Brain HerniationAli Siddiqui

Bindu N Setty, MD

CASE HISTORY

27 yo male with unknown PMH presenting after an unwitnessed fall of about 25 feet, with 3 seizure-like episodes during transport, now unresponsive with GCS of 6 and fixed and dilated left pupil and right eye laterally deviated

Vitals: HR 40s SBP 120s Intubated

Labs: WBC 17.0 Hgb 13.2 Hct 39.3 Plt 262

Na 140 K 3.1 Cl 108 HCO3 21.0 BUN 13 Cr 0.97 Gluc 137

Toxicology: no Etoh

CT of Subdural Hematoma with Subfalcine Herniation

Axial CT without contrast shows hyperdense fluid collection around left hemisphere with 8mm midline shift to the right (arrow) and effacement of left lateral ventricle, consistent with subdural hemorrhage complicated by subfalcineherniation.

CT Head and Cervical Spine Without Contrast of Head Trauma

Coronal CT without contrast shows hyperdense fluid collection around left hemisphere with 8mm midline shift to the right (arrows) and effacement of left lateral ventricle, consistent with subdural hemorrhage complicated by subfalcine herniation.

CLINICAL FOLLOW UP

The patient underwent emergent decompressive left frontotemporoparietal craniectomy to relieve ICP.

Course subsequently complicated by persistent intraparenchymal hemorrhage and transcalvarial herniation

IN A NUTSHELL

Most important findings include

• Shift of septum pellucidum and midline structures to left or right

• Effacement of lateral ventricle ipsilateral to lesion causing mass effect

• Dilation of contralateral lateral ventricle

• More likely by anterior falx

Other relevant findings include:

• Depression of ipsilateral corpus callosum

• Elevation of contralateral cingulate gyrus

Potential complications include:

• Hydrocephalus

• Focal necrosis of cingulate gyrus

• ACA infarction

Remember: other herniations may co-occur, and should address increased ICP emergently

VOICE RAD CT and subfalcine herniation

by Dr. Setty(2020)

OLA

Infarction of which of the following arteries is a possible complication of a subfalcine herniation?

A. PCA

B. MCA

C. ACA

D. PICA

IMAGING SPECTRUM of DISEASE

• Integrated with discussion to follow

DISCUSSION

• This case is followed by other slides in which you can learn about the many other types of brain herniation syndromes. Many neurological conditions can cause mass effect, and the subsequent effects on the patient vary by the location of the mass and the anatomy affected. Knowing a little bit about the signs and symptoms of herniation syndromes can help when taking care of patients with neurological symptoms. It is also important to identify these syndromes as many are neurological emergencies due to progressive compromise of critical brain structures.

• General note on imaging for herniation: CT is often preferred due to speed even if MRI is comparable. However, MRI may be considered if additional risks are addressed and there is need for additional characterization of brain changes

Types of Herniation

• Supratentorial: • Transtentorial

• Descending types• Lateral herniation (often uncal herniation)

• Central herniation

• Subfalcine herniation• Transalar/transsphenoidal herniation

• Ascending or descending types

• Extracranial brain herniation• Paradoxical brain herniation

• Infratentorial: • Tonsillar herniation• Ascending transtentorial herniation

Quick anatomy review

Subfalcine herniation

• Also called midline shift or cingulate herniation

• Most common cerebral herniation

• Unilateral frontal, temporal or parietal lobe disease →medial mass effect→ ipsilateral cingulate gyrus under falx

• Severe herniation→ compression of corpus callosum and contralateral cingulate gyrus and ipsilateral lateral ventricle and foramen of Monro→ dilation of contralateral lateral ventricle

• Imaging: CT or MRI• Measure distance between line drawn in the midline at the level of foramen of Monro and

displaced septum pellucidum on an axial CT scan• Medial deviation of anterior falx• Depression of ipsilateral corpus callosum• Elevation or compression of contralateral cingulate gyrus• Compression of ipsilateral lateral ventricle• Dilation of contralateral lateral ventricle

Subfalcine herniation continued

• Complications• Hydrocephalus• Ipsilateral ACA infarct• Focal necrosis of cingulate gyrus

• Clinical signs of ACA infarct• Dysarthria• Aphasia• Contralateral motor weakness (Legs > arms/face)• Limb apraxia• Urinary incontinence

• Prognosis: good if midline shift less than 5mm; poor if over 15 mm

58 yo male presenting with sudden onset

left-sided weakness and facial droop found

to have right sided M1 MCA occlusion now

s/p tPA, transferred for thrombectomy, and

subsequently developed hemorrhagic

conversion of right MCA territory infarct with

mass effect.

