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Intracranial Hypertension and Brain Herniation Syndromes

Radiology Cases in Pediatric Emergency Medicine

Volume 5, Case 6

Loren ! "amamoto, M#, MPH

$apiolani Medical Center %or &omen 'nd C(ildren

)ni*ersity o+ Haaii -o(n '! Burns Sc(ool o+ MedicineThis is a 5-year old female who is brought to the

emergency department at 8:00 a.m. because she was

poorly responsive when her mother awoke her in the

morning. This prompted her mother to drive her to the

E.. There is a history of headache and vomiting

during the evening and night. There is no history of

trauma.

E!am: "# T$%.& 'rectal() *+,) $,) * /$&+&.

#he is minimally responsive. *upils e1ual and reactive.

There are no signs of e!ternal trauma. 2ithin minutes of arrival) she e!hibits e!tensor

posturing. #he is orally intubated using the rapid

se1uence induction method with atropine) thiopental)

and vecuronium. #he is hyperventilated. End-tidal

34, monitoring is used to keep her p34, in the ,5

mmg range. 6 loading dose of phenytoin is

administered.

6n emergency 3T scan is ordered.

"iew 3T scan.


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There is obvious bilateral intraventricular

hemorrhage and ventricular dilatation. 3linically)

e!tensor posturing suggests the possibility of impending

herniation. #he sustains episodes of bradycardia which

respond to doses of 7" mannitol. 6 neurosurgeon

decompresses her ventricles immediately. #herecovers well without neurological deficits. #ubse1uent

studies demonstrate the presence of a choroid ple!us

arteriovenous malformation. This is neurosurgically

ablated.

iscussion

7ncreases in intracranial pressure '73*( compress

the brain within the rigid skull. This reduces cerebral

blood flow prompting refle! hypertension to maintain

cerebral perfusion. 6s intracranial pressure increasesfurther) the contents of the skull can no longer remain

in

place. ocal increases in pressure) such as with

tumors and acute hemorrhages) result in focal

deviations in anatomy. 2hile the term 9herniation9 is

used loosely when intracranial pressure increases)

there are specific herniation syndromes with different

mechanisms and outcomes. 7dentifying increases in

intracranial pressure by clinical and radiographic means

is important to intervene early to prevent herniation. 3linical signs and symptoms of acute increased

intracranial pressure include) headache) vomiting) vision

distortion) diminished sensorium) pupillary dysfunction)

hypertension) bradycardia) fle!ore!tensor posturing)

etc. *apilledema may not be present if 73* increases

acutely.

2hen intracranial hypertension is suspected) an

immediate 3T scan should be obtained to assess the

degree of 73* increase and to identify the cause of the

this. The following areas should be assessed on 3T

when attempting to determine the presence and

severity of intracranial hypertension. These are

discussed in more detail below.

/. *rominence of sulcigyri.

,. ateral ventricle si;e.


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$. uadrigeminal cistern.

There are several brain herniation syndromes.

These are discussed in more detail below. /. ?ncal herniation.

,. Transtentorial herniation.

$. Tonsillar herniation.

=. #ubfalcine herniation.

5. #uperior vermian herniation.

3T signs of intracranial hypertension:

/. *rominence of sulcigyri: 2hen intracranial pressure increases) this

compresses the cerebral corte! against the calvarium.

This attenuates the visibility of the sulci and gyri.

6dditionally) the space between the corte! and the

calvarium is minimal when 73* increases.

"iew loss of sulcigyri.

The image on the left is a high 3T cut which should

show the sulci and gyri well. ue to increased 73*) the


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corte! is compressed up against the calvarium losing

the distinctness of the sulci and gyri. The space

between the corte! and the calvarium is obliterated.

The sulcigyri sign cannot be totally relied upon in

some instances. 7n cases of e!ternal hydrocephalus orchronic 'or subacute( subdural effusions) fluid collects

over the corte!. The fluid space between the corte!

and the calvarium appears to be increased and the

sulcigyri may appear prominent.

