Cranial ultrasound anatomy

Coronal sections

Far anterior coronal

anterior to the genu of the corpus callosum the interhemispheric fissure is undisturbed; this is the section to best study abnormal interdigitation of the hemispheres Abbreviations:
ihf interhemispheric fissure
sfs sulcus frontalis superior
sol sulcus orbitalis lateralis

Anterior coronal — orbit

in front of the foramen of Monro there is no choroid plexus; the anterior insular border becomes visible Abbreviations:
cing sulcus cinguli
gr gyrus rectus
gti gyrus transversus insulae
ihf interhemispheric fissure
lv lateral ventricle
olf sulcus olfactorius

Coronal @ Monro

in the midline the anterior tip of tela choroidea, as it turns around into the plexus of the lateral ventricle, becomes visible in the section at the foramen of Monro; underneath it the third ventricle cavity may appear as a darker vertical slit, above it is cavum septi pellucidi; the anterior portion of temporal lobes is visible Abbreviations:
cc corpus callosum
cing sulcus cinguli
csp cavum septi pellucidi
gti gyrus transversus insulae
ihf interhemispheric fissure
lv lateral ventricle
mc migrating cells
sfm sulcus frontalis medius
sfs sulcus frontalis superior
sis sulcus circularis insulae superior

Coronal at ventrolateral thalamus

halfway between Monro and the choroid glomus, the ventrolateral and ventral posterior nuclei of thalamus appear as a mildly hyperechoic column, bordered by the darker ribbon of the posterior limb of the internal capsule; the sulcus collateralis is the floor of the parahippocampal gyrus Abbreviations:
cc corpus callosum
cing sulcus cinguli
cm cisterna magna
ft fissura transversa (Bichat)
ihf interhemispheric fissure
lf lateral fissure
lv lateral ventricle
pci sulcus precentralis inferior
scoll sulcus collateralis
sfm sulcus frontalis medius
sfs sulcus frontalis superior
sis sulcus circularis insulae superior
vlt ventrolateral thalamus

Coronal at atrial level

between the upper atrium and the lateral fissure runs the optic radiation (best observed before 37w PMA); the lateral fissure remains visible posterior to the sulcus circularis superior of the insula Abbreviations:
cc corpus callosum near splenium
cing sulcus cinguli
cp choroid plexus
ihf interhemispheric fissure
lf lateral fissure
lv lateral ventricle
or optic radiation
sfm sulcus frontalis medius
sfs sulcus frontalis superior
sts sulcus temporalis superior

Coronal behind the atria (post-atrial)

white matter posterior to the atria is homogeneously hyperechoic, rostral to the sulcus parieto-occipitalis and calcar avis; in many infants the three vertical (peri)central sulci can be visualized; the ramus supramarginalis sulci cinguli always ends at the hemisphere margin and points in the direction of the sulcus postcentralis Abbreviations:
calc sulcus calcarinus
ihf interhemispheric fissure
pcs sulcus precentralis superior
po sulcus parieto-occipitalis
poc sulcus postcentralis
rsm ramus supramarginalis sulci cinguli
sc sulcus centralis
sts sulcus temporalis superior

Coronal far posterior

in a far posterior section the sulcus intraparietalis can be visualised, dividing the parietal lobe in a superior (medial) and inferior (lateral) lobule Abbreviations:
ihf interhemispheric fissure
po sulcus parieto-occipitalis
poc sulcus postcentralis
rsm ramus supramarginalis sulci cinguli
sc sulcus centralis
sip sulcus intraparietalis
ssp sulcus subparietalis

(Para)sagittal sections

Mid sagittal

the mid sagittal section has the complete corpus callosum and vermis inferior plus superior, with the cisterna magna and a sulcus parieto-occipitalis from one hemisphere; the sulcus calcarinus variably leaves the latter in the direction of the occipital pole; cingulum (part of the limbic system) surrounds corpus callosum up to its isthmus Abbreviations:
calc sulcus calcarinus
cing sulcus cinguli
cm cisterna magna
cq cisterna quadrigemina
g genu corporis callosi
ic isthmus cinguli
po sulcus parieto-occipitalis
rsm ramus supramarginalis sulci cinguli
s splenium corporis corporis callosi
srp sulcus rostralis superior
ssp sulcus subparietalis
t tela choroidea

Parasagittal @ matrix

only millimeters parasagittal of the midline, the caudothalamic groove is visualised; it contains matrix in preterms, which is echo poor unless affected by disease; matrix cavitation is often present here Abbreviations:
cing sulcus cinguli
ctg caudothalamic groove
g genu corporis callosi
ic isthmus cinguli
po sulcus parieto-occipitalis
rsm ramus supramarginalis sulci cinguli
s splenium corporis corporis callosi
srp sulcus rostralis superior
ssp sulcus subparietalis
th mediodorsal thalamus

