operate on, it can often be the only effective method of treatment that remains.
Prevention & Prophylaxis
Endolymphatic sac tumors typically do not metastasize or cause death in the patient. However, since most patients who have this tumor also have VHL syndrome, this usually will not be the only tumor that develops in their body, and these other tumors may indeed prove fatal for the patient if not detected or treated.