Rare locations of schwannomas: a few comments.

Dear Editor;

With curiosity I read the original article by Jeong et al. [1]. They proposed to modify the classification of trigeminal schwannomas (TSs) according to their extension into the adjacent compartment, shape, and location of origin, and concluded that TSs could be removed safely and effectively according to their modified classification. The authors are to be congratulated for conducting such a well-managed study on a topic of schwannomas. Here, I would like to add some additional points about the rare locations origin of schwannomas.

Schwannomas may originate from any cranial, peripheral or autonomic nerve of the body and are uncommon nerve sheath tumors. About one-third of schwannomas are identified to arise in the neck and head region. TSs are known to arise from the ganglion, root, or intracranial portion of the peripheral divisions of the nerve-mandibular, maxillary, and ophthalmic. Schwannomas including the mandibular division of trigeminal nerve and localizing particularly in the parapharyngeal space is entirely rare. The most common nerves of origin of TSs in the parapharyngeal space are the sympathetic chain and the vagus nerve [2].

On the other hand, an exceedingly rare schwannomas is olfactory schwannoma as the olfactory nerve is unsheathed by schwann cells, till today, only 48 cases have been reported worldwide [3]. Also, there have been no persuasive theories that are comprehensively accepted to define the origin of olfactory schwannoma. Additionally, a rare bone tumor is intraosseous schwannomas which is accounting for less than 1%. Notably, mandible is the most common site of intraosseous schwannoma, however, intraosseous skull vault schwannomas are very rare [4].

As is obvious from above discussion, parapharyngeal, olfactory, and intraosseous spaces are extremely rare locations origin of schwannomas which the management of them is a clinical challenge. In this regard, more studies may need to focus on this area.