Chordae Willisii of the dural sinuses: an anatomical study using magnetic resonance imaging.

PURPOSE: The chordae Willisii (CWs), trabecular projections into the lumen of the dural sinuses, are not well understood. We aimed to explore them using magnetic resonance imaging (MRI). METHODS: Eighty-five patients underwent volumetric contrast-enhanced MRI, while another 30 underwent a fluid-attenuated inversion recovery (FLAIR) sequence in the coronal section. RESULTS: The CWs were detected as linear filling defects lying in the dural sinuses, adjacent to the surrounding dura mater. They were found in the superior sagittal sinus (SSS) in 68.2% of the patients, most frequently in the middle third, with laminar appearance. In 27.1% of the patients, the CWs divided the SSS lumen into separate channels. The CWs were identified in the transverse sinus, transverse-sigmoid sinus junctional area and sigmoid sinus, and straight sinus in 54.1, 47.1, and 8.2%, respectively. On the FLAIR images, dural septi partially dividing the SSS lumen were identified in all patients. In addition, in 73.3% of the patients, fine linear structures were observed in the lumen with inconstant arrangements. CONCLUSIONS: The CWs may be constant structures distributed over the lumen of the intracranial dural sinuses. Contrast-enhanced MRI may be useful for detecting laminar CWs. The FLAIR sequence may be advantageous for delineating the dural septi projecting into the lumen of the dural sinuses.

Diameters of the optic sheath and superior ophthalmic vein can expand and contract at positional changes: a magnetic resonance imaging study.

PURPOSE: This study aimed to explore the diameters of the optic sheath (OSD) and superior ophthalmic vein (SOVD) in response to positional changes using magnetic resonance imaging (MRI). MATERIALS AND METHODS: Fifty adult outpatients who presented to the hospital underwent thin-slice coronal T2-weighted MRI in the supine position followed by the prone position. RESULTS: The OS and SOV were well delineated in all the patients. The OSD in the anterior orbit was measured in the supine and prone positions on both sides. In addition, the SOVD in the anterior and posterior orbits was measured in the supine and prone positions on both sides. The OSD demonstrated an increase on both sides in 100% of the cases. The SOVD demonstrated an increase on both sides in 94% of the cases, whereas the remaining 6% demonstrated a decrease. The OSD measured at the anterior orbit and the SOVD at the anterior and posterior orbits significantly increased on both sides with positional changes from the supine to the prone position. CONCLUSION: OSD and SOVD may expand and contract in response to alterations in the intracranial pressure and venous flow patterns. MRI examination in the supine position combined with positional changes can help to better understand the OS and SOV as dynamic structures.

Unusually elongated superior thyroid cornu associated with recurrent cerebral embolisms.

The superior thyroid cornu (STC) is a normal anatomic structure that forms part of the thyroid cartilage. Here, we report a patient with unusually elongated and ossified STC that might result in recurrent cerebral embolisms. During a second endovascular therapy for recurrent middle cerebral artery embolism, a segment with an irregular filling defect was noted in the internal carotid artery (ICA), at the C1 level. This defect was unnoticed during the initial endovascular procedure. Three-dimensional computed tomography angiography performed after the second endovascular procedure revealed an ICA segment located between the STC and C1 with a tortuous course and irregular wall of the ICA. Therefore, we assumed that STC compression of the ICA could have resulted in thrombus formation at the site and consequent cerebral embolism. The STC should be considered a structure responsible for cerebral embolism. Careful evaluation of the entire ICA course is imperative prior to performing an endovascular thrombectomy for acute embolic occlusion of the middle cerebral artery.

[Clinical features of acyclovir encephalopathy without acute kidney injury].

