Primary intracranial germ cell tumors are rare tumors that often occur in children and young adults. We report a case of a 17-year-old male, who presented with vomiting, headache, and blurring of vision of the left eye on the temporal aspect for two months. His biological assessment showed panhypopituitarism. Serum markers showed elevated beta human chorionic gonadotropin and lactate dehydrogenase. A solid cystic lesion was noted on imaging, involving the sella, parasellar region, and pineal region with calcifications within. Diagnosis of bifocal germinoma was confirmed by tumor biopsy. The treatment protocol for the patient involved four cycles of chemotherapy using etoposide and carboplatin, followed by a course of radiotherapy.

Pineal tumors are rare but surgically challenging due to their deep location and proximity to major veins and brainstem.1,2 Getting a biopsy along with an endoscopic third ventriculostomy is essential before surgical resection.3,4 The supracerebellar infratentorial approach provides direct symmetrical exposure of the pineal region inferior to the vein of Galen.5,6 3-Dimensional (3D) exoscopes are increasingly used due to better ergonomics, greater depth of field, and equivalent image quality of microscope. The endoscope provides angled optics to visualize hidden areas of tumor adherent to neurovascular structures, avoiding blind dissection. These become especially advantageous during suboccipital keyhole surgery in the sitting position, which averts both cerebellar retraction and frequent soiling of the endoscope. In this case of a giant pineal papillary tumor in a 16-year-old patient, we used both a 3D-exoscope and a 45-degree angled endoscope complementarily (Video 1). The tumor underwent straight-ahead internal decompression using an exoscope. Once some space became available, the angled endoscope was inserted to excise the tumor initially in the inferior aspect and then rotated toward either side to dissect the tumor from the basal veins of Rosenthal. Lastly, the superior pole stuck to the undersurface of the vein of Galen was gradually excised. There were no neurologic deficits. Histopathology was a high-grade papillary tumor. Magnetic resonance imaging confirmed gross total resection. This is probably the first report of a supracerebellar infratentorial keyhole approach for gross total resection of a giant pineal tumor, effectively using the better ergonomics and depth of field of a 3D exoscope along with angled optics provided by an endoscope, resulting in an excellent outcome.

Circadian rhythms and the sleep/wake cycle allows us, and most life on Earth, to function optimally in a dynamic world, adjusting all aspects of biology to the varied and complex demands imposed by the 24-hour rotation of the Earth upon its axis. A key element in understanding these rhythms, and the success of the field in general, has been because researchers have adopted a comparative approach. Across all taxa, fundamental questions relating to the generation and regulation of sleep and circadian rhythms have been address using biochemical, molecular, cellular, system and computer modelling techniques. Furthermore, findings have been placed into an ecological and evolutionary context. By addressing both the \"How\" - mechanistic, and \"Why\" - evolutionary questions in parallel, the field has achieved remarkable successes, including how circadian rhythms are generated and regulated by light. Yet many key questions remain. In this special issue on the Comparative Physiology of Sleep and Circadian Rhythms, celebrating the 100th anniversary of the Journal of Comparative Physiology, important new discoveries are detailed. These findings illustrate the power of comparative physiology to address novel questions and demonstrate that sleep and circadian physiology are embedded within the biological framework of an organism.

Neuroendoscopy procedures in pediatrics have expanded beyond the endoscopic third ventriculostomy. As such, a direct and angled endoscope allows further visualization around the corner, capturing the surrounding anatomy. Intraoperative live images look different than radiological images. Hence, in this single institutional experience, we correlate neuroradiology images with intraoperative intraventricular endoscopic views of the third-fourth ventricle, pituitary, pineal gland, cerebral aqueduct, and foramen magendie and luschka. Our collective case series reveals a few interesting case scenarios of normal and abnormal findings during the procedure. Careful navigation of the neuroendoscope is crucial to prevent injury to the neurovascular bundle. A close relationship with normal anatomy from radiological imaging is necessary to prevent it from getting lost once inside the ventricular cavity.

Falcotentorial meningiomas are rare tumors, representing only 2-3% of all intracranial meningiomas. These tumors can grow rapidly, leading to severe neurological complications. They grow at the junction of the tentorium cerebelli and the falx cerebri, in close proximity to the great vein of Galen. The surgical approach depends on several factors, such as the tumor\'s size, the patency of the straight sinus, and its location, either above or below the tentorium. Complete removal of the tumor in this area is difficult due to its deep location near major neurovascular structures. Various surgical approaches can be employed to remove these tumors, and the decision on which approach to use should be based on its advantages and disadvantages.

Temporal signals such as light and temperature cycles profoundly modulate animal physiology and behaviour. Via endogenous timing mechanisms which are regulated by these signals, organisms can anticipate cyclic environmental changes and thereby enhance their fitness. The pineal gland in fish, through the secretion of melatonin, appears to play a critical role in the circadian system, most likely acting as an element of the circadian clock system. An important output of this circadian clock is the locomotor activity circadian rhythm which is adapted to the photoperiod and thus determines whether animals are diurnal or nocturnal. By using a genetically modified zebrafish strain known as Tg (Xla.Eef1a1:Cau.asip1)iim04, which expresses a higher level of the agouti signalling protein 1 (Asip1), an endogenous antagonist of the melanocortin system, we observed a complete disruption of locomotor activity patterns, which correlates with the ablation of the melatonin daily rhythm. Consistent with this, in vitro experiments also demonstrated that Asip1 inhibits melatonin secretion from the zebrafish pineal gland, most likely through the melanocortin receptors expressed in this gland. Asip1 overexpression also disrupted the expression of core clock genes, including per1a and clock1a, thus blunting circadian oscillation. Collectively, these results implicate the melanocortin system as playing an important role in modulating pineal physiology and, therefore, circadian organisation in zebrafish.

