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Midline shiftFrom Wikipedia, the free encyclopedia

Midline shift (arrow) is present in this brain after a stroke(infarct depicted in shaded area).

Thissubdural hematoma/epidural hematoma(arrows) is causing midline shift of the brain

Midline shiftis a shift of the brainpast its center line.!"The sign may be e#ident on neuroimagingsuch as $T

scanning.!"The sign is considered ominous because it is commonly associated with a distortion of thebrain

stemthat can cause serious dysfunction e#idenced byabnormal posturingand failure of the pupils to constrict

in response to light.!"Midline shift is often associated with highintracranial pressure(%$&), which can be

deadly.!"%n fact, midline shift is a measure of %$&' presence of the former is an indication of the latter.

"&resence of midline shift is an indication for neurosurgeons to take measures to monitor and control %$&.

!"%mmediate surgery may be indicated when there is a midline shift of o#er mm.*"+"The sign can be caused

by conditions includingtraumatic brain inury,!" stroke,hematoma,or birth deformity that leads to a raised

intracranial pressure.

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Methods of Detection

-octors detect midline shift using a #ariety of methods. The most prominent measurement is done by

a computed tomography($T) scan and the $T old tandard is the standardi0ed operating procedure for

detecting M1."ince the midline shift is often easily #isible with a $T scan, the high precision of Magnetic

2esonance %maging(M2%) is not necessary, but can be used with e3ually ade3uate results."4ewer methods

such as bedsidesonographycan be used with neurocritical patients who cannot undergo some scans due to

their dependence on #entilators or other care apparatuses. 5"onography has pro#en satisfactory in the

measurement of M1, but is not e6pected to replace $T or M2%. 5"7utomated measurement algorithms are

used for e6act recognition and precision in measurements from an initial $T scan. 8"7 maor benefit to using the

automated recognition tools includes being able to measure e#en the most deformed brains because the

method doesn9t depend on normal brain symmetry.8"7lso, it lessens the chance of human error by detecting

M1 from an entire image set compared to selecting the single most important slice, which allows the computer

to do the work that was once manually done.8"

Structures of the Midline

Three main structures are commonly in#estigated when measuring midline shift. The most important of these is

the septum pellucidum, which is a thin and linear layer of tissue located between the right and left #entricles. 8"%t

is easily found on $T or M2% images due to its uni3ue hypodensity.8"The other two important structures of the

midline include thethird #entricleand the pineal glandwhich are both centrally located and caudal to the

septum pellucidum.5"8"%dentifying the location of these structures on a damaged brains compared to an

unaffected brain is another way of categori0ing the se#erity of the midline shift. The terms mild, moderate, and

se#ere are associated with the e6tent of increasing damage.

Midline Shift in Diagnoses

Midline shift measurements and imaging has multiple applications. The se#erity of brain damage is determined

by the magnitude of the change in symmetry. 7nother use is secondary screening to determine de#iations in

brain trauma at different times after a traumatic inury as well as initial shifts immediately after.*"The se#erity of

shift is directly proportional to the likeliness of surgery ha#ing to be performed. M1 also has the aptitude to

diagnoses the #erypathologythat caused it. The M1 measurement can be used to successfully distinguishbetween a #ariety of intracranial conditions including acute subdermal hematoma, "8"malignant middle cerebral

artery infarction,*"epidural hematoma,subarachnoid hemorrhage,chronic subdermal hematoma,infarction,

intra#entrical hemorrhage, a combination of these symptoms, or the absence of pertinent damage altogether.8"

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