INTRODUCTION: Few reports have described acyclovir (ACV) encephalopathy without acute kidney injury (AKI). OBJECTIVE: This study clarified the clinical features of ACV encephalopathy without AKI compared to that with AKI. METHODS: Creatinine (Cre) levels were measured on admission. After admission, Cre was measured in a timely manner for the first seven hospital days. The minimum Cre level in these measurements was then determined. ACV encephalopathy was defined when two criteria were met: 1) neurological symptoms appeared after valacyclovir (VACV) administration, and 2) neurological symptoms improved after VACV discontinuation. AKI was defined when the Cre level on admission was >1.5 times higher than the minimum Cre level. The subjects were divided into AKI and non-AKI groups based on these findings. RESULTS: Eighteen patients had ACV encephalopathy (5 males, mean age 81.3±5.5 years old). All patients were prescribed VACV 3,000 mg/day. The minimum Cre was 1.93±1.76 mg/dL. AKI occurred in 10 (56.6%) patients. VACV was discontinued in all patients, and emergency hemodialysis treatment was administered in 10 (55.6%) patients. All patients recovered. Compared to the AKI group, the non-AKI group had a lower history of taking a Ca-blocker (33.3% vs 80.0%, p=0.092), a lower rate of emergency dialysis (16.9% vs 70.0%, p=0.059) and a longer time to clinical improvement (3.67±1.86 vs 2.20±0.63 days, p=0.073). CONCLUSION: ACV encephalopathy without AKI is characterized by a low rate of emergency dialysis, which may be linked to a prolonged duration of symptoms.

Phase II clinical trial to study the safety and efficacy of combined S-1 + oxaliplatin therapy as neoadjuvant chemotherapy for locally advanced gastric cancer in older patients.

BACKGROUND: Gastrectomy with D2 dissection and adjuvant chemotherapy is the standard treatment for locally advanced gastric cancer (LAGC) in Asia. However, administering chemotherapy with sufficient intensity after gastrectomy is challenging. Several trials demonstrated the efficacy of neoadjuvant chemotherapy (NAC). However, limited studies explored the feasibility of NAC-SOX for older patients with LAGC. This phase II study (KSCC1801) evaluated the safety and efficacy of NAC-SOX in patients with LAGC aged ≥ 70 years. METHODS: Patients received three cycles of SOX130 (oxaliplatin 130 mg/m2 on day 1, oral S-1 40-60 mg twice daily for two weeks every three weeks) as NAC, followed by gastrectomy with lymph node dissection. The primary endpoint was the dose intensity (DI). The secondary endpoints were safety, R0 resection rate, pathological response rate (pRR), overall survival, and relapse-free survival. RESULTS: The median age of 26 enrolled patients was 74.5 years. The median DI in NAC-SOX130 was 97.2% for S-1 and 98.3% for oxaliplatin. Three cycles of NAC were administered in 25 patients (96.2%), of whom 24 (92.3%) underwent gastrectomy with lymphadenectomy. The R0 resection rate was 92.3% and the pRR (≥ grade 1b) was 62.5%. The major adverse events (≥ grade 3) were neutropenia (20.0%), thrombocytopenia (11.5%), anorexia (11.5%), nausea (7.7%), and hyponatremia (7.7%). Postoperative complications of abdominal infection, elevated blood amylase, and bacteremia occurred in one patient each. Severe diarrhea and dehydration caused one treatment-related death. CONCLUSIONS: NAC-SOX130 is a feasible therapy for older patients, although systemic management and careful monitoring of adverse events are necessary.

Trends in cervical laminoplasty and 30-day postoperative complications: 10-year results from a retrospective, multi-institutional study of 1095 patients.

