Brain Tumor Res Treat.  2014 Oct;2(2):62-68. 10.14791/btrt.2014.2.2.62.

A Suggestion of Modified Classification of Trigeminal Schwannomas According to Location, Shape, and Extension

• Jeong SK
• Lee EJ
• Hue YH
• Cho YH
• Kim JH
• Kim CJ

• KMID: 2134273
• DOI: http://doi.org/10.14791/btrt.2014.2.2.62

Abstract

BACKGROUND
Comprehensive knowledge of the anatomical features of trigeminal schwannomas (TSs) is essential in planning surgery to achieve complete tumor resection. In the current report, we propose a modified classification of TSs according to their location of origin, shape, and extension into the adjacent compartment, and discuss appropriate surgical strategies with this classification.
METHODS
We retrospectively analyzed 49 patients with TS who were treated surgically by a single neurosurgeon at the Asan Medical Center between 1993 and 2013.
RESULTS
There were 22 males and 27 females, with the median age of 40 years (range, 21-75 years). Median tumor size was 4.0 cm in diameter (2.0-7.0 cm). Tumors were classified as follows: Type M (confined to the middle fossa; 8 cases, 19.0%), P (confined to the posterior fossa; 2 cases, 4.8%), MP (involving equally both middle and posterior fossae; 5 cases, 11.9%), Mp (predominantly middle fossa with posterior fossa extension; 6 cases, 14.3%), Pm (predominantly posterior fossa with middle fossa extension; 16 cases, 38.1%), Me (predominantly middle fossa with extracranial extension; 4 cases, 9.5%). Surgical approach was chosen depending on the tumor classification. More specifically, a frontotemporal craniotomy and extradural approach with or without zygomatic or orbitozygomatic osteotomy was applied to M- or Mp-type tumors; a lateral suboccipital craniotomy with or without suprameatal approach was applied to the majority of P- or Pm-type tumors; and a posterior transpetrosal approach was used in four tumors (three Pm and one MP). Gross total resection was achieved in 95.9% of patients, and the overall recurrence rate was 4.1% (2 patients). Postoperatively, trigeminal symptoms were improved or unchanged in 51.0% of cases (25 patients). Surgical complications included meningitis (5 patients) and cerebrospinal fluid leakage (3 patients). There was no mortality.
CONCLUSION
TSs are well to be classified with our modified classification and able to be removed effectively and safely by selecting appropriate surgical approaches.

Keyword

Classification; Neurilemmoma; Surgical procedure; Trigeminal nerve

MeSH Terms

Cerebrospinal Fluid
Chungcheongnam-do
Classification*
Craniotomy
Female
Humans
Male
Meningitis
Mortality
Neurilemmoma*
Osteotomy
Recurrence
Retrospective Studies
Trigeminal Nerve

Figure

• 

  Fig. 1 Classification of trigeminal schwannomas. 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.

• 

  Fig. 2 A: Magnetic resonance images obtained in a 43-year-old woman with an MP-type tumor. Axial preoperative T1-weighted images obtained after administration of gadolinium (left). Postoperative image revealing no residual tumor (right). B: Magnetic resonance images obtained in a 39-year-old woman with a Pm-type tumor. Axial preoperative T1-weighted images obtained after administration of gadolinium (left). Postoperative image revealing no residual tumor (right).

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