Definition

Cholesterol granulomas are uncommon, benign cysts that may occur in various parts of the body and head, including the petrous apex, a part of the temporal bone of the skull that is next to the middle ear. They can be challenging to diagnosis as they resemble several other lesions. They are thought to be an inflammatory immune system response to cholesterol deposits left by the breakdown of blood vessels and cells. Cholesterol granulomas are made up of fluids, lipids, and cholesterol.


Pre-operative MRI showing a left petrous apex cholesterol granuloma

Causes

Within the skull there are numerous air-containing spaces called air cells. It was previously thought that blockage of those air cells caused cholesterol granuloma. A more recent theory, the "exposed marrow" hypothesis, suggests an inflammatory response to the by-products of eroded bone marrow cavities in the temporal bone.

Chronic middle ear infections

A few cases of cholesterol granuloma have been noted in families with familial hypercholesteremia.

Risks

Risk factors are things associated with an increased chance of developing a disease or condition. Anything that contributes to obstruction of the air cells in the bone, such as chronic ear infections or head trauma, can lead to cholesterol granuloma.

Symptoms

Patients may be asymptomatic or symptoms may be vague and non-specific, delaying accurate diagnosis. Symptoms are related to the location and size of the tumor.

  • Hearing loss
  • Vertigo
  • Headaches
  • Facial pain or spasm
  • Facial weakness
  • Change in facial sensation
  • Eustachian tube dysfunction, and middle ear effusion
  • Tinnitus
  • Earache
  • Cerebrospinal fluid leak
  • Speech and swallowing problems
  • Double vision
  • Seizure


Pre-operative CT of the above lesion showing destructive changes extending medially to the skull base

Diagnosis

Cholesterol granulomas are generally diagnosed after patients present with symptoms. Your doctor will take a medical history and order additional tests, such as:

  • CT
  • MRI

Treatment 

The decision to treat or not to treat depends on the size of the lesion and the severity of symptoms.

  • Stable, asymptomatic lesions can be monitored by serial imaging. Because cholesterol granulomas have been known to suddenly grow after years of no growth, monitoring is lifelong.
  • Drainage and removal of some or all of the capsule
  • Drainage of the cyst
  • Surgical resection is indicated for large, destructive, and symptomatic lesions. The petrous apex contains many critical structures and surgery should be performed only by neurosurgeons experienced in the treatment of these difficult lesions. The approach depends on the location and anatomy of the lesion and the status of the patient's hearing.
  • Increasingly, cholesterol granulomas are being treated using minimally invasive, endoscopic techniques. Frequently they can be treated transnasally or through the mastoid bone, without a need for a craniotomy.

Prevention

Aside from treatment of middle ear infections, there is no known way to prevent cholesterol granuloma.

Case Study

A fifty year old woman presented with intermittent facial numbness and pain over several months, which led to a MRI of the brain. A left medial petrous cholesterol granuloma was found, and she underwent extended transethmoidal microendoscopic surgery with Dr. Joshua B. Bederson and Dr. Eric M. Genden. She was discharged home on the third day. She did well and returned to work the following month. She continues to have annual MRIs with no sign of recurrence.

If you want to learn more about Cholesterol Granuloma and its treatment call the Mount Sinai Department of Neurosurgery at 212-241-2377.

Images used with permission from Joshua B. Bederson, MD