Parasagittal @ gangliothalamic egg

in the plane through the uncus, the deep grey matter nuclei forming the gangliothalamic egg can be recognised Abbreviations:
cing sulcus cinguli
ctg caudothalamic groove
gc glomus choroideum
rsm ramus supramarginalis sulci cinguli
sr sulcus rhinalis
tf transverse fissure (Bichat)
VA ventral anterior thalamus
vf ventral forebrain
VL ventrolateral thalamus

Parasagittal @ insula of Reil

the insular triangle is contained by the sulcus circularis insulae (anterior, superior, inferior and posterior); the posterior long gyri are behind the sulcus centralis insulae, the anterior short gyri can be completed in front by a gyrus accessorius insulae; the gyri breves converge on the insular pole, posterior to the limen insulae (piriform cortex lateral to the lateral olfactory stria) Abbreviations:
circ sulcus circularis insulae
ga gyrus accessorius insulae
gb gyri breves: anterior, middle, posterior
gl gyri longi
lf lateral fissure
sc sulcus centralis (cerebri)
sci sulcus centralis insulae

Parasagittal @ frontal and cerebral sulci

the frontal lobe has two parts: gyrus precentralis is in front of sulcus centralis, the other frontal areas are in front of the sulci precentrales; frontal sulci subdivide the frontal lobe in a superior, middle and inferior frontal gyrus; the latter contains Broca's area around the ramus ascendens of the lateral fissure Abbreviations:
f1,2 sulci frontales (superior, medius)
pci sulcus precentralis inferior
pcs sulcus precentralis superior
poc sulcus postcentralis
PT pars triangularis (Broca area)
ra ramus ascendens fissurae lateralis
sc sulcus centralis (cerebri)

Posterior fontanel sections

Posterior fontanel

the posterior fontanel window looks at sulcus parieto-occipitalis and cuneus, including splenium and the vascular tangle in the cavum veli interpositi and cisterna quadrigemina; this is also the window where a linear probe provides full display of the superior sagittal sinus and its Willis' cords; vermis cerebelli is often also well depicted Abbreviations:
calc sulcus calcarinus
po sulcus parieto-occipitalis
s splenium
SSS sinus sagittalis superior

Mastoid fontanel

mastoid views offer inspection of the transverse sinus, cerebellar hemispheres and vermis, pons, plus the outlet foramina of the fourth ventricle (with Blake's pouch remnants in many preterms); with high frequency probes details of the hippocampus can also be seen Abbreviations:
TS transverse sinus
V4 fourth ventricle
ac aqueductus cerebri
ca cornu Ammonis
th temporal horn

Temporosquamosal window

above the auricula many preterms have an accessible window above the temporal squame; white matter of the temporal lobe and hippocampus can be visualised in part; often clear views of mesencephalon and pons are present, including the aqueduct

Foramen magnum (nuchal) window

in small preterm infants there is good access to the posterior fossa from the nuchal window, especially in coronal planes with high resolution probes; sigmoid sinus and PICA can be visualised from this angle; especially details of cerebellar structure and abnormalities in the cisterna magna can be depicted in detail Abbreviations:
cm cisterna magna
scoll sulcus collateralis courtesy dr Mühlbacher, Zürich

Primary sulci: scheme

Cunningham 1892 — 3D mesh model of primary gyration according to descriptions by Cunningham 1892

Primary sulci: convexity

Abbreviations:
f1 sulcus frontalis superior
f2 sulcus frontalis medius
f3 sulcus frontalis inferior
fl ramus posterior fissurae lateralis
fm sulcus frontomarginalis (Wernicke)
h ramus horizontalis of pci
he Heschl gyri
j Jensen anterior inferior parietal sulcus
lun sulcus lunatus
olf sulcus and tractus olfactorius
pci sulcus precentralis inferior
pcs sulcus precentralis superior
po sulcus parieto-occipitalis
poc sulcus postcentralis
PT pars triangularis
ra ramus ascendens fissurae lateralis
rh ramus horizontalis fissurae lateralis
sang sulcus angularis
sc sulcus centralis (Rolando)
sd sulcus diagonalis (Eberstaller)
sip sulcus intraparietalis
soa sulcus occipitalis anterior
soi sulcus occipitalis inferior
spt sulcus parietalis transversus (Brissaud)
ssa sulcus subcentralis anterior
ssp sulcus subcentralis posterior
st sulcus occipitalis transversus (Ecker)
sts sulcus temporalis superior
sti sulcus temporalis inferior

