Clinical, Anatomical, and Histological Features of the Rhomboid Lip and Considerations for Surgery Using a Retrosigmoid Approach: A Retrospective Study.

OBJECTIVE: The rhomboid lip is a neural tissue encountered during cerebellopontine angle surgery, with differing shape and extent among individuals. This study aimed to investigate the variation of rhomboid lips during posterior fossa surgery. METHODS: In this retrospective study, we examined posterior cranial fossa surgeries performed using a retrosigmoid approach. Rhomboid lips were classified according to thickness, extent, and appearance, with some subjected to histological analysis. T2-weighted magnetic resonance imaging of rhomboid lips was conducted. RESULTS: Among 304 surgeries, rhomboid lips were observed in 75 patients who underwent schwannoma or meningioma resection, facial spasm-related neurovascular decompression, and other surgeries (37, 2, 32, and 4 patients, respectively). Rhomboid lips were categorized based on apparent thickness: thin membranous type, resembling an arachnoid membrane, and thick parenchymal type. Rhomboid lip extension was classified by position relative to the choroid plexus: nonextension, lateral extension, and jugular foramen (41, 22, and 12 patients, respectively). Veins were observed on the rhomboid lip surface in 37 cases. The rhomboid lip was visible in only 1 case (parenchymal jugular foramen type) on magnetic resonance imaging. Histologically, the rhomboid lip comprised an ependymal cell layer, a glial layer, and connecting tissue. The glial layer thickness determined the rhomboid lip thickness, which was greater in the parenchymal type than in the membrane type. In 42 patients, the rhomboid lip was dissected with no complications observed. CONCLUSIONS: Morphological classification of the rhomboid lip and understanding of its anatomical details contribute to safe surgical field development for neurosurgeons.

The importance of the palatine bone for endoscopic endonasal skull base surgery.

Endoscopic endonasal skull base surgery is increasingly prevalent, with its scope expanding from pathogens in the midline region to those in the paramedian region. Maximizing anterior sphenoidectomy is important for the median approach, and lateralizing the pterygopalatine fossa is crucial for the paramedian approach. Maximizing the surgical corridor in the nasal cavity and minimizing damage to neurovascular structures are vital for establishing a surgical field with minimal bleeding, ensuring safe, precise, and gentle procedures. However, the relationship between the maxillofacial and skull base bones in endoscopic endonasal skull base surgery is difficult to understand because these bones are intricately articulated, making it challenging to visualize each bone's outline. Understanding important bones and their related neurovascular structures is essential for all skull base surgeons to maximize the surgical corridor and minimize iatrogenic injury to neurovascular structures. This study aimed to elucidate the role of the palatine bone from a microsurgical anatomical perspective. Three dry skulls were used to demonstrate the structure of the palatine bone and its relationship with surrounding bones. A formalin-perfused cadaveric head was dissected to show the related neurovascular structures. The arteries and veins of the cadaveric heads were injected with red- and blue-colored silicon. Dissection was performed using a surgical microscope and endoscope. In addition, the utilization of the palatine bone as a landmark to identify neurovascular structures, which aids in creating a wider surgical field with less bleeding, was shown in two representative cases. The palatine bone consists of unique complex structures, including the sphenoidal process, ethmoidal crest, pterygopalatine canal, and sphenopalatine notch, which are closely related to the sphenopalatine artery, maxillary nerve, and its branches. The ethmoidal crest of the palatine bone is a well-known structure that is useful for identifying the sphenopalatine foramen, controlling the sphenopalatine artery and nerve, and safely opening the pterygopalatine fossa. The sphenoidal process of the palatine bone is a valuable landmark for identifying the palatovaginal artery, which is a landmark used to safely and efficiently expose the vidian canal. The sphenoidal process is easily cracked with an osteotome and removed to expose the palatovaginal artery, which runs along the pharyngeal groove, just medial to the vidian canal. By opening the pterygopalatine canal (also known as the greater palatine canal), further lateralization of the periosteum-covered pterygopalatine fossa contents can be achieved. Overall, the sphenoidal process and ethmoidal crest can be used as important landmarks to maximize the surgical corridor and minimize unnecessary injury to neurovascular structures.

