Bulent Sam

Review of complications due to foramen ovale puncture

We aim to evaluate the mechanisms responsible for complications during trigeminal rhizotomy via foramen ovale puncture. Ten dry skulls and 10 skull-base specimens were investigated in the present study. In cadaveric skull-base specimens, the anatomical relationships between the foramen ovale, mandibular nerve and Gasserian ganglion and the surrounding neurovascular structures were investigated intradurally. The distance between the foramen ovale and Gasserian ganglion was measured as 6 mm. The abducent nerve, adjacent to the anterior tail of the petrolingual ligament, was observed passing along the lateral wall of the cavernous sinus. Advancement of the catheter more than 10 mm from the foramen ovale is likely to damage the internal carotid artery and the abducent nerve at the medial side of the petrolingual ligament. Thermocoagulation of the lateral wall of the cavernous sinus may damage the cranial nerves by heat, giving rise to pareses.

Duplication of the abducens nerve at the petroclival region. An anatomic study

OBJECTIVEDuring its course between the brainstem and the lateral rectus muscle, the abducens nerve usually travels forward as a single trunk, but it is not uncommon for the nerve to split into two branches. The objective of this study was to establish the incidence and the clinical importance of the duplication of the nerve. METHODSThe study was performed on 100 sides of 50 autopsy materials. In 10 of 11 cases of duplicated abducens nerve, colored latex was injected into the common carotid arteries and the internal jugular veins. The remaining case was used for histological examination. RESULTSFour of 50 cases had duplicated abducens nerve bilaterally. In seven cases, the duplicated abducens nerve was unilateral. In 9 of these 15 specimens, the abducens nerve emerged from the brainstem as a single trunk, entered the subarachnoid space, split into two branches, merged again in the cavernous sinus, and innervated the lateral rectus muscle as a single trunk. In six specimens, conversely, the abducens nerve exited the pontomedullary sulcus as two separate radices but joined in the cavernous sinus to innervate the lateral rectus muscle. In 13 specimens, both branches of the nerve passed beneath the petrosphenoidal ligament. In two specimens, one of the branches passed under the ligament and the other passed over it. In one of these last two specimens, one branch passed over the petrosphenoidal ligament and the other through a bony canal formed by the petrous apex and the superolateral border of the clivus. In all of the specimens, both branches were wrapped by two layers: an inner layer made up of the arachnoid membrane and an outer layer composed of the dura during its course between their dural openings and the lateral wall of the cavernous segment of the internal carotid artery. This finding was also confirmed by histological examination in one specimen. CONCLUSIONDouble abducens nerve is not a rare variation. Keeping such variations in mind could spare us from injuring the VIth cranial nerve during cranial base operations and transvenous endovascular interventions.

Microsurgical and endoscopic anatomy of Liliequist's membrane and the prepontine membranes: cadaveric study and clinical implications.

BackgroundLiliequist’s membrane is mostly described as having a diencephalic leaf, mesencephalic leaf, and diencephalic-mesencephalic leaves in the literature. Also different descriptions of the prepontine membranes were reported. In this study, we visualized the regular structural forms of membranes without disturbing any attachments and defined infrachiasmatic and prepontine safety zones. We discussed the clinical significance of these structures.Materials and methodsThe study was carried out on 24 adult human cadavers at the Morgue Specialization Department of the Forensic Medicine Institution following the initial autopsy examination. Liliequists membrane and the prepontine membranes were explored after retraction of the frontal lobes. Dissections were performed under the operative microscope. A 0- and 30-degree, 2.7-mm angled rigid endoscope (Aesculap, Tuttlingen, Germany) was advanced through the prepontine cistern from the natural holes of membranes, or small holes were opened without damaging the surrounding structures.ResultsThe basal arachnoid membrane (BAM) continued as Liliequists membrane (LM) without any distinct separation in all specimens. The LM coursed over the posterior clinoids and split into two leaves as the diencephalic leaf (DL) and mesencephalic leaf (ML) in 18 specimens; the medial pontomesencephalic membrane (MPMM) coursed anterolaterally as a continuation of the ML and attached to the medial surfaces of the fifth and sixth nerves, joining with the lateral pontomesencephalic membrane (LPMM), which was also a posterolateral continuation of the ML in all specimens. The medial pontomedullar membrane (MPMdM) and lateral pontomedullar membrane (LPMdM) were observed in 21 specimens. The MPMdM membrane was a continuation of the MPMM, and the LPMdM was a continuation of the LPMM in all 21 specimens.ConclusionWe observed that the LM is a borderless continuation of the BAM. The MPMM and LPMM split from the ML without any interruptions. The MPMdM and LPMdM were a single membrane continuing from the MPMM and LPMM. We determined infrachiasmatic and prepontine areas that can be important for inferior surgical approaches.

