M2 ANATOMY
CLINICAL ANATOMY CASEPresenting to your primary care clinic is a new patient. He is a 60-year-old gentleman suffering from right-sided facial weakness which began five days previously. The onset was rapid, occurring over the course of six to eight hours. Initially, questioning reveals that the patient’s primary concerns include drooping of the right side of his mouth, soreness of his right eye, and an inability to fully close the lids of his right eye. Less problematic, but also present, are difficulty in eating, drinking, and speaking. Food accumulates in the right oral vestibule between the teeth and the cheek, and liquids run out of the corner of the mouth on the right side. Swallowing, however, is unaffected. Further detailed questioning leads the patient to disclose that sounds of any type are, in his words, “irritating and just way too loud”. Overall, the patient is anxious and shares with you that he is worried that he may have suffered a stroke as his father passed away from a stroke in his early fifties.
Following the history, examination of the patient’s head and neck reveals right-sided facial immobility with a lack of facial expression. All wrinkles have disappeared from the patient’s right forehead and his right eyebrow and lower eyelid droop. His right nasolabial fold is less distinct than that on the left. The corner of his mouth on the right side also sags, and both his nose and mouth appear to deviate toward the left side. The patient is emotional and is crying during the examination. Both eyes produce tears, but tears only run down the right side of the patient’s face. He is embarrassed about his condition and wishes to be seen by the minimum number of health care workers.
A full test of the muscles of facial expression exhibit weakness of the musculature of the right forehead, right eyelids, right cheek, and right side of the mouth. A corneal reflex is absent on the right side. The patient cannot raise his right eyebrow, shut his right eye, smile or frown on the right side when asked to do so. When asked to show his teeth, the patient can only uncover them on the unaffected left side.
Questions to Consider
What is the most likely diagnosis?
What aspect of the course of the facial nerve could contribute to the development of Bell’s palsy?
What is the name of the foramen at the lower end of the canal through which the nerve emerges from the skull? What other structures traverse this opening and canal? (for faculty: an artery which serves the facial nerve within the canal)
What are the effects of paralysis of some key muscles of facial expression?
Paralysis of which muscle explains the inability to close the right eye and causes the sagging of the lower eyelid?
What muscle opens the eye? Is it affected in facial nerve palsies?
Why is the patient’s face distorted (asymmetrical) in appearance, particularly when he is smiling?
Paralysis of which important muscle causes food to collect between the cheek and teeth within the oral vestibule?
Why is the corneal reflex absent? How is this reflex tested and what are its pathways?
How do you account for the aching pain in and around the ear? Does the facial nerve contain any afferent pain fibers? In which ganglion are these cell bodies located?
Why does this patient experience hyperacusis (increased loudness associated with sounds)?
Why does a peripheral facial nerve lesion involve the forehead but a central lesion spares it?