The Anterolateral Limit of the Occipital Lobe: An Anatomical and Imaging Study.

Objectives The boundaries of the temporal lobe, the parietal lobe, and the anterior portion of the occipital lobe (OL) are poorly defined. Lesions in these areas can be difficult to localize. Therefore, we studied the anterolateral limit of the OL to identify reliable anatomical landmarks. Design In 10 formalin-fixed cadaveric heads, the boundaries of the OL and relative anatomical landmarks were studied. Main Outcome Measures Distances between the following structures were measured: (1) preoccipital tentorial plica (POTP) to the junction between lambdoid suture and superior border of the transverse sinus (POTP-SL), (2) POTP to the sinodural angle of Citelli (POTP-PP), (3) lambda to parietooccipital sulcus (L-POS), and (4) preoccipital notch to termination of the vein of Labbé (PON-VL). Landmarks in 559 computed tomography and magnetic resonance images were also studied. Results The POTP was found on the tentorium of all anatomical specimens, located at the same coronal level as the PON and its attachment to the bony protuberance (BP) at the lateral cranial wall. The mean distances were POTP-SL, 6.5 ± 6.4 mm; POTP-PP, 18.1 ± 7.8 mm; L-POS, 10.8 ± 5.0 mm; and PON-VL, 8.8 ± 10.1 mm. Conclusion Osseous (asterion, lambda, and BP), dural (POTP), and vascular (VL) landmarks can be used as reference structures to identify the anterolateral limit of the OL.

Midline as a landmark for the position of the superior sagittal sinus on the cranial vault: An anatomical and imaging study.

BACKGROUND: Craniotomies involving the midline are regular practice in neurosurgery, during which injury to the superior sagittal sinus (SSS), an uncommon yet devastating event, may occur. The midline tends to be the most common landmark used to identify the position of the SSS. In this study we examined the reliability of the midline as a landmark for the SSS. METHODS: We performed bilateral craniectomies on eight cadaveric heads, preserving the coronal, sagittal, and lambdoid sutures. The width of the SSS and its displacement from midline were measured on the cadaveric specimens and on 105 normal magnetic resonance images (MRIs) of the head at the following locations: halfway between nasion and bregma (NB), bregma (B), halfway between bregma and lambda (BL), lambda (L), and inion (I). RESULTS: In all cadaveric specimens, the SSS was partially or totally displaced toward one side of midline, usually to the right. It tended to be closer to midline in the frontal region and more displaced posteriorly. The SSS usually drained into the right-side transverse sinus. The mean width of the SSS was 4.3, 5.9, 6.9, 7.9, and 7.8 mm, and the average displacement from midline was 4.3, 6.3, 5.5, 6.9, and 6.0 mm for NB, B, BL, L, and I, respectively. These measurements were then compared with those obtained from the MRIs. CONCLUSION: The SSS was consistently displaced on either side of midline. Thus, the midline is not reliable for identifying the SSS, and caution should be used within 6-10 mm on either side of midline.

Delimitação dos acessos cranianos / Definition of cranial approaches

São descritos os pontos craniométricos e, a partir deles, definidos os pontos referenciais e as linhas para delimitar os principais acessos cranianos: pterional, fronto-orbital, frontobasal, frontal, temporal anterior, parietal, occipital, suboccipital e pontos de punção dos cornos frontal e occipital do ventrículo lateral.

Craniometric points are described, and from them, set the reference points and lines to delimit the main cranial approaches: pterional, fronto-orbital, frontobasal, frontal, anterior temporal, parietal, occipital, suboccipital and points for puncture of the frontal and occipital horns of the lateral ventricles.

Avaliação da trajetória dos parafusos bicorticais pela técnica de harms e melcher em relação à artéria carótida interna: estudo experimental em cadáveres / Evaluación de la trayectoria de los tornillos bicorticales en la técnica de harms y melcher en relación con la arteria carótida interna: un estudio experimental en cadáveres / Evaluation of the trajectory of the bicortical screws in relation to the internal carotid artery, in fixation by the harms and melcher technique: an experimental study in cadavers

