A classic presentation of endolymphatic sac tumor
A 20-year-old female presented with left-sided headache and progressive sensorineural hearing loss. There was also a history of chronic left-sided visual impairment. Findings on the initial head CT prompted dedicated temporal bone CT and MR imaging, and then preoperative catheter angiography. Shortly afterward, the patient underwent surgical resection of a left temporal bone tumor.
The temporal bone CT scan demonstrates an area of extensive retrolabyrinthine destruction. The inferior aspect of the lesion involves the posterior border of the jugular fossa, and there is also extension into the middle ear cavity. There are spicules of residual bone throughout the involved region. The MRI examination demonstrates a mass with T2-hyperintensity and robust enhancement, corresponding to the area of bone destruction seen on the CT. There are also areas of intrinsic T1-hyperintensity on the noncontrast images. In order to decrease blood loss during surgery, a preoperative angiogram was performed for embolization of the mass before surgical resection. The angiogram demonstrates a hypervascular mass with arterial supply from the ascending pharyngeal artery.
Photos courtesy of M. Ghesani, MD
The temporal bone lesion is an endolymphatic sac tumor (ELST). In this particular case, involvement of the jugular fossa and middle ear cavity may raise the question of paraganglioma. However, the mass is centered in the retrolabyrinthine area. This location, and the residual bone fragments visible on the CT, are classic for ELST.
The heterogeneous T1 hyperintensity is typical, from proteinaceous content/blood products. ELST is a highly vascular lesion, supplied from the ascending pharyngeal artery or posterior auricular artery (stylomastoid branch). On MRI, vascular flow voids may be visible in tumors larger than 2 cm, which may also make distinction from paraganglioma difficult. Preoperative embolization is helpful in larger, more vascular tumors.
Patients with ELST who present with vestibulocochlear symptoms may have no visible tumor on imaging, although endolymphatic hydrops or blood products may be present. Hearing loss is the most common presenting symptom and may be acute or stepwise. Other symptoms will depend upon the involvement of adjacent structures, such as the lower cranial nerves.
Histologically, ELST is a low-grade papillary adenocarcinoma, but may resemble the papillary cystadenoma of the epididymis/broad ligament seen in patients with von Hippel-Lindau syndrome (VHL). Unfortunately, light microscopy of ELST may also resemble several of the important entities in the imaging differential diagnosis, especially paraganglioma, but also thyroid and renal metastases or middle ear adenocarcinoma. Immunohistochemistry may help, but clinical and radiologic features are essential.
VHL has been linked to chromosome 3. Sporadic ELST is rare, but may be seen with higher frequency in the setting of VHL. Bilateral ELST occur more frequently in patients with VHL than do sporadic ELST. Many clinicians advocate screening audiometric and imaging studies to detect subclinical ELST in patients with VHL, as well as screening abdominal imaging due to the high incidence of tumors of the pancreas, adrenal glands and kidneys. Although ELST is locally destructive, metastases are very rare.
In this particular case, a key finding is the left ocular hemorrhage, manifesting as T1 and T2 signal abnormality on the MR images. Given the imaging findings that are consistent with ELST, the ocular abnormality may be presumed to be due to a retinal hemangioma, leading to the further diagnosis of VHL.
Daniel E. Meltzer, MD, is an assistant professor of radiology at St Luke’s-Roosevelt Hospital Center.
Munir Ghesani, MD, is an attending radiologist at St. Luke’s-Roosevelt Hospital Center and associate clinical professor of radiology at Columbia University College of Physicians and Surgeons.
Disclosures: Drs. Ghesani and Meltzer report no relevant financial disclosures.
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