The petrosal nerves: anatomy, pathology, and surgical considerations.

The literature lacks a comprehensive review of the petrosal nerves, which often have a complicated course and nomenclature. The medical literature was reviewed comprehensively for information regarding the anatomy, pathology, and surgery of the petrosal nerves. The terminology and anatomy of the petrosal nerves are often complicated. Our review found multiple nomenclatures used in the description of these structures. Information regarding the petrosal nerves may assist those who observe or operate at or near the skull base. To our knowledge, this is the first comprehensive review of these structures.

Use of autologous scapula for cranioplasty: cadaveric feasibility study.

INTRODUCTION: Replacement sources for calvarial defects include synthetic materials, donor grafts, and autologous bones such as ribs or split-thickness calvarial cranioplasty. When these sources are not available or are inadequate, other structures or sites would be desirable. However, and to our knowledge, the scapula has not been explored as a potential source for calvarial reconstruction. Therefore, the following study was performed to verify the utility of this bone for cranioplasty. MATERIALS AND METHODS: Six adult (mean age 71 years) cadavers (four formalin-fixed and two fresh specimens) were used in this study. In the prone position, an incision was made over the midpart of the infraspinous fossa. Soft tissues were then removed from the anterior and posterior aspects of the scapula in this region avoiding the glenohumeral articulation superiorly. Previously made cranial defects were then filled using available scapula as a bony replacement. RESULTS: An average of 9 x 12 x 7 cm of scapula was available for harvest inferior to the glenohumeral joint. Lateral and medial borders of the scapula were found to have a mean thickness of 9 mm. No obvious injury to surrounding vessels or nerves was found using this procedure and good coverage of calvarial defects was afforded by this bony replacement. CONCLUSIONS: Such a bony substitute as autologous scapula might be of utility when other replacements are not available or are of a limited size. Examples of such a use would include patients in whom a hemispheric bone flap is lost. Following clinical confirmation, the neurosurgeon may wish to consider the scapula as an alternative site for bone harvest for cranioplasty as this was a feasible technique in the cadaver.

The transverse genicular ligament: anatomical study and review of the literature.

There is scant information in the literature regarding the transverse genicular ligament. In order to elucidate further the anatomy and controversial function of this structure, we dissected 28 cadavers. This ligament was identified in 55% of knee joints. Morphometrically, we found a mean length and width of this ligament of 35.4 and 2.5 mm, respectively. Two (3.7%) specimens were found to have a duplicated ligament. The mean distance between the anterior attachment site of the anterior cruciate ligament onto the tibia to the transverse genicular ligament was 2.5 mm and the mean distance to this ligament to a midpoint of the tibial tuberosity was 40.5 mm The transverse genicular ligament was found to be slightly taut in extension and lax in flexion of the knee joint. Lateral and medial forces applied manually to the knee had no effect on this ligament. No tension was noted of the transverse genicular ligament with rotation of the knee. With transection of the ligament, no discernable difference in the integrity of the knee joint was observed. The mean tensile strength of this ligament was 67 N. Based on our study, the transverse genicular ligament plays a minimal part in the proper function of the knee joint. Moreover, with only approximately one-half of the knees in our study harboring this structure, one would expect a significant portion of the population to exhibit signs of biomechanical dysfunction of the knee joint which is not the case. This structure may represent a vestigal/insular part of the mesenchyme forming the menisci.

The intriguing history of the human calvaria: sinister and religious.

INTRODUCTION: A review of the ancient world finds multiple documentations describing the use of the human calvaria as a drinking implement. TERMINOLOGY: This term, which is frequently and incorrectly called the "calvarium," has a unique history among multiple cultures of the world. For example, the purported site of Jesus' crucifixion "Calvary" is derived from this term calvaria. The present report explores the derivation, misuse, and history of the human calvaria.

Peroneotalocalcaneus muscle.

Variations within the musculature of the lateral compartment of the leg are uncommon. However, clinicians and radiologists should be aware of anatomical alterations in this region when involved in diagnosis or imaging interpretation. The present report describes a well-developed muscle of the lateral compartment of the leg that inserted distally onto the talus and calcaneus. This muscle could be considered a variation of the so-called peroneus quartus muscle. To the authors' knowledge this muscle variation has not been described as having an attachment onto the talus thus the term 'peroneotalocalcaneus muscle' is proposed.

