meniere

Author Topic: Labyrinthectomy operation  (Read 11063 times)

Offline Alec

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Labyrinthectomy operation
« on: Feb 06 2007, 02:57 PM »
Here is a good description of a Labyrinthectomy operation.

An ear operation used for Meniere's syndrome. It destroys the balance organ of the affected inner ear in order to stop attacks of vertigo. It also destroys any remaining hearing. For this reason it is never done when there is still useful hearing in that ear (usually defined as an average hearing threshold on pure tone audiometry of worse than 60dB and a speech discrimination score of less than 50%).

Anatomy and Physiology

The bone of each ear contains a series of tiny channels called the labyrinth. These contain thin membranous tubes that make up the inner ear. This has two principal parts; the cochlea, for hearing and the vestibular apparatus, for balance and motion sense.


Destruction of the vestibular apparatus will stop the intermittent spells of vertigo that occur in Meniere's. Immediately after the operation there will be acute vertigo due to the loss of one balance organ, but the brain will gradually compensate for this and come to rely on the vestibular apparatus of the other ear. This vertigo gradually settles over about 6 weeks.

It may take less time in younger people or those where the Meniere's has already caused considerable damage to the vestibular apparatus. It may take longer in the elderly. There may be some persistent imbalance.

Anaesthetic

General anaesthesia is essential.

Surgical Technique

There are several different ways to destroy the function of the vestibular apparatus. In all cases an operating microscope is used.

Trans-canal/oval window labyrinthectomy. Depending on the size of the ear canal the operation may be possible without any external incision. A tiny cut is made around the edge of the eardrum and it is folded forwards. One of the small bones of hearing (ossicles) called the stapes (stirrup) is removed. This exposes the inner ear at the oval window. A small amount of bone is drilled to link this with the nearby round window. This gives access to the vestibule, a major part of the vestibular apparatus. Labyrinthine membranes can be hooked out. It may be difficult to reach all 5 sensory organs of balance and so a drop of an agent toxic to any remaining nerve endings is inserted. Alcohol or gentamicin is commonly used for this. If any nerve ends persist then vertigo may still occur.


Lateral canal labyrinthectomy. Either through the ear canal or the mastoid the lateral semi-circular canal is opened. This is part of the vestibular apparatus. Membranes are hooked out and a toxic agent as above is inserted. This is a less reliable method.


Trans-mastoid labyrinthectomy. An incision is made behind the ear. A hole is drilled in the mastoid bone behind the ear. The bony coverings of the various components of the vestibular apparatus are found and opened. The membranes are hooked out. The ear canal and eardrum are not affected. This procedure is longer but more thorough.


Trans-labyrinthine vestibular neurectomy. The trans-mastoid operation is extended and the nerve into the labyrinth is cut as well as removing all the nerve endings and sensory organs. There may be a slightly better chance of stopping vertigo but there is increased risk of long-term imbalance and of CSF leak.

Length of Operation

1-2 hours depending on technique employed.

Time Off Work and Post-Operative Limitations

There will be a period of vertigo called the compensation phase. In the first days there may be vomiting. Medications will be required regularly. Return home is usual in 2-7 days. A period of several weeks off work may be needed. Driving will not be possible until compensation is complete.

Risks and Complications

Incomplete labyrinthectomy (5%): If all the sensory parts of the inner ear are not fully removed there may be some persistent vertigo.

CSF Leakage: The fluids of the inner ear are linked with the cerebro-spinal fluid surrounding the brain. Release of fluids from the inner ear can cause a leak. Rarely infection of these occurs causing meningitis. The leak is usually noted during the operation and plugged or it develops later and stops spontaneously. Occasionally re-operation is needed.

Facial Nerve Weakness: This nerve lies close to the labyrinth and may rarely be damaged. This results in weakness or paralysis of movement of one side of the face. Usually this is temporary and partial but may be severe and permanent.

Outcome/Prognosis

Vertigo: Sudden attacks of vertigo cease in at least 80% of patients.

Tinnitus: Improves in 50% of patients.

Hearing: Complete loss in that ear in almost 100%, this is important because up to 1/3 of people with Meniere's will get the condition in the other ear. This will result in a variable amount of hearing loss in the other ear.


Other Treatments

Intratympanic Gentamicin Injections: These may be direct or through a grommet or catheter placed in the eardrum. They may be effective by damaging the vestibular apparatus enough to stop it causing vertigo. This is called chemical labyrinthectomy. In about 10% of patients they cause some hearing loss. Usually 2 or more treatments are given and later repetition may be required. Should be tried before considering surgical labyrinthectomy.

Saccus Decompression: Drainage or ablation. Less effective than Labyrinthectomy in controlling vertigo, but preserves hearing.

Cochleo-sacculotomy: Aims to make a permanent link between the fluids within the membranes of the inner ear (endolymph) and those that surround them (perilymph), releasing pressure and preserving hearing. Effectiveness variable, considerable risk to hearing and now rarely performed.

Vestibular Neurectomy (by retro-labyrinthine route): This cuts the nerve to the balance organ. It is very effective for vertigo. It aims to save hearing but there is a 5% risk of loss. Risk of facial nerve damage has been variously reported as between 3% and 44%. Recovery takes longer and there may be more long-term dysequilibrium than after labyrinthectomy. It is an operation close to the brain and risks are more significant.


Links

http://oto.wustl.edu/men/

http://www.skullsurgery.aust.com/html/menieres_disease.html

http://www.entnet.org/meniere.html

http://www.tchain.com/otoneurology/disorders/menieres/menieres.html


By Mr M.C.F Smith FRCS

Alec (forum Moderator)

Whenever I hear the term, 'let's go for a spin', it makes me cringe.