Head and Neck ImagingFacial nerve palsy
paralysis of the facial muscles supplied by the facial nerve (seventh cranial nerve). In the central type, the
lesion is located above the pontine nuclei (producing contralateral facial paralysis excluding the forehead muscles). In the peripheral type, the
lesion is between the pontine nuclei and the end branches of the facial nerve (producing ipsilateral facial paralysis of all facial muscles).
In a patient with peripheral facial nerve paralysis, the facial nerve must be imaged over its entire course, from the level of the pontine nuclei to the branches in the parotid gland. The lesions causing peripheral facial nerve paralysis are diverse; they can be classified according to the anatomical region where they occur (Table 1).
Facial nerve palsy, Table 1. Overview of causes of facial nerve paralysis (adapted from Joel D. Schwartz and H. Ric Harnsberger: Imaging of the temporal bone, 3 Edit., 1998, Thieme Verlag, p. 368 and 370).
| Brain stem lesions | tumour | glioma, metastasis, lymphoma |
| inflammation | multiple sclerosis, abscess, cerebritis |
| vascular lesion | vascular malformation, ischaemia |
| Cisternal/intracanalicular lesions | tumour | acoustic schwannoma, meningioma, epidermoid cyst |
| inflammation | granulomatous disease, bacterial infection, facial neuritis |
| vascular lesion | neurovascular injury (may cause hemifacial spasm) |
| Intratemporal lesions | congenital | primary cholesteatoma |
| traumatic | fracture (Fig. 1), postsurgery |
| tumour | facial nerve schwannoma, metastasis (Fig. 2), haemangioma, sarcoma (Fig. 3), ..... |
| inflammation | secondary cholesteatoma (Fig. 4), Bells palsy |
| Extracranial lesions | malignant tumour in parotid gland, malignant otitis externa | |
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Axial T1-weighted spin-echo image in a patient with a longitudinal fracture of the left temporal bone and post-traumatic facial nerve paralysis. Abnormal enhancement is seen at the level of the first bend (arrow), the labyrinthine segment (upper arrowhead) and intracanalicular segment (lower arrowhead) of the facial nerve. On a parasagittal reconstruction along the facial nerve (not shown), the entire tympanic and mastoid segment appeared thickened (courtesy by Bert De Foer, MD, Antwerp, Belgium).
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Facial nerve palsy, Fig.1 | | Facial nerve palsy, Fig.2 | | Facial nerve palsy, Fig.3 |
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Facial nerve palsy, Fig.4 | |