Anatomy of the cranial nerves in medieval Persian literature: Esmail Jorjani (AD 1042-1137) and The treasure of the Khwarazm shah.

Esmail Jorjani was an influential Persian physician and anatomist of the 12th century who did most of his writing after his seventh decade of life. Jorjani's comprehensive textbook of medicine, Zakhirey-e Khwarazmshahi (The Treasure of the Khwarazm Shah) was written in approximately AD 1112 and is considered to be the oldest medical encyclopedia written in Persian. This was an essential textbook for those studying medicine during this time. We describe the life and times of Jorjani and provide a translation and interpretations of his detailed descriptions of the cranial nerves, which were written almost a millennium ago. Medieval Persian and Muslim scholars have contributed to our current knowledge of the cranial nerves. Some of these descriptions, such as the eloquent ones provided by Jorjani, were original and have gone mostly unknown to post-Vesalian European scholars.

Anatomy and potential clinical significance of the vastoadductor membrane.

Few reports are found in the extant medical literature regarding the vastoadductor membrane. This membrane effectively creates a subcompartment within the subsartorial canal. The lower limbs of 16 embalmed adult cadavers were dissected to identify the vastoadductor membrane and note its measurements. A vastoadductor membrane was identified in all specimens and was derived from the medial intermuscular septum. This membrane connected the medial edge of the vastus medialis muscle to the lateral edge of the adductor magnus muscle. Membranes were all wider proximally and narrowed distally. The mean length of this structure was 7.6 cm. The mean width of the vastoadductor membrane at its proximal, midportion, and distal parts was 2.2, 1.7, and 0.5 cm, respectively. The mean distance from the anterior superior iliac spine to the proximal border of the vastoadductor membrane was 28 cm. The mean distance from the distal border of the membrane to the adductor tubercle was 10 cm. Seventy-five percent of specimens exhibited a fenestrated vastoadductor membrane. Branches of the saphenous nerve to the skin of the medial thigh pierced the vastoadductor membrane in 31% of specimens. Two specimens demonstrated branches derived from the branch of the obturator nerve that pierced this membrane en route to the skin of the medial thigh. Perforating venous branches from the great saphenous vein were identified in 22% of specimens. As compression of the femoral artery at the adductor hiatus is a well-recognized entity, the clinician may also try to explore potential compression of this vessel more proximally by an overlying vastoadductor membrane. The authors would also hypothesize that due to the interconnection between the adductor magnus and vastus medialis by the vastoadductor membrane that a potential synergy exists between the functions of these two muscles.

Anatomy of the falcine venous plexus.

OBJECT: The superior and inferior sagittal sinuses have been well studied. Interestingly, other venous structures within the falx cerebri have received scant attention in the medical literature. The present study was performed to elucidate the presence and anatomy of these midline structures. METHODS: The authors examined 27 adult latex- or ink-injected cadaveric specimens to observe the morphological features of the sinuses within the falx cerebri (excluding the inferior and superior sagittal sinuses). RESULTS: All specimens were found to have an extensive network of small tributaries within the falx cerebri that were primarily concentrated in its posterior one third. In this posterior segment, these structures were usually more pronounced in the inferior two thirds. The portion of the falx cerebri not containing significant falcine venous sinus was termed a "safe area." These vascular channels ranged in size from 0.5 mm to 1.1 cm (mean 0.6 mm); 100% of these vessels communicated with the inferior sagittal sinus. Classification of the structures was then performed based on communication of the falcine venous sinus with the superior sagittal sinus. Type I falcine sinuses had no communication with the superior sagittal sinus, Type II falcine sinuses had limited communication with the superior sagittal sinus, and Type III falcine sinuses had significant communication with the superior sagittal sinus. Seventeen (63%) of 27 specimens communicated with the superior sagittal sinus (Types II and III). Further subdivision revealed 10 Type I, seven Type II, and 10 Type III falcine venous plexuses. CONCLUSIONS: There are other venous sinuses in the falx cerebri in addition to the superior and inferior sagittal sinuses. Neurosurgical procedures that necessitate incising or puncturing the falx cerebri can be done more safely via a described safe area. Given that the majority of specimens in the authors' study were found to have a plexiform venous morphology within the falx cerebri, they propose that these channels be referred to as the falcine venous plexus and not sinus. The falcine venous plexus should be taken into consideration by the neurosurgeon.

