This is my third in a series of posts on orofacial pain.
In the first post, I briefly introduced the concept of non-dental toothaches, and highlighted different disorders that can present with symptoms that can mimic a regular toothache.
The second post was focused on identifying red flags when taking a pain history.
Today's post is focused on trigeminal nerve examination.
Cranial Nerve Examination
When evaluating patients with orofacial pain, it is essential to complete a cranial nerve examination because facial pain may arise from neurological (nerve) disorders or in rare instances, intracranial neoplasms (brain tumors). Obviously, treating a neurological disorder (nerve pain) with a dental procedure will delay the correct diagnosis and further complicate the patient's pain.
The goal of cranial nerve examination is to compare the strength and sensation from the structures in the distribution of the cranial nerves on both sides of the head and neck.
I'll focus on trigeminal nerve examination today and save the discussion on the remaining eleven cranial nerves for a future post.
Trigeminal Nerve Examination
The trigeminal nerve is the primary sensory nerve of the face, and is responsible for facial sensation. It also innervates the muscles of mastication (chewing muscles). Therefore, trigeminal nerve dysfunction will present as alterations in facial sensation and weakness of the chewing muscles.
Motor Component
The trigeminal nerve supplies the muscles of mastication (chewing muscles). Therefore, to assess the motor fibers, the patient is asked to clench their teeth. At the same time, the examiner palpates (feels) the trigeminal and masseter muscles, which function to close the mouth.
The size of the muscles and strength of contraction should be equal on both sides. If any weakness on palpation is detected, it should be noted.
Sensory Component
The trigeminal nerve is responsible for facial sensation. Therefore, sensory testing is accomplished by applying sharp, blunt, soft, cold, and warm objects on both sides of the face, across the three divisions of the trigeminal nerve.
ophthalmic/V1,
maxillary/V2, and
mandibular/V3) .
During the examination, the patient is asked to discriminate between the various sensations and confirm that both sides of the face are equally sensitive.
Areas with increased, decreased, altered sensation, or complete numbness are noted during the trigeminal nerve examination.
Corneal Reflex/Blink Reflex
Testing for the corneal reflex is achieved by observing whether a patient blinks in response to a light touch on the cornea with a wisp of cotton twisted to a pointed tip. During a normal response, the tested eye should blink, and the other eye should also blink simultaneously (consensual response).
It is important to note that the sensory innervation for the corneal reflex is mediated by the ophthalmic division of the trigeminal nerve, while the motor innervation for the blink response is provided by the facial nerve (cranial nerve VII).
Therefore, if there is damage to the ophthalmic division of the trigeminal nerve, no response will be seen in both eyes. However, if there's weakness of the facial nerve on the side being tested, the tested eye will not blink, while the other eye will still blink due to the consensual response.
Clinical Applications for Trigeminal Nerve Examination
Trigeminal neuropathic pain, trigeminal neuralgia, multiple sclerosis, and the rare case of brain tumor are some examples of conditions that can present with trigeminal nerve dysfunction.
Trigeminal neuralgia patients may report pain to stimulus such as light touch that would not normally induce pain. They may also have trigger spots - areas within the distribution of the trigeminal nerve that when lightly stimulated, triggers excruciating pain.
Patients with multiple sclerosis are more likely to exhibit dysfunction of the trigeminal nerves on both sides of the face than trigeminal neuralgia patients.
Conclusion
Cranial nerve examination, should be performed on all new patients presenting with orofacial pain.
© 2021. Trigeminal Nerve Examination. Dr. Chizobam Idahosa.