Primary sulci: mesial

Abbreviations:
calc sulcus calcarinus
cing sulcus cinguli
olf sulcus and tractus olfactorius
paracing sulcus paracinguli
po sulcus parieto-occipitalis
rsm ramus supramarginalis sulci cinguli
sc sulcus centralis (Rolando)
scc sulcus corporis callosi
scoll sulcus collateralis
sh sulcus hippocampi
sol sulcus olfactorius
sot sulcus occipito-temporalis
spa sulcus paracentralis
spt sulcus parietalis transversus (Brissaud)
sr sulcus rhinalis
srs sulcus rostralis superior
ssp sulcus subparietalis

Primary sulci: full scheme

Abbreviations:
c sulcus precentralis medialis
calc sulcus calcarinus
cing sulcus cinguli
f1 sulcus frontalis superior
f2 sulcus frontalis medius
f3 sulcus frontalis inferior
fl ramus posterior fissurae lateralis
fm sulcus frontomarginalis (Wernicke)
LL limbic lobe
pci sulcus precentralis inferior
pcm sulcus precentralis medius
pcs sulcus precentralis superior
po sulcus parieto-occipitalis
poc sulcus postcentralis
PT pars triangularis
r sulcus centralis (Rolando)
ra ramus ascendens fissurae lateralis
rh ramus horizontalis fissurae lateralis
rsm ramus supramarginalis sulci cinguli
sang sulcus angularis
scoll sulcus collateralis
sd sulcus diagonalis
sip sulcus intraparietalis
sl sulcus lunatus
soa sulcus occipitalis anterior
soi sulcus occipitalis inferior
sot sulcus occipito-temporalis
spa sulcus paracentralis
sr sulcus rhinalis
sri sulcus rostralis inferior
srs sulcus rostralis superior
ssp sulcus subparietalis
st sulcus occipitalis transversus (Ecker)
sts sulcus temporalis superior
sti sulcus temporalis inferior Gyri:
1 gyrus parahippocampalis
2 gyrus fusiformis
3 gyrus lingualis
4 lobulus paracentralis
5 precuneus
6 cuneus
7 gyrus supramarginalis
8 gyrus angularis

Additional sulci list

fm sulcus frontomarginalis (Wernicke)
olf sulcus and tractus olfactorius
ra ramus ascendens fissurae lateralis
rh ramus horizontalis fissurae lateralis
scoll sulcus collateralis
sol sulcus orbitalis lateralis
som sulcus orbitalis medialis
sotr sulcus orbitalis transversus
sot sulcus occipito-temporalis
sr sulcus rhinalis rsm ramus supramarginalis sulci cinguli
sang sulcus angularis
sc sulcus centralis (Rolando)
scoll sulcus collateralis
sd sulcus diagonalis (Eberstaller)
sip sulcus intraparietalis
soa sulcus occipitalis anterior
soi sulcus occipitalis inferior
sol sulcus orbitalis lateralis
som sulcus orbitalis medialis
sotr sulcus orbitalis transversus
sot sulcus occipito-temporalis
spa sulcus paracentralis
sr sulcus rhinalis
sri sulcus rostralis inferior
srs sulcus rostralis superior
ssa sulcus subcentralis anterior
ssp sulcus subcentralis posterior
sspa sulcus subparietalis
st sulcus occipitalis transversus (Ecker)
sts sulcus temporalis superior
sti sulcus temporalis inferior

Matrix areas

Insula

Abbreviations:
1 medial
2 anterior
3 posterior
4 lateral orbital gyri PP planum polare
PT planum temporale
H Heschl gyri (transverse gyri)

How does the brain function?

Sulci, gyri and regional cortical activity

although many sulci do not follow cytoarchitectonic patterns, to therefore conclude that the shape and location of sulci is of little relevance, is wrong for many good reasons: - plenty of sulci do correspond to a border between functional entities
- the central groove does separate the motor brain from the other parts
- the sulci and lobules of the left inferior frontal gyrus do differ from the right because they are special in language operations
- development of sulci does correlate with a regression of the olfactory dominance and a progression of the visual dominance in the mammalian neocortex
- the complexity of the insula in phylogenetics does relate to the more elaborate "awareness" in the human (and some other) species
- the lateral fissure is not a sulcus, neither are the transverse and interhemispheric fissure
- cortex between sulcus cinguli and corpus callosum is the output area of the limbic system
- the pericentral area, with connections to the brainstem and spinal cord, is vulnerable to injury in newborns, in itself and due to subjacent white matter lesions
- gyrus temporalis superior is crucial in language processsing
- annectant gyri cross sulci at specific sites, not in disorder
…

