同: 気脳撮影

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/12 01:35:30」(JST)

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Pneumoencephalography (sometimes abbreviated PEG; also referred to as an "air study") was a common medical procedure in which most of the cerebrospinal fluid (CSF) was drained from around the brain by means of a lumbar puncture and replaced with air, oxygen, or helium to allow the structure of the brain to show up more clearly on an X-ray image. It was derived from ventriculography, an earlier and more primitive method where the air is injected through holes drilled in the skull.

The procedure was introduced in 1919 by the American neurosurgeon Walter Dandy^[1] and was performed extensively until the late-1970s when it was replaced by more sophisticated and less-invasive modern neuroimaging techniques.

Procedure

Though pneumoencephalography was the single most important way of localizing brain lesions of its time, it was, nevertheless, extremely painful and generally not well tolerated by conscious patients. Headaches and severe vomiting were common side effects. During the procedure, the patient's entire body would be rotated into different positions in order to allow air to displace the CSF in different areas of the ventricular system and around the brain. This further added to the patient's already heightened level of discomfort (if not anesthetized). Following the exam, replacement of the drained CSF occurs by natural production, which restores its volume in less than a day. Video of the procedure is documented in a BBC documentary of an early EMI CT installation. [1]. A related procedure is pneumomyelography, where gas is used similarly to investigate the spinal canal.

Limitations

Pneumoencephalography makes use of plain X-ray images. Unfortunately, these are very poor at resolving soft tissues, such as the brain. Moreover, all the structures captured in the image are superimposed on top of each other, which makes it difficult to pick out individual items of interest (unlike modern scanners which are able to produce fine virtual slices of the body, including of soft tissues). Therefore, pneumoencephalography did not usually image abnormalities directly, rather their secondary effects. The overall structure of the brain contains crevices and cavities which are filled by the CSF. Unfortunately, both the brain and the CSF produce similar signals on an X-ray image. However, draining the CSF allows for greater contrast between the brain matter and the (now drained) crevices in and around it, which then show up as dark shadows on the X-ray image. The aim of pneumoencephalography is to outline these shadow-forming air-filled structures so that their shape and anatomical location can be examined. Following the procedure, an experienced radiologist reviews the X-ray films to see if the shape or location of these structures have been distorted or shifted by the presence of certain kinds of lesions. Unfortunately, this also means that in order to show up on the images, lesions have to either be located right on the edge of the structures or if located elsewhere in the brain, be large enough to push on surrounding healthy tissues to an extent necessary to cause a distortion in the shape of the more distant air-filled cavities (and hence distal tumors detected this way tended to be fairly large).

Despite its overall usefulness, there were major portions of the brain and other structures of the head that pneumoencephalography was unable to image. This was partially compensated by increased use of angiography as a complementary diagnostic tool, often in an attempt to infer the condition of non-neurovascular pathology from its secondary vascular characteristics. This additional testing was not without risk though, particularly due to the rudimentary catheterization techniques and deleterious radiocontrast agents of the day. Another drawback of pneumoencephalography was that the risk and discomfort it carried meant that repeat studies were generally avoided, thus making it difficult to assess disease progression over time.

Current usage

Modern imaging techniques such as MRI and CT have rendered pneumoencephalography obsolete.^[2] Widespread clinical use of diagnostic tools using these newer technologies began in the mid-to-late 1970s. These revolutionized the field of neuroimaging by not only being able to non-invasively examine all parts of the brain and its surrounding tissues, but also by doing so in much greater detail than previously available with plain X-rays, thus making it possible to directly visualize and precisely localize soft-tissue abnormalities inside the skull. This led to significantly improved patient outcomes while reducing discomfort. Today, pneumoencephalography is limited to the research field and is used under rare circumstances.

In popular culture

Pneumoencephalography appears in popular culture in the movie Jimmy P starring Benicio Del Toro and Mathieu Amalric. Pneumoencephalography is referred to in Episode 7, Season 7 of House M.D. (2010) as an example of a dangerous procedure. In a 1961 episode of the TV series Naked City entitled Which is Joseph Creeley? the procedure was used to detect the presence of a brain lesion in an amnesiac murderer. But it is most well-known as the painful test Regan undergoes to check for a brain lesion in The Exorcist.

