The Quadrangular Space, Endonasal Access to the Meckel Cave: Technical Considerations and Clinical Series.

OBJECTIVE: An anteromedial corridor via an expanded endoscopic endonasal approach to the Meckel cave (MC) was described more than a decade ago. However, few clinical series or endoscopic endonasal technical contributions exist concerning this type of approach to this complex region. METHODS: We present a detailed description of the surgical technique for this approach reviewing the original technique and adding clarifying conceptual notions. We conducted a multicenter retrospective study selecting patients who underwent endonasal endoscopic surgery for lesions exclusively limited to the MC in the past 6 years. Intraoperative and postoperative complications were analyzed. The study of 10 cadaveric specimens provides additional information. RESULTS: We performed a fully endoscopic anteromedial corridor to the MC in 18 patients. The most prevalent pathologic finding was schwannoma of the V nerve in 4 patients. Sixth cranial nerve palsy (13 patients) and trigeminal dysfunction (10 patients) were the predominant preoperative clinical signs. There were no remarkable intraoperative complications. Corneal keratopathy caused by dry eye syndrome affected 3 patients and V2 residual neuralgia appeared postoperatively in 2 patients. Six patients recovered from sixth cranial nerve palsy, and 2 showed improvement in preoperatively referred facial pain. CONCLUSIONS: The front door to the MC via the endonasal anteromedial corridor could be a good option. Understanding of the anatomy and the concept of the quadrangular space is crucial to performing this technique safely, which has few complications in experienced hands. Recovery from sixth nerve palsy is possible with this approach. Corneal keratopathy in these patients is a potential complication.

Identification and localization of procalcitonin-like immunoreactivity in the rat hypothalamus.

Procalcitonin (PCT) is a 116-amino acid polypeptide physiologically produced, as the precursor protein of calcitonin (CT), in the parafollicular cells of the thyroid gland, but physiological functions and other major sources of PCT remains unclear. The distribution of PCT-like immunoreactivity (PCT-LI) in the rat hypothalamus was examined by immunohistochemistry using a monoclonal antibody raised against the mid-region of human PCT (60-77-amino acid fragment). This antibody cross-reacts well with rat PCT and immature CT, but it cross-react poorly with free mature CT. Abundant expression of PCT-LI was found in zones at the interface between brain and cerebrospinal fluid (CSF) such as the ependymal layer and ventral glia limitans (VGL). Double labeling of PCT and glial fibrillary acidic protein (GFAP) identified this population of small cells as astrocytes, possibly tanycytes, a type of specialized glial cell that interacts in neuroendocrine functional dynamics. The fibers of these cells extend to circumventricular organs (CVOs) and to astrocytes located inside the parenchyma of key autonomic regulatory hypothalamic areas, with highest densities in the supraoptic nucleus (SO), arcuate nucleus (Arc), area postrema (AP), median eminence (ME), medial preoptic nucleus, tuber cinereum, and accessory neurosecretory nuclei. No strongly labeled cells were found in the paraventricular nucleus. The wide distribution of PCT-LI in the hypothalamus, in close correspondence with previous mapping of CT receptors in the rat brain, suggests that PCT may influence a multitude of biological activities associated with the hypothalamic-pituitary axis.