Immersive Surgical Anatomy of the Craniometric Points

Abstract

Craniometric points (CPs) have been used in neurosciences since the 1800s. Localization of the CPs allows for the identification of crucial intracranial structures. Despite the contribution of advanced technology to surgery, the knowledge of these points remains crucial for surgical planning and intraoperative orientation. The understanding of these crucial points can be facilitated with the use of three-dimensional technology combined with anatomical dissections. The present study is part of a stereoscopic collection of volumetric models (VMs) obtained from cadaveric dissections that depict the relevant anatomy of the CPs. Five embalmed heads and two dry skulls have been used to depict these points. After the anatomical dissection, stereoscopic images and VMs were generated to show the correlation between external and internal landmarks. The CPs identified were divided into sutures, suture junctions, prominences and depressions, and cortical surface landmarks. The VMs represent an interactive way to define these points easily and their correlation with different intracranial structures (vascular structure, ventricle cavity, and Brodmann's areas).

Keywords: cerebral cortex; cranial sutures; craniometric points; keyholes; motor cortex; speech area; vascular landmarks; ventricular access; volumetric models.

Figure 1. Overview of the main cortical gyri: (A) lateral surface and (B) medial surface of the brain.

AG: angular gyrus; CC: corpus callosum; Cing. G: cingular gyrus, Cu: cuneus; FP: frontal pole; GR: gyrus rectus; IFG: inferior frontal gyrus; ITG: inferior temporal gyrus; IOG: inferior occipital gyrus; LG: lingual gyrus; MFG: middle frontal gyrus; MOG: middle occipital gyrus; MTG: middle temporal gyrus; OG: orbital gyrus; Op: pars opercularis of the IFG; Orb: pars orbitalis of the IFG; PCu: precuneus; PoCG: post-central gyrus; PPG: posterior parietal gyrus; PreCG: pre-central gyrus; SFG: superior frontal gyrus; SMG: supramarginal gyrus; SOG: superior occipital gyrus; SPL: superior parietal lobule; STG: superior temporal gyrus; Th: thalamus; TP: temporal pole; Tr: pars triangularis of the IFG.

Figure 2. Overview of main sutures, suture junction points, and prominences of the human skull: (A) anterior view, (B) lateral view, (C) superior view, and (D) posterior view.

Ast: asterion; Br: bregma; Eu: euryon; In: inion; Lm: lambda; Na: nasion; Oph: ppisthocranium; Pt: pterion; STL: superior temporal line; St: stephanion; V: vertex.

Figure 3. Depiction of the principal craniometric points on the skin: (A) superior view and (B) posterior view of the head.

Br: bregma; Eu: euryon; In: inion; IPP: intraparietal point; Lm: lambda; Oph: opisthocranium; PCoP: posterior coronal point; SSagP: superior sagittal point; St: stephanion.

Figure 4. Osteometric points and prominences of the human skull. (A) Lateral view of the skull with the representation of the mean distance of the main craniometric points; (B) posterior view of the skull with an underline of the principal points and prominences.

Br: bregma; Eu: euryon; In: inion; Lm: lambda; Na: nasion; Oph: opisthocranium; St: stephanion.

Figure 5. Relationship of relevant craniometric points and cortical surface structures. After performing the dissection of the superficial layer, seven bony windows were created outlining the main cranial landmarks. The correlation between the craniometric points and the brain surface is visible. (A) Lateral view of the head - superior frontal, inferior frontal, sphenoidal, superior parietal, inferior parietal, and temporal windows are shown; (B) superior-posterolateral view of the head - superior parietal, inferior parietal, and temporal windows are shown; (C) inferior-posterolateral view of the head - superior parietal, inferior parietal, temporal, and occipital windows are shown; (D) posterior view of the head - superior parietal and occipital windows are visible.

AG: angular gyrus; ASP: anterior squamous point; Ast: asterion; Br: bregma; dECaS: distal extremity of the calcarine sulcus; Eu: euryon; IFS/PreCS point: inferior frontal sulcus/pre-central sulcus meeting point; In: inion; IOG: inferior occipital gyrus; IPS: intraparietal sulcus; IRP: inferior Rolandic point; ITG: inferior temporal gyrus; Lm: lambda; MFG: middle frontal gyrus; MOG: middle occipital gyrus; MTG: middle temporal gyrus; Op: pars opercularis of the IFG; Oph: ophistocranium; Orb: pars orbitalis of the inferior frontal gyrus (IFG); PoCG: post-central gyrus; POinc: parieto-occipital incisure point; PPG: posterior parietal gyrus; PreCG: pre-central gyrus; PTP: posterior temporal point; SFG: superior frontal gyrus; SFS/PreCS point: superior frontal sulcus/pre-central sulcus meeting point; SMG: supramarginal gyrus; SPL: superior parietal lobule; SSP: superior squamous point; SRP: superior Rolandic point; STG: superior temporal gyrus; STL: superior temporal line; St: stephanion; TP: temporal pole; Tr: pars triangularis of the IFG.

Figure 6. Subcortical structures and craniometric points. (A) Superior view of the head with windows craniotomies including white matter dissection showing the correlation of the anterior segment of the perisylvian network and the craniometric points; (B) superior view of the head with windows craniotomies with further with matter dissection showing the correlation of the body of the lateral ventricle and the craniometric points.

Ant. segm.: anterior segment; Br: bregma; ChP: choroid plexus; FM: foramen of Monro; MFG: middle frontal gyrus; PSN: perisylvian network; SFG: superior frontal gyrus; STL: superior temporal line; St: stephanion; Th: thalamus.

Figure 7. Representation of the main craniometric methods used to identify the central sulcus: (A) Taylor-Haughton method, (B) Broca’s method, and (C) Rhoton’s method.

Red points and dashed lines represent the superior Rolandic point, inferior Rolandic point, and central sulcus. ABL: auriculobregmatic line; In: inion; Na: nasion.

Figure 8. Overview of the major dural sinuses and veins of the brain. (A) Superior view of the head after removal of the superior sagittal suture and visualization of the SSS; (B) posterior view of the head after removal along the superior sagittal suture and opening of the posterior fossa, visualization of the SSS, torcula Herophili, transverse sinus, and sigmoid sinus; (C) visualization of the anterior portion of the brain underlying the venous structures (SSS, arachnoid granulations, and bridging veins); (D) visualization of the posterior portion of the brain underlying the venous structures (SSS, arachnoid granulations, bridging veins, torcula Herophili, transverse sinus).

SSS: superior sagittal sinus; TSSJ: transverse-sigmoid sinus junction.

Figure 9. Overview of the SF and the vein of Labbé. (A) Lateral view of the head with exposure of the SF after selective drilling was performed over the central portion of the squamosal suture; (B) lateral view of the head with focus bone removal above the SF and the course of the vein of Labbé.

ASyP: anterior Sylvian point; PSyp: posterior Sylvian point; SF: Sylvian fissure; St: stephanion.

Figure 10. Overview of the Asterion and the transverse-sigmoid sinus junction. (A) Postero-lateral view of the skull; (B) interior view of the postero-lateral aspect of the skull; (C) inferior view of the postero-lateral aspect of the skull.

Ast: asterion; TSSJ: transverse-sigmoid sinus junction.

Figure 11. Representation of the strategic burr hole position (green spheres) on the lateral aspect of the skull.

Ast: asterion; Pt: pterion; PmSqJ: parietomastoid-squamosal suture junction.