CASE 3127 Published on 21.07.2005

Geniculate ganglia schwannoma

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Gahide G, Gerardin E, Dacher JN, Thiebot J

Patient

42 years, female

Categories
No Area of Interest ; Imaging Technique CT, MR, MR
Clinical History
A patient presented with a headache. A clinical examination done did not show any other anomaly.
Imaging Findings
A 42-year-old woman presented in the emergency department with a subacute headache. The physical examination done was found to be normal. CT scan photographs disclosed a large oval enhancing mass with a sharply defined bone erosion extending from the geniculate ganglion to the middle cranial fossa and into the anterior tympanic cavity. It came into contact with the malleus without any erosion or displacement. The MRI results showed a well-delineated mass involving the geniculate ganglion. The tumor protruded into the middle cranial fossa and its mass effect was felt on the temporal lobe. The mass displayed a homogeneous hyposignal on T1 images and a heterogeneous one on T2 images. Pathologically, the mass was diagnosed as a schwannoma.
Discussion
The facial nerve and its canal are usually divided into the labyrinthine, tympanic and mastoid segments. Facial nerve schwannoma can occur along any segment of the nerve with the geniculate ganglion appearing to be a predilection site. The presenting symptoms are diverse and depend upon the size of the tumor and the site of origin. Gradual facial palsy is regarded as being the most common clinical presentation. Most frequently, facial palsy is associated with other findings or is absent as in our case. Hearing loss is then the most frequent complaint. The hearing loss may be sensorineural resulting from acoustic nerve compression in the IAC or from cochlear destruction by geniculate lesions. The hearing loss may be conductive when the tumor protrudes into the tympanic cavity. It may also cause a hemifacial spasm. Because the clinical presentation may be so confusing to interpret and because an accurate diagnosis is crucial for proper patient management and preservation of the facial function, diagnostic imaging plays an important role in the detection and characterization of facial schwannoma. The CT scan photographs demonstrate a sharply marginated erosion with an enlargement of the facial canal and an enhancing soft-tissue mass. On MRI, facial schwannoma appears hypointense and hyperintense relative to the brain as seen on T1 and T2 images and there is frequently a slightly heterogeneous signal. Hemangioma is the main differential diagnosis of the geniculate ganglia schwannoma. On CT, hemangiomas are often detected as small-sized enhancing lesions that erode the adjacent bone with unsharp margins; intratumoral bony spicules may be present.
Differential Diagnosis List
Geniculate ganglia schwannoma.
Final Diagnosis
Geniculate ganglia schwannoma.
Case information
URL: https://www.eurorad.org/case/3127
DOI: 10.1594/EURORAD/CASE.3127
ISSN: 1563-4086