Neurotrauma Review Series—Part 1: Why Evaluate the Cranial Nerves?

In this four-part series of articles, we look at how and why to assess a patient who has suffered an insult to the head or spine. This first article focuses on the importance of the cranial nerve exam. In subsequent articles we will consider the neurologic exam, talk about what selective spinal immobilization protocols actually assess, and review what dermatomes are and how to use them to our advantage. In a follow-up article, we will review what happens to our patients in the months and years that follow a severe spinal injury.

Cranial nerves begin and, for the most part, end in the head, which makes them very useful in detecting brain injury, sometimes long before a patient becomes severely ill. They innervate, and thereby give movement and sensation to, the eyes, ears, nose, mouth and face in the same way peripheral nerves give motion and sensation to our torso, arms, legs, hands and feet. Anatomically, the cranial nerves travel through distinct locations in the brain, and because of this assessing them can sometimes give us early and detailed information about brain injury.

Brain Injury Detectors

Brain injury stemming from stroke, trauma and even a combination of both is commonly encountered in the prehospital environment. Perhaps because of this frequency, most providers are adept at diagnosing “classic” brain injury. We all know to be vigilant for obvious signs, particularly in at-risk patients such as children, alcoholics, the elderly and persons on anticoagulant medications. In all patient groups, we listen carefully for slurred speech and look for one-sided weakness, changes in mental status, alterations in pupillary reaction and pronator drift.

But the patients who present with these obvious signs or had an impressive mechanism of injury are the easy cases. We know these patients are significantly injured and need immediate in-hospital neurologic care. These are not the patients a cranial nerve exam will likely benefit. When considering the importance of learning the cranial nerve exam, don’t think of your experiences with grossly brain-injured patients; instead, ask yourself how many times you’ve seen patients who suffered seemingly minor head trauma and wished you had a few more tools at your disposal to more thoroughly evaluate them. These are the patients who have fallen from a standing position and bumped their head or been hit on the head by a stray baseball or walked into some unexpectedly hard object and developed a large scalp hematoma. And how many times have you evaluated a patient who has vague complaints that might resemble stroke and wanted to have another tool to add to your usual stroke exam? These are the times when the cranial nerve exam can be very helpful.

These minor-injury and low-suspicion patients are sometimes reluctant to be transported, and we, being good medical providers, often respond by coaching them to be transported anyway, or at least be seen on their own at a facility where emergency care and a CT scanner are available. Should they happen to be taking warfarin, be elderly or alcoholic, or have a history of prior brain injury or some other risk factor for intracranial bleeding, our alarm bells start ringing and we balk hard at taking “no” for a transport answer. This is good standard practice; it is how good providers ensure a minor head injury yielding a small amount of intracranial hemorrhage doesn’t evolve into a larger, problematic hemorrhage without someone detecting it in time.

The problem is that when brain-injured patients don’t yet appear to be acutely ill or have risk factors that put them on our radar, they are notoriously hard to assess. We know this intuitively because most of us have seen, or at least heard stories about, patients who originally exhibited few symptoms from a brain injury but later became very ill and were found to have intracranial hemorrhage. The case of Natasha Richardson, an actress who died in 2009 from traumatic brain injury after falling on a ski slope and initially refusing care,¹ brought this type of injury to the forefront of national awareness as well. We need to have some strategies to anticipate this kind of change.

Assessing a cranial nerve exam can be one of these strategies. Although it cannot be used to rule out brain injury, this exam can occasionally pick up subtle signs of brain injury we otherwise might miss and help us get our patients to the most appropriate hospital care. As prehospital providers it is our job to perform the initial triage of every one of our patients. Not only do we decide which patients get transported to the ED, but in many cases we recommend the appropriate destination hospital for their care. Positive findings in the cranial nerve exam can help us by providing an early clue that a major injury may have followed minor trauma. This is important in our effort to advocate appropriately for patient transport, and can also aid in deciding whether a patient needs a hospital with a neurosurgery service or whether one without will, at least initially, suffice. On arrival, it is our presentation to the ED staff that largely determines which patients get seen immediately in an acute room (and get an immediate CT) and which may wait for assessment and treatment. In the case of patients with minor-appearing head injuries or vague symptoms of stroke, positive cranial nerve exam findings can sometimes help determine correct emergency department triage.

Subtle Signs

Cranial nerve exams are quick and easy. Particularly when they are done serially (every 5 or 10 minutes throughout the time we spend with our patient) and analyzed for any change, they can help us pick up subtle signs of worsening injury. One of the easiest ways to learn the exam is to memorize a simple pattern of tests the patient should be able to complete. Keep the pattern in order. Be consistent when you use it and don’t skip steps. Don’t bother learning the nerve names until you have gotten lots of practice with the exam pattern and know it cold. To be normal, the findings of all tests should be bilateral and symmetrical.

