Neurology, more than any other specialty, rests on clinicoanatomic correlation. Patients do not arrive at the neurologist's office saying “the motor cortex in my right hemisphere is damaged,” but they do tell, or show, the neurologist that there is weakness of the face and arm on the left. Since the nervous system is constructed in a modular manner, with different parts of the brain and spinal cord subserving different functions, it is often possible to infer, from a careful physical examination and history together with knowledge of neuroanatomy, which part of the nervous system is affected, even prior to ordering or viewing imaging studies. The neurologic clinician thus attempts, with each patient, to answer two questions: (1) Where is (are) the lesion(s)? and (2) What is (are) the lesion(s)?
Lesions of the nervous system can be anatomic, with dysfunction resulting from structural damage (examples are provided by stroke, trauma, and brain tumors). Lesions can also be physiologic, reflecting physiologic dysfunction in the absence of demonstrable anatomic abnormalities. An example is provided by transient ischemic attacks, in which reversible loss of function of part of the brain occurs without structural damage to neurons or glial cells, as a result of metabolic changes caused by vascular insufficiency.
This chapter gives a brief overview of clinical thinking in neurology and emphasizes the relationship between neuroanatomy and neurology. It has been included to help the reader begin to think as the clinician does and thus to place neuroanatomy, as outlined in the subsequent chapters, in a patient-oriented framework. Together with the Clinical Illustrations and Cases placed throughout this book, this chapter provides a clinical perspective on neuroanatomy.
In taking a history and examining the patient, the neurologic clinician elicits both symptoms and signs. Symptoms are subjective experiences resulting from the disorder (ie, “I have a headache”; “The vision in my right eye became blurry a month ago”). Signs are objective abnormalities detected on examination or via laboratory tests (eg, a hyperactive reflex or abnormal eye movements).
The history may provide crucial information about diagnosis. For example, a patient was admitted to the hospital in a coma. His wife told the admitting physician that “my husband has high blood pressure but doesn't like to take his medicine. This morning he complained of the worst headache in his life. Then he passed out.” On the basis of this history and a brief (but careful) examination, the physician rapidly reached a tentative diagnosis of subarachnoid hemorrhage (bleeding from an aneurysm, ie, a defect in a cerebral artery into the subarachnoid space). He confirmed this diagnostic impression with appropriate (but focused) imaging and laboratory tests and instituted appropriate therapy.
The astute clinical observer may be able to detect signs of neurologic disease by carefully observing the patients' spontaneous behavior as they walk into the room and tell their story. Even before touching the patient, the clinician may observe ...