=====Nasal polyp=====
Nasal polyps are polypoidal masses arising mainly from the mucous membranes of the nose and paranasal sinuses.

They are overgrowths of the mucosa that frequently accompany allergic rhinitis, and are freely movable and nontender.

Nasal polyps are usually classified into antrochoanal polyps and ethmoidal polyps. Antrochoanal polyps arise from the maxillary sinuses and are the much less common, ethmoidal polyps arise from the ethmoidal sinuses.

Symptoms of polyps include nasal congestion, sinusitis, anosmia (loss of smell), and secondary infection leading to headache. They may be removed by surgery, but are found to recur in about 70% of cases. Sinus surgery requires a great amount of precision as this involves risk of damage to orbit matter.

====Case series====
In a retrospective study 12 patients were included who had undergone endoscopic sinus surgery for nasal polyposis and were referred to the author for revision surgery after iatrogenic trauma of the anterior skull base during the procedure. Each patient had been operated by a different surgeon, all of the physicians being in an advanced stage of their surgical career and being board certified otolaryngologists.

During endoscopically controlled revision surgery, all lesions could be detected, 10 of them being located in the ethmoid roof, while one injury had occurred in the lateral lamella of the cribriform plate and another one in the olfactory groove between the medial turbinate and the nasal septum.

In contrast to reports in the literature, the preferred site for anterior skull base injuries during endoscopic sinus surgery in our group was not the lateral lamella of the cribriform plate, but the anterior part of the ethmoid roof, just behind the frontal recess. Apparently the course of the ethmoid roof might be misinterpreted during sinus surgery even by surgeons who are familiar with the operative technique
((Grevers G. Anterior skull base trauma during endoscopic sinus surgery for
nasal polyposis preferred sites for iatrogenic injuries. Rhinology. 2001
Mar;39(1):1-4. PubMed PMID: 11340688.
)).

====Case reports====
Holzer et al. report the first case of an intracranial and intradural nasal polyposis occurring in a close topographical relation to a previous, iatrogenic anterior [[skull base defect]]. The tumour was resected and the skull base defect was closed transnasally by an interdisciplinary team. The histopathological report confirmed recurrent polyposis
((Holzer M, Thon N, Stelter K, Rachinger W, Betz CS. Intracranial and intradural
nasal polyposis after iatrogenic skull base defect: A case report. Br J
Neurosurg. 2016 Jan 13:1-3. [Epub ahead of print] PubMed PMID: 26761416.
)).