Surgical anatomy and landmarks for the basal vein of rosenthal.

OBJECT: The basal vein of Rosenthal (BV) courses from the premesencephalic cistern, through the ambient cistern, and terminates in the quadrigeminal cistern. The aim of this study was to describe and quantitate the surgical anatomy of this structure and specifically to provide landmarks for identifying this vessel along its course. These data may be of use, for example, to surgeons using subtemporal operative approaches through regions where this vessel is concealed. METHODS: The authors examined 15 latex-injected adult cadaveric brains (30 sides) to delineate the morphological characteristics of the BV. Dissections of the BV were then performed and measurements were made between this structure and the tentorial incisura at the anterior, middle, and posterior borders of the lateral midbrain. All specimens were found to have a left and right BV with varying morphological characteristics. The mean distance between the BV and posterior cerebral artery at the midpoint of the lateral midbrain was 16 mm. The BV was always found superomedial to the posterior cerebral artery along the lateral aspect of the midbrain, and the BV ranged in diameter from 1 to 5 mm. The BV drained into the vein of Galen in all but two specimens. The mean distances from the tentorial edge to the BV at the anterior, middle, and posterior borders of the lateral midbrain were 11, 1 3, and 4 mm, respectively. No statistically significant differences were found when comparing left and right sides or male and female specimens. CONCLUSIONS: The authors hope that these data will help the neurosurgeon operating near the BV to avoid injury to this important structure.

The basilar venous plexus.

The basilar venous plexus is the anteromedian venous channel of the posterior cranial fossa that has many conflicting and brief descriptions in the extant literature. To our knowledge, no single study has been performed that analyzed this venous structure in detail. The aim of the current study was to elucidate further the anatomy of this structure of the posterior cranial fossa. The authors examined twenty adult cadaveric specimens following injection of the internal jugular veins or cavernous sinus to observe the morphology of the basilar plexus. All specimens were found to have a basilar plexus which was always plexiform and very variable in nature. This structure was dorsal to the clivus superiorly and dorsal clivus and overlying tectorial membrane inferiorly. The mean diameter of the channels making up this plexus was 1.1 mm. Communication was always found between the basilar plexus and the inferior petrosal sinuses and this was the primary route used to drain the basilar sinus out of the cranium. In fact, these two venous structures were more or less contiguous across the midline at multiple levels. In seven specimens (35%), the basilar plexus communicated with veins draining into the hypoglossal canal. The basilar plexus communicated with the marginal sinus in 12 specimens (60%). This plexus became much less concentrated as it descended inferior to a plane between the jugular tubercles. No specimen was found to have connections with veins of the anterior brain stem or ventral surface of the clivus. The basilar plexus is a highly variable posterior fossa venous structure. Clinicians and radiologists should take into account this variability when managing cerebral venous disorders or interpreting imaging studies of the skull base.

Cisterna chyli: a detailed anatomic investigation.

With recent laparoscopic advancements in retroperitoneal and thoracic surgical procedures, familiarity with major lymphatic structures, such as including the cisterna chyli (CC) and thoracic duct (TD), has proven beneficial in avoiding misdiagnosis and iatrogenic intraoperative injury. In this light, the aim of our study was to explore and delineate the topography of the CC, classify the different patterns of lymphatic tributaries, and categorize its varying location with respect to the vertebral bodies. The anatomy of the CC was examined in 120 adult human cadavers. The CC was found in 83.3% of the specimens and both the tributaries of the CC and the location, with respect to vertebral level, demonstrated wide variation. The results were classified into four types. The most common tributary configuration (type I), found in 45% specimens, was a single CC formed by the union of the left lumbar trunk (LT) and the intestinal trunk (IT). In 30% the CC was formed where the IT opened into the TD and the right lumbar trunk (RT), LT, retroaortic nodes (RN) and branches from the intercostal lymphatics (IL) joined variably (type II). In 20% the CC was formed by the junction of the RT and IT (type III), while in 5% there was a variable confluence pattern of lymphatic trunks that could not be classified (type IV). The CC was located at L1-L2 (type A) in 63%, T12-L1 (type B) in 21%, T11-T12 (type C) in 8%, T10-11 (type D) in 5%, and T9-10 (Type E) in 3%, of the specimens. The CC was found in the retrocrural space and, in 75% of the cases, to the right of the abdominal aorta. We hope that the data supplied by this study will provide useful information in the future to anatomists, radiologists and surgeons alike.