CT shows large hemorrhage in right

frontotemporoparietal region and right

insula and basal ganglia, consistent with

hemorrhagic conversion of r infarct with

increase in size since prior imaging, with

internal worsening of mass effect, sulcal

effacement, effacement of right lateral and

third ventricles, effacement of basal

cisterns, midline shift increased to 2.1 cm

from 1.7cm prior, subfalcine herniation and

uncal herniation (not shown in image).

Diffuse cerebral edema. Focal dilation of

atria of both lateral ventricles and left

temporal horn, consistent with entrapment.

CT without contrast of subfalcine herniation before decompressive craniectomy

Case continued…

8 hours after prior imaging, now s/p right

frontotemporoparietal decompressive craniectomy

with evacuation of hematoma. CT shows

postsurgical changes, evolution of right MCA infarct,

new hypodense demarcation of right ACA and PCA

territories suggestive of infarct. Interval increase in

size of hemorrhage with multifocal pneumocephalus

consistent with clot evacuation and instrumentation.

Interval improvement of mass effect with decreased

effacement of right lateral and third ventricles and

basal cisterns. Now 1.4cm midline shift and

subfalcine herniation. Interval effacement of the atria

of the right lateral ventricle with prominence of the

atria of the left lateral ventricle with suggestion of

transependymal flow, concerning for ventricular

entrapment.

CT without contrast of subfalcine herniation after decompressive craniectomy

58 yo male presented with sudden onset left-sided weakness and facial droop found to have right sided M1 MCA occlusion s/p tPA, transferred

for thrombectomy, and subsequently developed hemorrhagic conversion of right MCA territory infarct with mass effect. Now s/p right

frontotemporoparietal decompressive craniectomy with evacuation of hematoma complicated by acute right ACA and PCA infarcts 5 days ago.

MRI shows post surgical changes with partial herniation of right cerebral hemisphere through craniectomy defect. Diffuse sulcal effacement,

edema, and loss of gray-white differentiation in right ACA, MCA, and PCA territories. In the right frontal, temporal, and parietal lobes and the

right thalamus/thalamocapsular junction, there is diffusely increased T2/FLAIR signal with confluent hyperintense DWI signal with patchy

ADC correlates, likely corresponding to subacute infarcts (not shown).

CT without contrast of ACA and PCA infarcts after herniation

Uncal and lateral herniations

• Innermost part of temporal lobe, the uncus, is displaced past tentorium cerebelli → brainstem and midbrain compression

• Clinical presentation

• Anterior subtype• Ipsilateral dilated pupil due to oculomotor nerve compression• Ptosis due to oculomotor nerve palsy• Lateral deviation from unopposed abducens input• Vertical gaze palsy if compression of the rostral interstitial nucleus of the MLF • Altered mental status due to compression of reticular activating system• Contralateral hemiparesis• Posterior subtype → tectum/superior colliculus involvement → Parinaud syndrome• May see ipsilateral hemiparesis due to Kernohan notch phenomenon/false localizing sign due to

compression of contralateral cerebral peduncle and descending corticospinal tract• Can compress ipsilateral PCA → homonymous hemianopsia

Uncal and lateral herniations continued

• Imaging: MRI or CT (though harder to see actual herniation on CT)• Medial displacement of uncus and parahippocampal gyrus of temporal lobes and temporal horn of lateral ventricle• Early sign: encroachment of ipsilateral suprasellar cistern • Effacement of all basal cisterns• Widening of ipsilateral cerebellopontine angle• Asymmetric inferior midbrain displacement and effacement• Ipsilateral midbrain hemorrhage• Inferomedial displacement of posterior communicating and PCA• If bilateral → complete obliteration suprasellar cistern and midbrain effaced and displaced inferiorly

• If diagnosed – life threatening and should notify referring physician!

• Complications: • Focal necrosis of uncus and brainstem ischemia• Duret hemorrhage (poor prognosis)• Kernohan phenomenon• PCA infarct• Respiratory failure

CT without contrast of uncal herniation

75 yo male presenting with right sided facial numbness and mastication muscle weakness, and exertional chest pain. CT shows large right-sided hyperdense subdural collection causing 1.3 cm leftward shift, producing a leftward subfalcine herniation (not shown), mild right uncal herniation with suggestion of impending downward transtentorialherniation; near complete effacement of right lateral ventricle with dilatation of left ventricle’s temporal horn, and significant effacement of 3rd ventricle; hypodensity by right posterior temporal occipital region.

CT without contrast of uncal herniation

58 yo male presenting with sudden onset left-sided

weakness and facial droop found to have right sided M1

MCA occlusion now s/p tPA, transferred for thrombectomy,

and subsequently developed hemorrhagic conversion of

right MCA territory infarct with mass effect.

CT now shows large hemorrhage in right

frontotemporoparietal region and right insula and basal

ganglia, consistent with hemorrhagic conversion of right

MCA territory infarct with increase in size since prior

imaging, with internal worsening of mass effect, sulcal

effacement, effacement of right lateral and third ventricles,

effacement of basal cisterns, midline shift increased to 2.1

cm from 1.7cm prior, subfalcine herniation (not shown

here) and bilateral uncal herniation. Diffuse cerebral

edema. Focal dilation of atria of both lateral ventricles

and left temporal horn, consistent with entrapment.

