The Posterior Auricularis Muscle as Superficial Landmark for the Sigmoid Sinus and Transverse-Sigmoid Sinus Junction: An Anatomical Study.

OBJECTIVE: Neuronavigation systems coupled with previously reported external anatomical landmarks assist neurosurgeons during intracranial procedures. We aimed to verify whether the posterior auricularis muscle (PAM) could be used as an external landmark for identifying the sigmoid sinus (SS) and the transverse-sigmoid sinus junction (TSSJ) during posterior cranial fossa surgery. METHODS: The PAM was dissected in 10 adult cadaveric heads and after drilling the underlying bone, the relationships with the underlying SS and TSSJ were noted. The width and length of the PAM, and the distance between the muscle and reference points (asterion, mastoid tip, and midline), were measured. RESULTS: The PAM was identified in 18 sides (9 left, 9 right). The first 20 mm of the muscle length (mean 28.28 mm) consistently overlay the mastoid process anteriorly and the proximal half of the SS slightly posteriorly on all sides. The superior border was a mean of 2.22 mm inferior to the TSSJ and, especially when the muscle length exceeded 20 mm, this border extended closer to the transverse sinus; it was usually found at a mean of 3.11 mm (range 0.0-13.80 mm) inferior to the distal third of the transverse sinus. CONCLUSIONS: Superficial landmarks give surgeons improved surgical access, avoiding overexposure of deep neurovascular structures and reducing brain retraction. On the basis of our cadaveric study, the PAM is a reliable and accurate direct landmark for identifying the SS and TSSJ. The PAM could potentially be used for guiding the retrosigmoid approach.

L5 spondylolysis: Anatomical study comparing healed and unhealed lesions.

The anatomy and pathogenesis of spondylolysis has been widely studied; however, the microanatomy of spondylolysis of the lumbar vertebra has not been well described. Therefore, we aim to better elucidate this anatomy. Twenty dry bone specimens of healed and unhealed spondylolysis of the L5 vertebra were collected from human skeletal remains. Twelve L5 vertebrae were examples of unhealed spondylolysis and eight specimens exhibited a healed (i.e., bony fusion of the lesion) spondylolysis lesion. The specimens underwent macro and microanatomical analysis followed by CT and microCT imaging. Finally, selected healed and unhealed lesions were submitted for histological analysis using Mason Trichrome staining. The pars interarticularis of two L5 vertebrae without signs of healed/unhealed spondylolysis were evaluated histologically as controls. Of the 12 unhealed L5 pars defects, three were unilateral on left side. Of the eight healed pars defects, all were unilateral and seven of these were on left sides. One unilateral pars defect also had spina bifida occulta. Both on imaging and histological analysis, healed pars defects were only so superficially and not at deeper levels. Histologically, unhealed edges were made up of dense cortical bone while healed edges were made up primarily of trabecular bone. Based on our anatomical findings, the so-called healed spondylolysis lesions, although externally fused, are not thoroughly fused internally. Moreover, the anterior and posterior edges of the unhealed spondylosysis lesions are irregular and show signs of long-term disarticulation. Taken together, these data suggest that such 'healed' lesions might not be as stable as the normal L5 pars interarticularis.

A rare case of the auriculotemporal and inferior alveolar nerves communication.

This case study describes anatomical variations in the branching pattern of the posterior division of the trigeminal nerve and its clinical implications for dental and craniofacial surgery. The study presents two uncommon variations observed in an elderly male cadaver. A communicating branch connecting one of three roots of the auriculotemporal nerve and inferior alveolar nerve just before entering the mandibular foramen on the right side, and three communicating branches between the IAN and lingual nerve on the left side. The presence of such variations may complicate anesthesia associated with oral surgery procedures.

Bilateral Sternalis Muscle With the Absence of Unilateral Sternocostal Part of the Pectoralis Major and Variation of Pectoralis Minor Muscles.