PURPOSE: This study aimed to investigate the recent 10-year trends in cervical laminoplasty and 30-day postoperative complications. METHODS: This retrospective multi-institutional cohort study enrolled patients who underwent laminoplasty for cervical spondylotic myelopathy (CSM) or ossification of the posterior longitudinal ligament. The primary outcome was the occurrence of all-cause 30-day complications. Trends were investigated and compared in the early (2008-2012) and late (2013-2017) periods. RESULTS: Among 1095 patients (mean age, 66 years; 762 [70%] male), 542 and 553 patients were treated in the early and late periods, respectively. In the late period, patients were older at surgery (65 years vs. 68 years), there were more males (66% vs. 73%), and open-door laminoplasty (50% vs. 69%) was the preferred procedure, while %CSM (77% vs. 78%) and the perioperative JOA scores were similar to the early period. During the study period, the rate of preservation of the posterior muscle-ligament complex attached to the C2/C7-spinous process (C2, 89% vs. 93%; C7, 62% vs. 85%) increased and the number of laminoplasty levels (3.7 vs. 3.1) decreased. While the 30-day complication rate remained stable (3.9% vs. 3.4%), C5 palsy tended to decrease (2.4% vs. 0.9%, P = 0.059); superficial SSI increased significantly (0% vs. 1.3%, P = 0.015), while the decreased incidence of deep SSI did not reach statistical significance (0.6% vs. 0.2%). CONCLUSIONS: From 2008 to 2017, there were trends toward increasing age at surgery and surgeons' preference for refined open-door laminoplasty. The 30-day complication rate remained stable, but the C5 palsy rate halved.

Spinal endodermal cyst undergoing malignant transformation and marked elevation of serum carbohydrate 19-9 level.

Endodermal cyst (EC) is a benign tumor that can arise along the craniospinal axis. Infrequently, ECs undergo malignant transformation. A 43-year-old man presented with numbness in the right arm, leg and occipitalgia. MRI revealed a multicystic, intradural extramedullary tumor at C2 with enhancement along the ventral surface of the spinal cord. Blood test showed an abnormal increase in serum carbohydrate antigen 19-9 (CA 19-9) level. Systemic positron emission tomography-computed tomography was normal. He underwent total tumor resection and was diagnosed with EC. He developed double vision, hearing loss, and swallowing difficulty on postoperative day 70. Cerebral MRI revealed marked extensions of leptomeningeal dissemination. The serum CA 19-9 level increased continuously and finally reached 1515.0 U/ml. He died of respiratory failure on day 108. An autopsy did not reveal abnormalities in the abdominal and chest organs. On microscopic examination, the post-mortem specimen revealed adenocarcinoma. Immunohistochemically, both the surgical and autopsy specimens were positive for CA 19-9. Spinal ECs may lead to malignant transformation with leptomeningeal dissemination that causes abnormal elevation of serum CA 19-9 levels.

Do the mammillary bodies atrophy with aging? A magnetic resonance imaging study.

PURPOSE: This retrospective study aimed to explore age-related atrophy of the mammillary bodies (MBs) based on their temporal change using magnetic resonance imaging (MRI). MATERIALS AND METHODS: The study included 30 adult outpatients who presented to the hospital and were followed for more than 100 months with annual MRIs. The bi-ventricular width (BVW), third ventricle width (TVW), and bi-mammillary dimension (BMD) were measured on axial T2-weighted imaging and analyzed. RESULTS: The 30 patients comprised 1 in their 40s, 5 in their 50s, 6 in their 60s, 11 in their 70s, 5 in their 80s, and 2 in their 90s. The MBs were consistently detected with left-to-right symmetry. The mean BVW was 32 ± 2.2 mm on the initial (BVW1) and 32 ± 2.4 mm on the last (BVW2) MRI. The mean TVW was 7.0 ± 2.3 mm on the initial (TVW1) and 7.6 ± 2.7 mm on the last (TVW2) MRI. Furthermore, the mean BMD was 9.9 ± 1.3 mm on the initial (BMD1) and 10 ± 1.3 mm on the last (BMD2) MRI. Statistically, no age ranges had a large dimension for BVW1, BVW2, TVW1, TVW2, BMD1, or BMD2. Changes between TVW1 and TVW2 were significantly different in the patients in their 80s; changes between BMD1 and BMD2 were not different for any age range or between sexes. CONCLUSIONS: Aging alone does not seem to promote MB atrophy. In healthy brains, the MBs may be stationary structures throughout life.

Delineation of intermammillary relationships using magnetic resonance imaging.

