Dev Brain Sweep & Run BOX Case Stack

“The hardest brain malformation to find is the second one!”

(Satisfaction of Search Errors) Multiple anomalies Same anomaly, different causes (insult, genetic, metabolic) Single genetic defect, multiple anomalies over time

Early Brain Development  Prosencephalon  Diencephalon

 Thalami, hypothalami, globi pallidi

 Telencephalon  Putamin, caudate  Neocortex

 Mesencephalon  Midbrain

 Rhombencephalon  Myelencephalon  Pons, medulla

 Metencephalon  Cerebellum, vermis

Day 25

Classification Prosencephalon Anomalies

of

 Anomalies of Dorsal Induction  Commissuration Anomalies  Cerebral Cortex Anomalies

 Stem Cell Proliferation or Apoptosis  Neuronal Migration  Post Migrational Cortical Organization  Anomalies of Ventral Induction  Holoprosencephaly  Septooptic Dysplasia  Arrhinia/Arrhinencephaly  Hypothalamic-Pit Axis  Eye and Orbit

Hind Brain Anomalies  Dorsal Induction  Occipital Encephalocele

 Ventral Induction  Rhombencephalosynapsis  Isolated Vermian Hypoplasia

(IVH)  Dandy Walker malformation  Unilateral Cerebellar Dysplasia/Hypoplasia  May be single disruptive event

 Pontocerebellar Hypoplasia

Spectrum, non progressive

But what is normal?

Use the Sweep & Run approach to developmental pediatric brain MRI…

 Sweep the Midline  Map the Myelin  Run the Rim  Ice the Cake

Start with the Anterior Commissure.

Why start with the anterior commissure?  Three midline commissures involved in

abnormalities of the Corpus Callosum:  Anterior Commissure  Corpus Callosum  Hippocampal Commissure: typically rudimentary, fibers between the body of the fornix

Sweep the Midline  Anterior commissure  Corpus Callosum  Rostrum, genu, body, splenium

Sweep the Midline  Anterior commissure  Corpus Callosum 

Rostrum, genu, body, splenium

 Sella/Suprasellar region  optic nerve & chiasm size, posterior

pituitary “bright spot”, stalk

Sweep the Midline  Anterior commissure  Corpus Callosum 

Rostrum, genu, body, splenium

 Sella/Suprasella 

ON, post pit “bright spot”, stalk

 Midbrain  Patency aqueduct

 Pons  Relative size to midbrain and

medulla, the Goldilocks principle: “not too big, not too small, just right…”

Sweep the Midline  Anterior commissure  Corpus Callosum 

rostrum, genu, body, splenium

 Sella/Suprasella 

ON, post pit bright spot, stalk

 Midbrain 

Patency aqueduct

 Pons 

Relative size to midbrain and medulla,“just right”

 Vermis – 3 lobes 

3 lobes: Anterior (40%) , Posterior (60%) , small Flocculonodular lobe  Ant and Post lobes separated by the Primary fissure



closed 4th ventricle, closed fastigial point

Sweep the Midline  Anterior commissure  Corpus Callosum 

rostrum, genu, body, splenium

 Sella/Suprasella 

ON, Post pit bright spot, stalk

 Midbrain 

Patency aqueduct

 Pons 

“just right”

 Vermis 

3 lobes, closed fastigial point

 Cerebellar Tonsils terminate

normally at or above the foramen magnum

Sweep the Midline…Name the parts…where do we start?

Normal Sag T2 Cube NonGated

Sweep the Midline

Normal Sag T2 Cube nongated

Sweep the Midline

Normal Sag T2 Cube nongated

Sweep the Midline

Normal Sag T2 Cube Nongated: CSF dephasing in the aqueduct on this sequence

Sweep the Midline

Normal Sag T2 Cube nongated

Primary fissure 3 lobes Closed fastigial point

Sweep the Midline 

Anterior commissure



Corpus Callosum 



Sella/Suprasella 

Normal Sag T2 Cube



“just right…”

Vermis 



Patent aqueduct

Pons 



ON, post pit bright spot, stalk

Midbrain 



Rostrum, genu, body, splenium

3 lobes

Cerebellar Tonsils

Sweep the Midline:

T1

T2

Map the Myelin: Use both T1 and T2 to evaluate myelin.