Microsurgical anatomy of membranous layers of the pituitary gland and the expression of extracellular matrix collagenous proteins

BackgroundThere are several reports about the microanatomical and histological features of sellar and parasellar membranous structures and clinical studies about MMP proteinase as a predictive factor. However, studies on collagen contents of sellar and parasellar membranous structures are limited. We demonstrated the membranous structures surrounding the pituitary gland and defined extracellular matrix (ECM) collagenous proteins, collagen I-IV expression patterns of sellar and parasellar connective tissues.MethodsThe study was carried out on ten fresh postmortem human bodies at the Forensic Medicine Institution. Cavernous sinuses were resected with sellar structures and were stored at −80°C liquid nitrogen tanks. Medial wall of the cavernous sinus, pituitary capsule and pituitary tissue samples were obtained for RT-PCR. Opposite side specimens were used for histological and immune staining studies. Collagens I-IV were studied by immunohistochemical and reverse transcription polymerase chain reaction (RT-PCR) methods.FindingsThe pituitary capsule and medial wall were identified as two different structures. The fibrous membrane, as the third membrane, was identified as staying whole in eight of ten specimens. Increased type IV collagen was determined in the pituitary gland, medial wall and pituitary capsule, respectively, in both RT-PCR and immunhistochemical studies. Immunhistochemical studies revealed that collagen I was strongly expressed in both the medial wall and pituitary gland.ConclusionIncreased type IV collagen was detected especially in pituitary tissue, the medial wall and the pituitary capsule by immune staining and RT-PCR. Type IV collagen was considered to be an important factor in the progression of adenoma and invasion.

The perforating branches of the P1 segment of the posterior cerebral artery

The perforating branches of the P1 segment of the posterior cerebral artery are vulnerable to injury. Because of their close proximity to the basilar artery, the vulnerability occurs especially during surgical interventions for vascular pathologies such as basilar apex aneurysms. Therefore, extensive knowledge of the microsurgical anatomy of this area is mandatory to prevent poor post-operative outcomes. We microscopically examined 28 P1 segments obtained from 14 adult fresh cadaver brains (6 silicone injected, 8 freshly examined). The P1 segments ranged between 2.8mm and 12.2mm (mean 6.8mm) in length with a mean outer diameter of 1.85 mm (range 0.8-4.5mm). All 94 thalamoperforating branches identified in 27 P1 segments (mean 3.35 branches per segment) arose from the postero-superior aspect of P1 and were the most proximally originating branch in nearly all specimens (96.4%). In addition in 28 P1s, 12 short circumflex arteries (42.8%; mean 0.42 branches per segment), 16 long circumflex arteries (57.1%; mean 0.57 branches per segment) and 10 medial posterior choroidal arteries (35.7%; mean 0.35 branches per segment) were identified and all originated from the posterior or postero-inferior surface of the P1 segment. When the P1 segment had more than one type of branch, it was the short circumflex arteries that were always more proximal in origin than the others. The medial posterior choroidal arteries were always more distal in origin. All three branches were not observed together in any of the P1 segments. The findings in this, and future, anatomical studies may help to reduce the post-surgical morbidity and mortality rates after surgery for posterior circulation aneurysms.

Microsurgical anatomy of the cisternal anterior choroidal artery with special emphasis on the preoptic and postoptic subdivisions

