The Abducens Nerve: Anatomy and Pathology.

The abducens, or the sixth cranial nerve, is purely motor and runs a long course from the brainstem to the lateral rectus. Travels with the inferior petrosal sinus through the Dorello's canal before entering the cavernous sinus. Based on the location of an abnormality, other neurologic structures may be involved with the disturbs related to this nerve. This article aims to review the abducens nerve anatomy and demonstrates the imaging aspect of the diseases that most commonly affect it.

Multiple cranial neuropathy: Clinical findings in a case series of 142 patients.

INTRODUCTION: Multiple cranial neuropathies (MCN) is an entity frequently seen in clinical practice but there is a lack of studies published about this entity, with most of them based on case reports and small case series. OBJECTIVE: The aim of this study is to describe the clinical involvement of different cranial nerves, the location within the central or peripheral nervous system and the diagnosis in a group of patients with MCN managed in one hospital in Bogotá-Colombia. METHODOLOGY: A case series study was conducted using the electronic clinical records of a teaching hospital in Bogota-Colombia. Clinical data were collected from patients aged ≥18 with a clinical diagnosis of MCN between 2015 and July 2021. RESULTS: The cranial nerves most commonly affected were III and VII, with the most prevalent combinations being III-IV, III-VI, and V-VII. Among etiologies, the most frequently found were autoimmune, vascular and neoplastic and most common locations included peripheral nerves, neuromuscular junction, cavernous sinus and lateral medulla. CONCLUSIONS: The differential diagnosis of MCN is broad, but clinical clues may aid in identifying the underlying etiology. According to our results, MG was the most frequent etiology, so it should be considered in any patient with a clinical diagnosis of MCN associated with fatigability.

Trochlear cistern of the cavernous sinus: an anatomical study using magnetic resonance imaging.

PURPOSE: The present study aimed to explore the trochlear cistern (TC) of the cavernous sinus using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, a total of 73 patients underwent the constructive interference steady-state (CISS) sequence in thin-sliced coronal sections. Moreover, three injected cadaver heads were dissected. RESULTS: In the cadaver specimens, the extent of the TC was difficult to identify on any dissected side. On the CISS images, the TC was identified in 98.6% on the right side and 94.5% on the left, while transmitting the trochlear nerve (TN) was identified in 83.6% on the right and 79.5% on the left. Most TNs were delineated as a single trunk, while duplication of the nerve was found in 3% of cases. The TC, commonly located inferior or inferolateral aspect of the oculomotor trigone. The size and extent of TC were highly variable. The TN location in the TC was also variable and was identified throughout the upper, middle, and lower parts of the TC. Moreover, relationships between the TC and Meckel's cave were highly variable. CONCLUSIONS: TC shows morphological variability. The coronal CISS sequence is useful for exploring TC and TN in clinical practices.

Cavernous sinus and abducens nerve in human fetuses near term.

A long tortuous course of the abducens nerve (ABN) crossing a highly curved siphon of the internal carotid artery is of interest to neurosurgeons for cavernous sinus surgery. Although a "straight" intracavernous carotid artery in fetuses can change into an adult-like siphon in infants, there is no information on when or how the unique course of ABN is established. Histological observations of 18 near-term fetuses (12 specimens of frontal sections and 6 specimens of sagittal sections) demonstrated the following: (I) the ABN consistently took a straight course crossing the lateral side of an almost straight intracavernous carotid artery; (II) the straight course was maintained when sympathetic nerves joined; (III) few parasellar veins of the developing cavernous sinus separated the ABN from the ophthalmic nerve; and (IV) immediately before the developing tendinous annulus for a common origin of extraocular recti, the ABN bent laterally to avoid a passage of the thick oculomotor nerve. Since the present observations strongly suggested morphologies at birth and in infants, major angulations of the ABN as well as the well-known course independent of the other nerves in the cavernous sinus seemed to be established during childhood. In the human body, the ABN might be a limited example showing a drastic postnatal change in course. Consequently, it might be important to know the unique course of ABN before performing endovascular interventions and skull base surgery for petroclival and cavernous sinus lesions without causing inadvertent neurovascular injuries to neonates or infants.

[Optic neuropathy from connected intra- and extraorbital lesions in IgG4-related disease].