PURPOSE: No study has investigated intermammillary relationships using neuroimaging modalities. This study aimed to explore them using magnetic resonance imaging (MRI). MATERIALS AND METHODS: We enrolled 72 patients who underwent conventional MRI examinations, followed by constructive interference steady-state sequence in the coronal plane. The intermammillary distances (IMDs) were measured at the uppermost level of the intermammillary gap (IMDupp) and the lowest level (IMDlow) of the mammillary bodies (MBs). RESULTS: MBs with varying morphologies were consistently delineated. The appearance of both MBs could be classified into four patterns based on the size and relative levels, with the symmetrical type being the most common. Intermammillary relationships exhibited five patterns. In 69%, the IMDupp was discernible and measured 0.7 ± 0.4 mm, while it was not discernible in 31% due to the presence of intermammillary connection and adhesion. The age distribution did not differ between populations with and without discernible IMDupp. The IMDlow was measured 4.4 ± 0.9 mm. Although the IMDlow was not significantly different between both sexes; it was longer in subjects in their 70s. CONCLUSIONS: Intermammillary relationships show variable morphologies with gaps formed between both MBs. The IMDlow may become more evident in association with age-related increase in the width of the third ventricle and atrophy of the MBs.

Delineation of the lacrimal vein: a magnetic resonance imaging study.

PURPOSE: To our knowledge, anatomical knowledge about the lacrimal vein (LV) is missed. Therefore, this retrospective study aimed to explore them using magnetic resonance imaging (MRI). MATERIALS AND METHODS: Eighty-one patients who underwent contrast-enhanced MRI and three donated bodies to science were enrolled. RESULTS: On the sagittal images, the measured mean right long (LD) and short diameters (SD) of the lacrimal gland (LG) were 17.3 ± 2.4 mm and 13.7 ± 2.1 mm, while the left LD and SD were 17.0 ± 2.6 mm and 13.6 ± 2.6 mm, respectively. Laterality or sex differences were not found in the LD and SD groups. In addition, no specific age range was associated with a significantly longer LD or SD. LVs were identified in 94% of axial images. Their course was classified into as follows: three types: connecting to the superolateral cavernous sinus (CS), to the superior ophthalmic vein (SOV), and the diploic channels of the greater wing of the sphenoid bone (DCGW). The CS type was the most frequently identified, followed by the SOV and DCGW types. In dissected specimens, the LVs consistently coursed between the posterior margin of the LG and the superolateral part of the CS, above the upper margin of the lateral rectus muscle. CONCLUSIONS: The LV may consistently emerge from the upper posterior margin of the LG. It commonly pours into the SOV or superolateral part of the CS.

Delineation of the central retinal artery using computed tomography: a pilot study.

PURPOSE: The prospective study aimed to examine the central retinal artery (CRA) using computed tomography (CT). MATERIALS AND METHODS: Seventy adult outpatients comprising 32 men and 38 women, at a mean age of 60.6 ± 13.3 years, were enrolled in the study. The patients underwent contrast-enhanced CT. The scan timing was set to start 5.0 s after the circle of Willis began to be delineated. RESULTS: The ophthalmic arteries (OphAs) were comfortably delineated in all. In 97% of the patients, the CRA was delineated from the original site on the OphA to a more distal segment coursing on the optic sheath. Unilateral and bilateral CRA delineations were observed in 44% and 53% of cases, respectively. The delineated CRAs demonstrated highly variable morphologies in terms of the course and length on the optic sheath. In addition, the distance between the original site of the CRA and the posterior limit of the bulb was measured. The mean distance was 18.6 ± 5.0 mm on the right and 17.8 ± 4.3 mm on the left, respectively. No significant right-to-left differences in the measurements (p > 0.05) were observed. CONCLUSIONS: If optimal scan timing is adopted, the CRA segments coursing on the optic sheath can be delineated using contrast-enhanced CT. CT may be a useful diagnostic modality for the CRAs and associated pathological conditions.

Phase II study of S-1 and oxaliplatin as neoadjuvant chemotherapy for locally advanced adenocarcinoma of the gastric or esophagogastric junction: KSCC1601.

