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relieving pressure (especially bringing a compressed person gradually back to atmospheric pressure) (同)decompressing
restoring compressed information to its normal form for use or display

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減圧

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/06/21 23:31:01」(JST)

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Microvascular decompression (MVD), also known as the Jannetta procedure,^[1] is a neurosurgical procedure used to treat trigeminal neuralgia, a pain syndrome characterized by severe episodes of intense facial pain, and hemifacial spasm.

History

Nicholas Andre first described trigeminal neuralgia 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.^[2] With the advent of the operative microscope, Peter J. 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.^[3]

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 anaesthesia 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 around 30 mm (1.2 inches) in diameter 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.

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.^[4] Other series report similar or better results.^[5]

Complications

Serious complications from an MVD include death (0.1%), stroke (1%), hearing loss (3%) and facial weakness (0.5%). 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.^[6]

Other procedures

Several other surgical procedures exist for the treatment of trigeminal neuralgia, including percutaneous rhizotomy, percutaneous glycerol injection, percutaneous balloon compression, rhyzotomy and Gamma Knife radiosurgery. When compared to the other procedures, MVD carries the highest long-term success rate but it also carries the highest risk.^{[citation needed]}

References

^ http://neurosurgery.ucsf.edu/index.php/pain_treatment_trigeminal_neuralgia.html#MVD
^ Dandy WE. Trigeminal neuralgia and trigeminal tic douloureux. In: Lewis D, ed. Practice of Surgery. Hagerstown, MD: WF Prior CO, 1932: 177-200.
^ Jannetta PJ. Arterial compression of the trigeminal nerve at the pons in patients with trigeminal neuralgia. Journal of Neurosurgery 1967: 26: 159-162.
^ Barker FG II, Jannetta PJ, Bissonette DJ, et al. The long-term outcome of microvascular decompression for trigeminal neuralgia. New England Journal of Medicine 1996; 334: 1077-1083.
^ Apfelbaum RI. Neurovascular decompression - the procedure of choice? In: Grady MS, ed. Clinical Neurosurgery, Vol 46. Baltimore: Williams & Wilkins, 2000.
^ Weigel G and Casey K. Striking Back! The trigeminal neuralgia handbook. Trigeminal Neuralgia Association Press. Gainesville, Florida 2000.

UpToDate Contents

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1. 三叉神経痛 trigeminal neuralgia
2. 頭蓋顔面痛の概要 overview of craniofacial pain
3. 短時間持続性片側神経痛様頭痛発作：治療 short lasting unilateral neuralgiform headache attacks treatment
4. 中間神経神経痛 nervus intermedius neuralgia
5. ミオクローヌスの治療 treatment of myoclonus

English Journal

Analysis of Wave III of Brain stem Auditory Evoked Potential Waveforms During Microvascular Decompression of Cranial Nerve VII for Hemifacial Spasm.

Thirumala PD1, Krishnaiah B, Crammond DJ, Habeych ME, Balzer JR.Author information 1*Department of Neurologic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, U.S.A., and †Department of Neuroscience, University of Pittsburgh Medical Center, Pittsburgh, PA, U.S.A., and ‡Department of Neurology, University of Pittsburgh Medical Center, Pittsburgh, PA, U.S.A.AbstractINTRODUCTION: Intraoperative monitoring of brain stem auditory evoked potential during microvascular decompression (MVD) prevent hearing loss (HL). Previous studies have shown that changes in wave III (wIII) are an early and sensitive sign of auditory nerve injury.
Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.J Clin Neurophysiol.2014 Apr;31(2):127-32. doi: 10.1097/WNP.0000000000000042.
INTRODUCTION: Intraoperative monitoring of brain stem auditory evoked potential during microvascular decompression (MVD) prevent hearing loss (HL). Previous studies have shown that changes in wave III (wIII) are an early and sensitive sign of auditory nerve injury.OBJECTIVE: To evaluate the changes
PMID 24691229

Continuous intraoperative monitoring of abnormal muscle response in microvascular decompression for hemifacial spasm; a real-time navigator for complete relief.