We present the case of a 74-year-old woman complaining of blurred vision in the left eye who was found to have a unilateral, continuous lesion of the optic nerve and nerve sheath accompanied by an intracranial mass next to the cavernous sinus and meninges. Surgical decompression of the left optic nerve in the optic canal and partial resection of the mass followed by prednisolone administration were successful. Immunohistochemical analysis disclosed abundant infiltration of IgG4-positive plasma cells at >10 cells/high power field. These findings indicated a new pattern of compressive optic neuropathy with confirmed IgG4 histopathological findings. Such an extensive lesion may produce visual disturbance.

Cavernous Nerve Stimulation and Recording of Intracavernous Pressure in a Rat.

The stimulation of the cavernous nerve (CN) and measurement of intracavernous pressure (ICP) have been used extensively to test and evaluate therapies for erectile dysfunction. However, the methods used vary between laboratories, and pitfalls still exist. The goal of this study was to describe a surgical technique that would provide a reliable and reproducible model. By exposing the ischiocavernosus muscle at its point of insertion on the ischial tuberosity, the penile crus could be cannulated with minimal dissection and injury to the structures involved in erectile function. Repeated stimulation of the CN, without the need for lifting and drying, was achieved by using a 125 µm bipolar silver electrode and biocompatible silicon glue to isolate the electrode-nerve complex. This method prevents neuropraxia by reducing stretching and drying the nerve and provides complete isolation of the nerve, negating electrical leakage and preventing stimulation of alternative pathways.

Adipose tissue-derived stem cell therapy for prevention and treatment of erectile dysfunction in a rat model of Peyronie's disease.

Peyronie's disease (PD) is a localized connective tissue disorder that involves the tunica albuginea (TA) of the penis. While surgical correction remains the gold standard, the search for an effective and less invasive therapy continues. The objective of this study was to evaluate the effects of intratunical injection of adipose tissue-derived stem cells (ADSCs) for the prevention and treatment of erectile dysfunction in a rat model of PD. Twenty-four male Sprague-Dawley rats (300-350 g) were randomly divided into four groups: sham, PD, PD + ADSC (prevention) and PD + ADSC (treatment). All rats underwent penile injections into the TA with 50 µL vehicle (sham) or 0.5 µg transforming growth factor (TGF)-ß1 (remaining groups). The ADSC groups received intratunical injections with 0.5 million rat-labelled ADSCs on day 0 (prevention) or day 30 (treatment). Forty-five days following TGF-ß1 injection, rats underwent cavernous nerve stimulation (CNS) with total intracavernous-to-mean arterial pressure ratio (ICP/MAP) and total ICP recorded to measure response to therapy. Tissues were evaluated histologically and for mRNA expression of tissue inhibitors of metalloproteinases (TIMPs), matrix metalloproteinases (MMPs) and zymographic activity of MMPs. Statistical analysis was performed by analysis of variance followed by the Tukey test for post hoc comparisons. In both prevention and treatment groups, intratunical injection of ADSCs resulted in significantly higher ICP/MAP and total ICP in response to CNS compared with the PD group. Local injection of ADSCs prevented and/or reduced Peyronie's-like changes by decreasing the expression of TIMPs, and stimulating expression and activity of MMPs. This study documents the preventive and therapeutic benefits of ADSC on penile fibrosis and erectile function in an animal model of PD.

Location of the abducent nerve within the cavernous sinus.

AIM: Knowing the distance between the superior and inferior border of Parkinson's triangle and the location of the abducent nerve within the cavernous sinus is important to decrease the complications which may occur during surgery. We aimed to investigate the cavernous sinus to decrease the complications that may occur during surgery to this area. MATERIAL AND METHODS: Fifty MRIs without pituitary gland abnormality were chosen for radiological assessment of CS. These images were from 18 males and 32 females, with ages ranging from 9 to 58 years and a median age of 28 years. We evaluated structures within and on the lateral wall of the cavernous sinus (especially Parkinson's triangle) with magnetic resonance imaging. The position of the abducent nerve and its level according to the cranial nerves running close the lateral wall were examined. RESULTS: At the level of pituitary stalk, the distance between the trochlear nerve and the ophthalmic nerve ranged from 1 to 4 mm bilaterally. The abducent nerve was located between the trochlear and the ophthalmic nerves in 30% cases bilaterally. CONCLUSION: The knowledge of the position of the abducent nerve will provide a great benefit in minimizing the rate of complications that may occur during the resection of tumors of the cavernous sinus.

[Depiction of the cranial nerves around the cavernous sinus by 3D reversed FISP with diffusion weighted imaging (3D PSIF-DWI)].

