Endolymphatic sac tumor

Endolymphatic sac tumours (ELST) are very rare, locally invasive tumours of endolymphatic sac. Early detection of these tumours is critical, because early surgical intervention may prevent further hearing loss. Endolymphatic sac tumours do not metastasize, but are highly locally aggressive. 

Epidemiology

Typically endolymphatic sac tumours are encountered in young individuals, with a mean age at onset is 22 years ².

Clinical presentation

Endolymphatic sac tumours typically present with the following symptoms and signs:

• hearing loss: 95%,
  • acute in 43% and stepwise in the second half(43%)
  • gradual (remainder)
• tinnitus: 92%
• vertigo or disequilibrium: 62%
• aural fullness: 29%
• facial paresis: 8%

Pathology

These tumours are composed of two histological types:

• mixed type: generally confined
• papillary adenomatous type: more aggressive and often locally invades the temporal bone

Associations

Endolymphatic tumours are most often associated with von Hippel-Lindau disease (vHL) and are detected in 11-16% patients with vHL ². That having been saidHowever, in almost 60~60% of patients with vHL and vestibulocochlear symptoms, there is no evidence on imaging of an endolymphatic sac tumour ².  

When these tumours are present in the setting of vHL, then 30% of tumours are bilateral ².

Radiographic features

Generally, endolymphatic sac tumours always arise from and involve the endolymphatic sac or duct.

CT

When visible, it gives a picture

• erosion of petrous bone erosion and thein an infiltrative or "moth-eaten" petrous bone. Endolymphatic sac tumours commonly enhance intensely on CT.pattern
• often intense enhancement

MRI

Signal characteristics include:

• T1: may show high-intensity
• T1 C+ (Gd): typically show enhancement in the non-cystic component of the tumour
• T2: often of heterogeneous signal

Treatment and prognosis

Surgical excision is the treatment of choice when possible ³.

History and etymology

It was first described in 1989 by Dennis K Heffner, an American physician ⁴. Earlier than this they were probably misdiagnosed as choroid plexus tumours, adenomas, and adenocarcinomas of posterior fossa or cerebellopontine angle. 

Differential diagnosis

Possible imaging differential considerations include:

• glomus jugulare tumour
  • the centre of the lesion will be inat the jugular bulb rather than the vestibular aqueduct
• enlarged vestibular aqueduct
  • expansion of aqueduct, with smooth margins
  • maintains the normal shape of the aqueduct maintained
• petrous apicitis
  • located in the petrous air cells.
  • the bone around the aqueduct is not usually aerated
• cholesterol granuloma
  • most often located in the petrous apex, not vestibular aqueduct
• meningioma
  • hyperostotic underlying bone
• bony metastasis