Run the Rim:

Start at noon and evaluate the cortex clockwise, should be 2-33 mm thick.

Ice the Cake:

Use remaining sequences (GRE, DWI, contrast) to refine your diagnosis.

Difussion

Ready Set Go!

Remember to start with Sweep the Midline…

Where is the anterior commissure?

Always finish the sweep looking for second anomaly…

Near Complete Agenesis of the CC Collosal Remnant , intact AC

Parallel ventricles Radial or pallisading gyri in sagittal plane Colpocephaly Longhorn or Viking helmit frontal horns High riding 3rd vent “Keyhole” temporal horns Vascular anomalies: “wandering ACAs”

Tricommissural Agenesis of the CC: All 3 commissures are absent.

Bundles of Probst

myelinated WM fibers along medial ventricles

Cingulate gyrus (black arrows) “mirrors” the development of the corpus callosum.

Agenesis of the CC and AC Enlarged Hippocampal Commissure HC

Enlarged HC connects fornices, not cerebral hemispheres

Classification of ACC with Interhemispheric Cyst Type I Communicating Cyst Cyst communicates with the third ventricle.

Type II Complex Noncommunicating Cyst(s) Cysts demonstrate differing signal characteristics than CSF.

Sweep the Midline: What parts are missing?

Run the Rim…where is the cortex “too thick?”

Lobar Holoprosencephaly “missing anterior Corpus”

“Missing”=disorganized rostrum, genu, anterior body of the corpus callosum

Cortex of the anterior medial frontal lobes “too thick” with fused grey matter across the anterior midline where the “genu” should be.

Holoprosencephaly Spectrum (DeMyers 3 subtypes) Alobar Most severe, complete lack of “cleavage”, fused thalami.

Semilobar “ in between” with separated occipital lobes

Lobar Mild, often only anterior frontal lobe fused, with separate thalami

Sweep the Midline: “Comma shaped Corpus Callosum with abnormal mid body…”

Syntelencephaly: Midline CC “lack of cleavage” Middle Interhemispheric “MIH” Variant of Holoprosencephaly Dorsal Induction Anomaly

 Presentation  Motor defects  Oromotor dysfunction

 Associated with:  Azygous ACA  Polymicrogyria PMG  Cortical dysplasias  GM heterotopia  Absent septum pellucidi

Blunted anterior Corpus, with subtle fusion at the level of the anterior commissure…?

Septopreoptic (aka “Suprachiasmatic”) Subtype of Holoprosencephaly

Fusion (lack of cleavage) is just anterior /superior to the anterior commissure.

Sweep the Midline…

T1 Sag Without

T1 Sag With C+

Ectopic posterior pituitary “bright spot.”

Missing infundibular stalk.

T1 Sag Without

T1 Sag With C+

Ectopic Posterior Pituitary Gland  Contrast or ultra thin T2 needed to

confirm.

 Thin or truncated stalk 

IGHD – Growth Harmone Deficiency if stalk is present but abnormal  PanHypoPit Deficiencies if stalk is completely absent.

 Need repeated endocrine

evaluations if normal at first imaging.

 Neonate: Hypoglycemia, jaundice,

Failure to Thrive

 Normal or shallow sella  Abscent or hypoplastic

stalk  Ectopic posterior pituitary

Too little or too much…

Duplicated Pit Plus Syndrome

Abnormal notocord integration, related to lack of fusion of the initial two notochord “enlages” at gastrulation, results in notocord “duplication” with double ventral induction structures…can be seen with split tongue, palate, cranial base encephaloceles with splite dens, vertebrobasilar vascular anomalies.

What did this patient present with?

