Microvascular decompression
Encyclopedia
Microvascular decompression (MVD), also known as the Jannetta procedure, is a neurosurgical
procedure used to treat trigeminal neuralgia
, a pain syndrome characterized by severe episodes of intense facial pain and hemifacial spasm
.
in 1756. In 1891 Sir Victor Horsley
proposed the first open surgical procedure for the disorder involving the sectioning of preganglionic rootlets of the trigeminal nerve
. Walter Dandy
in 1925 was an advocate of partial sectioning of the nerve in the posterior cranial fossa
. During this procedure he noted compression of the nerve by vascular loops, and in 1932 proposed the theory that trigeminal neuralgia was caused by compression of the nerve by a blood vessel. With the advent of the operative microscope, Peter Jannetta was able to further confirm this theory in 1967 and advocated moving the offending vessel and placing a sponge to prevent the vessel from returning to its native position as a treatment for trigeminal neuralgia.
In addition to having the proper type of pain, candidates for an MVD must also be healthy enough to undergo surgery. The risk of surgery may increase with increasing patient age.
and are positioned on their back with their head turned or on their side with the symptomatic side facing up. Electrical monitoring of facial function and hearing is used. A straight incision is made two finger-breadths behind the ear about the length of the ear. A portion of the skull the size of a half-dollar is removed exposing the underlying brain covering known as the dura
. The dura is opened to expose the cerebellum
. The cerebellum is allowed to fall out of the way exposing the side of the brainstem. Using a microscope and micro-instruments, the arachnoid membrane is dissected allowing visualization of the 8th, 7th and finally the trigeminal nerve. The offending loop of blood vessel is then mobilized. Frequently a groove or indentation is seen in the nerve where the offending vessel was in contact with the nerve. Less often the nerve is thin and pale. Once the vessel is mobilized a sponge like material is placed between the nerve and the offending blood vessel to prevent the vessel from returning to its native position.
After the decompression is complete, the wound is flushed clean with saline solution. The dura is sewn closed. The skull is reconstructed and the overlying tissues are closed in multiple layers. The patient is allowed to wake up and is taken to an intensive care unit or other close observation unit.
Other complications include leakage of spinal fluid and wound infection (1%). Most patients will have transient neck pain and stiffness from the surgical incision and from seeding of the spinal fluid with small amounts of blood.
Neurosurgery
Neurosurgery is the medical specialty concerned with the prevention, diagnosis, treatment, and rehabilitation of disorders which affect any portion of the nervous system including the brain, spine, spinal cord, peripheral nerves, and extra-cranial cerebrovascular system.-In the United States:In...
procedure used to treat trigeminal neuralgia
Trigeminal neuralgia
Trigeminal neuralgia , tic douloureux is a neuropathic disorder characterized by episodes of intense pain in the face, originating from the trigeminal nerve. It has been described as among the most painful conditions known...
, a pain syndrome characterized by severe episodes of intense facial pain and hemifacial spasm
Hemifacial spasm
Hemifacial spasm or HFS is a neurological disorder in which blood vessels constrict the seventh cranial nerve and cause varying degrees of facial spasm, typically originating around the eye of the afflicted side of the face...
.
History
Nicholas Andre first described trigeminal neuralgiaTrigeminal neuralgia
Trigeminal neuralgia , tic douloureux is a neuropathic disorder characterized by episodes of intense pain in the face, originating from the trigeminal nerve. It has been described as among the most painful conditions known...
in 1756. In 1891 Sir Victor Horsley
Victor Horsley
Sir Victor Alexander Haden Horsley was an accomplished scientist and professor. He was born in Kensington, London. He was educated at Cranbrook School, Kent and studied medicine at University College London and in Berlin, Germany , and in the same year started his career as a house surgeon and...
proposed the first open surgical procedure for the disorder involving the sectioning of preganglionic rootlets of the trigeminal nerve
Trigeminal nerve
The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
. Walter Dandy
Walter Dandy
Walter Edward Dandy, M.D. was an American neurosurgeon and scientist. He is considered one of the founding fathers of neurosurgery, along with Victor Horsley and Harvey Cushing...
in 1925 was an advocate of partial sectioning of the nerve in the posterior cranial fossa
Posterior cranial fossa
The posterior cranial fossa is part of the intracranial cavity, located between the foramen magnum and tentorium cerebelli. It contains the brainstem and cerebellum.This is the most inferior of the fossae. It houses the cerebellum, medulla and pons....
. During this procedure he noted compression of the nerve by vascular loops, and in 1932 proposed the theory that trigeminal neuralgia was caused by compression of the nerve by a blood vessel. With the advent of the operative microscope, Peter Jannetta was able to further confirm this theory in 1967 and advocated moving the offending vessel and placing a sponge to prevent the vessel from returning to its native position as a treatment for trigeminal neuralgia.
Patient selection
Patients most likely to benefit from a microvascular decompression have a classic form of trigeminal neuralgia. The diagnosis of this disorder is on the basis of the patients' symptoms and from a neurological examination. No blood test or genetic marker exists to diagnosis the disease. An MRI scan can help eliminate other diagnosis. Newer MRI techniques may allow for the visualization of vascular compression of the nerve. Patients who improve with an MVD are likely to have pain which is episodic rather than constant. The pain typically has an electrical quality to it and is intense. The pain can usually be triggered. Common triggers include light touch, eating, talking or putting on make-up. Most patients whose face pain improved with an MVD also improved at least temporarily with medication.In addition to having the proper type of pain, candidates for an MVD must also be healthy enough to undergo surgery. The risk of surgery may increase with increasing patient age.
Surgical technique
Patients are put to sleep using general anaesthesiaGeneral anaesthesia
General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...
and are positioned on their back with their head turned or on their side with the symptomatic side facing up. Electrical monitoring of facial function and hearing is used. A straight incision is made two finger-breadths behind the ear about the length of the ear. A portion of the skull the size of a half-dollar is removed exposing the underlying brain covering known as the dura
Dura mater
The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
. The dura is opened to expose the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. The cerebellum is allowed to fall out of the way exposing the side of the brainstem. Using a microscope and micro-instruments, the arachnoid membrane is dissected allowing visualization of the 8th, 7th and finally the trigeminal nerve. The offending loop of blood vessel is then mobilized. Frequently a groove or indentation is seen in the nerve where the offending vessel was in contact with the nerve. Less often the nerve is thin and pale. Once the vessel is mobilized a sponge like material is placed between the nerve and the offending blood vessel to prevent the vessel from returning to its native position.
After the decompression is complete, the wound is flushed clean with saline solution. The dura is sewn closed. The skull is reconstructed and the overlying tissues are closed in multiple layers. The patient is allowed to wake up and is taken to an intensive care unit or other close observation unit.
Results
The largest reported series of MVDs was reported by Jannetta and published in The New England Journal of Medicine in 1996. The initial success rate was 82% for complete relief with an additional 16% having partial relief for a combined initial success rate of 98%. At 10 year follow-up, 68% had excellent or good relief. 32% had recurrent symptoms. Other series report similar or better results..Complications
Serious complications from an MVD include death (.1%), stroke (1%), hearing loss (3%) and facial weakness (.5%). Dr. Jannetta has called facial paralysis (as opposed to weakness) a "major and common complication of the MVD." (2 separate depositions under oath: Levy v Jannetta, CCP Allegheny County, GD 81-7689.Other complications include leakage of spinal fluid and wound infection (1%). Most patients will have transient neck pain and stiffness from the surgical incision and from seeding of the spinal fluid with small amounts of blood.