Clinical anatomy of the C1 dorsal root, ganglion, and ramus: a review and anatomical study.

Discrepancies abound in the literature regarding the anatomy and incidence of the C1 dorsal roots, ganglia, and rami. The present study was performed to elucidate further the detailed anatomy of these structures and to review their clinical relevance. Thirty-adult cadavers were used for this study. The mean age for this group was 72 years. C1 and C2 spinal nerves were identified in 100% of the specimens examined. In 46.6% of specimens, C1 dorsal rootlets were identified and of these, 28.5% had an associated dorsal root ganglion. In 50% of specimens, the spinal accessory nerve joined with dorsal rootlets of C1. C1 in these cases did not possess a dorsal root ganglion. There were no significant differences between left sides, gender, and age (P > 0.05). Additional knowledge regarding the C1 dorsal roots, ganglia, and rami may be of use to the clinician who treats various pain syndromes including medically and surgically intractable occipital neuralgia.

Gimbernat y Arbós, Antonio de (1734-1816).

Don Manuel Louise Antonio de Gimbernat y Arbós, Spanish anatomist and surgeon, was one of the pioneers during the "age of dissection" (late eighteenth century). A bright young mind, Gimbernat was confident and audacious, which allowed him to become a recognized surgeon with a famed reputation that influenced his colleagues internationally. The Spaniard was most widely recognized for his advancements in the treatment of strangulated femoral hernias, and the lacunar ligament was named "Gimbernat's ligament" in his honor. In 1793, he published Nuevo Método de operar en la Hernia Crural dedicated to King Charles IV, which was translated into English by Thomas Beddoes 2 years later. Gimbernat's daring procedures helped improve safety and efficiency of hernia surgery. A person of great determination, he was known as a brilliant, meticulous, and creative man who exemplified the importance of surgeons. His devoted study of anatomy, especially of inguinal anatomy, allowed him to devise a legendary surgical technique in repairing femoral hernias, influencing renowned surgeons of his time and thereafter.

The lateral atlantooccipital ligament.

INTRODUCTION: Stability of the atlantooccipital joint is of vital importance. The ligaments of this region, for the most part, have been thoroughly investigated, except for the lateral atlantooccipital ligament (LAO), which is not described in most modern texts. MATERIALS AND METHODS: The authors examined 20 adult cadaveric specimens to observe the morphology of the LAO. RESULTS: All specimens were found to have an LAO, bilaterally, immediately posterior to the rectus capitis lateralis muscle with a fiber direction more or less opposite to this muscle. The LAO was found in intimate contact with the vertebral artery posteriorly and with the contents of the jugular foramen anteriorly. In all specimens, the origin of this ligament was from the anterolateral aspect of the transverse process of the atlas and the insertion onto the jugular process of the occipital bone. The fibers of the LAO had a mean angle of 26 degrees from the midline. The mean length and width of this ligament was 2.2 and 0.5 cm, respectively. The mean thickness of the LAO was 2 mm. The average tensile strength of this band was 37.5 degrees N. The LAO remained lax with flexion and extension of the craniocervical junction. With contralateral lateral flexion of the craniocervical junction, the LAO became fully taut at a mean of 8 degrees . Partial, but never complete, tautness was observed with rotation of the occipital on the atlas bilaterally. Following sectioning of the LAO, approximately an additional 3 degrees -5 degrees of contralateral lateral flexion was observed. CONCLUSIONS: The LAO is a constant anatomical structure of the craniocervical junction that might be of concern to the clinician. This ligament inhibits lateral flexion of the atlantooccipital joint and its disruption appears to add to instability at this articulation.