BACKGROUND: Perioperative chemotherapy is the standard of care for locally advanced gastric cancer (LAGC). This phase II study investigated the efficacy and safety of S-1 and oxaliplatin (SOX) as neoadjuvant chemotherapy (NAC) for LAGC and esophagogastric junction cancer (EGJC). METHODS: Patients completed up to three cycles of SOX130 (oxaliplatin 130 mg/m2 on day 1, oral S-1 40-60 mg twice daily for 2 weeks every 3 weeks), followed by gastrectomy and D2 lymphadenectomy. The primary endpoint was the pathological response rate (pRR). The anastomosis leakage rate was the secondary endpoint in patients with EGJC, and other secondary endpoints were the R0 resection, overall survival (OS), and relapse-free survival (RFS) rates. RESULTS: Between April 2016 and July 2017, 47 patients (24 EGJC, 23 LAGC) were enrolled in this study. Forty-two patients (89.4%, 95% confidence interval [CI] = 76.9-96.5) underwent surgery, and R0 resection was achieved in 41 patients. The pRR was 59.5% (90% CI = 45.7-72.3). The major grade 3 or 4 toxicities were appetite loss in six patients (12.8%), thrombocytopenia in five patients (10.6%), and neutropenia and diarrhea in three patients (6.4%) each. The rate of severe anastomotic leakage (Clavien-Dindo classification grade III or higher) in 20 EGJC was 25.0% (90% CI = 10.4-45.6). The 3-year OS and RFS rate were 62.9% (95% CI = 47.2-75.1) and 53.2% (95% CI = 38.1-66.2), respectively. CONCLUSION: SOX130 demonstrated substantial benefit for LAGC and EGJC. However, special attention should be paid to anastomotic leakage during surgery for EGJC.

Fluid-Filled Dehiscences in the Anterior Cranial Fossa Floor: A Magnetic Resonance Imaging Study.

OBJECTIVE: To date, only limited information regarding the anterior cranial fossa floor (AFF) and the appearance of sites of dehiscence and potential channels has been available. We aimed to evaluate this region with thin section magnetic resonance imaging (MRI). PATIENTS AND METHODS: A total of 65 patients underwent thin-sliced coronal T2-weighted MRI. The AFF was divided into 3 parts for analysis: the anterior, middle, and posterior. RESULTS: Dehiscences were identified in 84.6% of 65 patients with apparently transmitting channels. In 49.2% of the patients, the dehiscences were located in the anterior part, whereas they were located in the middle and posterior parts in 52.3% and 12.3%, respectively. The morphology and number of these dehiscences were highly variable. In 12.3%, channels in the dehiscences were distributed extradural. Statistically, dehiscences were more frequently identified on the left side in any part of the AFF. CONCLUSIONS: With thin-sliced, coronal T2-weighted MRI, dehiscences were frequently identified in the anterior two-thirds of the AFF. Further study is warranted to determine the role of AFF channels and dehiscences, including possibly for cerebrospinal fluid drainage.

Prognostic significance of intrahepatic lymphatic invasion in colorectal liver metastases.

BACKGROUND: Intrahepatic lymphatic invasion is an adverse prognostic factor after hepatectomy for colorectal liver metastases (CLMs). However, most patients in previous reports had liver resection before the era of FOLFOX/FIRI-based chemotherapy. METHODS: Forty-six patients who underwent hepatectomy for CLMs from 2004 to 2020 were evaluated. We histologically evaluated portal invasion, intrahepatic lymphatic invasion, and biliary invasion on hematoxylin-eosin slides. We also collected the following clinicopathologic factors: gender, age, timing, the number and maximum size of CLMs, preoperative tumor markers, neutrophil/lymphocyte ratio, location, and lymph node metastases of primary cancer, and chemotherapy after hepatectomy. A multivariate Cox proportional hazard model was used to define the relationship between overall (OS) or disease-free survival (DFS) and clinicopathologic factors. RESULTS: Histological invasions were portal invasion in 8 (17.4 %), intrahepatic lymphatic invasion in 6 (13.0 %), and biliary invasion in 5 (10.9 %). Chemotherapy for recurrence after hepatectomy (n = 29) was performed in 22 and 14 of those who received FOLFOX/FIRI-based chemotherapy. By multivariate analysis, the number of CLMs (p < 0. 01) and presence of intrahepatic lymphatic invasion (p = 0.02) were independent predictors of recurrence. The number of CLMs (p = 0.02) and prehepatectomy carcinoembryonic antigen level (p = 0.02), but not intrahepatic lymphatic invasion (p = 0.18), were independent predictors of survival using multivariate analysis. CONCLUSIONS: The presence of intrahepatic lymphatic invasion adversely affected patient's DFS, but not OS in patients with CLMs in the era of FOLFOX/FIRI chemotherapy. FOLFOX/FIRI-based chemotherapy might improve OS, even in patients with positive intrahepatic lymphatic invasion.

