Tag: fiber dissection technique

Posted on

The frontal longitudinal system as revealed through the fiber microdissection technique

J Neurosurg 133:1503–1515, 2020

The purpose of this study was to investigate the morphology, connectivity, and correlative anatomy of the longitudinal group of fibers residing in the frontal area, which resemble the anterior extension of the superior longitudinal fasciculus (SLF) and were previously described as the frontal longitudinal system (FLS).

METHODS Fifteen normal adult formalin-fixed cerebral hemispheres collected from cadavers were studied using the Klingler microdissection technique. Lateral to medial dissections were performed in a stepwise fashion starting from the frontal area and extending to the temporoparietal regions.

RESULTS The FLS was consistently identified as a fiber pathway residing just under the superficial U-fibers of the middle frontal gyrus or middle frontal sulcus (when present) and extending as far as the frontal pole. The authors were able to record two different configurations: one consisting of two distinct, parallel, longitudinal fiber chains (13% of cases), and the other consisting of a single stem of fibers (87% of cases). The fiber chains’ cortical terminations in the frontal and prefrontal area were also traced. More specifically, the FLS was always recorded to terminate in Brodmann areas 6, 46, 45, and 10 (premotor cortex, dorsolateral prefrontal cortex, pars triangularis, and frontal pole, respectively), whereas terminations in Brodmann areas 4 (primary motor cortex), 47 (pars orbitalis), and 9 were also encountered in some specimens. In relation to the SLF system, the FLS represented its anterior continuation in the majority of the hemispheres, whereas in a few cases it was recorded as a completely distinct tract. Interestingly, the FLS comprised shorter fibers that were recorded to interconnect exclusively frontal areas, thus exhibiting different fiber architecture when compared to the long fibers forming the SLF.

CONCLUSIONS The current study provides consistent, focused, and robust evidence on the morphology, architecture, and correlative anatomy of the FLS. This fiber system participates in the axonal connectivity of the prefrontal-premotor cortices and allegedly subserves cognitive-motor functions. Based in the SLF hypersegmentation concept that has been advocated by previous authors, the FLS should be approached as a distinct frontal segment within the superior longitudinal system.

Posted on

The anatomy of Meyer’s loop revisited

The anatomy of Meyer’s loop revisited

J Neurosurg 122:1253–1262, 2015

The goal in this study was to explore and further refine comprehension of the anatomical features of the temporal loop, known as Meyer’s loop.

Methods The lateral and inferior aspects of 20 previously frozen, formalin-fixed human brains were dissected under the operating microscope by using fiber microdissection.

Results A loop of the fibers in the anterior temporal region was clearly demonstrated in all dissections. This temporal loop, or Meyer’s loop, is commonly known as the anterior portion of the optic radiation. Fiber microdissection in this study, however, revealed that various projection fibers that emerge from the sublentiform portion of the internal capsule (IC-SL), which are the temporopontine fibers, occipitopontine fibers, and the posterior thalamic peduncle (which includes the optic radiation), participate in this temporal loop and become a part of the sagittal stratum. No individual optic radiation fibers could be differentiated in the temporal loop. The dissections also disclosed that the anterior extension and angulation of the temporal loop vary significantly.

Conclusions The fiber microdissection technique provides clear evidence that a loop in the anterior temporal region exists, but that this temporal loop is not formed exclusively by the optic radiation. Various projection fibers of the IC-SL, of which the optic radiation is only one of the several components, display this common course. The inherent limitations of the fiber dissection technique preclude accurate differentiation among individual fibers of the temporal loop, such as the optic radiation fibers.

Posted on

Microsurgical anatomy of the ventral callosal radiations: new destination, correlations with diffusion tensor imaging fiber-tracking, and clinical relevance

J Neurosurg 112:512–519, 2010.DOI: 10.3171/2009.6.JNS081712

In the current literature, there is a lack of a detailed map of the origin, course, and connections of the ventral callosal radiations of the human brain.

Methods. The authors used an older dissection technique based on a freezing process as well as diffusion tensor imaging to investigate this area of the human brain.

Results. The authors demonstrated interconnections between areas 11, 12, and 25 for the callosal radiations of the trunk and rostrum of the corpus callosum; between areas 9, 10, and 32 for the genu; and between areas 6, 8, and 9 for the ventral third of the body. The authors identified new ventral callosal connections crossing the rostrum between both temporal poles and coursing within the temporal stem, and they named these connections the “callosal radiations of Peltier.” They found that the breadth of the callosal radiations slightly increases along their course from the rostrum to the first third of the body of the corpus callosum.

Conclusions. The fiber dissection and diffusion tensor imaging techniques are complementary not only in their application to the study of the commissural system in the human brain, but also in their practical use for diagnosis and surgical planning. Further investigations, neurocognitive tests, and other contributions will permit elucidation of the functional relevance of the newly identified callosal radiations in patients with disease involving the ventral corpus callosum.

Proudly powered by WordPress