The vertebral nerve revisited.

There is significant paucity in the literature regarding the vertebral nerve. Moreover, descriptions of this structure are conflicting. To evaluate further the anatomy and potential clinical significance of this structure, 10 fresh adult cadavers (20 sides) underwent dissection and macroscopic observation of this structure. All specimens were found to have a vertebral nerve that originated from the stellate ganglion with the exception of two left sides (10%) in which this nerve arose from the inferior cervical ganglion. This nerve ascended posteromedial to the vertebral artery. The vertebral nerve was found to be, in essence, a long and deep gray ramus communicans that connected most commonly the stellate ganglia to C6 or C7 spinal nerves by passing through the C6 and C7 transverse foramina. Fifteen percent of sides were found to have a vertebral nerve that was plexiform in its configuration. Fifty percent were found to have very small branches that entered the fibrous capsule of adjacent zygapophyseal and intervertebral joints. Some specimens were noted to have meningeal branches of the vertebral nerve. Based on our observations, the vertebral nerve is simply a deep ramus communicans, which often provides articular and meningeal branches to the adjacent spine. As neck pain is a significant reason for physician office visits, additional knowledge of the nerves innervating the joints and adjacent meninges of the neck could be important for both surgical and medical blockade of nerve fibers.

The sphenoparietal sinus.

OBJECTIVE: There is minimal detailed information regarding the sphenoparietal venous sinus found in the extant medical literature. Furthermore, there is controversy in the literature regarding drainage of the Sylvian vein into this sinus. The sphenoparietal sinus can potentially be encountered with cranial base approaches near the lesser wing of the sphenoid bone and may be found as one surgically traverses the superior orbital fissure. METHODS: To further elucidate the anatomy of this structure, we injected this intracranial venous sinus with blue latex in 15 adult cadavers (30 sides) via cannulation of the cavernous sinus near the posterior part of the oculomotor trigone. Observations and measurements of this and nearby structures were then made. RESULTS: A left and right sphenoparietal sinus were found in all specimens and had a mean diameter of 2.5 mm for left sides and 3 mm for right sides. No statistical difference was noted between sides or sexes (P > 0.05). This structure generally began at the lateral tip of the lesser wing of the sphenoid bone and ended in the cavernous sinus near the passage of the ophthalmic nerve. In seven left sides and eight right sides, no discernible connection with the middle meningeal veins was noted. This sinus was found to have a connection with the Sylvian vein in all but one side. One sinus did not drain into the cavernous sinus but rather into the veins of the foramen rotundum. Ten specimens were noted to have previously undocumented temporal veins from the anterior temporal tip that drained into the sphenoparietal sinus. CONCLUSION: We think that these data will aid the clinician in the diagnosis of the pathology of this region and decrease morbidity that may follow manipulation of this venous sinus.

Branches of the petrous and cavernous segments of the internal carotid artery.

Microsurgical approaches to the skull base require a thorough knowledge of the microvasculature of this region. Interestingly, most standard texts of anatomy do not mention the branches of the internal carotid artery as it travels through the temporal bone and cavernous sinus. Although small and with often conflicting descriptions, these arterial branches may be of significance when contributing to the vascular supply of such pathological entities as meningiomas and vascular malformations. Furthermore, multiple anastomoses exist between these branches and branches of the external carotid artery, thus providing a potentially important collateral circulation between these two systems and thus retrograde flow needed to maintain the patency of the distal internal carotid artery (ICA) when this vessel is obstructed proximally. We review the literature regarding these branches of the internal carotid artery and their clinical significance.

Superficial temporal artery as an external landmark for deeper-lying brain structures.