References

^ "Walter Dandy". Walter Dandy. Society of Neurological Surgeons. Retrieved 2011-04-28.
^ Greenberg, Mark (2010). Handbook of Neurosurgery. Thieme.

English Journal

E. Graeme Robertson--dynamics in fluid and light.

Kempster PA, Gerraty RP, Bower SP.Author information Neurosciences Department, Monash Medical Centre, 246 Clayton Road, Clayton, Victoria 3168, Australia. peter.kempster@southernhealth.org.auAbstractAn eponymous lecture at the Australian and New Zealand Association of Neurologists Annual Scientific Meeting commemorates E. Graeme Robertson (1903-75), and some neurologists will know that particular Australian practices in clinical neurology, so far as they exist, have origins in his career. This is a historical article on the literary record of a man who had his own sense of history--an affinity with the past as well as an awareness of future generations of readers. He wrote authoritative texts on pneumoencephalography before new technology made it obsolete, and he produced a series of books on decorative architectural cast iron in Australian cities. A talent for visual interpretation seems to have drawn him to both of these topics; a common theme is contrast between light and dark, which is expatiated in images and in clear, well-written prose in his publications. We review his medical writings, including some largely forgotten principles of cerebrospinal fluid physics that he discovered when researching pneumoencephalography. We also explore his obsession with cast iron--its architectural historical significance, his techniques for photographing it, and some of the ways that it related to his life's work as a clinical neurologist.
Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia.J Clin Neurosci.2013 Feb;20(2):204-11. doi: 10.1016/j.jocn.2012.07.003. Epub 2012 Nov 11.
An eponymous lecture at the Australian and New Zealand Association of Neurologists Annual Scientific Meeting commemorates E. Graeme Robertson (1903-75), and some neurologists will know that particular Australian practices in clinical neurology, so far as they exist, have origins in his career. This
PMID 23151435

Skull base anatomy and CSF rhinorrhea.

Lam A, Holbrook E.Author information Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA. allen_lam@meei.harvard.eduAbstractThe skull base is an intricate interface between the cranium and face allowing the passageway of vital structures. Anatomic conceptualization forms the platform for surgical approaches and solutions to skull base pathology. Understanding embryogenesis provides further depth into the pathophysiology of congenital defects. This chapter aims to highlight skull base anatomy and embryology along with cerebrospinal fluid physiology and diagnostic evaluation of cerebrospinal fluid leaks.
Advances in oto-rhino-laryngology.Adv Otorhinolaryngol.2013;74:1-11. doi: 10.1159/000342263. Epub 2012 Dec 18.
The skull base is an intricate interface between the cranium and face allowing the passageway of vital structures. Anatomic conceptualization forms the platform for surgical approaches and solutions to skull base pathology. Understanding embryogenesis provides further depth into the pathophysiology
PMID 23257547

Neuroradiology investigations before scanning.

Brown TC.Author information Royal Childrens Hospital, Melbourne, Victoria, Australia. tckbrown@netspace.net.auAbstractCoaxial tomography (CT) and magnetic resonance imaging (MRI) scans are so much part of neurological investigation these days and provide such detailed information that even thorough neurological clinical examination may be neglected. The investigations in common use forty years ago were pneumoencephalography, ventriculography in babies with hydrocephalus, and carotid angiography with the injection of X-ray contrast to outline the arteries.
Paediatric anaesthesia.Paediatr Anaesth.2012 Aug;22(8):826-7. doi: 10.1111/j.1460-9592.2011.03778.x. Epub 2011 Dec 26.
Coaxial tomography (CT) and magnetic resonance imaging (MRI) scans are so much part of neurological investigation these days and provide such detailed information that even thorough neurological clinical examination may be neglected. The investigations in common use forty years ago were pneumoenceph
PMID 22211983