Microvascular decompression

from Wikipedia, the free encyclopedia

The microvascular decompression (operation according to Jannetta ) is a neurosurgical procedure in which pathological contacts between arteries and cranial nerves in the posterior fossa are removed. It includes the opening of the skull ( trepanation ), the identification of the pathological vascular-nerve contacts and their elimination by interposing a cushion (using muscle tissue or small sponges made of Teflon).

Basics

In the posterior fossa of the skull (viewed from behind) there are initially some arteries (basilar artery, cerebellar arteries, etc.) on the base of the skull, which is lined with meninges . On top of it lies the brain stem from which the cranial nerves emerge at the side. The cerebellum lies on top of it, and the large venous blood conductors (sinuses) follow on the outside. The posterior fossa is closed by the occipital scale of the skull.

Usually, the cerebral base arteries and cranial nerves do not touch. If prolonged high blood pressure (probably aided by a disposition for it) leads to an elongation and widening of the arteries, they meander and can thus gain contact with the cranial nerves or their entry / exit zone on the brain stem. Direct pressure (vascular = vessel-related compression) and the pulsation of the arteries damage the insulation layers (myelin sheaths) of the nerve fibers (demyelination) and direct irritation of the nerve fibers. Especially at the nerve exit point, the cranial nerves do not yet have a fully developed nerve sheath, which is why they are particularly vulnerable there.

The demyelination and thus the removal of the electrical insulation between the nerve fibers as well as the direct mechanical stimulation can lead to electrical impulses jumping between different fibers. In the case of the trigeminal nerve this can lead to severe pain (trigeminal neuralgia, see below), in the case of the facial nerve it can lead to unilateral facial cramps (see below). Such diseases are summarized as microvascular compression syndromes .

The Microvascular decompression eliminates the abnormal contact between vessel and nerve. This often leads to a reduction in the symptoms immediately after the operation, which corresponds to the removal of the direct pressure effect. The recovery of the myelin sheaths often leads to a further reduction in symptoms over the next one to two weeks, even if complete healing is not always achieved. If the symptoms recur (relapse), either the interposal may have slipped or a further elongation of the vessel may have resulted in a new contact.

The operation should be performed by an experienced neurosurgeon in a specialized center after the diagnosis and indication have been thoroughly confirmed. The success rate for trigeminal neuralgia is well over 90%, the complication rate of the center should not significantly exceed 1%. For other indications (see below) the chances are sometimes significantly lower, depending on the actual importance of the vascular-nerve contacts.

Neurological diseases caused by vascular contacts of the cranial nerves

The skipping of electrical impulses from one nerve fiber to another leads to sudden complaints that are brief but can be repeated quickly. An increase in the overall activity in the affected cranial nerve increases the risk of such skipping impulses. The complaints affect the area for which the cranial nerves are responsible: face, mouth and throat, neck and shoulders.

Diseases and symptoms that occur depend on the affected cranial nerve:

  • Trigeminal neuralgia (tic douloureux): shooting, shooting pain in the facial area (secured).
  • Glossopharyngeal neuralgia : shooting shooting pain in the throat (confirmed).
  • Facial spasm ( hemifacial spasm ): shooting spasms of the facial muscles (probably).
  • Eyelid cramp ( blepharospasm ): cramping of both eyelids (unlikely: bilateral symptoms due to damage to a cranial nerve are unlikely, if one-sided occurrence rather incomplete facial hemispasm).
  • Wry neck ( torticollis ): prolonged cramping of head-moving neck muscles (unlikely: not shooting in, too slow, patients on average too young and no hypertension)
  • Ringing in the ears ( tinnitus ): whistling in one ear (unlikely: too long lasting, cause ultimately unclear)
  • Dizziness ( vertigo ): only conceivable in exceptional cases with very short and violent attacks of dizziness.

Neuralgia and facial cramps are considered reliable indications for surgery if they cannot be treated with medication. (Compare the clear indication at Harvard University and the broad field of action of the neurosurgeon at the University of Padua in the web links!)

diagnosis

The diagnosis of vascular compression syndrome must first be made clinically ( anamnesis and examination). However, it must be secured by special diagnostics:

High-resolution magnetic resonance tomography with special sequences for the posterior fossa is able to make conventional angiography unnecessary in many cases. 3D reconstructions help in a special way to prove the spatial relationships of the vascular-nerve contacts. Sometimes it is also possible to directly detect demyelination (see above).

Other diseases should be considered as differential diagnoses , especially in younger patients (under 50 years of age). Inflammatory diseases ( multiple sclerosis , abscess , meningitis ), congenital changes ( syringobulbie , Chiari malformation ) and tumors ( acoustic neuroma , meningioma ) play an important role. Further, one of dystonia to consider. If there is any doubt about the diagnosis of microvascular compression, Jannetta surgery should not be performed.

Web links

Specialized institutes / interest groups