Neuro: LAB = Face & Parotid Region (Dr. Severson - 1 hr)
Parotidectomy
About 80% of salivary gland tumors occur in the parotid glands. Most tumors of the parotid glands are benign, but most salivary gland cancers begin in the parotid glands. Surgical excision of the parotid gland (parotidectomy) is often performed as part of the treatment. Because the parotid plexus of CN VII is embedded in the parotid gland, the plexus and its branches are in jeopardy during surgery. An important step in parotidectomy is the identification, dissection, isolation, and preservation of the facial nerve. A superficial portion of the gland is removed, after which the parotid plexus can be retracted to enable dissection of the deep portion of the gland. The parotid gland makes a substantial contribution to the posterolateral contour of the face, the extent of its contribution being especially evident after it has been surgically removed.
Mandibular Nerve Block
An anesthetic agent is injected near the mandibular nerve where it enters the infratemporal fossa. In the extra-oral approach, the needle passes through the mandibular notch of the ramus of the mandible into the infratemporal fossa. The injection usually anesthetizes the auriculotemporal, inferior alveolar, lingual, and buccal branches of CN V3.
Inferior Alveolar Nerve Block
An inferior alveolar nerve block anesthetizes the inferior alveolar nerve, a branch of CN V3. The site of the anesthetic injection is around the mandibular foramen, the opening into the mandibular canal on the medial aspect of the ramus of the mandible. This canal gives passage to the inferior alveolar nerve, artery, and vein. When this nerve block is successful, all mandibular teeth are anesthetized to the median plane. The skin and mucous membrane of the lower lip, the labial alveolar mucosa and gingivae, and the skin of the chin are also anesthetized because they are supplied by the mental nerve, a branch of the inferior alveolar nerve. There are possible problems associated with an inferior alveolar nerve block, such as injection of the anesthetic into the parotid gland or the medial pterygoid muscle. This would affect ability to open the mouth (pterygoid trismus)
Infra-Orbital Nerve block
For treating wounds of the upper lip and cheek or, more commonly, for repairing the maxillary incisor teeth, local anesthesia of the inferior part of the face is achieved by infiltration of this nerve with an anesthetic agent. The injection is made in the region of the infra-orbital foramen Because the orbit is located just superior to the injection site, a careless injection could result in passage of anesthetic fluid into the orbit, causing temporary paralysis of the extra-ocular muscles.
Temporomandibular joint (TMJ) dislocation
Sometimes during yawning or taking a large bite, excessive contraction of the lateral pterygoids may cause the heads of the mandible to dislocate anteriorly (pass anterior to the articular tubercles). In this position, the mandible remains depressed and the person is unable to close his or her mouth. Most common external causes are a sideways blow to the chin by a fist when the mouth is open. This dislocates the TMJ on the side that received the blow. Dislocation of the TMJ may also accompany fractures of the mandible. Posterior dislocation is uncommon, being resisted by the presence of the postglenoid tubercle and the strong intrinsic lateral ligament. Because of the close relationship of the facial and auriculotemporal nerves to the TMJ, care must be taken during surgical procedures to preserve both the branches of the facial nerve overlying it and the articular branches of the auriculotemporal nerve that enter the posterior part of the joint. Injury to articular branches of the auriculotemporal nerve supplying the TMJ, associated with traumatic dislocation and rupture of the articular capsule and lateral ligament, leads to laxity and instability of the TMJ.
Squamous Cell Carcinoma of Lip
Squamous cell carcinoma (cancer) of the lip usually involves the lower lip. Overexposure to sunshine over many years, is a common factor in these cases. Chronic irritation from pipe smoking is also a contributing cause. Cancer cells from the central part of the lower lip, the floor of the mouth, and the apex of the tongue spread to the submental lymph nodes, whereas cancer cells from lateral parts of the lower lip drain to the submandibular lymph nodes.
Mental and Incisive Nerve Block
Occasionally, it is desirable to anesthetize one side of the skin and mucous membrane of the lower lip, and the skin of the chin (e.g., to suture a severe laceration of the lip). Injection of an anesthetic agent into the mental foramen blocks the mental nerve that supplies the skin and mucous membrane of the lower lip from the mental foramen to the midline, including the skin of the chin.
Temporomandibular joint (TMJ) arthritis
The TMJ may become inflamed from degenerative arthritis, for example. Abnormal function of the TMJ may result in structural problems such as dental occlusion (teeth coming together) and joint clicking (crepitus). The clicking is thought to result from delayed anterior disc movements during mandibular depression and elevation.
Testing Sensory function of CN V
The sensory function of the trigeminal nerve is tested by asking the person to close his or her eyes and respond when types of touch are felt. For example, a piece of dry gauze is gently stroked across the skin of one side of the face and then to the corresponding position on the other side. The test is then repeated until the skin of the forehead (CN V1), cheek (CN V2), and lower jaw (CN V3) have been tested. The person is asked if one side feels the same as or different from the other side. The testing may then be repeated using warm or cold instruments and the gentle touch of a sharp pin, again alternating sides.