Embryonal and pineal tumours represent a diverse group of central nervous system (CNS) neoplasms. While many of the small round blue cell tumours that make up the embryonal neoplasms share similar histologic qualities, there are several morphologic and cytologic characteristics that are useful in distinguishing different tumour types. Similarly, pineal parenchymal tumours represent clinically diverse tumours, ranging from benign to overtly malignant. The most recent iteration of the World Health Organization Classification of CNS Tumours expanded greatly on the significance of molecular alterations in brain tumour diagnostics. In this article, we summarize the salient cytologic and histologic features of CNS embryonal and pineal tumours, and highlight diagnostically relevant molecular alterations within each tumour type.

In this morphometric study, we describe the anatomy of the TIGR triangle, which is bordered by the tentorial surface of the cerebellum, the internal cerebral vein and vein of Galen complex, and the vein of Rosenthal. These structures define the window, or deep keyhole, to access the pineal region in non-midline supracerebellar infratentorial approaches.
The posterior fossa anatomy of 16 patients was studied in virtual reality (VR), and the TIGR triangles were defined and measured with special attention on its angular orientation in the posterior fossa. The angular expanse of the posterior fossa was measured and recorded as the transverse-sigmoid junction (TSJ) angle. Because a perpendicular corridor through an anatomic aperture provides the best exposure, we studied the starting point along the TSJ angle that offers the best exposure of TIGR.
In the 31 posterior fossa sides included in the study, the perpendicular trajectory through the TIGR triangle was on average 27.13° CI 95% (range: 5.97°-48.53°) from the midline. When comparing the SCIT variants, both the paramedian and lateral approaches provided near-perpendicular trajectory through the TIGR triangle in a majority of specimens. However, the modified paramedian approach, with starting point defined as TSJ angle/3, provided the most perpendicular path through the TIGR triangle.
We studied the size, spatial orientation, and morphology of the TIGR triangle. Our data indicated that the best exposure of TIGR is through a modified paramedian SCIT approach, in which the starting point one third of the way from midline to the TSJ.

BACKGROUND: Pineal cysts are a rare lesion of the pineal gland. Pineal cysts are benign lesions, generally asymptomatic, and are usually an incidental discovery on MRI performed for other problems. The management of pineal cysts in children remains a matter for debate. Here, we report our own retrospective paediatric cases that have been surgically treated and review the paediatric literature on this topic.
METHODS: This is a retrospective monocentric study. All patients operated by the senior author (CM) for a benign pineal cyst from 2000 to 2021 were included. All other pineal region cystic lesions were excluded. Medical and surgical data were extracted from the hospital medical database.
RESULTS: Twelve patients were included. The clinical symptomatology was characterized by headaches in seven patients, visual troubles in two patients, precocious puberty in one patient, signs of intracranial hypertension in two patients, seizures associated with headache in one patient, and headaches associated with behavioural troubles in another patient. No major post-operative complications were observed in this series. It is to noted that surgery was performed because a suspicion of a true pineal parenchymal tumour has been made. Histopathological study came back with the diagnosis of pineal cyst.
CONCLUSIONS: Pineal cyst is rare. If the radiological diagnosis is clear, no surgery is advocated except in cases associated with hydrocephalus and rapid growth. In case of a suspicion of a true pineal parenchymal tumour, a surgery may be needed to confirm the diagnosis. Lastly, we stress that only cystic lesions of the pineal gland itself should be considered as pineal cyst.

UNASSIGNED: Primary intracranial germ cell tumors (ICGCTs) are rare and are histologically classified as germinomas and non-germinomatous with distinctive prognostic and therapeutic implications. ICGCTs, essentially due to the inherent difficulty of surgical access, pose different challenges and management connotations than their extracranial counterparts. This is a retrospective analysis of histologically verified ICGCTs, which was undertaken to evaluate various clinicopathological features and their implications on patient management.
UNASSIGNED: Eighty-eight histologically diagnosed cases (over 14 years) of ICGCT at our institute formed the study cohort and were classified into germinoma and non-germinomatous germ cell tumors (NGGCTs). Additionally, germinomas were further subdivided on the basis of 1) tumor marker (TM) levels, as germinoma with normal TM, mildly elevated TM, and markedly elevated TM and 2) radiology features, as germinomas with typical radiology and atypical radiological features.
UNASSIGNED: ICGCT with age ≤6 years (P = 0.049), elevated TM (P = 0.047), and NGGCT histology (P < 0.001) showed significantly worse outcomes. Furthermore, germinomas with markedly elevated TM and certain atypical radiological features showed prognosis akin to NGGCT.
UNASSIGNED: Analysis of our largest single cancer center Indian patient cohort of ICGCT shows that inclusion of age ≤6 years, raised TM, and certain radiological features may assist clinicians in overcoming the limitations of surgical sampling, with better prognostication of histologically diagnosed germinomas.