The surgical intervention for pineal region tumors.

Histological and molecular characterization is essential for the diagnosis of pediatric brain tumors. In the pineal region tumors, it is necessary to remove a sufficient tumor volume to make a diagnosis. However, surgery in this region is challenging due to its deep anatomical location and surrounded by critical structures and complex venous system. Knowledge of the anatomy and function of the pineal region and tumor histological types is imperative for the successful management of pineal region tumors. This article describes surgical approaches to pineal tumors, focusing on the occipital transtentorial approach and adding the author's experience to what has been known in the literature. Recent innovations have made this approach more popular and can be applied to occipital fossa lesions.

A Case of Tardive Dystonia with Task Specificity Confined to the Lower Extremities only during Walking.

Background: Task-specific dystonia (TSD) confined to the lower extremities (LE) is relatively rare. This report describes dystonia confined to the LE only during forward walking. This case required careful neurological and diagnostic assessment because the patient was taking several neuropsychiatric drugs that cause symptomatic dystonia, such as aripiprazole (ARP). Case: A 53-year-old man visited our university hospital with a complaint of abnormalities in the LE that appeared only during walking. Neurological examinations other than walking were normal. Brain magnetic resonance imaging revealed meningioma in the right sphenoid ridge. The patient had been treated for depression with neuropsychiatric medications for a long time, and his abnormal gait appeared about 2 years after additional administration of ARP. After the meningioma was removed, his symptoms remained. Surface electromyography showed dystonia in both LE during forward walking, although his abnormal gait appeared to be accompanied by spasticity. The patient was tentatively diagnosed with tardive dystonia (TD). Although dystonia did not disappear clinically, it was alleviated after discontinuing ARP. Administration of trihexyphenidyl hydrochloride and concomitant rehabilitation improved his dystonia until return to work, but some residual gait abnormalities remained. Discussion: We report an unusual case of TD with task specificity confined to the LE. The TD was induced by the administration of ARP in combination with multiple psychotropic medications. Careful consideration was required for clinical diagnosis, rehabilitation, and assessment of its relevance to TSD.

Utility of real-time polymerase chain reaction for the assessment of CDKN2A homozygous deletion in adult-type IDH-mutant astrocytoma.

The World Health Organization Classification of Tumors of the Central Nervous System 5th Edition (WHO CNS5) introduced a newly defined astrocytoma, IDH-mutant grade 4, for adult diffuse glioma classification. One of the diagnostic criteria is the presence of a CDKN2A/B homozygous deletion (HD). Here, we report a robust and cost-effective quantitative polymerase chain reaction (qPCR)-based test for assessing CDKN2A HD. A TaqMan copy number assay was performed using a probe located within CDKN2A. The linear correlation between the Ct values and relative CDKN2A copy number was confirmed using a serial mixture of DNA from normal blood and U87MG cells. The qPCR assay was performed in 109 IDH-mutant astrocytomas, including 14 tumors with CDKN2A HD, verified either by multiplex ligation-dependent probe amplification (MLPA) or CytoScan HD microarray platforms. Receiver operating characteristic curve analysis indicated that a cutoff value of 0.85 yielded optimal sensitivity (100%) and specificity (99.0%) for determining CDKN2A HD. The assay applies to DNA extracted from frozen or formalin-fixed paraffin-embedded tissue samples. Survival was significantly shorter in patients with than in those without CDKN2A HD, assessed by either MLPA/CytoScan or qPCR. Thus, our qPCR method is clinically applicable for astrocytoma grading and prognostication, compatible with the WHO CNS5.

Application of intra-operative magnetic resonance imaging for intracranial epidermoid cysts.