Facial Lacerations and Incisions
The skin must be carefully sutured to prevent scarring. The looseness of the subcutaneous tissue also enables fluid and blood to accumulate in the loose connective tissue following bruising of the face. Similarly, facial inflammation causes considerable swelling (e.g., a bee sting on the root of the nose may close both eyes). As a person ages, the skin loses its resiliency (elasticity). As a result, ridges and wrinkles occur in the skin perpendicular to the direction of the facial muscle fibers. Skin incisions along these cleavage or wrinkle lines (Langer lines) heal with minimal scarring.
Buccal nerve Block
To anesthetize the skin and mucous membrane of the cheek (e.g., to suture a knife wound), an anesthetic injection can be made into the mucosa covering the retromolar fossa, a triangular depression posterior to the 3rd mandibular molar tooth between the anterior border of the ramus and the temporal crest.
****Bell Palsy
Unilateral facial paralysis Injury to the facial nerve (CN VII) or its branches produces paralysis of some or all facial muscles on the affected side. Bell palsy involves paralysis of the facial muscles on the affected side. Usually involves the facial nerve in the distal facial canal or its exit from the stylomastoid foramen. Symptoms and Signs -Drooping of the lips on the affected side with food and saliva dribbling out the side of the mouth -Lower eyelid falls away from eyeball -Food accumulates between the gums and the cheek -Loss of facial expression
***Trigeminal Neuralgia*
*Characterized by severe lightning-like pain due to an inflammation of the fifth (trigeminal) cranial nerve* Trigeminal neuralgia or tic douloureux is a sensory disorder of the sensory root of CN V that occurs in most often in middle-aged and elderly persons. It is characterized by sudden attacks of excruciating, lighteninglikejabs of facial pain. A paroxysm (sudden sharp pain) can last for 15 minutes or more. The pain may be so intense that the person winces; hence the common term tic (twitch). In some cases, the pain may be so severe that psychological changes occur, leading to depression and even suicide attempts. ***CN V2 (maxillary) is most frequently involved, then CN V3 (Mandibular), and least frequently, CN V1 (opthalmic). The paroxysms are often set off by touching the face, brushing the teeth, shaving, drinking, or chewing. The pain is often initiated by touching an especially sensitive trigger zone, frequently located around the tip of the nose or the cheek. In trigeminal neuralgia, demyelination of axons in the sensory root occurs. Medical or surgical treatment or both are used to alleviate the pain. After this operation, the sensation of pain, temperature, and simple (light) touch is lost over the area of skin and mucous membrane supplied by the affected component of the CN V. This loss of sensation may annoy the patient, who may not recognize the presence of food on the lip and cheek or feel it within the mouth on the side of the nerve section, but these disabilities are usually preferable to excruciating pain.
Herpes Zoster Infection of Trigeminal Ganglion
Herpes zoster virus infection may produce a lesion in the cranial ganglia. Involvement of the trigeminal ganglion occurs in approximately 20% of cases. The infection is characterized by an eruption of groups of vesicles following the course of the affected nerve (e.g., ophthalmic herpes zoster). Any division of CN V (trigeminal) may be involved, but the ***ophthalmic division (CN V1) is most commonly affected. Usually, the cornea is involved, often resulting in painful corneal ulceration and subsequent scarring of the cornea.
Infection of Parotid Gland
Infection of the gland causes inflammation (parotiditis) and swelling of the gland. Severe pain occurs because the parotid sheath limits swelling. Often the pain is worse during chewing because the enlarged gland is wrapped around the posterior border of the ramus of the mandible and is compressed against the mastoid process of the temporal bone when the mouth is opened. The mumps virus may also cause inflammation of the parotid duct, producing redness of the parotid papilla, the small projection at the opening of the duct into the superior oral vestibule. Because the pain produced by mumps may be confused with a toothache, redness of the papilla is often an early sign that the disease involves the parotid gland and not a tooth. Parotid gland disease often causes pain in the auricle and external acoustic meatus of the external ear, the temporal region, and TMJ because the auriculotemporal and great auricular nerves, from which the parotid gland and sheath receives sensory fibers, also supplies sensory fibers to the skin over the temporal fossa and auricle
Paralysis of Facial Muscles
Injury to the facial nerve (CN VII) or its branches produces paralysis of some or all facial muscles on the affected side (Bell palsy). The affected area sags, and facial expression is distorted, making it appear passive or sad. This results in loss of function for blinking or adequet washing of the eyes with tears thus leading to reduced vision. Inability to eat and impaired speach are other highly common factors with facial nerve injury
