Localization of Neurologic Disease
PURPOSE OF NEUROLOGIC LOCALIZATION
The purpose of neurologic localization—an essential component of neurologic diagnosis—is to determine where in the nervous system the patient’s dysfunction is occurring, paving the way for the second key element of neurologic diagnosis, the determination of the mechanism of that dysfunction (see Chapter 3, Mechanisms of Neurologic Disease).
WHEN TO PERFORM NEUROLOGIC LOCALIZATION
Neurologic localization needs to be performed in every patient who presents with a symptom that is potentially due to nervous system dysfunction. Localization is often not hard, especially if you initially think in terms of the gross neuroanatomic areas described in this chapter and don’t try to overcomplicate things. Neurologic localization is a thought process that should occur during and after every neurologic history and during and after every neurologic examination.
NEUROANATOMY OF NEUROLOGIC LOCALIZATION
Neurologic disease can occur due to dysfunction anywhere within the central or peripheral nervous system. The nervous system can be divided into eight major areas as listed in Box 2-1, and these are the regions to which you should initially try to localize neurologic disease. Although narrower localization is clearly optimal (i.e., where in the brain or spinal cord is the problem?), you’ve made a lot of headway if you can decide in which of these eight major areas your patient’s problem most likely resides.
The diagnostic importance of the ability to localize your patient’s neurologic dysfunction to one of these gross neuroanatomic regions should not be underestimated. Table 2-1 summarizes some of the diagnostically relevant functions of these eight regions of the nervous system; in Table 2-1, the brain (cerebral hemispheres) is subdivided into the cerebral hemispheric cortex and the deep cerebral hemisphere.
EQUIPMENT NEEDED TO LOCALIZE NEUROLOGIC DISEASE
None (other than the equipment used for the neurologic examination—localization is a thought process).
HOW TO LOCALIZE NEUROLOGIC DISEASE
Localization is based on the symptoms obtained from the history and the signs found during the neurologic examination. The process of localization consists of deciding which area of nervous system dysfunction best explains these symptoms and signs based on knowledge of the function of these regions. Table 2-2 summarizes some symptoms and signs that are helpful in localizing neurologic disease to the general regions of the nervous system.
These principles and the use of signs and symptoms to further narrow the regions of localization are described in greater detail throughout this book.
These principles and the use of signs and symptoms to further narrow the regions of localization are described in greater detail throughout this book.
BOX 2-1 General Locations of Nervous System Disease
Central Nervous System |
Brain (cerebral hemispheres)a |
Brainstem |
Cerebellum |
Spinal cord |
Peripheral Nervous System |
Nerve root |
Neuromuscular junction |
Muscle |
a Although the brainstem and cerebellum are technically part of the brain, most clinicians think of “the brain” as the cerebral hemispheres without the brainstem and cerebellum. |
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