The effectiveness and safety of intraoperative magnetic resonance imaging (iMRI) are evident from many reports over the past decade. However, these reports have mainly concerned surgeries for glioma and other intra-axial tumours, and applications of this approach for extra-axial tumours are poorly documented. We retrospectively examined three cases in which iMRI was used to assist in the removal of epidermoid cysts. T2-weighted images and diffusion-weighted images were acquired during the surgeries. The value to surgeons of images generated by iMRI, the length of interruption of surgery, and the safety of the patients were assessed. In this study, the images obtained through iMRI provided were clear representations of remnant tumours, even with a low-field system (0.4 Tesla). These images generated enough information to help surgeons decide whether to use an assistance device, such as an endoscope, to remove remnant tumours and whether further retraction of the brain was safe for patients and useful in tumour removal. Intraoperative MRI has long been thought unnecessary for surgery for tumours that are well demarcated and clearly visible under a surgical microscope; in this study, however, intraoperative MRI proved to be useful and safe for patients undergoing epidermoid cyst resection.

Case of penetrating brain injury caused by a ventriculoperitoneal shunting procedure.

Brain injury with ventricle puncture is a well-known complication of ventriculoperitoneal (VP) shunting. However, parenchymal injuries caused by a shunt tunneller are rare. Herein, we present a case of penetrating brain injury caused by a shunt tunneller during VP shunting. An 83-year-old woman with brainstem glioma underwent VP shunting to control hydrocephalus due to tumour growth. She underwent brainstem tumour biopsy with a lateral suboccipital approach. After the shunting, CT showed a linear haematoma in the left occipital lobe far from the site of the ventricular puncture. MRI revealed a small contusion in the left cerebellar hemisphere, disconnection of the left tentorial membrane and linear haematoma on a straight line. These facts suggested that the shunt tunneller had penetrated the skull through the craniotomy of the posterior fossa. This is a rare complication of VP shunting, with limited cases reported in the literature.

A case of solitary subependymal giant cell astrocytoma with histopathological anaplasia and TSC2 gene alteration.

We report a case of subependymal giant cell astrocytoma (SEGA) with anaplastic histological features in a 3-year-old girl. She had no clinical manifestations of tuberous sclerosis complex (TSC) and no relevant family history. A few cases have been reported in which patients with SEGA had no other clinical manifestations of TSC (solitary SEGA). Genetic analysis using a blood sample from the patient showed no germline alterations in TSC1 or TSC2 genes, while the tumor tissue exhibited loss of heterozygosity (LOH) in TSC2. SEGAs are benign, slowly growing tumors that rarely have significant mitotic activity. However, histopathological examination in the present case revealed high mitotic activity and necrosis besides the typical large plump cells arranged in sheets. This may be the first genetically proven case of a solitary SEGA with histopathological anaplastic features. In this report, we reviewed solitary SEGAs and histopathological malignancy in SEGA.

Classification of crista galli pneumatization and clinical considerations for anterior skull base surgery.

Cerebrospinal fluid (CSF) leakage caused by frontal sinus exposure is a serious complication in the basal interhemispheric approach (BIHA). Crista galli pneumatization (CGP) is often observed on preoperative computed tomography (CT) scan. The aim of this study was to classify and describe variations in anatomical measurements of CGP. We examined CT images of 300 patients with brain tumors to assess the morphology and incidence of CGP. Crista galli were classified according to their location relative to the cribriform plate and the presence of pneumatization. The paranasal sinuses were investigated as the origin of CGP. We assessed 24 patients using the BIHA for skull base tumors; these patients were included as clinical cases to assess the range of skeletonization of the crista galli and determine the route of CSF leakage in the other 276 patients. CGP was found in 28/300 CT scans, including upper, middle, and lower type CGPs. The origin of CGPs was the frontal sinus or ethmoid sinus. All CGPs were localized in the anterior half of the crista galli. In the 24 consecutive clinical cases, there were 13 tuberculum sellae meningiomas, 3 craniopharyngiomas, and 8 with other pathologies. The preoperative crista galli height was 12.3 mm and the distance from the top of the skeletonization to the cribriform plate was 5.2 mm. CGP originating from the paranasal sinuses can lead to CSF leakage. In cases where CGP originates from the ethmoid sinus, care should be taken to seal the exposed crista galli intradurally.