There are lots of renditions of the cranial nerve exam, some more exhaustive than others, so don’t worry if someone else’s exam is slightly different from yours, but do always take the opportunity to learn from them. An example of one good cranial nerve exam pattern for the emergency care setting follows. The mnemonic for this particular exam is PEEE FFUTSS (sounds like peanuts):

Pupils—Dim the dome lights and perform a pupil exam with your penlight. Pupils should be equal, round and reactive when you apply your light directly, and when you flash your light in one eye, both pupils should constrict.

Eyes—Test for eye motion. The patient should be able to follow your finger as you trace a large H-shaped pattern about one arm’s length away from their face (using the approximate length of the patient’s arm is most appropriate). This allows you to see whether they can move both of their eyes up, sideways and down in both the lateral and medial fields. Also, ask whether the patient is having any differences from their usual vision (new blurriness, double vision, etc.).

Eyelids—Instruct the patient to keep their eyelids squeezed tightly shut, then place your fingertips lightly upon the lids and gently see if you can open them. You should not be able to do so.

Ears—Rub your fingers together next to each of the patient’s ears and see if they can hear them to their usual (self-reported) ability.

Facial Sensation and Mastication—Lightly brush the patient’s skin at the forehead, cheeks and chin with your fingertips. Record whether they have sensation bilaterally, then hold your fingers on the sides of their mandible and have them squeeze their teeth together as if chewing. Make sure their chewing muscles tense beneath your fingers.

Facial Movement—Have the patient smile widely, showing their teeth, and raise their eyebrows. Their facial expression should be symmetrical.

Uvula—Have the patient open their mouth wide and say ‘A-a-ah.’ Look in the back of their throat as they do this. Their uvula should stay in a midline position.

Tongue—Have the patient stick out their tongue as if they are angry at you and see whether it sticks out straight (normal) or to one side (abnormal).

Swallow—Have the patient swallow. They should do so without distress or difficulty.

Shrug—Have the patient shrug their shoulders against resistance from your hands. The shrug should be strong and symmetrical.

You can learn the cranial nerve assessment pattern and use it without knowing exactly what the names of the cranial nerves are. If you are interested, however, you can go on to memorize which actual cranial nerves go with which assessment maneuvers. Again, the time to do this is usually after you’ve gotten really good at using the assessment pattern. This may keep your frustration to a minimum.

Good paramedic students learn (correctly) that there 12 cranial nerves. You can remember them with the “clean” rhyme below (On old Olympus’ towering top, a French and German viewed a hop) or with assorted more entertaining ones (Google can help you find those).

Conclusion

The cranial nerve exam is not a perfect assessment tool. Brain injury, especially when it involves intracranial hemorrhage, can be an evolving process. Therefore, a patient with a cranial nerve exam that shows no abnormal findings can certainly still go on to manifest later with life-threatening stroke or traumatic brain injury. Any abnormality that is found, however, should always be taken as a serious warning of worsening bleed. This is particularly true when the cranial nerve findings worsen over the course of two or more exams.

Consider these findings when deciding upon an appropriate destination hospital, and report them directly to a physician as well as the nursing staff as soon as possible upon arrival. Report of a cranial nerve abnormality, particularly if it is evolving, will usually prompt a more rapid evaluation and decision about the need for CT by ED staff. Evaluation of the cranial nerve exam is one more strategy to help prehospital providers find and treat brain injuries sooner, and for some of our brain-injured patients, time most certainly counts.

Special thanks to Marc Minkler, NREMT-P; Matthew Morgan, DO; Michael W. Dailey, MD; and the prehospital providers of the Albany County Sheriff’s Office for their kind assistance with these articles.

Footnote

1. Marikar S. Natasha Richardson Died of Epidural Hematoma After Skiing Accident. ABC News, https://abcnews.go.com/Entertainment/Movies/story?id=7119825&page=1#.UA8uqrSe6Ds.

References

Blumenfeld H. Neuroanatomy Through Clinical Cases. Sunderland, MA: Sinauer Associates, 2002.

Tintinalli J, et al. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 5^th ed. New York, NY: McGraw Hill, 2000.

Tiffany Bombard, NREMT-P, MD, has been an EMS provider, firefighter and paramedic for many years in Vermont, Utah, New York, New Hampshire and Maine. She is currently a resident emergency physician at Albany Medical Center and a paramedic for the Albany County Sheriff’s Office in New York. Contact her at bombieskifast@yahoo.com.