To evaluate the anatomy of cranial nerves running in and around the cavernous sinus, we employed three-dimensional reversed fast imaging with steady-state precession (FISP) with diffusion weighted imaging (3D PSIF-DWI) on 3-T magnetic resonance (MR) system. After determining the proper parameters to obtain sufficient resolution of 3D PSIF-DWI, we collected imaging data of 20-side cavernous regions in 10 normal subjects. 3D PSIF-DWI provided high contrast between the cranial nerves and other soft tissues, fluid, and blood in all subjects. We also created volume-rendered images of 3D PSIF-DWI and anatomically evaluated the reliability of visualizing optic, oculomotor, trochlear, trigeminal, and abducens nerves on 3D PSIF-DWI. All 20 sets of cranial nerves were visualized and 12 trochlear nerves and 6 abducens nerves were partially identified. We also presented preliminary clinical experiences in two cases with pituitary adenomas. The anatomical relationship between the tumor and cranial nerves running in and around the cavernous sinus could be three-dimensionally comprehended by 3D PSIF-DWI and the volume-rendered images. In conclusion, 3D PSIF-DWI has great potential to provide high resolution "cranial nerve imaging", which visualizes the whole length of the cranial nerves including the parts in the blood flow as in the cavernous sinus region.

Do dental infections really cause central nervous system infections?

In the post-World War I antibiotic era, the prevalence of central nervous system (CNS) infections is estimated to be 1 per 100,000 population. The literature is replete with anecdotal case reports of CNS infections of apparent dental etiology. Conversely, it is widely cited that the incidence of CNS infection of dental etiology is only in the range of 1% to 2%. We seek to answer the question if dental infections really cause CNS infections. In this article, we focus on septic cavernous sinus thrombosis and brain abscess and if it is a diagnosis of exclusion or evidence-based.

Continuous-wave infrared optical nerve stimulation for potential diagnostic applications.

Optical nerve stimulation using infrared laser radiation has recently been developed as a potential alternative to electrical nerve stimulation. However, recent studies have focused primarily on pulsed delivery of the laser radiation and at relatively low pulse rates. The objective of this study is to demonstrate faster optical stimulation of the prostate cavernous nerves using continuous-wave (cw) infrared laser radiation for potential diagnostic applications. A thulium fiber laser (λ=1870 nm) is used for noncontact optical stimulation of the rat prostate cavernous nerves in vivo. Optical nerve stimulation, as measured by an intracavernous pressure (ICP) response in the penis, is achieved with the laser operating in either cw mode, or with a 5-ms pulse duration at 10, 20, 30, 40, 50, and 100 Hz. Successful optical stimulation is observed to be primarily dependent on a threshold nerve temperature (42 to 45 °C), rather than an incident fluence, as previously reported. cw optical nerve stimulation provides a significantly faster ICP response time using a lower power (and also less expensive) laser than pulsed stimulation. cw optical nerve stimulation may therefore represent an alternative mode of stimulation for intraoperative diagnostic applications where a rapid response is critical, such as identification of the cavernous nerves during prostate cancer surgery.

Added value of contrast-enhanced CISS imaging in relation to conventional MR images for the evaluation of intracavernous cranial nerve lesions.

INTRODUCTION: The normal cranial nerves (CNs) of the cavernous sinus can be clearly demonstrated using contrast-enhanced constructive interference in steady-state (CISS) magnetic resonance imaging (MRI). This study used the method to evaluate pathological CNs III, IV, V(1), V(2), and VI in cavernous sinuses affected by inflammatory and neoplastic diseases. METHODS: MR images from 17 patients with diseases involving the cavernous sinuses and/or causing neuropathy in CNs III-VI were retrospectively evaluated. The patients were divided into inflammatory (n=11) and neoplastic (n=6) groups. We defined CNs as abnormal when they exhibited enlargement or enhancement. CNs were evaluated using both contrast-enhanced CISS and T1-weighted MRI. RESULTS: In the inflammatory group, abnormal CNs were identified by contrast-enhanced CISS MRI in 13 of 25 symptomatic CNs (52%) in eight patients, but in only two CNs (8%) in two patients by contrast-enhanced T1-weighted MRI. In the neoplastic group, both sequences of contrast-enhanced CISS and T1-weighted MRI detected abnormalities in the same three of eight symptomatic CNs (37.5%), i.e., the three CNs were all in the same patient with adenoid cystic carcinoma. CONCLUSION: Contrast-enhanced CISS MRI is useful for detecting CN abnormalities in inflammatory pathological conditions of the cavernous sinuses.