CT without contrast of descending transtentorialherniation

86 yo female who presented with drooling and seizure like activity an hour after having been at her baseline, now unresponsive with forced R gaze deviation and weakness of L side, with hypertension and respiratory distress, now admitted. CT shows worsening right hemispheric swelling, subfalcineherniation to the left at 22mm, new left ACA infarction due to herniation, severe right inferior transtentorial herniation with edematous brain tissue in the right perimesencephalic cistern and in the supracerebellar cistern, effacement of right lateral ventricle and right temporal horn and leftward displacement of 3rd

ventricle with enlargement of left lateral ventricle with periventricular edema, indicating obstructive hydrocephalus; previous subarachnoid hemorrhages

Ascending transtentorial herniation

• Clinical presentation: nausea/vomiting, rapid decrease in level of consciousness

• Imaging: CT or MRI• Early signs: compression and slight flattening of quadrigeminal plate cistern

• Further herniation → triangular or “squared off” appearance to quadrigeminal and superior cerebellar cisterns

• Severe herniation → efface cisterns and flattens posterior third ventricle

• May see obstructive hydrocephalus

• May also see reversal of posteriorly-directed convexity of colliculi –> “toothy smile” of quadrigeminal cistern becomes a “toothy frown”

• Followed by loss of quadrigeminal plate and superior cerebellar cisterns, and posterior flattening of 3rd ventricle

• “spinning top” appearance to midbrain

• Secondary signs: • Encroachment on the retrosellar/interpeduncular subarachnoid space

• Anterior displacement of brainstem

• Obliteration of pontine cisterns

• Anterosuperior displacement and compression of ambient cisterns by herniating vermis

• Complications: PCA or superior cerebellar artery infarct

CT of ascending trans-tentorial herniation and tonsillar herniation54 yo female presenting unresponsive

after fall down 13 steps after

consuming beer and clonopin,

transferred to BMC with prior CT

showing skull fracture and intracranial

hemorrhage. Clinically unconscious,

without vestibulo-ocular reflexes, no

corneal or gag reflexes, no response

to pain, nonreactive pupils.

Subsequently coded in the scanner.

CT shows extensive left-sided skull

fractures with associated left

cerebellar hemorrhage with

associated subarachnoid and subdural

components, resulting in ascending

transtentorial and inferior tonsillar

herniation. There is dilatation of the

temporal horns of the lateral ventricles

consistent with developing

hydrocephalus. The basilar cisterns

and 4th ventricle are effaced. A large

soft tissue hematoma overlying the left

parieto-occipital lobe.

Central herniation

• Descent of midbrain and diencephalon

• More likely if bilateral or midline mass effect

• Clinical presentation: rostral to caudal progression of deficits due to brainstem dysfunction• Flexor posturing (decorticate) → extensor posturing (decerebrate) → rigidity/paralysis → abnormal respiration due

to compression of medulla→ death

• Imaging – CT or MRI• Effacement of peri-mesencephalic cisterns

• Descent of diencephalon and lateral herniation of temporal lobes

• Oblong deformity of midbrain

• Descent of quadrigeminal plate and basilar artery

• Flattening of pons against clivus

• Complications• Duret hemorrhages

• PCA infarct

• Hydrocephalus

Tonsillar herniation

• Inferior descent of cerebellar tonsils below foramen magnum

• Also called coning

• May be seen congenitally (Chiari I malformation) which should not be confused with this acute process.

• Risk compression of brainstem against clivus• May affect cardiac and respiratory centers in the pons and medulla

• Imaging: MRI (preferred) or CT• Inferior descent tonsils past foramen magnum• Effacement of CSF cisterns around brainstem• Can see obstructive supratentorial hydrocephalus

• Complications• Cerebellar infarcts via posterior inferior cerebellar artery compression• Sudden respiratory arrest

MRI with contrast of tonsillar herniation

54 yo female presenting with intermittent frontal headaches and subjective dizziness with PMH of breast cancer treated by mastectomy but otherwise normal neurologic exam. MRI shows a 2.3x2.7x2.3cm enhancing mass centered in right cerebellum (not shown) and cerebellar vermis with surrounding edema, partial effacement of cerebral aqueduct and 4th ventricle and herniation of the cerebellar tonsils into foramen magnum by 1.6cm

Transalar/Transsphenoidal herniation

• Herniation in middle cranial fossa across greater sphenoid wing → compress against sphenoid bone

• Descending variant• Mass effect from the frontal lobe• Posterior and inferior displacement of posterior aspect of frontal lobe orbital surface• Small herniation affects orbital gyri• Larger herniation may involve the gyrus rectus• Can compress MCA against sphenoid ridge →MCA territory infarct