Additional localizing superficial landmarks for intracranial structures can be of use to the neurosurgeon. This study was performed to evaluate the usefulness of the superficial temporal artery (STA) as an external landmark for deeper brain structures. Thirteen adult cadavers (26 sides) underwent latex injection of their STA bilaterally. Dissections were next carried out to identify this vessel. Once the STA and its frontal and parietal branches were skeletonized, craniectomies were performed and the underlying dura mater excised. Measurements were made between the frontal and parietal branches of the STA and deeper brain structures. The STA was found to branch on average 3 cm superior to the tragus. The bifurcation of the STA was found to commonly bifurcate at the level of the floor of the middle cranial fossa or superior temporal gyrus. The Sylvian fissure was found at a mean of 2 cm superior to the STA bifurcation. The angle between the frontal branch of the STA and the zygomatic arch had a mean of 37 degrees. The angle between the frontal and parietal branches of the STA had a mean of 87 degrees. At the level of the glabella, the frontal branch of the STA was on average 3 cm posterior to the frontal pole. The temporal tip was located a mean of 3.2 cm anterior to the frontal branch of the STA. The plane of the foramen of Monro was found to lie at a mean distance of 2.3 cm posterior to the frontal branch of the STA. The parietal branch of the STA was noted to travel more or less parallel with the central sulcus in all specimens and to travel an average of 2 cm posterior to this sulcus. At the level of the lateral attachment of the tentorium cerebelli, the parietal branch of the STA was found to travel a mean of 4.8 cm anterior to the entrance of the vein of Labbé into the transverse sinus. The parietal branch of the STA was also found to travel a mean of 4.2 cm anterior to the angular gyrus and 3.9 cm anterior to the supramarginal gyrus. Palpation or Doppler identification of the STA and its branches with subsequent mapping on the lateral cranium may prove useful as an additional superficial landmark for the neurosurgeon.

The tectorial membrane: anatomical, biomechanical, and histological analysis.

There is minimal information in the literature regarding the tectorial membrane. Further, information in the literature regarding the anatomy and function of this structure is often contradictory. We performed the current study to elucidate further this structure's detailed anatomy, function, and histology. Thirteen adult cadavers underwent dissection of their tectorial membranes and detailed observations and measurements were made of them. Ranges of motion of the craniocervical junction were performed before and after transection of this structure. Histological analysis was performed on all membranes. The tectorial membrane was found to attach much more superiorly than previously described and was found to be firmly adherent to the cranial base and body of the axis but not to the posterior aspect of the odontoid process. The mean thickness of this membrane was found to be 1 mm. Flexion of the head made the tectorial membrane fully taut at 15 degrees and extension made it fully taut at 20 degrees; however, there was a buckling effect (redundant tectorial membrane) noted at the level of the odontoid process in extension. With the alar and transverse ligaments cut and with flexion of the head, the middle portion of this membrane was stretched over the odontoid process, thus acting as a "hammock" that inhibited the odontoid process from moving posteriorly. The tectorial membrane did not limit cervical flexion per se but rather helped to insure that the odontoid process did not impinge into the cervical canal. Lateral flexion was not found to be limited by this structure. Histologically, parallel collagen fibers with spindle-shaped fibrocytes were observed within this membrane and near its attachment to the posterior axis, the collagen fibers were noted to be more homogenous with larger non-spindled fibrocytes. At the cranial attachment of the tectorial membrane, multiple calcified areas were noted that interdigitated with the underlying bone. Also near this cephalic bony attachment, there was an increase in the number of elastic fibers, which were found running parallel with the surrounding Type III collagen fibers. The tectorial membrane was found to attach much more superiorly than previously described. We would propose that the tectorial membrane provides for a second line of defense, preventing the odontoid process from compressing the spinal cord and by doing so, secondarily limits movement of the craniocervical juncture. This hypothesis is strengthened by the finding of many elastic fibers in the tectorial membrane. To our knowledge, our study is the first to perform a detailed histological analysis of the tectorial membrane. We hope that these data are useful to the clinician who investigates this ligament of the craniocervical region.

Cadaveric findings of persistent fetal trigeminal arteries.

Persistence of fetal intracranial arteries is rare. We review this anatomical literature regarding the persistence of the trigeminal artery and discuss the findings in two cadaveric cases both found to harbor this vessel. This anomaly should be considered by the clinician and anatomist who view imaging of the skull base. Additionally, the relationships between such an artery and other structures within the cavernous sinus should be understood by the neurosurgeon who operates in this region, e.g., transsphenoidal approaches to the skull base.