Root exit zone of the trochlear nerve on the dorsal brainstem: an MRI study.

PURPOSE: To date, no study has explored the root exit zone of the trochlear nerve (TroN) on the dorsal brainstem; therefore, we aimed to characterize the location using magnetic resonance imaging (MRI). METHODS: A total of 85 patients underwent thin-slice axial T2-weighted MRI. RESULTS: TroN was identified in 91% of 85 patients, 60 (71%) on the right side, and 67 (79%) on the left. The distances between the apex of the inferior colliculus and the original site of TroN on the dorsal brainstem were variable, with mean values of 2.4 ± 1.8 mm (range 0-8 mm) on the right and 2.2 ± 1.7 mm (range 0-5 mm) on the left. Most of the root exit zones were distributed within 0-5 mm below the apex of the inferior colliculus. In addition, the distances between the midline and the root exit zones of the TroN were variable, with mean values of 4.4 ± 1.4 mm (range 1.9-7.5 mm) on the right and 4.6 ± 1.6 mm (range 1.1-7.8 mm) on the left. Most of the root exit zones were located within 1-7 mm range lateral to the midline. CONCLUSIONS: The root exit zone of the TroN may be mostly located in a small square area measuring 8 mm × 8 mm, lying at and below the apex of the inferior colliculus. The TroN may arise from any site in the square area, and significant attention is necessary when performing surgical maneuvers in and around it.

"Hammock" suspending the superior ophthalmic vein: a magnetic resonance imaging study.

PURPOSE: The present study aimed to explore the hammock-like structure suspending the superior ophthalmic vein (SOV) using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, 93 outpatients underwent thin-sliced, coronal T2-weighted and contrast imaging of the orbit. RESULTS: SOVs were consistently detected in all 93 patients. In 90.3% of patients, a hammock-like structure suspending the SOV was identified, which was present on both sides in 64.5% of patients. The structure was frequently located in the anterior and middle thirds of the retrobulbar orbit, suspended from the superolateral corner of the orbital walls. The medial edge of the hammocks did not reach the orbital walls; therefore, they partially encased the SOV. The morphology of the hammock was highly variable between patients, although none were tethered to the extraocular muscles. In addition, a septal band connecting the hammock and optic sheath was identified in 36.6% of patients, most frequently located in the posterior third of the retrobulbar orbit. CONCLUSIONS: The hammock suspending the SOV and the septal band connecting the hammock and optic sheath may be structures that loosely anchor the SOV to the orbital fat to maintain a constant SOV flow, in addition to preventing excessive bends and obstructions.

Bilateral vertebral artery fenestrations in the craniocervical junction region: the clinical role of 3D computed tomography angiography.

Fenestration of the vertebral artery (FVA) is a rare occurrence that comprises only 2% of fenestrations formed in the intracranial arteries. Herein, we report a unique case of bilateral FVA in the craniocervical junction (CCJ) region using conventional magnetic resonance angiography (MRA) and three-dimensional computed tomography angiography (3D-CTA). Compared to MRA, 3D-CTA was more sensitive in delineating the FVAs located in the region. Furthermore, it effectively depicted the relationships between the VAs and surrounding bony structures. The clinical implications of FVAs can be better understood in relation to the surrounding bony structures. 3D-CTA is mandatory when performing endovascular and open surgical interventions in and around the VA segments in the CCJ region.

