====== Trigeminal schwannoma classification ======


The first classification system was proposed by Jefferson 
((Jefferson G. The trigeminal neurinomas with some remarks on malignant invasion of the gasserian ganglion. Clin Neurosurg. 1953;1:11–54.))
in [[1955]] who categorized TSs into three different types: 

Type A, which described tumors originating from the Gasserian ganglion in the [[middle cranial fossa]]. see [[Middle fossa trigeminal schwannoma]]

Type B, which is comprised of tumors originating from the roots of the trigeminal nerve in the posterior fossa; and finally, Type C, or the so-called "hour-glass" tumors, which occupy both the middle and posterior fossae. 

Some authors have added a fourth classification, Type D, tumors with extracranial extension 
((Goel A, Muzumdar D, Raman C. Trigeminal neuroma: analysis of surgical experience with 73 cases. Neurosurgery. 2003;52:783–790. discussion 790.))
((Guthikonda B, Theodosopoulos PV, van Loveren H, Tew JM, Jr, Pensak ML. Evolution in the assessment and management of trigeminal schwannoma. Laryngoscope. 2008;118:195–203.))
((Samii M, Migliori MM, Tatagiba M, Babu R. Surgical treatment of trigeminal schwannomas. J Neurosurg. 1995;82:711–718.)).
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In 1986, Lesoin et al. 
((Lesoin F, Rousseaux M, Villette L, et al. Neurinomas of the trigeminal nerve. Acta Neurochir (Wien) 1986;82:118–122.))
classified TSs into three categories: 
Type I schwannomas, which originate from the roots of the posterior fossa

Type II schwannomas, which originate from the Gasserian ganglion

Type III schwannomas, which originate from the trigeminal branches. 
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Yoshida and Kawase 
((Yoshida K, Kawase T. Trigeminal neurinomas extending into multiple fossae: surgical methods and review of the literature. J Neurosurg. 1999;91:202–211.))
proposed a classification that categorized TSs into six types: 

Type P, which comprise posterior fossa tumors originating from the root of the trigeminal nerve

Type M, which comprise middle fossa tumors originating from the gasserian ganglion or the peripheral branch at the lateral wall of the cavernous sinus. see  [[Middle fossa trigeminal schwannoma]]

Type E, which include tumors arising from the extracranial peripheral branches of the trigeminal nerve

Type MP, ME, and MPE indicate a combination of P, M, and E tumors. 
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Jeong et al. modified Kawase's classification to offer information about the locational predominance, shape, and extension of the tumor into the adjacent compartment by representing them with capital (primary location) and lowercase letters (extension).
((Jeong SK, Lee EJ, Hue YH, Cho YH, Kim JH, Kim CJ. A Suggestion of Modified
Classification of Trigeminal Schwannomas According to Location, Shape, and
Extension. Brain Tumor Res Treat. 2014 Oct;2(2):62-68. Epub 2014 Oct 31. PubMed
PMID: 25408927; PubMed Central PMCID: PMC4231622.)).

{{::jeongclassification.png?400|}}

A: Type M: tumors confined to the middle fossa. B: Type Mp: tumors predominantly located at the middle fossa with posterior fossa extension. C: Type P: tumors confined to the posterior fossa. D: Type Pm: tumors predominantly located at the posterior fossa with middle fossa extension. E: Type MP: tumors involving both middle and posterior fossae.