"iew prominent sulcigyri.

#hown here is a focal e!tra-a!ial hematoma. @ote

the prominent sulci and gyri despite intracranial

hemorrhage.

,. ateral ventricle si;e:

7n acute hydrocephalus) due to obstruction in the

outflow of 3#) the lateral ventricles will be enlarged.

#imilarly) in acute intraventricular hemorrhage) the

lateral ventricles will be enlarged.

"iew dilated ventricles.


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#hown here are bilateral dilated lateral ventriclesdue to acute intraventricular hemorrhage.

7n other causes of intracranial hypertension) the

lateral ventricles will be compressed 'slit-like( or

obliterated due to increases in pressure in

compartments other than the lateral ventricles. This is

the case in generali;ed cerebral edema) subdural

hematoma) epidural hematoma) etc.

"iew compressed ventricles.


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#hown here are two cuts showing subarachnoid

hemorrhage. The ventricles are slit-like due to cerebral

edema and acute hemorrhage resulting in intracranial

hypertension.

$.


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"iew poor greywhite matter distinction.

=. #uprasellar cistern:


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The suprasellar cistern is a fluid-filled space

above

the sella turcica. 7t contains the circle of 2illis and

the

optic chiasm. 4n 3T scan) it has a star-shaped

appearance. 6nteriorly) the top point of the star isformed by the interhemispheric fissure between the two

frontal lobes. The lateral border of the suprasellar

cistern is formed by the uncal portion of the temporal

lobes. The posterior border is formed by the pons in

lower cuts and the cerebral peduncles of the midbrain in

higher cuts. 7n lower cuts where the pons forms the

posterior border of the suprasellar cistern) the

suprasellar cistern takes on the shape of a 5-pointed

star. 7n cuts where the cerebral peduncles 'which have

a central cleft( form the posterior border of thesuprasellar cistern) the suprasellar cistern takes on the

shape of a %-pointed star.

"iew the midline anatomic diagram of the brain.


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This is a midline sagittal cut of an A7 scan. 7dentify

the following structures:

# - suprasellar cistern

*o - pons

* - cerebral peduncles 'midbrain(

A - medulla 3 - 1uadrigeminal plate 'superior and inferior

colliculi(

" - fourth ventricle

> - 1uadrigeminal cistern

@ote that the fourth ventricle is connected to the

third ventricle by the cerebral a1ueduct which is very

thin and may not be visible on 3T.

"iew the anatomic diagram of the suprasellar cistern.

The midline sagittal A7 scan shows the levels of

the a!ial diagrams. @ote that the fourth ventricle is at

roughly the same level of the suprasellar cistern) but


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depending on the angle of the a!ial cut) the fourth

ventricle may be seen in cuts above) below) or at the

same level as the suprasellar cistern. The suprasellar

cistern is seen in cuts & and 8.

7n the lower cut '&() the suprasellar cistern 's(

takeson the shape of a five pointed star. The frontal lobes

'( form the anterior border with the anterior

interhemispheric fissure between the frontal lobes

forming the ape! of the star. The uncus '?( of the

temporal lobes forms the lateral borders. The pons

'*o( forms the posterior border. The fourth ventricle

'"(

is also seen in this cut.

7n the higher cut '8() the suprasellar cistern 's(

takeson the shape of a si! pointed star. The only difference

higher up is that the posterior border is formed by the

cerebral peduncles 'p( of the midbrain. The cleft

between the cerebral peduncles forms the si!th point of

the star. The inferior colliculi 'c( can also be seen at

this level of the suprasellar cistern.

"iew 3T scan of suprasellar cistern.

The left and center images show the suprasellar

cistern. 7ts anterior borders are formed by the frontal

lobes '(. 7ts lateral borders are formed by the uncus

'?( of the temporal lobes. The left image shows the


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5-pointed star appearance of the suprasellar cistern

where the posterior border is formed by the pons '*o(.