References, approach of the topic

Although apparently counter-intuitive to the body of "knowledge" about sulci, gyri, lobes and regional cortical activity, the question remains appropriate. On the one hand there is the certainty that consciousness (even we ever define what it is) is poor or absent without cortex and thalamus, on the other it is still not possible for many brain functions to delineate the parts of the brain (and cortex) involved in it. Memory may be organised (encoded and registered) by entorhinal cortex and hippocampus, but memory engrams are all over the brain (surface). Sensory perception of the body may occur in the postcentral gyrus, but lesions there can be followed by extra-ordinary plasticity and recovery of function. … Neither gross anatomy, nor histology and histochemistry, nor animal experiments, nor PET scan, nor fMRI have been able to describe how specific actions really operate. Images based on neurovascular coupling, like the bold signal in fMRI, are at best very crude surrogates of function. The same goes for EEG and derivatives. This is because of the daunting complexity of the circuits in our brain. Every neuron is in fact a microcomputer and billions of them all work together with nuance (modulation). Although one knows that some neurons in the fusiform gyrus are specialised in face recognition, this does not mean that they are "the tool" for face recognition. They are merely part of a complex circuitry with parallel and hierarchical pathways, with feed forward and backward communications, in itself integrated with networks for other functions, e.g. linking the perceived face to the sound it makes. On the other hand, as neonatologists, we all know that devastating brain damage as with asphyxia, leukomalacia, extensive focal infarction and other entities, is followed by profound weakening of the cognitive and motor repertoire. We also realised that subtle lesions, even just being born prematurely, changes the brain. This means that some structures, cells, tracts, are essential from early on in life and are best not damaged after a certain postmenstrual age. You cannot grow a new corticospinal tract or a long association tract in preterm infants at viable age, that process has occurred in utero. Subplate, with functions and fragilities, is a transient structure, no longer operating after about 34 w PMA. The neocortex is only formed once. Although neuronal precursors persist in hippocampus, repair after birth by neurogenesis in the central nervous system, is at best very limited. Cranial ultrasound uses a window in lifetime where direct access to structure is available because of the presence of fontanels. Many small preterm infants have rather large fontanels. Ultrasound vendors - rarely focusing on neonatal brain work - did provide probes with a round scanhead, so that major portions of the cranial content can be observed. Ultrasound, with no real documented side effects when used wisely as we do in clinical practice, can be performed bedside, with very limited disturbance to the infant, without pain. Above all it can be done serially at acceptable cost. There is no other tool that is practical to study the brain surface of one infant for weeks on end, every week, without harm.

Introduction

The cerebrum can be seen as a collection of four lobes (Gratiolet), in itself forming an outer neocortical circle around the middle ring of the cingulum, amygdala and insula, in themselves concentrated around the hippocampus and hypothalamus. The first sulci to emerge are the sulcus hippocampi between archi- and paleocortex (the latter covering gyrus parahippocampalis), and the sulcus rhinalis between paleocortex (hippocampal and piriform) and neocortex. Two pericentral gyri stand vertically between the transversely oriented frontal, parietal and temporal gyri. Gyri should not just be seen as structures between sulci, as many sulci, in their hidden deeper parts, harbor annectant (transverse or opposing) gyri that form bridges between the gyri. Some surface furrows are just the top of such annectant gyri. To identify sulci, and consequently gyri, the characterization of a given sulcus does not necessarily imply that it is composed of a single continuous space (Ribas 2010). A sulcus can consist of several parts, long or short, isolated or connected to other sulci. The parieto-occipital sulcus forms as a consequence of the appearance of the posterior most portion of the corpus callosum, which results in the invagination of the medial surface and the consequent creation of that sulcus. Sulci have been divided into 4 types: limiting, axial, opercular, and complete:
- limiting sulci separate functionally different areas (e.g. the central sulcus, which separates the motor and sensory area);
- axial sulci develop along the axis of a functionally homogeneous area, as in the case of the posterior portion of the calcarine fissure, which is actually a fold situated in the center of the striate visual cortex;
- opercular sulci are situated between cortical areas that are structurally and functionally different, but the separations exist only along their edges and not in their fundi (e.g. the lunate sulcus, which, when present, is oriented vertically, separating the striate from peristriate areas of the surface and including the submerged parastriate area within its walls);
- complete sulci are those whose fundi produce rises in the walls of the lateral ventricles (e.g. the collateral sulcus creates the collateral eminence on the floor of the inferior horn, and the calcarine fissure causes the calcar avis in the medial wall of the posterior horn). Gratiolet LP: Memoire Sur Les Plis Cérébraux de L'homme et des Primates. Paris: Bertrand, 1854
Ribas G (2010) The cerebral sulci and gyri. Neurosurg Focus 28(2): 1-24.

The human brain without gyri at 20w PMA

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