Hamartoma of the Tuber Cinerium (floor of the third ventricle)  Gelastic “Laughing” Seizures  Precocious puberty  Seizures  Rare calcification  Normal  Rarely increased T2 Flair signal

 No enhancement  Trigger Biopsy:  Enhancement  Growth

T1 Pre Con

T1 Post Con Different patient, same finding…

Diagnosis?

What procedure did this patient have?

What is the MRI sequence called?

Aqueductal Web with Hydrocephalus Post Endoscopic 3rd Ventriculostomy EVD

T2 CUBE Nongated Note the CSF flow dephasing through the defect in the floor of the third ventricle.

Differential for “cyst in the posterior fossa” starts with whether the vermis is normal or not.

Is the vermis normal? Can you identify the normal structures of the Vermis?

Malrotated hypoplastic vermis, with vertical primary fissure.

“OPEN” fastigial point of the fourth ventricle.

Hypoplastic cerebellar hemispheres.

Dandy Walker Malformation  Enlarged posterior fossa  Cystic dilatation 4th ventricle  Uplifted tentorium, TSV sinus, torcula 

“torcula-lambdoid inversion” with torcula above the lambdoid suture

 Agenetic or hypogenetic vermis with

“vermian tail, pushed upward

 Cerebellar hypoplasia  CC anomalies 32%  Hydrocephalus up to 90%  

Aqueductal stenosis 4th ventricle outlet obstruction

 Polymicrogyria, heteropia 5-10%  Occipital Meningo-Encephaloceles 16%  Syndromic = Extracranial anomalies 50%

Differential Comparison Case #2: Is the vermis normal or abnormal?

Lobes?

Primary Fissure?

Fastigial Point?

Congenital Hydrocephalus with Aqueductal Compression due to Arachnoid Cyst

Hint: Normally formed Vermis which is pushed forward

DDX: mega cisterna magna (no mass effect on the vermis) versus Blake’s pouch cyst (mass effect on inferior vermis pushing vermis superiorly.)

Are the structures of the vermis normal?

What is wrong with the fourth ventricle?

What is the diagnosis?

Are the structures of the vermis normal?

What is wrong with the fourth ventricle?

What is the diagnosis?

Rhombencephalosynapsis

Lack of cleavage of the hindbrain  Vermis appears “large and rounded”  Rounded fastigial point of the fourth

ventricle  Cerebellar dysgenesis  Fused hemispheres, absent or hypoplastic vermis, and superior cerebellar peduncles  Needs to have fusion of the dentate

nuclei

 Assn: hydrocephalus, limbic

anomalies, cortical malformations, absent septum pellucidum, multiples suture synostosis

Where is the vermis? Big or small?

Do you have a normal fastigial point?

What is the abnormal horizontally oriented structure?

What is the diagnosis?

Midline Sagittal

Slightly OFF Midline

Where is the vermis? Big or small? Too small…

Do you have a normal fastigial point? Yes, pointed…

What is the abnormal horizontally oriented structure? the superior cerebellar peducle…

What is the diagnosis?

Midline Sagittal

Slightly OFF Midline

What is the yellow arrow pointing to?

What is the diagnosis?

Molar Tooth Deformity seen in Joubert spectrum

 “molar tooth” midbrain  Large horizontally oriented superior

cerebellar peduncles  Small, dysplastic vermis  “bat wing” 4th ventricle configuration  Associated with:  Absence of decussation of WM

pathways in brain stem on DTI  Supratentorial:  Absent septum pellucidum  Fused fornices  Ventriculomegaly  Polymicrogyria

Sweep the Midline…

Brainstem Disconnection Syndrome 

White arrows: Small pons remnant with nonformation of the midportion of the brainstem  Clinical: cranial neuropathies  Associated with small cerebellum  Abnormal vertebrobasilar vasculature 

Etiology?  very early vascular insult?  No gliosis to suggest hypoxia or ischemia

 In animals: seen with hox gene deletions leading to lack of single rhombomere development, so brainstem “short” but typically not fully disconnected