Romain Tonnelet

The olfactory fascia: an evo–devo concept of the fibrocartilaginous nose

PurposeEvo–devo is the science that studies the link between evolution of species and embryological development. This concept helps to understand the complex anatomy of the human nose. The evo–devo theory suggests the persistence in the adult of an anatomical entity, the olfactory fascia, that unites the cartilages of the nose to the olfactory mucosa.MethodsWe dissected two fresh specimens. After resecting the superficial tissues of the nose, dissection was focused on the disarticulation of the fibrocartilaginous noses from the facial and skull base skeleton.ResultsDissection shows two fibrocartilaginous sacs that were invaginated side-by-side in the midface and attached to the anterior skull base. These membranous sacs were separated in the midline by the perpendicular plate of the ethmoid. Their walls contained the alar cartilages and the lateral expansions of the septolateral cartilage, which we had to separate from the septal cartilage. The olfactory mucosa was located inside their cranial ends.ConclusionThe olfactory fascia is a continuous membrane uniting the nasal cartilages to the olfactory mucosa. Its origin can be found in the invagination and differentiation processes of the olfactory placodes. The fibrous portions of the olfactory fascia may be described as ligaments that unit the different components of the olfactory fascia one to the other and the fibrocartilaginous nose to the facial and skull base skeleton. The basicranial ligaments, fixing the fibrocartilaginous nose to the skull base, represent key elements in the concept of septorhinoplasty by disarticulation.

Basilar Perforator Aneurysms: Presentation of 4 Cases and Review of the Literature

OBJECTIVE Basilar perforator aneurysms (BPAs) are rare lesions that present a therapeutic challenge. We present 4 cases of ruptured BPAs treated either conservatively or by flow diverter deployment and review the literature. METHODS Patients (age 78, 59, 53, and 62 years) presented with World Federation of Neurological Societies grade I-IV and Fisher grade 3-4 subarachnoid hemorrhage. Initial angiography results were normal in 3 patients and necessitated a second angiography. BPA diameter was 0.5-3 mm; BPAs were located in the mid-third of the basilar artery in 2 patients and the upper third in 2 patients. RESULTS All patients were managed conservatively. One patient experienced rebleeding 10 days after initial ictus, which required the deployment of a flow diverter in the basilar artery. One patient developed a severe spontaneous pontine ischemic stroke with severe quadriparesis and refused further imaging. He was clinically stable at 1-year clinical follow-up. The other 3 patients showed complete resolution of BPAs on control follow-up imaging. CONCLUSIONS Ruptured BPAs are rare lesions that may heal spontaneously or be associated with spontaneous ischemic brainstem stroke or rerupture. These lesions can be managed conservatively initially with flow diverter deployment the most suitable therapeutic alternative in selected cases. Larger studies are needed to fully understand the natural history and refine the therapeutic strategy for these lesions.

Perioperative Bioccipital Watershed Strokes in Bilateral Fetal Posterior Cerebral Arteries During Spinal Surgery

BACKGROUND Vision loss due to cerebral infarction during spinal surgery is less described. Intraoperative hypotension would be a leading cause. Patients with variation of the circle of Willis could be more prone to present stroke in this context, but reports are lacking to sustain the theory. Bilateral occipital watershed ischemic strokes have never been described before. We report the case of a patient with a fetal origin of both posterior cerebral arteries (PCAs), presenting this particular anatomic stroke following lumbar laminectomy surgery for spinal stenosis during which intraoperative hypotension was observed. We discuss how this common anomaly associated with intraoperative hypotension could have promoted this serious complication. CASE DESCRIPTION A 55-year-old man woke up with cortical blindness after he had undergone lumbar surgery during which a marked decrease in blood pressure had occurred. Magnetic resonance imaging revealed bilateral symmetric infarctions of the occipital lobes in the distal territory of both PCAs and smaller anterior watershed ischemic strokes, suggesting a hemodynamic mechanism. Extended investigations, including conventional angiography, failed to find any cause of stroke but revealed bilateral fetal PCAs supplied by internal carotid arteries only. Two years later, the patient has not recovered and remains severely visually impaired. CONCLUSIONS The standing hypothesis would be posterior low-flow infarctions resulting from intraoperative hypotension on a variation of the circle of Willis more prone to decrease in cerebral blood flow. Moreover, this case supports the hypothesis of vascular insufficiency due to intraoperative hypotension as cause of stroke during spinal surgery.

Three Cases of Ruptured Basilar Artery Dissection: From Diagnosis to Endovascular Treatment.

BACKGROUND Ruptured basilar artery dissections are rare, and prognosis is often disastrous. CASE DESCRIPTION We report 3 recent cases of ruptured dissection from imaging diagnosis to endovascular treatment, presenting 3 different types of dissection and 3 different treatment approaches. These 3 patients presented major subarachnoid hemorrhage (Fisher grade 4): 2 of them were in a coma (World Federation of Neurosurgical Societies Grading System [WFNS] 5), and 1 patient presented with headache only (WFNS 1). Two of the 3 dissections presented a dilated pseudoaneurysm responsible for the bleeding (1 large and 1 small), and the remaining dissection was extensive. The dissection with the larger pseudoaneurysm was treated with coils, resulting in early recanalization requiring another endovascular treatment with coils and a flow diverter stent. The patient with the small pseudoaneurysm was treated with a flow diverter only. These 2 patients had a favorable outcome. The remaining patient with a large tear of the basilar artery had 3 overlapping stents, and fatal rebleeding occurred prematurely. CONCLUSIONS These 3 cases illustrate different patient management strategies. We discuss this challenging condition and the current position of endovascular therapeutic techniques.

Embryo Form Project: An original technique for the three-dimensional reconstruction of human embryo morphology

Our current knowledge on the developmental stages of human embryogenesis has derived from limited numbers of classical studies. Computer technology now permits accurate 3D reconstruction of embryo morphology from serial histological sections. We present a successful technique that uses either fresh or preserved serial histological sections to generate highly detailed 3D image reconstructions of very small human embryos. We present the data we obtained from the reconstruction in virtual space of previously sectioned 15 and 22.5mm embryos. Their morphologies were studied using a DICOM viewer which permitted the analysis of any specific structure in any required orientation. To our knowledge, this is the first time human embryos have been reconstructed in this way. We believe that this reconstruction technique could improve our knowledge on embryo morphogenesis, especially if coupled to the study of genes involved in embryonic development. It may also prove to be a useful pedagogical tool.