What is a cholesterol granuloma and how does it form?

Cholesterol granulomas are entirely benign fluid-filled cysts that occur within the bone of the base of the skull.  They arise in bone that is usually air-filled and, therefore, characteristically this is in the temporal bone (the bone that surrounds your ear structures).  The reason they arise is simply related to obstruction to the normal aeration of these air spaces.  When air cannot freely move in or out of an air cell (such as when there is an ear infection), this creates a high pressure within that air pocket.  This in turn (in a very small number of cases) leads to a small amount of bleeding and an inflammatory reaction being set up.  It is this that produces the fluid that makes up the cyst, which is sometimes described as being “chocolate-like”. 

What symptoms can result?

If the cholesterol granuloma is very small, it will often be asymptomatic.  If it is found as an incidental finding, it is perfectly reasonable to not embark on any surgical treatment for it.  In a few cases however, the cyst can gradually enlarge and creates a pressure effect on the structures running through the adjacent bone.  In other words, it can interfere with hearing, as well as some other nerves that pass through the temporal bone such as nerves that control eye movement or facial sensation.  Rare presentations of cholesterol granulomas, therefore, include double vision or changes in facial sensation (including trigeminal neuralgia).

When is treatment recommended?

Cholesterol granulomas are typically a condition that is dealt with by a Skull Base Multidisciplinary Team (MDT). This team holds fortnightly meetings at Salford Royal Hospital, with a team of experts with a huge combined experience of managing such problems. Your surgeon will convey the outcome and recommendations of this meeting to you.

How are cholesterol granulomas treated?

Cholesterol granulomas are often diagnosed as an incidental finding, in which case they will often require no treatment other than surveillance.  If, however, your cholesterol granuloma is creating a pressure effect on surrounding structures and thereby producing symptoms, it is likely it will require surgical intervention. 

The aim of surgery in cholesterol granulomas is to re-aerate the airspace that has become occluded.  This, therefore, means re-establishing some sort of connection between the cholesterol granuloma and one of the naturally occurring air spaces in the base of your skull such as air sinuses or the mastoid air cells.  Depending upon the exact location of the granuloma, an appropriate surgical approach will then be recommended.

On occasion, this can be done using endoscopes through the nasal cavity and air sinuses to break into the cholesterol granuloma through this route.  Once communication has been established, it can be maintained by placement of a small plastic tube to ensure that the cholesterol granuloma does not recur. 

Alternatively, this might be done through the bone of the middle ear through an operation carried out just behind the ear.  Again, once communication is established, it is often maintained by leaving a small drainage tube internally.  Once your cholesterol granuloma has been treated, it will still be followed up with further scans to ensure that it does not re-accumulate.  Very occasionally, further surgery can then be required.