Clinical History
A 26-year-old man shows a one and a half year history of progressive right-sided sensorineural hearing loss.
Imaging Findings
A 26-year-old man shows a one and a half year history of progressive right-sided sensorineural hearing loss. The patient also referred night tinnitus for the last three months. At physical
examination there was no evidence of peripheral facial nerve neuropathy. MR images show a well-defined extraaxial mass in the right cerebellopontine angle extending into the geniculate ganglion and
the labyrinthine, tympanic and intracanalicular portions of the facial nerve, with anterior spread through the facial hiatus and upward spread through the tegmen tympani involving the middle cranial
fossa. The mass is hypo- or isointense relative to gray matter on T1-weighted images and heterogeneously hyperintense on T2-weighted images. After administration of gadolinium it enhances brightly
and homogeneously, displaying a hypointense peripheral capsule which represents duramater. Axial and coronal CT scans show the enlargement of the internal auditory canal, labyrinth and geniculate
fossa. There is opacification of the epitympanum and mesotympanum by invading soft-tissue mass (hypotympanum and Prussak space are not affected) which also contacts the ossicular chain. The mass was
surgically removed.
Discussion
Facial nerve Schwannomas are uncommon tumors that come up from the Schwann cell sheath. These tumors may arise anywhere along the course of the facial nerve, from the cerebellopontine angle to
stylomastoid foramen. Multiple contiguous segments are affected. The most common location is the geniculate ganglion. From there the tumor may extend proximally (involving labyrinthine portion) or
distally (involving tympanic portion). Uncommonly it may extend projecting up into the middle cranial fossa (upward spread through the roof of the temporal bone or anterior spread through the facial
hiatus). These lesions may demonstrate a dumbbell appearance due to extension from the CPA-IAC through the labyrinthine segment into the geniculate fossa. The age range at time of imaging is 10-70
years. The clinical presentation is variable and depends on the size and the location of the tumor. The most common symptom is facial paresis followed by hearing loss. The facial paresis is often
gradually progressive. Conductive hearing loss is due to tympanic segment involvement and ossicular compression. Sensorineural hearing loss is due to internal auditive canal, CPA or both
involvements. Other less common symptoms are tinnitus, otalgia and hemifacial spasms. CT scans show a benign bone remodeling secondary to tumor, consisting of enlargement of the bony canal for the
labyrinthine segment of the facial nerve, widening of internal auditory canal and geniculate fossa, opacification of the mesotympanum by soft-tissue mass with scalloping of the apex of the petrous
temporal bone and ossicular encasement. There is no aggressive bone destruction. MR imaging shows a well-circumscribed extraaxial mass that is mildly hypo- or isointense relative to brain on
T1-weighted images. It is heterogeneously hyperintense on T2-weighted images, and it enhances brightly and homogeneously after administration of gadolinium. Cystic changes or heterogeneity may also
be observed in large tumors. Treatment is surgical resection. The surgical management depends on the size, the segments of facial nerve involved by tumor and the patient´s hearing status. A
transmastoid or middle cranial fossa surgical approach are generally used. These exposures may be used in combination.
Differential Diagnosis List
Facial nerve Schwannoma with middle cranial fossa involvement.
Final Diagnosis
Facial nerve Schwannoma with middle cranial fossa involvement.