The black arrow points to the fourth ventricle. The

center image shows a higher cut where the suprasellar

cistern has a %-pointed star appearance since the

posterior border is formed by the cerebral peduncles'*( which have a central cleft.

2hen 73* increases) the suprasellar cistern space

is compressed. The space may still be visibleB

however) with severe intracranial hypertension) the

cistern is obliterated due to encroachment of brain

tissue that normally forms the borders of the suprasellar

cistern. epending on the cause of the intracranial

hypertension) the suprasellar cistern may be totally

obliterated in global or severe 73* increase. 7n focal

lesions) brain tissue may encroach into only one part ofthe suprasellar cistern. 7n early unilateral uncal

herniation) the uncus of the temporal lobe 'lateral

border of the suprasellar cistern( will protrude into the

suprasellar cistern.

5. >uadrigeminal cistern:

6lso known as the 1uadrigeminal plate cistern) this

fluid filled space is located cephalad to the fourth

ventricle.

"iew the anatomic diagram of the 1uadrigeminal

cistern.


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The midline sagittal A7 scan shows the levels of

the a!ial diagrams. The 1uadrigeminal cistern is

located above 'anterior to( the 9>9 in the highest cut

shown 'number +(. The anterior border of the

1uadrigeminal cistern is formed by the superior colliculi

'c(. 7mage 8 'lower cut( also shows the 1uadrigeminal

cistern. 7n this case) its anterior border is formed by

the

inferior colliculi 'c(. This gives the anterior border

of the

1uadrigeminal cistern the appearance of a 9babyCs

bottom9. The 1uadrigeminal plate is comprised of the

superior and inferior colliculi. The 1uadrigeminal

cistern

is posterior to this 1uadrigeminal plate) thus its

anterior

border may be formed by the inferior or superior

colliculi.

"iew 3T scan of 1uadrigeminal cistern.


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The right image shows the 1uadrigeminal cistern'black arrow(. @ote the 9babyCs bottom9 appearance of

its anterior border. 2hen 73* is increased) the

1uadrigeminal cistern space is compressed or

obliterated.

7dentify the suprasellar and 1uadrigeminal cisterns in

the following e!amples.

"iew moderately increased 73*.


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The suprasellar cistern is slightly smaller than its

normal si;e 'the right uncus is pushing into the

suprasellar cistern( and the 1uadrigeminal cistern is

compressed. 6n epidural hematoma is noted.

"iew severe 73* increase.


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The suprasellar cistern 'left image( is tissue-

filled)

indicating the presence of brain tissue herniating intothis space. The 1uadrigeminal cistern is very

compressed and pushed posteriorly 'center image(.

The suprasellar cistern is located Dust above the base of

the skull 'above the sella(. 7t should be visible in the

cuts near the base of the brain. 7f it is not visible)

it

suggests that the suprasellar cistern is obliterated.

#imilarly) the 1uadrigeminal cistern should be located in

the cut above the suprasellar cistern. 6 subdural

hematoma is noted with a midline shift.

rain erniation #yndromes:

/. ?ncal herniation:

2hen mass effects within or adDacent to the

temporal lobe occur) the medial portion of the temporal

lobe 'uncus( is forced medially and downward over the

tentorium. There is ipsilateral pupillary dilation. The

uncus is pushed medially into the suprasellar cistern.

"iew uncal herniation.


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There is bilateral uncal herniation. Thesuprasellar

cistern is obliterated.

"iew early uncal herniation.


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The right uncus is pushing into the suprasellar

cisternB early right uncal herniation.

,. Transtentorial herniation: 7t should be noted that this term is somewhat vague.