[Selected problems from the descriptive and surgical anatomy of the cavernous sinus]. / Wybrane zagadnienia z zakresu anatomii opisowej i chirurgicznej zatoki jamistej.

The paper contains anatomical information concerning the cavernous sinus (CS) and the structures related to it topographically and constituting its direct surroundings. This information is a starting point for surgical interference in the CS, as well as a background for analyzing the clinical problems of CS disorders and the results of their surgical treatment. After considering developmental conditioning, the structure of three walls of the cavernous sinus was discussed: the medial, superior and lateral one. This enabled a precise topography of the cranial nerves connected with the CS to be created. The author sets forth information on the role of the CS as one of the main venous passages within the cranial cavity. The article describes the segments of the internal carotid artery which are connected with the CS. Moreover, it discusses the intracavernous branches of the artery and the range of their vascularisation. The paper ends with an analysis of the possible ways of surgical interference in CS, known as 'CS triangles'.

[Lateral approach to the cavernous sinus and its surroundings--analysis of surgical technique based on cadaver simulations]. / Dostep boczny do zatoki jamistej i jej otoczenia--analiza techniki operacyjnej w oparciu o symulacje na zwlokach.

BACKGROUND AND PURPOSE: The paper aims to present individual stages of a surgical approach to the cavernous sinus (CS) and its surroundings. MATERIAL AND METHODS: Twelve simulations of a surgical approach to the CS and its surroundings were performed in non-fixed cadavers. The subsequent stages of simulation were recorded in photographs and drawings. RESULTS: The starting point for the approach to the CS is a pterional craniotomy, as well as an osteotomy encompassing the anterior clinoid process and the surroundings of the superior orbital fissure, the optic canal, the foramen rotundum and the foramen ovale. The important phases of the approach include the delamination of the lateral CS wall and the mobilization of the dural rings of the internal carotid artery. Opening of the CS should be preceded with establishing proximal and distal control over the internal carotid artery. CONCLUSIONS: The surgical approach to the CS and its surroundings constitutes a repeatable method of penetration in this area of the cranial base, and it allows for limiting brain traction and preserving the anatomical integrity of the related vessel and nerve structures.

The antero-medial triangle: the risk for cranial nerves ischemia at the cavernous sinus lateral wall. Anatomic cadaveric study.

OBJECTIVE: Vascular damage in the cavernous sinus can cause ischemic injury to the cranial nerves. An appropriate anatomical knowledge of the blood supply to the cranial nerves can help to reduce the morbidity associated with cavernous sinus surgery. MATERIAL AND METHODS: Three formalin-fixed and six adult cadaveric fresh heads, with common carotid arteries injected, were used for anatomical dissection in this study. A fronto-temporal craniotomy was performed and the cavernous sinus was explored according to the Dolenc technique. With microsurgical dissection and photographic documentation, we demonstrate the anatomy of the superior orbital fissure artery in the antero-medial triangle. RESULTS: The 12 explored cavernous sinuses demonstrated the presence of two principal branches directly from the intracavernous internal carotid artery that supply the cranial nerves: the infero-lateral trunk and the meningohypophyseal trunk. The artery of the Superior Orbital Fissure (SOF), originated more often from the infero-lateral trunk, and vascularized the III, IV, VI, and VI, and ophtalmic division of the trigeminal nerve (TGN VI) at their entry in the fissure. CONCLUSION: In this study we demonstrate that the superior orbital fissure artery is a branch from the infero-lateral trunk which runs immediately under the reticularis layer at the level of the anteromedial triangle in the lateral wall of the cavernous sinus. The blood supply to all cranial nerves in the SOF is at risk to injury when the lateral wall of the cavernous sinus is transgressed at the anteromedial triangle since the SOF-artery runs superficially at this level.

Lesions and pseudolesions of the cavernous sinus and petrous apex.

Endoscopic surgery using an expanded endonasal approach now allows surgical access to an increasing range of parasellar, suprasellar, clivus, and petrous apex lesions. Accurate preoperative planning requires proper interpretation of CT and MRI results. It is essential to identify important anatomic landmarks and to recognize the appearance of common lesions and pseudolesions. Postoperative imaging must evaluate for residual tumors and identify iatrogenic conditions.

Preoperative depiction of cavernous sinus invasion by pituitary macroadenoma using three-dimensional anisotropy contrast periodically rotated overlapping parallel lines with enhanced reconstruction imaging on a 3-tesla system.

