Bilateral plexiform neurofibromas of the trigeminal and facial nerves - NF1

Case contributed by Ammar Haouimi
Diagnosis almost certain

Presentation

Bilateral proptosis with periorbital and facial swelling.

Patient Data

Age: 20 years
Gender: Female

Bilateral heterogeneously enhancing lobulated intraorbital extraconal masses, extending to the cavernous sinuses through enlarged superior orbital fissures, with bilateral proptosis grade 3.

Bilateral pterygopalatine fossa masses, extend through enlarged foramina rotunda in the greater sphenoid wings, which are dysplastic, with scalloping of the bone cortex.

Bilateral infratemporal fossa masses, as well as small heterogeneously enhancing masses of both parotid glands, mainly on the right.

On MRI sequences, the orbitofacial masses demonstrate low signal on T1, intermediate signal on FLAIR and high signal on T2, with central areas of low-signal "target sign" and heterogeneous enhancement on postcontrast sequences. They follow the course of the three branches of the trigeminal nerve (V1, V2, and V3), as well as the extratemporal segment of the facial nerve bilaterally:

  • V1 or ophthalmic division: intraorbital extraconal masses extending through enlarged superior orbital fissures to the Meckel cava (cavernous portion), as well as along the lacrimal and nasociliary nerves (terminal branches)
  • V2 or maxillary division: bilateral pterygopalatine fossa masses, located between the maxillary bone anteriorly, the orbital apex superiorly, and the pterygoid process posteriorly, extending through enlarged foramina rotunda in the greater sphenoid wing then to the cavernous sinuses inferior to the ophthalmic division; well-visualized on coronal sequences
  • V3 or mandibular division: bilateral infratemporal fossa masses coursing through enlarged foramina ovalia
  • extratemporal segment of the facial nerves: small heterogeneously enhancing masses of both parotid glands, mainly on the right

Case Discussion

CT and MRI features of orbitofacial masses following the course of the ophthalmic, maxillary and mandibular divisions of the trigeminal nerves, as well as the extratemporal segment of the facial nerve, in a patient with known neurofibromatosis type 1 (NF1).

The patient underwent a surgical biopsy of the right orbital mass with a histopathological exam that confirmed the diagnosis of plexiform neurofibromas.

Plexiform neurofibromas are essentially pathognomonic of neurofibromatosis type 1 (NF1) and are found in approximately 30% of patients with NF1. 

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