Malignant perivascular epithelioid cell tumor mimicking jugular foramen schwannoma: A case report and literature review.

BACKGROUND: Perivascular epithelioid cell tumors (PEComas) of the skull base are extremely rare. Here we report the first description of a malignant PEComa mimicking jugular foramen schwannoma and presenting as Collet-Sicard syndrome, and we review the previous literature on PEComas of the head, neck and skull base. CASE DESCRIPTION: A 29-year-old woman presented with hoarseness, dysphagia, vomiting, and headache. She was first diagnosed with Collet-Sicard syndrome caused by thrombosis of the sigmoid and transverse sinuses. She was treated with anticoagulant therapy, and the hoarseness and paralysis of the accessory nerve improved. Later, at age 31, the hoarseness again worsened. At another hospital, enhanced computed tomography revealed a tumor in the jugular foramen extending to the neck and medially displacing the internal carotid artery. She was referred to our hospital for further examination and was diagnosed with jugular foramen schwannoma causing thrombosis of the sinuses. At the one-year follow-up, the tumor had grown rapidly and had started to surround the internal carotid artery. We therefore performed a tissue biopsy of the tumor in the jugular foramen and neck. Based on pathological analysis, we made a definitive diagnosis of malignant PEComa. CONCLUSIONS: It may be extremely challenging to reach an accurate diagnosis of PEComa in the skull-base region, which can cause a delay in treatment initiation. When atypical clinical features for a skull-base tumor are found, we recommend preliminary biopsy to obtain a definitive diagnosis and initiate an appropriate treatment strategy as early as possible.

Surgical Anatomy of the Donor Arteries for Extracranial-Intracranial Bypass Surgery: An Anatomic and Radiologic Study.

OBJECTIVE: To review the microsurgical anatomy of the donor arteries for extracranial-intracranial bypass, namely, the superficial temporal artery (STA), occipital artery (OA), and internal maxillary artery (IMA). METHODS: Seven cadaveric specimens were dissected to identify the relationships between each artery and its surrounding structures. Nineteen computed tomographic angiographic images of Japanese adult patients (38 sides) were analyzed to examine the course of each artery and to measure the diameters and distances from various anatomic landmarks to each artery. RESULTS: The courses of the STA, OA, and IMA, which must be exposed during revascularization procedures, were shown via cadaver dissection with special reference to the following relationships to surrounding structures: STA, soft tissue layers of the temporoparietal region and facial nerve; OA, suboccipital muscles; and IMA, mandibular nerve. In addition, we measured the diameter of the anastomotic site for each artery and its relationship with surrounding muscles. CONCLUSIONS: A precise understanding of the anatomic characteristics of the donor arteries and their relationships with surrounding structures provides safe access to these arteries.

The Rhomboid Lip: Anatomy, Pathology, and Clinical Consideration in Neurosurgery.

OBJECTIVE: To describe microsurgical anatomy of the rhomboid lip (RL) and to consider its role by presenting histology and clinical cases. METHODS: We examined 10 (20 sides) formalin-fixed adult human cadaveric heads injected with colored silicone. A total of 20 RLs were examined posteriorly. We examined the expansion of the RL in the cerebellopontine cistern. We assessed the relationship between the RL and choroid plexus and the RL and cranial nerve IX and classified the RL. We also observed these relationships in clinical cases during surgeries and examined histologic assessments of the RL. RESULTS: The RL was divided into 3 types, non-extension type, lateral extension type, and jugular foramen type, according to the relationship between the RL and choroid plexus. There were many variations of the extension of the RL. The jugular foramen type was rare. CONCLUSIONS: Histologically, the RL is the remnant of the fourth ventricle covered with ependymal cells. Knowledge of the detailed anatomy and proper dissection of the RL may help surgeons to obtain good visualization of structures around the foramen of Luschka.