Hirono S1, Yamakami I, Sato M, Kado K, Fukuda K, Nakamura T, Higuchi Y, Saeki N.Author information 1Department of Neurological Surgery, Chiba University Graduate School of Medicine, Chiba, Japan, seiichirohirono@chiba-u.jp.AbstractIntermittent monitoring of abnormal muscle response (iAMR) has been reported to be useful for improving the surgical outcome of microvascular decompression (MVD) for hemifacial spasm (HFS). However, iAMR has not elucidated the relationship between AMR change and the corresponding surgical procedure, or the pathogenesis of AMR and HFS. The purpose of this study is to clarify the usefulness of continuous AMR monitoring (cAMR) for improving the surgical results of MVD and for understanding the relationship between AMR change and corresponding surgical procedure, and the pathogenesis of AMR and HFS. Fifty consecutive patients with HFS treated by MVD under cAMR monitoring, which continuously records AMR every minute throughout the surgical period, were retrospectively analyzed. The patients were assessed for the presence of HFS 1 week after the surgery and at final follow-up. Forty-six patients showed the complete disappearance of HFS. In 32, AMR disappeared abruptly and simultaneously with decompression of an offending vessel. AMR showed dynamic and various changes including temporary disappearance, or sudden, gradual, or componential disappearance before and during the decompression procedure, and even during the dural and skin closure after the initial decompression procedure. Facial spasm remained in four patients despite permanent AMR disappearance. cAMR monitoring improves the outcome of MVD. Although the main cause of HFS and AMR is vascular compression at the facial nerve, hyperexcitability of the facial nucleus is also involved in the pathogenesis of HFS and AMR. The proportional involvement of these causes differs between patients.
Neurosurgical review.Neurosurg Rev.2014 Apr;37(2):311-20. doi: 10.1007/s10143-013-0507-5. Epub 2013 Nov 24.
Intermittent monitoring of abnormal muscle response (iAMR) has been reported to be useful for improving the surgical outcome of microvascular decompression (MVD) for hemifacial spasm (HFS). However, iAMR has not elucidated the relationship between AMR change and the corresponding surgical procedure,
PMID 24272304

The Neurosurgical Treatment of Neuropathic Facial Pain.

Brown JA.Author information Neurological Surgery, PC, 600 Northern Boulevard #118, Great Neck, NY 11021, USA. Electronic address: jbrown@nspc.com.AbstractThis article reviews the definition, etiology and evaluation, and medical and neurosurgical treatment of neuropathic facial pain. A neuropathic origin for facial pain should be considered when evaluating a patient for rhinologic surgery because of complaints of facial pain. Neuropathic facial pain is caused by vascular compression of the trigeminal nerve in the prepontine cistern and is characterized by an intermittent prickling or stabbing component or a constant burning, searing pain. Medical treatment consists of anticonvulsant medication. Neurosurgical treatment may require microvascular decompression of the trigeminal nerve.
Otolaryngologic clinics of North America.Otolaryngol Clin North Am.2014 Apr;47(2):343-349. doi: 10.1016/j.otc.2013.10.003. Epub 2013 Nov 28.
This article reviews the definition, etiology and evaluation, and medical and neurosurgical treatment of neuropathic facial pain. A neuropathic origin for facial pain should be considered when evaluating a patient for rhinologic surgery because of complaints of facial pain. Neuropathic facial pain i
PMID 24680498

Japanese Journal

Secondary Trigeminal Neuralgia Caused by a Tentorial Dural Arteriovenous Fistula : A Case Report and Literature Review

Wakuta Naoki,Ueba Tetsuya,Abe Hiroshi,Nonaka Masani,Higashi Toshio,Inoue Tooru
福岡大学医学紀要 40(1/2), 61-65, 2013-06-00
NAID 110009576992

後頭蓋窩における内視鏡手術の基本的知識

荻原雅和,木内博之,西山義久
Japanese Journal of Neurosurgery 22(5), 379-387, 2013
脳深部に位置し, 脳神経が密に走行する後頭蓋窩病変の手術は, 手術用顕微鏡では十分な視野確保が困難であるが, 内視鏡の併用により全体像の観察が可能となることが少なくない. 椎骨脳底動脈瘤のクリッピング術では, ネックや壁の性状に加えて穿通枝の走行が, 微小血管減圧術では, 小脳の圧排を最小限にした血管圧迫部位の観察が, さらに, 脳腫瘍摘出術では, 早い段階で背後の脳神経の走行が確認できるという …
NAID 130003379623

Surgical Results of Microvascular Decompression Procedures and Patient's Postoperative Quality of Life: Review of 139 Cases

SHIBAHASHI Keita,MORITA Akio,KIMURA Toshikazu
Neurologia medico-chirurgica 53(6), 360-364, 2013
… Microvascular decompression (MVD) is effective for the relief of symptoms, but little is known about the impact of the MVD procedure on patient's quality of life (QoL) or which QoL factors are important. …
NAID 130003364266

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リンク元	「後頭蓋窩神経血管減圧術」「神経血管減圧術」「微小血管減圧術」
関連記事	「decompression」「microvascular」