OBJETIVO: O objetivo deste trabalho é estudar, em peças anatômicas; a relação entre os parafusos bicorticais pela técnica de Harms e Melcher e a artéria carótida interna. MÉTODOS: Nossa amostra consiste em cinco cadáveres. RESULTADOS: Os resultados encontrados foram: a média da menor distância entre o orifício de saída do parafuso e a borda medial da artéria carótida interna direita foi de 11,55 mm (com variação de 10,05 a 14,23 mm), enquanto do lado esquerdo a média foi de 7,50 mm (variando de 2,75 a 12,42 mm). A média da menor distância entre a borda posterior da artéria carótida interna e a cortical anterior da massa lateral de C1 à direita foi de 4,24 mm (variando de 2,08 a 7,48 mm), enquanto do lado esquerdo a média obtida foi de 2,98 mm (com variação de 1,83 a 3,83 mm). CONCLUSÃO: Os resultados encontrados estão de acordo com os estudos similares existentes na literatura que enfatizam a necessidade de uma avaliação imaginológica criteriosa da posição anatômica da artéria carótida interna antes da utilização de parafusos bicorticais na massa lateral de C1 por via posterior.

OBJECTIVE: The objective of this study is to study the relationship between bicortical screws and the internal carotid artery, in anatomical body parts, in screw fixation by the Harms and Melcher technique. METHODS: Our sample consisted of five cadavers. RESULTS: The results were as follows: the average shortest distance between the outlet of the screw and the medial edge of the right internal carotid artery was 11.55 mm (range 10.05 to 14.23 mm), while on the left side, the average was 7.50 mm (ranging from 2.75 to 12.42 mm). The average shortest distance between the posterior edge of the internal carotid artery and the anterior cortical C1 lateral mass on the right was 4.24 mm (ranging from 2.08 to 7.48 mm), while the left side, the average was 2.98 mm (ranging from 1.83 to 3.83 mm). CONCLUSION: The results are consistent with similar studies in the literature that emphasize the need for a careful assessment of images of anatomical position of the internal carotid artery prior to the use of bicortical screws in the C1 lateral mass by posterior access.

OBJETIVO: O objetivo de este estudio es, en las piezas anatómicas, la relación entre los tornillos bicorticales, mediante la técnica de Harms y Melcher, y la arteria carótida interna. MÉTODOS: La muestra se compone de cinco cadáveres. RESULTADOS: Los resultados fueron: la distancia más corta promedio, entre la salida del tornillo y el borde medial de la arteria carótida interna derecha, fue 11,55 mm (rango de 10,05 a 14,23 mm), mientras que, en la izquierda, el promedio fue 7,50 mm (rango 2,75 a 12,42 mm). La distancia más corta promedio, entre el borde posterior de la arteria carótida interna y la cortical anterior C1 de la derecha, fue 4,24 mm (que van desde 2,08 hasta 7,48 mm), mientras que, en el lado izquierdo, el promedio fue 2,98 mm. (que van desde 1,83 hasta 3,83 mm). Conclusión: Los resultados son consistentes con estudios similares en la literatura que hacen hincapié en la necesidad de una evaluación cuidadosa de las imágenes y posición anatómica de la arteria carótida interna, antes del uso de tornillos bicorticales de masa lateral de C1 por acceso posterior.

The ascending pharyngeal artery and its relevance for neurosurgical and endovascular procedures.

OBJECTIVE: The ascending pharyngeal artery (APA), a branch of the external carotid artery (ECA), supplies the lower cranial nerves, superior cervical ganglion, and nasopharyngeal structures. The APA can also supply blood to various intracranial lesions. We studied the anatomy of the APA in the context of its neurosurgical and endovascular relevance. METHODS: The cervical origin, branching pattern, and course of the APA were studied in 20 human cadaveric craniocervical sides. The diameter of the APA, the extension of its main trunk, and the distance of its origin from the common carotid artery bifurcation were measured. The relationships between the APA and surrounding structures were also observed. RESULTS: In 80% of the specimens, the APA originated from the ECA. It originated from its medial wall in 56% and from the posterior wall in 44%. The APA originated from the internal carotid artery, common carotid artery bifurcation, occipital artery, and a trunk common to the lingual and facial arteries in 5% each. The APA was usually the third branch of the ECA (40%). The mean distance from the origin of the APA to the common carotid artery bifurcation was 15.3 mm (range, 0-32; standard deviation, +/- 8.3 mm). The APA was frequently the second smallest branch of the ECA (caliber, 1.54 mm; range, 1.1-2.1; standard deviation, +/- 0.25 mm). CONCLUSION: The APA is an important channel for supplying neural structures of the posterior fossa. Knowledge of its anatomy, variants, and anastomotic channels is essential in the treatment of lesions supplied by its branches and to avoid complications related to its inadvertent injury.