Trigeminal schwannoma classification
The first classification system was proposed by Jefferson 1) 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 2) 3) 4).
In 1986, Lesoin et al. 5) 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.
Yoshida and Kawase 6) 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.
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). 7).
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.