This study aims to report a 57-year-old male cadaver with a rare muscular variation of the sterno-pectoral region. An unusual sternalis muscle was observed on both sides, arising from the external oblique muscle aponeurosis. The fibers converged upwards and medially in a curved course, producing a bundle 99.50 mm long on the right side and 74.60 mm on the left. The muscles on both sides were supplied by the second, third, and fourth intercostal nerves. In the right pectoralis major (PM) muscle, the sternocostal head was completely absent, and the clavicular head arose from the medial two-thirds of the clavicle, whereas abdominal fibers arose from the aponeurosis of the external abdominal oblique muscle and ran upward and laterally and joined the clavicular fibers with a wide triangular gap. On the left side, there was an anatomically normal PM muscle. The origin of the pectoralis minor was unusually high on both sides. The morphological variations of sterno-pectoral musculature have significant implications for clinical practice, which allows more precise surgical or radiological outcomes. Clinicoradiological evaluation of these variations is important to achieve appropriate dissection planes during chest wall surgery.

Anatomy and Histology of the Petrous Carotid Membrane: Application to Skull Base Surgery.

BACKGROUND: Published reports regarding the tissue types that surround the internal carotid artery (ICA) as it travels through the carotid canal vary. Reports have variably defined this membrane as periosteum, loose areolar tissue, or dura mater. With such discrepancies and realizing that knowledge of this tissue might be important for skull base surgeons who expose or mobilize the ICA at this location, the present anatomical/histological study was performed. METHODS: In 8 adult cadavers (16 sides), the contents of the carotid canal were evaluated; specifically, the membrane surrounding the petrous part of the ICA was studied, and its relationship to the deeper lying artery was observed. These specimens were stored in formalin and submitted for histological evaluation. RESULTS: Grossly, the membrane within the carotid canal traversed the entire carotid canal and was loosely adherent to the underlying petrous part of the ICA. Histologically, all membranes surrounding the petrous part of the ICA were consistent with dura mater. The dura mater of the carotid canal had an outer endosteal layer and an inner meningeal layer as well as a clear dural border cell layer in most specimens that approximated and was loosely applied to the adventitial layer of the petrous part of the ICA. CONCLUSIONS: The membrane that surrounds the petrous part of the ICA is dura mater. To our knowledge, this is the first histological investigation of this structure and thus serves to establish the true identity of this membrane and correct previous reports in the literature that have erroneously concluded that it is periosteum or loose areolar tissue.

Evaluation of Progesterone Receptor Antagonist and Maxi-K Channel Agonist as Neuroprotective in Feeney's Weight Drop Model of TBI.

Background: Neuroprotection in traumatic brain injury (TBI) is an unmet medical need. Objective: We evaluated two agents, aglepristone (progesterone receptor antagonist) and N-salicyloyltryptamine (STP) (activator of Maxi-K channel in GH3 cells), for neuroprotection in Feeney's weight drop model of TBI. Material and Methods: Forty-eight male Wistar rats were divided into six groups (n = 8 per group). A battery of six neurobehavioral tests was evaluated at the end of the first week (EO1W), second week (EO2W), and third week (EO3W). In addition, histopathological and immunohistochemistry (BAX, Bcl-2, and M30 Cytodeath) tests were performed at EO3W. Results: Aglepristone at 10 mg/kg showed significant neuroprotection compared to control as assessed by Rota-rod test at EO1W, VEFP right paw and 28-point neurobehavioral test at EO2W, MWM test at EO3W, and positive histopathological and IHC findings. Aglepristone at 20 mg/kg showed negative results as assessed by BAX expression, downregulation of Bcl-2, and positive M30 Cytodeath, thereby suggesting toxicity at higher doses. STP 100 mg/kg showed modest neuroprotective activity but failed to show a dose-response relationship at a dose of 50 mg/kg. Conclusion: The study shows that progesterone receptor antagonists have neuroprotection at lower doses and toxicity at higher doses.