OBJECTIVES: Three-dimensional anisotropy contrast (3DAC) magnetic resonance (MR) imaging provides clear depiction of neuronal fibers. The aim of this study was to identify intracavernous cranial nerves in patients with pituitary macro-adenoma and in healthy volunteers by using 3DAC MR imaging on a 3-tesla system and to preoperatively predict cavernous sinus invasion by pituitary macroadenoma. METHODS: Thirty-three patients (cavernous sinuses in 66 sides) with pituitary macroadenomas and 25 healthy volunteers (50 sides) participated in this study. Coronal 3DAC MR images constructed from diffusion weighted images, acquired with periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) sequences, and T2-weighted reverse images were obtained at the same anatomical locations using a 3-tesla MR imaging system. Attempts were made to identify the cranial nerves. RESULTS: The oculomotor and ophthalmic/maxillary nerves were preoperatively identified in all sides (66 sides in patients and 50 sides in healthy volunteers) on 3DAC MR images. In the 33 patients, cavernous sinus invasion was revealed in 10 (12 [18.2%] of 66 sides) by intraoperative endoscopic observation. Coronal 3DAC MR images revealed that the oculomotor nerves were half surrounded with adenoma in all 12 of these sides, and the ophthalmic/maxillary nerves were half encapsulated with tumor (sensitivity/specificity: 100%/100% and 83%/100%, respectively). CONCLUSIONS: Preoperative evaluation of pituitary macroadenomas using 3DAC PROPELLER MR imaging on a 3-tesla system is likely to be a powerful noninvasive method of detecting cavernous sinus invasion, which can potentially dominate the therapeutic strategy for these lesions.

Microsurgical anatomy of the superior orbital fissure.

The microanatomy of the superior orbital fissure (SOF) was studied in 96 sides of cadaver specimens. The SOF is a narrow bony cleft that lies at the apex of the orbit between the greater and lesser wings of the sphenoid. Through this fissure, many important structures enter the orbit from the middle cranial fossa including the third, fourth, sixth cranial nerves, and the ophthalmic branch of the fifth nerve. In addition, the superior opthalmamic vein exits the orbit to drain into the cavernous sinus via the SOF. The fissure can be divided into three anatomical regions by the annulus of Zinn (common annular tendon): the lateral, central, and inferior regions. The lateral wall of the SOF can also be divided between the upper and lower segments, and the angle between them was measured to be 144.27 degrees +/- 20.03 degrees . Defining these regions is useful in describing the course and placement of the nerves and vasculature in the SOF. Managing lesions at the orbital apex requires an extensive knowledge of the cranial base and the intracranial and extracranial relationships of the anatomical structures coursing through the SOF. The goal of this study was to describe the microanatomy of the SOF region in detail and to provide a reference for surgical procedures involving the orbital apex.

Normal cranial nerves in the cavernous sinuses: contrast-enhanced three-dimensional constructive interference in the steady state MR imaging.

BACKGROUND AND PURPOSE: Three-dimensional (3D) constructive interference in steady state (CISS) MR imaging is useful for demonstrating cranial nerves (CNs) in the cistern. The purpose of this study was to evaluate normal CNs III, IV, V1, V2, and VI in the cavernous sinuses by using contrast-enhanced, three-dimensional (3D), Fourier transformation CISS MR imaging. METHODS: In 76 normal cavernous sinuses from 38 patients, detectability of CNs III-VI in the bilateral cavernous sinuses was evaluated by using contrast-enhanced 3D CISS MR imaging. In 40 cavernous sinuses from 20 patients, contrast-enhanced 3D CISS and contrast-enhanced T1-weighted MR imaging were compared for the detectability of these CNs. RESULTS: Each CN was separately demonstrated, and in 11 patients (29%), all CNs in the cavernous sinuses were identified on contrast-enhanced 3D CISS MR imaging. The images depicted the intracavernous segments of CNs III, IV, V1, V2, and VI in 76 (100%), 46 (61%), 70 (92%), 67 (88%), and 73 (96%) of the 76 sinuses, respectively. In comparison of imaging techniques, contrast-enhanced 3D CISS MR imaging had a detection rate significantly higher than that of enhanced T1-weighting imaging (P < .05) in all CNs except for CN III, which was detected in 100% of cases with both techniques. CONCLUSION: Contrast-enhanced 3D CISS MR imaging provides clear images of each CN in the cavernous segment. This useful method may contribute to the diagnosis of diseases involving the cavernous sinuses, such as Tolosa-Hunt syndrome.