A 75-year-old male comes in with complaints of right-sided hearing loss and facial paralysis that occurred one-and-a-half years ago. He states that he has a difficult time hearing on that side and his ear feels plugged. He noted that one year prior, he lost his entire facial function suddenly for over a week. He is otherwise healthy and has never worn hearing aids. Examination of his ears reveals a serous effusion in the right ear. His face has no function on the right side with very poor eye closure. He has right temporal wasting (hollowed temple) and decreased sensation of the face on the right mid face. His audiogram is to the right.
Diagnosis: Tumor of the Deep Lobe of the Parotid Gland
The most common cause of facial paralysis is Bell's palsy, a viral infection caused by the herpes simplex virus (HSV) that affects the facial nerve. The virus generally grows for seven days but the inflammation from the immune reaction to the virus can last for much longer. The swelling (edema) caused by the inflammatory response to the virus around the facial nerve causes pressure on the nerve fibers (axons) and leads to facial paralysis. A vast majority of patients (85%) with facial paralysis will recover to normal or near normal function within six months. If a patient has not recovered within the first six months, the clinician has to be suspicious of another underlying etiology for the facial paralysis.
Technically, Bell's palsy is a diagnosis of exclusion; other diagnoses have to be ruled out before Bell's palsy (HSV) is implicated as the cause of the paralysis. The patient with facial paralysis needs a thorough examination of his/her ear and hearing when evaluating the cause of the paralysis. In addition, examination of the parotid gland (saliva gland in front of the ear) through which the facial nerve travels is necessary to ensure that a tumor is not the underlying cause. Obtaining imaging, such as an MRI, is usually not necessary until six months post onset or if the history or examination is suspicious for another cause. If no recovery has occurred by six months, an MRI is necessary to further evaluate for a tumor.
Other reasons to obtain imaging include:
- a slow onset of paralysis (greater than two days from onset to worse function),
- history of facial spasms on the same side,
- bilateral simultaneous paralysis,
- a history of skin cancer of the face,
- a history of a parotid tumor,
- previous radiation to the head and neck,
- an abnormal middle ear examination,
- asymmetric sensorineural or mixed hearing loss on the same side,
- slow onset of paralysis (more than two days from onset to worse outcome), or
- recurrent paralysis on the same side (Djalilian. N Engl JMed 2005;352:416 http://bit.ly/2cymLaE).
If a patient presents with facial paralysis, a few questions should be asked on history. The first is the time period over which the facial paralysis occurred. The second is if the patient has a history of skin cancers of the face or other cancers/radiation to the head and neck. Next, the clinician must establish if any facial function remained at the worse time point post-onset. The smallest amount of remaining facial function indicates that the nerve fibers are in continuity and that the function will return quickly (within a few weeks). Any degree of partial paralysis generally indicates a good prognosis for recovery. All branches of the facial nerve should be examined (raising eye brows, eye closure, puckering the nose, smiling, puckering the lips, and tightening the neck).
Patients who lose complete function (Grade 6/6) need evaluation with electrodiagnostic testing to determine prognostic information. An electronystagmogram (ENoG) provides the clinician with the ability to compare the function of the two sides. The ENoG test is most useful between three and 21 days post onset of the paralysis; outside of that range the test is inaccurate in providing prognostic information. The test is performed by placing a stimulating electrode just anterior and inferior to the ear lobe, which stimulates the facial nerve at the stylomastoid foramen. The compound action potential (the action potential of all the nerve fibers firing together) is compared between the two sides. It is best to stimulate each side a few times prior to measuring the compound action potential. This allows for better synchronization of the nerve fibers.
Patients with greater than 90 percent degeneration on the ENoG who are less than 14 days from the onset of the paralysis may benefit from a surgical decompression of the nerve in its labyrinthine segment. A landmark study shows facial function will recover to normal or near normal level in 89 percent of patients who undergo the decompression surgery, compared with 42 percent of those who did not undergo the surgery (Gantz. Laryngoscope 1999;109:1177 http://bit.ly/2bTpdZ0). Patients who fulfill these criteria are generally uncommon, as a vast majority (85%) of patients with Bell's palsy recover to normal or near normal function.
Facial nerve EMG is beneficial in understanding prognostic information after 21 days post onset of the paralysis. While the ENoG test is commonly performed by audiologists, the facial nerve EMG test is primarily performed by a neurologist. When a decision for surgery is to be made, an EMG test is generally obtained if 100 percent degeneration is found on the ENoG test. The test is performed by placing needles in the facial muscles and recording facial muscle EMG activity during spontaneous motion. An ENoG is essentially an EMG test performed using surface electrodes (instead of needles) and using stimulation of the facial nerve from the surface. Neurologists often refer to an ENoG as an evoked EMG.
This patient had an MRI approximately one year prior to the onset of the facial paralysis. However, given the loss of function in both cranial nerve V and VII, in addition to the serous effusion on the right side, we obtained a new MRI. It showed a tumor of the deep lobe of the parotid gland that invaded the second branch of cranial nerve V (V2), had grown proximally through the skull base, and was abutting the brainstem (Figs. 2 and 3). As it traversed the skull base, it caused blockage of the Eustachian tube and involved the facial nerve.
Facial paralysis in conjunction with an abnormal middle ear exam should always be worked up further and not dismissed as Bell's palsy.
BONUS VIDEOS: VISUAL DIAGNOSIS
Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself.
- Video 1 shows the Axial CT images of the right temporal bone showing the normal course of the facial nerve and fluid in the middle ear and mastoid.
- Video 2 shows the Axial CT images of the head showing the skull base and the enlargement of foramen ovale (skull opening through which V3 travels) caused by the tumor involving cranial nerve V3.
- Video 3 shows the Axial T1 post gadolinium MRI showing the tumor involving cranial nerve V with enlarged nerve along its course.
- Video 4 shows the Coronal T1 post gadolinium MRI demonstrating the tumor traversing the skull base involving cranial nerve V2.
- Video 5 shows the Sagittal T1 post gadolinium MRI showing the tumor involving cranial nerve V3 and its course through the foramen ovale.
- Video 6 shows the Axial FLAIR MRI showing the hemorrhage and edema in the brainstem caused by the tumor.
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