Hyperintense areas in the cisternal segments of the cranial nerves: a magnetic resonance imaging study.

PURPOSE: The study aimed to explore hyperintense areas in the cisternal segments of the cranial nerves using magnetic resonance imaging (MRI). METHODS: Seventy outpatients underwent thin-sliced, coronal constructive interference steady-state (CISS) sequence and sagittal T2-weighted MRI following conventional MRI examination. RESULTS: With the coronal CISS sequence, hyperintense areas were located in the central parts of the olfactory bulbs in 65.7% of patients. For the intracranial optic nerve and optic chiasm, hyperintense areas were detected in 98.6% of the CISS sequences and 100% of the T2-weighted images. In the optic tract, hyperintense areas were detected in 51.4% of cases. In 35% of the patients who underwent the CISS sequence, the intracranial optic nerves were considerably compressed by the internal carotid and anterior cerebral arteries, with hyperintense areas similar to those in patients without vascular compression. Hyperintense areas of the cisternal segments of the oculomotor nerve and trigeminal root were identified in 52.9% and 87.1% of the patients, respectively. CONCLUSIONS: The hyperintense areas found within the cisternal segments of the cranial nerves delineated on the coronal CISS sequence and sagittal T2-weighted imaging may indicate the intracranial part of the glymphatic pathway through the cranial nerves. The cranial nerves may function as part of the glymphatic pathway.

Oculomotor nerve segment between proximal posterior and superior cerebellar arteries: an MRI study.

PURPOSE: No study has documented the oculomotor nerve (OMN) segment lying between the posterior cerebral (PCA) and superior cerebellar (SCA) arteries adjacent to the brainstem. The present study aimed to characterize it. METHODS: A total of 71 patients underwent thin-sliced, sagittal T2-weighted magnetic resonance imaging for analysis. RESULTS: The OMN segments lying between the PCA and SCA were identified in all patients. The OMN segment in relation to the PCA and SCA was classified into five types. Of them, the PCA-OMN contact type was the most frequent and found in 35.2% of 71 sides on the right and 39.4% on the left. Also, the PCA-OMN compression type was identified in 12.7% on the right and 15.5% on the left. In these types, the mean distance between the brainstem and contact/compression sites were measured 4.4 ± 2.3 mm on the right and 4.4 ± 1.6 mm on the left. In more than forty percent, the sites were located at the level of the pontomesencephalic junction. CONCLUSIONS: The OMN may be frequently in contact with the PCA near the brainstem. The site located more distal than the central-peripheral myelin junction of the OMN can attribute to a low frequency of neurovascular compression syndrome of the nerve.

Correlation of the external occipital protuberance with venous sinuses: a magnetic resonance imaging study.

PURPOSE: To date, no study has explored the external occipital protuberance (EOP) using neuroimaging modalities. This study aims to characterize them using magnetic resonance imaging (MRI). METHODS: A total of 96 patients underwent thin-sliced, post-contrast MRI. The sagittal images were analyzed. RESULTS: In 97%, the EOPs were delineated as a focal external protrusion of the midline region of the occiput with varying morphologies. In 89% of 93 patients with identifiable EOPs, parts of the intracranial dural sinuses were found to lie just below the inion, the most prominent point of the EOP. The most frequently targeted dural sinus was the confluence of sinuses that was found in 57%, followed by the superior sagittal sinus. In 16%, a bony foramen and transmitting vessel were detected in the EOP, connecting between the diploic channels and the subcutaneous veins. Furthermore, in 33%, bony foramina and transmitting venous structures were identified in the region just below the EOPs, connecting between the diploic channels and the subcutaneous veins. CONCLUSIONS: The intracranial dural venous sinus is located just below the EOP with a high probability. Most bony foramina in the EOP and midline suboccipital region may transmit veinous structures connecting to the diploic channel.