A novel surgical approach for intraorbital optic nerve tumors.

Although orbital tumors involving the optic nerve are rare, it is well-known that they are very likely to cause serious visual impairment in a patient. Unfortunately, at present, there are no effective interventions that can reliably preserve visual function while controlling tumor growth into intracranial spaces. To ensure visual function of the non-affected side, transection of the optic nerve together with the tumors involved is necessary in some cases. For this procedure large craniotomy and orbital unroofing are commonly utilized. As an alternative, we propose a novel surgical intervention for transection of the optic nerve having optic nerve tumors, which utilizes a lateral orbitotomy approach. To evaluate the invasiveness of different surgical approaches, we compared the days of hospitalization after surgery across patients who underwent the transcranial, lateral, and anterior approaches, respectively. We successfully removed 2 optic nerve tumors using the lateral approach, which required significantly shorter hospitalization than the transcranial approach. The transection of the optic nerve together with tumor removal by the lateral approach may be one of the novel surgical interventions for optic nerve tumors as this method is considerably less invasive than the transcranial removal method.

A rare presentation of a pediatric neurenteric cyst as an intra-axial pontine lesion: A case report with a 5-year follow-up.

BACKGROUND: Intracranial neurenteric cysts are rare, benign, and slow-growing tumors. However, we encountered a pediatric case that the cyst expansion occurred in a short period of time resulting in rapid deterioration of the patient's symptoms. CASE DESCRIPTION: A previously healthy 7-year-old girl had a week history of dysarthric speech and diplopia along with headaches. Her magnetic resonance images (MRI) showed an abnormal cystic mass in her brainstem. Her symptoms were deteriorated for 1 month and her second MRI revealed an enlargement of the cystic lesion. The tumor biopsy and cyst drainage were carried out and histopathological examination of the cyst wall showed columnar epithelium containing ciliated cells. The final diagnosis of her tumor was neurenteric cyst. CONCLUSION: We report a pediatric case of a neurenteric cyst in the brainstem, which expanded in a short period, and review this rare entity.

[Awareness of harm to others from secondhand smoke and smokers' interest in smoking cessation].

Objectives　Because smoking presents various health hazards, smoking cessation is important for health promotion. It is known that awareness of the harm of smoking to smokers themselves is associated with attempts to quit. However, the association between smoking cessation and awareness of harm to others from secondhand smoke has not been well examined. Therefore, in this research, we examined the association between smokers' awareness of the harm to others from secondhand smoke and their interest in smoking cessation, focusing on current smokers in an Internet survey of the general population of Japan.Methods　We conducted a cross-sectional Internet survey of the general population of Japan between January 27 and March 13, 2017. A total of 1,586 respondents aged 15-71 years (1,128 men and 458 women) who were current smokers were analyzed. We used multivariable-adjusted logistic regression to examine the association among awareness of smoking's harm to smokers themselves, awareness of harm to others from secondhand smoke, and the smokers' interest in smoking cessation.Results　Of current smokers, 81.6% of men and 88.2% of women were aware of the harm caused to others by secondhand smoke; 52.7% of men and 64.6% of women were interested in smoking cessation. Using awareness of harm to smokers themselves and awareness of harm to others from secondhand smoke as predictor variables in multivariable-adjusted logistic regression, odds ratios were 2.53 and 2.92, respectively. In the model using both awareness of harm to smokers themselves and harm to others from secondhand smoke, both have a significant independent positive association with smokers' interest in quitting.Conclusions　Current smokers aware of the harm caused to others by secondhand smoke were more interested in quitting than those who were not. Awareness of the harm caused to smokers themselves by smoking and awareness of the harm caused to others by secondhand smoke have a significant independent positive association with smokers' interest in quitting. Although this study is a cross-sectional study and did not investigate causal relationships, the findings suggest that raising awareness of the harm to other people from secondhand smoke may lead to more interest in smoking cessation, and the data can be used to promote tobacco control in the future.

