oral medicine & Pathology

Neurofibromatosis Type 2 : imaging , clinical findings , pathology , treatment , epidemiology

 

Neurofibromatosis Type 2     

 

Epidemiology

  •  Neurofibromatosis (NF) type 2 is characterized by multiple cranial nerve schwannomas, but associated peripheral and cutaneous neurofibromas are uncommon.
  • These lesions may be associated with multiple meningiomas or ependymomas.
  • The most common site for schwannomas involves the eighth cranial nerve.
  • The reported incidence is about 1 :2 1 0,000, which is 10 times less frequent than NF type 1 .
  • This entity has an autosomal dominant pattern of inheritance and shows no predilection based on race or sex.

Clinical Findings

  •   Patients with vestibular schwannomas typically present with symptoms of hearing loss in the second and third decades and 30s.
  • Young patients with meningiomas may present with symptoms related to raised intracranial pressure.
  • These patients should be suspected to have NF2.
  • In addition, patients may present with juvenile subcapsular lens opacity.

Pathology

  •  Unlike neurofibromas, which are made up of all neural elements, schwannomas are composed of only Schwann’s cells.
  • Schwannomas are encapsulated tumors and they typically show a dense component (Antoni A tissue) and a looser component (Anroni B tissue). Schwannomas tend to undergo cystic changes and show hemorrhagic areas as they enlarge.

Treatment

  •   Because NF type 2 may involve multiple sites and structures, surgery is warranted only if there are symptoms and significant compression of vital structures.

Imaging Findings

CT

  •   When the mandibular nerve is thickened, it causes smooth enlargement of the foramen ovale.
  • Contrast-enhanced CT shows an enhancing tumor with sharp outline.

MR

  •     On T I -weighted images, schwannomas are isointense with skeletal muscles.
  • Mandibular nerve schwannomas may obliterate the fat just below the opening of the foramen ovale.
  • They show high signals on T2-weighted images and strong contrast enhancement

Imaging Pearls

  • A fusiform mass in the expected course of the mandibular nerve should raise the possibility of a schwannoma or a neurofibroma.
  • The rest of the trigeminal nerve should be examined for neurofibromata.
  • This diagnosis of N F type 2 can easily be made in the presence of associated meningiomas or schwannomas involving the other cranial nerves, especially the eighth cranial nerve

 

 Neurofibromatosis Type 2 Neurofibromatosis Type 2

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