• Ascending variant• Middle cranial fossa or temporal lobe mass effect• Displacement of temporal lobe medially and superiorly across sphenoid ridge• Can compress supraclinoid ICA against anterior clinoid process → ACA and MCA territory infarct

• Imaging: MRI preferred, though CT may show indirect signs, like anterior displacement of ipsilateral MCA

Extracranial brain herniation

• Herniation brain external to the calvaria

• Often due to post-traumatic or post-surgical skull defect

• May be result of craniectomy for patients who needed to be treated for increased ICP

• Eventually needs surgical reduction due to risk of ischemia and venous infarct from occluded cortical veins

CT Brain without Contrast of transcalvarialherniation

• CT without contrast of the brain of a 27yo male shows postsurgical changes s/p left craniectomy complicated by transcalvarial herniation and heterogenous hyperdense intraparenchymal hemorrhages in the left frontal, temporal, and parietal lobes with surrounding vasogenic edema, severe effacement of left ventricle and prominence of right lateral and third ventricles. Complication includes transcalvarial and subfalcineherniation.

Paradoxical brain herniation

• Also called sinking skin flap syndrome or syndrome of the trephined

• Pathology: atmospheric pressure exceeds ICP → displacement of brain at craniectomy site into intracranial space

• Pressure imbalance often due to CSF drainage or lumbar puncture• May cause subfalcine or transtentorial herniations

• Clinical presentation: ranges from asymptomatic to acute neurological degeneration, along with symptoms from other herniations

• Imaging: CT or MRI• Marked concavity of skin flap

• Mass effect (effacement of superficial sulci, buckling of gray-white matter)

• Paradoxical midline shift contralateral to craniectomy site

• Treatment & prognosis: neurosurgical emergency!• Put in Trendelenburg to increase ICP• Correct underlying cause (CSF drains, LP sites)• Consider cranioplasty

CT Brain without Contrast of paradoxical brain herniation

46 yo male who presents 6 weeks after a left decompressive craniectomy for left MCA stroke complicated by intraparenchymal hemorrhages, now with altered orientation and concavity of the brain beneath the helmet. CT without contrast shows postsurgical changes, encephalomalacia from prior left ICA infarctions and in right parietal and occipital lobes; 6mm paradoxical midline shift to the right with sunken skin flap but no effacement of ambient and basilar cisterns (not shown), concerning for sunken flap syndrome that may progress to paradoxical herniation. Right frontal lobe gliosis from prior ventriculostomy catheter tract. Ex vacuo dilatation of lateral horn of left ventricle and occipital horn of right ventricle.

LINKS AND REFERENCESNational Guidelines

N/A

Consistent References: 1. https://radiopaedia.org/articles/subfalcine-herniation?lang=us2. https://radiopaedia.org/articles/uncal-herniation-1?lang=us3. https://radiopaedia.org/articles/kernohan-phenomenon?lang=us4. https://radiopaedia.org/articles/transtentorial-herniation?lang=us5. https://radiopaedia.org/articles/ascending-transtentorial-herniation?lang=us6. https://radiopaedia.org/articles/central-herniation?lang=us7. https://radiopaedia.org/articles/tonsillar-herniation?lang=us8. https://radiopaedia.org/articles/extracranial-brain-herniation?lang=us9. https://radiopaedia.org/articles/paradoxical-brain-herniation?lang=us10. https://radiopaedia.org/articles/transalar-herniation?lang=us11. https://radiopaedia.org/articles/cerebral-herniation?lang=us

12. https://radiopaedia.org/articles/anterior-cerebral-artery-aca-infarct?lang=us

Other Journals and Texts

1. https://emedicine.medscape.com/article/337936-overview

2. https://www-ajronline-org.ezproxy.bu.edu/doi/abs/10.2214/ajr.130.4.755

3. https://www-ajronline-org.ezproxy.bu.edu/doi/pdfplus/10.2214/ajr.165.4.7677003

4. https://epos.myesr.org/poster/esr/ecr2020/C-15306/

5. https://www-ncbi-nlm-nih-gov.ezproxy.bu.edu/books/NBK542246/

6. https://epos.myesr.org/poster/esr/ecr2019/C-2732/findings%20and%20procedure%20details

7. https://www.nuemblog.com/blog/2018/4/20/emergency-neuroimaging

8. https://en.wikipedia.org/wiki/Dura_mater#/media/File:Sobo_1909_589.png

Additional Resources for Students:

https://sugarytooth.wordpress.com/2017/09/02/basal-cisterns/

https://slideplayer.com/slide/7932469/

https://www.youtube.com/watch?v=Rp96BYmikrw

https://www.youtube.com/watch?v=nFwJic2mYCU

Videos

OLAS