Microsurgical anatomy of the auditory radiations: revealing the enigmatic acoustic pathway from a surgical viewpoint.

OBJECTIVE: The thalamocortical projections of the auditory system have not been detailed via microanatomical fiber dissections from a surgical viewpoint. The aim of this study was to delineate the course of the auditory radiations (ARs) from the medial geniculate body to their final destination in the auditory cortex. The authors' additional purpose was to display the relevant neural structures in relation to their course en route to Heschl's gyrus. METHODS: White matter fibers were dissected layer by layer in a lateral-to-medial, inferolateral-to-superomedial, and inferior-to-superior fashion. RESULTS: The origin of ARs just distal to the medial geniculate body was revealed following the removal of the parahippocampal gyrus, cingulum bundle, and mesial temporal structures, in addition to the lateral geniculate body. Removing the fimbria, stria terminalis, and the tail of the caudate nucleus along the roof of the temporal horn in an inferior-to-superior direction exposed the lateral compartment of the sublenticular segment of the internal capsule as the predominant obstacle that prevents access to the ARs. The ARs were initially obscured by the inferolaterally located temporopulvinar tract of Arnold, and their initial course passed posterolateral to the temporopontine fascicle of Türck. The ARs subsequently traversed above the temporopulvinar fibers in a perpendicular manner and coursed in between the optic radiations at the sensory intersection region deep to the inferior limiting sulcus of insula. The distal part of the ARs intermingled with the fibers of the anterior commissure and inferior fronto-occipital fasciculus during its ascent toward Heschl's gyrus. The ARs finally projected to a large area over the superior temporal gyrus, extending well beyond the anteroposterior boundaries of the transverse temporal gyri. CONCLUSIONS: The ARs can be appreciated as a distinct fiber bundle ascending between the fibers of the sublenticular segment of the internal capsule and traversing superiorly along the roof of the temporal horn by spanning between the optic radiations. Our novel findings suggest potential disruption of the ARs' integrity during transsylvian and transtemporal approaches along the roof of the temporal horn toward the mesial temporal lobe. The detailed 3D understanding of the ARs' relations and awareness of their course may prove helpful to secure surgical interventions to the region.

Cervical Oblique Corpectomy: Revitalizing the Underused Surgical Approach With Step-By-Step Simulation in Cadavers.

ABSTRACT: Recently, the World Federation of Neurosurgical Societies Spine committee recommended that additional research on cost-benefit analysis of various surgical approaches for cervical spondylotic myelopathy be carried out and their efficacy with long-term outcomes be compared. Unfortunately, it is highly probable that the oblique corpectomy (OC) will not be included in cost-benefit investigations due to its infrequent application by neurosurgeons dealing with the spine. In this cadaveric study, head and necks of 5 adult human cadavers stained with colored latex and preserved in 70% alcohol solution were dissected under a table-mounted surgical microscope using 3× to 40× magnifications. The OC approach was performed to simulate real surgery, and the neurovascular structures encountered during the procedure and their relations with each other were examined. Oblique corpectomy was performed unilaterally, although neck dissections were performed bilaterally on 10 sides in all 5 cadavers. At each stage of the dissection, multiple three-dimensional photographs were obtained from different angles and distances. For an optimal OC, both the anterior spinal cord must be sufficiently decompressed and sufficient bone must be left in place to prevent instability in the cervical spine. Oblique corpectomy is a valid and potentially low cost alternative to other anterior and posterior approaches in the surgical treatment of cervical spondylotic myelopathy. However, meticulous cadaver studies are essential before starting real surgical practice on patients in order to perform it effectively and to avoid the risks of the technique.

Retrospective Analysis and Comparison of 48 Intracranial Meningioma Cases As Two Groups According to Their Size.