Prosthetic material degeneration over time as a possible factor in delayed recurrence of hemifacial spasm after successful microvascular decompression.

BACKGROUND: The effectiveness of microvascular decompression in treating hemifacial spasm is widely accepted. However, some experience recurrence of hemifacial spasm after successful decompression surgery. Especially, delayed recurrence more than 5 years after surgery is rare and the cause of this phenomenon is unknown. CASE DESCRIPTION: A female underwent microvascular decompression to treat her hemifacial spasm 6 years ago. Six years later, her hemifacial spasm recurred and she underwent a second surgery. The second surgery revealed that the sponge had become fragile, losing the ability to absorb the impact of pulsatile compression of the offending artery on the root exit zone of her facial nerve. CONCLUSION: We report a case in which degeneration of material, a sponge (polyurethane), used in decompression surgery caused delayed recurrence of hemifacial spasm. The selection of appropriate prosthetic materials is essential in such functional surgeries.

A Comprehensive Method for Detecting Fusion Genes in Paediatric Brain Tumours.

BACKGROUND: Fusion genes driving tumourigenesis have drawn the attention of researchers and oncologists. Despite the importance of such molecular alterations, there are no comprehensive reproducible methods for detecting fusion genes. MATERIALS AND METHODS: Nineteen paediatric brain tumours of five types, namely pilocytic astrocytoma, oligodendroglioma, anaplastic astrocytoma, glioblastoma and, ganglioglioma, were examined to detect fusion genes using a pyrosequencing-based method following RNA isolation, cDNA synthesis and real-time polymerase chain reaction. RESULTS: Our method successfully detected KIAA1549-v-raf murine sarcoma viral oncogene homolog B1 (BRAF) fusion in 14 out of 19 patients suffering from five types of paediatric brain tumours providing information on fusion breakpoints within 2 h. CONCLUSION: A comprehensive method for detecting fusion genes in paediatric brain tumours was evaluated. This method identified KIAA1549-BRAF fusion variants quickly. Our results may help researchers interested in the role of fusion genes in tumourigenesis.

Spatial Restriction within Intracranial Epidermoid Cysts Observed Using Short Diffusion-time Diffusion-weighted Imaging.

We report two cases of pathologically proven intracranial epidermoid cysts. Both cases were scanned with diffusion-weighted imaging using pulsed gradient spin-echo (PGSE) and oscillating gradient spin-echo (OGSE; 50 Hz) prototype sequences with diffusion times of 47.3 ms and 8.5 ms, respectively. The apparent diffusion coefficient measured by OGSE was higher than that measured by PGSE, indicating the spatial restriction of water diffusion in the laminated keratin layers within the cyst as demonstrated by histopathology.

Changes in delta ADC reflect intracranial pressure changes in craniosynostosis.

BACKGROUND: In patients with craniosynostosis, intracranial pressure (ICP) has been reported to increase even in the absence of overt symptoms. The early and non-invasive detection of intracranial hypertension is important for reducing the risk of abnormal brain development in pediatric patients. PURPOSE: To assess whether the apparent diffusion coefficient (ADC) of white matter during the cardiac cycle (ΔADC) would change after surgery to relieve ICP in children with craniosynostosis. MATERIAL AND METHODS: This prospective study included ten patients diagnosed with craniosynostosis and four normal controls. All ten patients underwent magnetic resonance (MR) examinations before and after surgical treatment. Single-shot diffusion MR imaging (MRI) triggered by an electrocardiogram was performed, with regions of interest (ROIs) placed on frontal white matter and basal ganglia. RESULTS: In all ten patients, ΔADC values after surgery were higher than those before surgery. This difference was statistically significant (Wilcoxon signed-rank test, P = 0.005). CONCLUSION: The change in ΔADC in the frontal white matter before and after surgery in patients with craniosynostosis indicates that it might reflect the change in ICP. Measurements of ΔADC could be a promising tool for non-invasive monitoring of ICP.