SUMMARYThe piloneural collar in mammalian hairy skin comprises an intricate pattern of circumferential and longitudinal sensory afferents that innervate primary and secondary pelage hairs. The longitudinal afferents tightly associate with terminal Schwann cell processes to form encapsulated lanceolate nerve endings of rapidly adapting mechanoreceptors. The molecular basis for piloneural development, maintenance and function is poorly understood. Here, we show that Nefh-expressing glutamatergic neurons represent a major population of longitudinal and circumferential sensory afferents innervating the piloneural collar. Our findings using a VGLUT2 conditional-null mouse model indicate that glutamate is essential for innervation, patterning and differentiation of NMDAR + terminal Schwann cells during piloneural collar development. Similarly, treatment of adult mice with a selective NMDAR antagonist severely perturbed piloneural collar structure and reduced excitability of these mechanosensory neurons. Collectively, these results show that DRG-derived glutamate is essential for the proper development, maintenance and sensory function of the piloneural mechanoreceptor.

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Objective: To evaluate rates of epiphora after transection and marsupialization of the nasolacrimal duct (NLD) during endoscopic sinus and skull base surgery. Introduction: The nasolacrimal canal forms part of the medial wall of the maxillary sinus. Transecting the NLD is sometimes necessary for tumor resection or surgical access to maxillary sinus and infratemporal fossa pathology. There is no consensus for the endoscopic management of the NLD when only the duct is transected without involving the nasolacrimal sac. Methods: Medical records of 29 patients from 2 academic institutions who underwent endoscopic sinus and skull base surgery with transection of the NLD were retrospectively reviewed. Whether the duct was marsupialized or simply transected was recorded, and the postoperative rate of epiphora was calculated. Results: Mean age was 59 years (range, 14-86 years). Mean follow-up was 10.5 months (range, 1-33 months). The NLD was marsupialized in 16 (55%) and simply transected in 13 (45%) patients. Six patients underwent postoperative radiation. No patients in the marsupialization group had epiphora postoperatively, all with Munk score of 0. One patient in the transection group developed postoperative epiphora with Munk score of 1. Pathology included inverted papilloma (8), acute on chronic inflammation (6), B-cell lymphoma (3), juvenile nasopharyngeal angiofibroma (2), squamous cell carcinoma (2), Schneiderian papilloma (2), metastatic melanoma (1), HPV-related carcinoma (1), adenocarcinoma (1), benign epithelial cyst (1), adenoid cystic carcinoma (1), and erosive chronic sinusitis without nasal polyposis (1). Conclusion: Management after transection of the NLD varies widely. The duct may be simply transected or marsupialized, or a formal dacryocystorhinostomy can be performed. The surgeon must also choose whether to place a stent. Based on our small series and review of the literature, marsupialization or simple transection of the NLD results in a low rate of postoperative epiphora in the setting of endoscopic sinus and skull base surgery.

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