7t is used rather loosely and it may sometimes be used

similarly to the terms temporal lobe herniation and uncal

herniation. The uncus may herniate over the tentorium

as described above. #upratentorial lesions on one side


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may initially result in uncal herniation. 6s 73*

increases

further) bilateral temporal lobe herniation occurs

transtentorially. Early unilateral uncal herniation is

more accurately called uncal herniation. The terms

cranial-caudal transtentorial herniation) rostro-caudaltranstentorial herniation) or central transtentorial

herniation more accurately describe what is generally

meant by 9transtentorial herniation9. Thus) uncal

herniation is described separately above.

7n transtentorial herniation the medial portions of

the

temporal lobes 'uncus( and the brainstem herniate

downward from supratentorial to the infratentorial

compartment. The clinical signs include headache)

decreasing level of consciousness and ipsilateral fi!eddilated pupil 'from compression of the third cranial

nerve on the ipsilateral side(. 6s herniation worsens)

decerebrate 'e!tensor( posturing) contralateral 'ie.)

bilateral( pupillary dilation and 3ushingCs triad occur.

3ushingCs triad includes alteration in respiration)

bradycardia) and systemic hypertension. 7t is rare to

have all three present in children. 4ften there is Dust

bradycardia alone. 3hildren tolerate brainstem

compression produced by herniation better than adults.

7mmediate early intervention can result in recovery.7ntervention at the stage of unilateral pupillary

dysfunction is likely to have a better prognosis

than intervention at the stage of bilateral pupillary

dysfunction) decerebrate posturing and bradycardia.

3T scan shows obliteration of the suprasellar and

1uadrigeminal cisterns. ater findings include infarcts

and brainstem hemorrhage."iew transtentorial herniation.


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The suprasellar cistern 'left image( is obliterated.

The 1uadrigeminal cistern is very compressed and

pushed posteriorly 'center image(. 6 subdural

hematoma with a midline shift is noted. There is centraltranstentorial and subfalcine herniation.

$. Tonsillar herniation:

7n tonsillar herniation 'rare() a mass effect in the

posterior fossa causes the cerebellar tonsils to

herniate inferiorly through the foramen magnum

compressing the medulla and upper cervical spinal

cord. 3onscious patients complain of neck pain and

vomiting. They may have nystagmus) pupillarydilatation) bradycardia) hypertension and respiratory

depression. Early tonsillar herniation is difficult to

recogni;e in an unconscious patient. 7t may not be

evident on 3T scan since a!ial views cannot see the

pathology well. 7t is best seen on sagittal A7.

3linically changes in vital signs may be the only

clinical

clue in an unconscious patient.

=. #ubfalcine herniation 'cingulate herniation(: 6 unilateral supratentorial mass or hemorrhage

results in a midline shift. 7f the pressure pushing the

brain to one side is great enough) one of the

hemispheres is pushed under the fal! 'subfalcine(. This

may compress the anterior cerebral artery. There is

ipsilateral lateral ventricle compression and


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contralateral lateral ventricle dilation 'due to

obstruction

of the foramen of Aonroe(.

"iew subfalcine herniation.

The suprasellar cistern 'left image( is obliterated.

The 1uadrigeminal cistern is very compressed and

pushed posteriorly 'center image(. 6 subdural

hematoma with a midline shift is noted. There is central

transtentorial and subfalcine herniation.

5. #uperior vermian herniation: 6lso called ascending transtentorial herniation)

this

involves upward herniation of the vermis and cerebellar

hemispheres through the tentorial incisura due to a

mass effect in the posterior fossa. There is effacement

of the 1uadrigeminal cistern. There is hydrocephalus

due to compression of the a1ueduct of #ylvius.

eferences


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//0,-///+.

Girkwood H. ead Trauma. 7n: Girkwood H.

Essentials of @euroimaging) second edition. 3hurchill

ivingstone) @ew ork) /++5) pp. $$+-$5+.

Truwit 3) empert TE. igh esolution 6tlas of

3ranial @euroanatomy. 2illiams F 2ilkins) altimore)/++=.

2illing #H.

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