The Neurological Exam: Evaluating the Master Organ
How does a mind contemplate itself? That's a philosophical question I'll leave to minds smarter than mine, but what I can tell you is how to examine the brain and other parts of the nervous system.
Most people are familiar with how doctors examine a heart or set of lungs. The physical exam of these organs consists mainly of using a stethoscope to listen to them in action. But when it comes to examining components of the nervous system-consisting of the brain, spinal cord, peripheral nerves and muscles-a stethoscope is pretty useless. The nervous system doesn't make sounds that the doctor can listen to (though the arteries in the neck that deliver blood to the brain can be usefully listened to). But because people can have medical disorders that damage the nervous system, it is every bit as important to have a method for evaluating this organ as for any other.
The method is called the neurological exam. Because different parts of the nervous system do different things, the basic idea of the neurological exam is to put the patient through a number of mini-exams, each evaluating the function of a different component. And what a variety of functions there are! In fact, apart from exposure to an inspiring teacher, this is what drew me into the study of neurology in the first place-the sheer diversity of the neurological exam.
This is an organ responsible for jobs as diverse as thinking, remembering, smelling, tasting, seeing, hearing, speaking, moving, walking, balancing, feeling and, yes, even contemplating itself-though I confess that my neurological exam doesn't include an assessment of self-contemplation. Moreover, the nervous system handles many infrastructure tasks like controlling body-temperature, pulse, blood-pressure, breathing and enabling a person to urinate at a time and place of their choosing. What's not to admire about an organ system that can do so many things!
The many mini-tests of the neurological exam are bundled together in the following sub-groupings: mental status exam, cranial nerve exam, motor exam, sensory exam and evaluation of stance and walking. I'll provide a brief overview of each.
The mental status exam focuses on the cerebrum which has a wrinkly, gray, outer surface usually shown in pictures of the brain. The cerebrum is divided into eight lobes which includes pairs of frontal lobes, parietal lobes, temporal lobes and-bringing up the rear-the occipital lobes. Each handles different mental tasks. In fact, even within a lobe, many different jobs are handled. So the usual mental status exam consists of observing the patient's behavior in the exam room and using a variety of standard tests to check the patient's orientation to time and place, attention, memory, speech, comprehension of language, memory, calculation and ability to track the relative positions of objects in space.
The next grouping of mini-tests, the cranial nerve exam, also assesses the functioning of parts of the cerebrum, but additionally focuses on the brainstem. The brainstem is located at the base of the brain and connects the cerebrum above to the spinal cord below. The cranial nerve exam includes tests of smelling, vision, constriction of the pupils, eye-movement, facial sensation, facial movement, hearing, and action of certain muscles in the throat, tongue, neck and shoulders.
I'll single out one item on the cranial nerve exam as deserving special mention, and that is the visual field exam. The visual fields are evaluated one eye at a time. While the patient stares at an unmoving object, the doctor asks if the patient can see objects (like the doctor's fingers) appearing in different locations of the patient's peripheral vision. In order to detect objects in the four corners of each eye's vision, the patient must have proper functioning of each of six lobes of the brain-both parietal lobes, both temporal lobes and both occipital lobes. In fact, this is the only portion of the entire neurological exam that checks the right temporal lobe. Despite its importance, the visual field exam sometimes gets skipped by medical students (in which case the ones under this author's supervision must endure hearing an earful).
The motor exam includes some pretty obvious things like checking the strength of different muscles in the arms and legs, but also includes less obvious components like muscle tone, coordination, and the presence of involuntary movements. It also includes an inspection of muscles for loss of size or the presence of spontaneous twitches. Additionally, this is the part of the exam in which the doctor pulls out his or her rubber hammer and checks reflexes in the arms and legs. The motor exam also includes a briefly painful maneuver-called the Babinski test-in which the bottom of the foot is scraped with a metal object while the doctor observes for a reflexive response in certain foot-muscles.
The sensory exam focuses on the processing of inputs from sensory nerve-endings in the patient's skin and joints. It can include awareness of light touch, pain, warmth, coldness and vibration. In addition, the doctor examines position-sense by moving the patient's toes and fingers up or down and asking the patient to say, without looking, which way they moved.
Finally, we have those portions of the exam related to stance and walking, but also including the patients' ability to transfer in and out of their chair. While on their feet, patients are asked to walk in their usual fashion, as well as on tiptoes. They are also observed while doing a "tandem gait," known more commonly as the "state trooper test," in which they walk flat-footed in a straight line with the heel of the leading foot touching the toes of the trailing foot. Last, the doctor checks the patients' ability to remain standing after closing their eyes. This is called the Romberg test.
That's about it. In the hands of experienced clinicians the neurological exam doesn't take much longer to perform than to describe, and yet provides a wealth of information about the functioning of the patient's nervous system. In this age of high-tech imaging devices the neurological exam might seem archaic or old-fashioned, but it is still indispensable, and provides diagnostic information that even a battery of CT or MRI scans might miss.
(C) 2005 by Gary Cordingley
Gary Cordingley, MD, PhD, is a clinical neurologist, teacher and researcher who works in Athens, Ohio. For more health-related articles, see his website at: http://www.cordingleyneurology.com
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