Objective This study aims to examine the possible demographic, clinical, and surgical differences between giant and smaller meningiomas. Materials and Methods Forty-eight meningioma patients who were operated on in our clinic between 2016-2020 were included in our study. Fourteen meningiomas larger than 5 cm in diameter were defined as giant meningiomas and placed in group 1. Thirty-four remaining meningiomas, with sizes less than 5 cm, were placed in group 2. These patients were evaluated regarding age, sex, localization, symptoms and neurological findings, surgical results, histopathology, and postoperative results. Results The most common localization in group 1 was falcine-parasagittal, whereas in group 2 it was convexity. Simpson's grade I resection rate in group 1 was 35.71%, while in group 2 this rate was 67.65%. In histopathological examination, transitional type meningiomas (35.71%) were the most common in group 1, whereas fibrous type meningiomas (32.35%) were seen the most in group 2. Group 1 Karnofsky Performance Scale score average was 75.71 preoperatively and 85.71 postoperatively. In group 2, the preoperative and postoperative average was 97.35 and 96.76, respectively. The comparative statistical analysis reflects that: A) Resection rates were significantly lower in the giant meningioma group. B) Similarly, Karnofsky Performance Scale scores were also lower than group 2. C) When statistical comparisons were made according to sex, age, localization, histopathological results, postoperative complications, and recurrence rates, no significant differences were observed. Conclusion The term "Giant Meningioma" is a type of distinction that is frequently made in the literature. However, the single major difference we see in our study was the surgical results. The general condition of patients before and after surgery may be more critical than others in giant meningiomas. Although surgical resection is the main form of treatment in giant meningiomas, the risks arising from the size of the tumor should be taken into account, and necessary plans should be made for a successful surgical intervention.

Secondary Parkinsonism in a Patient With a Cerebral Cavernous Hemangioma Treated With Stereotactic Radiosurgery.

Secondary parkinsonism is defined with some symptoms similar to idiopathic Parkinson's disease, but with different etiologies. And cerebral cavernous hemangioma is one of the rare cases. A 51-year-old, male patient was consulted with tremor, rigidity and bradykinesia on the right upper extremity. The Hoehn and Yahr Parkinson's scale was Stage І. Radiological evaluations showed a deep-seated cerebral cavernous hemangioma at the left posterior insular region. The patient received stereotactic radiosurgery (CyberKnife®, Accuray Incorporated, Sunnyvale, CA, USA). Clinical and radiological improvements revealed within follow-up, respectively. Stereotactic radiosurgery may be an alternative treatment for secondary parkinsonism by reducing the risk of re-bleeding and reducing its size.

Fiber dissection and 3-tesla diffusion tensor tractography of the superior cerebellar peduncle in the human brain: emphasize on the cerebello-hypthalamic fibers.

Experimental studies in various species using tract-tracing techniques showed clear evidence of the presence of cerebello-hypothalamic projections. However, these connections were not clearly described in humans. In the present study we aimed to describe the direct cerebello-hypothalamic connections within the superior cerebellar peduncle (SCP) using fiber dissection techniques on cadaveric brains and diffusion tensor tractography (DTI) in healthy adults. Fiber dissection was performed in a stepwise manner from lateral to medial on 6 cerebral hemispheres. The gray matter was decorticate and fiber tracts were revealed. The SCP was exposed and the fibers were traced distally using wooden spatulas. The MRI examinations were performed in seven cases using 3-tesla 3T unit. The direct cerebello-hyothalamic pathways were exposed using high-spatial-resolution DTI. The present study using both fiber dissection and DTI in adult human showed direct cerebello-hypothalamic fibers within the SCP. The SCP fibers course anterolateral to the cerebral aqueduct reaching the level of the red nucleus of the midbrain. The majority of the fibers crosses over and reached the contralateral diencephalic structures and some of these fibers terminated at the contralateral anterior hypothalamic area. Some of the uncrossed SCP fibers reached the ipsilateral diencephalic structures and terminated at the ipsilateral posterior hypothalamic area. We further reported the close relationship of the SCP with the MCP, lateral lemniscus, red nucleus and substantia nigra. In the DTI evaluations of the SCP we exposed unilateral left cerebello-hypothalamic fibers in five cases and bilateral cerebello-hypothalamic fibers in two cases. The present study demonstrates the direct cerebello-hypothalamic connections within the SCP for the first time using fiber dissection and DTI technique in the human brain. The detailed knowledge of the cerebello-hypothalamic fibers can outline the unexplained deficit that may occur during regional surgery.