Cholesterol Granuloma

Introduction

The cholesterol granuloma can be defined as a granulation tissue that is found at the level of the middle ear. The tissue is well-known for being prone to bleeding, which makes it a frequent cause of haemotympanum. In fact, we are talking about a rare condition, characterized by the presence of non-cancerous cysts at the level of the middle ear (in particular at the tip of the petrous apex). As you will have the opportunity to find out, these cysts are actually comprised out of fluid, lipids and crystal of cholesterol, all of them being surrounded by a fibrous lining (the cyst is often presented as an expanding mass).

Even though it is said that granulomas in general are not dangerous, the cholesterol granuloma presents a series of risks due to the fact that it is located at a close distance from the ear and some pretty important nerves. If the condition is left untreated and the cholesterol granuloma continues to expand, the following complications can occur: permanent hearing loss, damage to the nerves or destruction of the bone.

Epidemiology

In general, the cholesterol granuloma is identified in individuals who have reached middle-age. The patient’s history of chronic otitis media comes to complete the picture. So far, no gender or race predilections have been identified for the cholesterol granuloma.

Pathophysiology

It is important to understand that the cholesterol granuloma can develop in any aerated portion of the temporal bone. The most common area in which the cholesterol granuloma develops is presented by the mastoid cells. This tissue is also found at the level of the petrous apex, being one of the most often encountered cystic lesions in the respective area.

There are two major theories incriminated when it comes to the appearance of the cholesterol granuloma. The obstruction-vacuum theory considers that the dysfunction of the Eustachian tube is mainly responsible for the problem. If the Eustachian tube does not function properly, this leads to the edema of the mucosa and repeated bleeding episodes. The second is known as the exposed marrow theory – the proposers of this theory suggest that the bone is invaded by the mucosa, which results in the exposure of bone marrow and the repeated bleeding.

Regardless of the proposed theory, it is important to remember that the blood will undergo a process of degeneration (upon being trapped), leading to a chronic inflammatory response (infection might also be presented). The histopathological analysis of the cholesterol granulomas reveals the following consistence: cholesterol crystals, giant cells, red blood cells and hemosiderin. The fluid is surrounded by fibrous connective tissue; plus, the blood vessels in the area are quite fragile and prone to rupture (because of such changes, the resolution is more difficult).

Pictures of Cholesterol Granuloma

Cholesterol granuloma Picture : Diagram showing the fibrous tissue, mastoid trabecula, cholesterol granuloma and small remnant of air.

Diagnosis

These are the most common methods used for the diagnosis of the cholesterol granuloma:

• Medical history of the patient
• Physical examination
  • The doctor will examine the ears using an otoscope
    • Bluish color of the eardrum
    • Identification of protrusion behind the eardrum (brownish tinge)
• Audiogram
  • Investigation performed to assess the hearing (whether or not hearing loss has occurred; if yes, to what extent)
• Imaging studies
  • CT
    • Lesion with demarcated margins
    • The overlying bone appears to be thinned
    • Peripheral enhancement (post-contrast)
    • Location – deciding factor on the appearance of the lesion
      • Petrous apex – aggressive appearance, bony erosion, the lesion can extend to the carotid canal or to the cerebellopontine angle
      • Middle ear – rare associated erosion
  • MRI
    • Thinned adjacent bone
    • High signal – cholesterol component
    • Hemosiderin identified as well.

The differential diagnosis can be made with the following conditions: middle ear effusion, cholesteatoma, base of skull tumor (metastasis, chondrosarcoma), pneumatization or normal asymmetry of fatty marrow. Other medical problems that present a similar appearance include the hydrated mucocele and the thrombosed ICA aneurysm.

Symptoms of Cholesterol Granuloma

The symptoms of the cholesterol granuloma depend on the location.

If present at the level of the middle-ear, the patient will experience the following:

• Vertigo
• Conductive hearing loss
• Dysfunction of the cranial nerves (VII)

When found at the level of the petrous apex, these are the most common symptoms:

• Conductive hearing loss (middle ear effusion)
• Ringing sound in the affected ear (tinnitus)
• Dysfunction of the cranial nerves (VI)
• It is also possible that the patient does not present any symptoms.

In the situation that it is located at the level of the mastoid cells, the patient might suffer from headaches or even by asymptomatic. Other symptoms of the cholesterol granuloma include the facial twitching and/or facial numbness.

Treatment and Prognosis

In the situation that the cholesterol granuloma leads to the appearance of the above-mentioned symptoms or it is too large in size (causing destruction in the area), the surgical excision should be considered as the first line of treatment. The removal of the cyst wall should be performed at the same time. The surgical approach is considered in relation to the location of the cholesterol granuloma. In deciding upon a particular approach, the surgeon will also consider the amount of hearing loss that has occurred. Some patients can benefit from mastoidectomy as a form of treatment. Unfortunately, the recurrence rate for the cholesterol granuloma is quite high.

One of the most common forms of surgical intervention for the cholesterol granuloma is the endoscopic endonasal approach. This has the advantage of being minimally-invasive, with the nasal cavities being used to access what would otherwise have been an inoperable cyst. Among the benefits of this procedure, there are: better and faster recovery, no nasty scars or incisions that take time healing. And, what is more important, this intervention preserves hearing. Other approaches for the surgical intervention include the infralabyrinthine or infracochlear ones; these guarantee the preservation of hearing as well. There is one more approach – the translabyrinthine one – but this is rarely used nowadays. This approach is recommended in the patients who are already experiencing severe hearing loss, as it can lead to complete hearing loss. No matter the approach, be sure to remember that the treatment has to guarantee both the drainage and the ventilation of the cholesterol granuloma.