OBJECT The object of this study was to delineate the microsurgical anatomy of the cisternal segment of the anterior choroidal artery (AChA). The authors also propose a new classification of this segment on the basis of its complicated course within the carotid and crural cisterns in relation to important neurovascular structures, and the site of origin, course, and areas of supply of perforating arteries. METHODS Thirty cadaveric cerebral hemispheres injected with colored latex were dissected under surgical magnification to view the cisternal segment of the AChA and its perforators. Fiber dissections using the Klingler technique were performed in two additional latex injected hemispheres to follow the penetration points, courses, and terminal areas of supply of perforating branches that arise from the cisternal segment of the AChA. RESULTS The cisternal segment of the AChA was divided into pre- and postoptic parts that meet at the arterys genu, the most medial extension point of the cisternal segment where the artery makes an abrupt turn after passing under the optic tract. The preoptic part of the AChA extended from its origin at the inferomedial side of the internal carotid artery to the arterys genu, which is commonly located just inferomedial to the initial part of the optic tract. The postoptic part coursed within the crural cistern and extended from the genu to the inferior choroidal point. The genu of the AChA was 8 mm medial to the arterys origin and was located medial to the optic tract in 13% of the hemispheres. The postoptic part was longer than the preoptic part in all hemispheres and had more perforating arteries supplying critical deep structures (preoptic 3.4 per hemisphere vs postoptic 4.6 per hemisphere), and these results were statistically significant (p = 0.01). At the preoptic part, perforating arteries arose from the superolateral portion of the artery and coursed laterally; at the postoptic part, perforators arose from the inferomedial portion of the artery and coursed medially. Perforating arteries from both segments passed most commonly to the optic tract, followed by the anterior segment and apex of uncus in the preoptic part and the cerebral peduncle in the postoptic part. CONCLUSIONS Both parts of the cisternal segment of the AChA come into surgical view during surgeries for different pathologies in and around the perimesencephalic cisterns. However, attending to the arterys genu and defining pre- and postoptic parts during surgery may help the surgeon locate the origin and eventual course of these perforators, and even estimate the terminal areas of supply of most of the perforating arteries. The proposed classification system can prove helpful in planning any operative procedure along the crural cistern and may reduce the probability of inadvertent injury to perforating branches of the cisternal segment.

A quick-solidifying, coloured silicone mixture for injecting into brains for autopsy: technical report

The injection of cadaver brains is invaluable for anatomic study, but cadavers that have been properly handled are not easy to obtain. A large number of cadavers pass through forensic departments around the world, and these cadavers could provide hundreds of research specimens, though they remain in the forensic unit for only a short time. The injection of a silicone mixture that quickly solidifies during autopsy would provide greater numbers of fresh specimens for study. The authors describe a technique for injecting a self-curing silicone mixture that can be used on autopsy specimens in a forensic unit. This technique does not interfere with routine autopsy findings. We describe the preparation of the mixture and autopsy specimens, the injection process, and the method for removing injected brains from cadavers. The solidifying process took a 1-h duration in this injection method and was in accord with autopsy procedure. The arterial bed was satisfactorily filled, and even small perforating branches and pial anastomoses were well demonstrated. Injecting autopsy specimens with the quick-solidifying silicone mixture allows anatomical studies of specimens even from cadavers admitted to forensic departments for only a short time. This method can provide neurosurgery laboratories with sufficient numbers of specimens appropriate for various studies.

Electron Microscopic Description of the Sylvian Arachnoid Membrane

Background:The aim of this study was to investigate the potential role of the arachnoid membrane of the Sylvian cistern in the secretion and absorption of cerebrospinal fluid (CSF). Materials and Methods:Arachnoid specimens including the Sylvian cistern were obtained from the widest portion of the limen insulae region and were taken from 6 human cadavers within 12 hours postmortem. For electron microscopic examinations, specimens were fixed immediately in a solution of 2.5% cacodylate-buffered glutaraldehyde. Postfixation was performed with 2% osmic acid. After fixation, the tissue was dehydrated through a graded series of alcohol and blocked with Epon 812. Thick sections of the Epon-blocked tissue were stained with toluidine blue and examined under light microscopy. Ultrathin sections of 400 to 600 Å were obtained using an ultramicrotome. The thin tissue sections were then processed with lead citrate and uranyl acetate for contrast and examined under transmission electron microscopy. Results:The Sylvian arachnoid membrane is composed of 3 main layers. Neuroepithelial cells richly occupy the outermost layer. Ultrastructural analysis revealed electron-lucent cells, electron-dense cells, cells with cytoplasmic processes, numerous tight junctions, desmosomes, and gap junctions. There were macrophage-like cells, pinocytotic vesicles, intercellular clefts, and interdigitation. These findings suggest the potential for fluid transport. The inner layers were composed of collagen fibers and fibroblasts and separated from the outer layer by a basement membrane. Conclusions:Our study suggests that CSF might be transported across the Sylvian arachnoid membrane. Our findings demonstrate the potential of CSF transport to function in a secretory and/or absorptive manner.