Signs and Symptoms in Neurologic Diagnosis: Approach to the Patient
Lewis P. Rowland
Timothy A. Pedley
Accurate diagnosis is essential to making rational decisions about management and, increasingly in neurology, instituting effective treatment. Making a neurologic diagnosis requires a systematic approach to the patient. The history and physical examination provide essential but complementary data that form the cornerstone of diagnosis. Of course, laboratory tests are often necessary and are sometimes pathognomonic. They should, however, be ordered selectively, and students have to learn which tests are appropriate and when to order them. It is therefore necessary to know which diagnostic possibilities are reasonable considerations for a particular patient. Overreliance on laboratory tests and technology and analysis that is uninformed by clinical reasoning and appropriate differential diagnosis can lead to errors and delay suitable therapy.
The clinical data obtained by a careful history and physical examination are used to address three questions:
1. What anatomic structures of the nervous system are affected? Progressive weakness in the legs, for example, could be due to a myopathy, peripheral neuropathy, or myelopathy, but each of these possibilities can usually be distinguished by the presence or absence of characteristic symptoms and signs. It is usually not possible to make a specific etiologic diagnosis without knowing what parts of the nervous system are affected. In addition, knowing the probable anatomic substrate restricts the etiologic possibilities. Thus, making an accurate anatomic diagnosis should be the first step in analyzing a neurologic disorder. Clues to identifying the anatomic sites of neurologic disorders are discussed in the following section and later in this chapter.
2. What is the nature of the neurologic disorder? An individual patient’s symptoms and signs usually cluster into broad syndromes or categories of disease: developmental disorder, peripheral neuropathy, acute encephalopathy, progressive dementia, parkinsonian syndrome, cerebrovascular syndrome, and so on. A syndromic diagnosis assists in clarifying the nature of the disease and further focuses on possible specific causes.
3. What are the most likely etiologies for the patient’s illness? These derive from consideration of the anatomic and syndromic diagnoses in light of the tempo (rapid or slow) and course (fixed from onset, steadily progressive or stepwise) of the illness, relevant past history and family history, and whether there is evidence of systemic involvement. The possible etiologies listed in order of probability constitute the differential diagnosis, and this in turn determines which laboratory tests need to be ordered and the urgency with which the evaluation should proceed.
An experienced clinician is likely to deal with these three questions simultaneously or even reverse the order. To take an obvious example, if a patient suddenly becomes speechless or awakens with a hemiplegia, the diagnosis of stroke is presumed. The location is then deduced from findings made upon examination, and both site and pathophysiologic process are ascertained by computed tomography (CT) or magnetic resonance imaging (MRI). If there are no surprises in the imaging study (e.g., demonstration of a tumor or vascular malformation), further laboratory tests might be considered to determine the precise cause of an ischemic infarct.
A reliable and accurate history is essential. This should be obtained directly from the patient if at all possible, but it is often necessary to verify the patient’s account or obtain additional information by speaking with relatives or close friends. This is particularly true if the illness has compromised the patient’s mental function or use of language. Particular attention should be paid to the onset of symptoms, the circumstances in which they occurred, and their subsequent evolution. Have any of the symptoms resolved? Have similar or different neurologic symptoms occurred previously? To avoid errors, it is important that the physician avoids leading questions and clarifies what the patient means by ambiguous terms, such as dizziness or weakness. Discrepancies and inconsistencies in details obtained by different examiners are often the source of diagnostic confusion and must be resolved.
Performing an accurate neurologic examination (Chapter 3) requires practice and skill. It begins with observations made as the patient enters the room and continues while his or her history is being obtained. Abnormalities of gait and balance may be readily apparent. The manner in which the patient tells the history may reveal confusion, aphasia, or memory loss. It is preferable to record exact observations (what the patient actually did or did not do) rather than interpretations that may introduce ambiguity. It is best to perform the examination in a standard sequence to avoid omissions, although it may be necessary to modify this based on the patient’s condition and ability to cooperate. The usual order is mental status, cranial nerves, strength and coordination, sensation, and reflexes.
The specific nature of different symptoms and findings obtained from examination are reviewed in the following chapters. Other considerations that influence diagnosis are briefly described here.
IDENTIFYING THE SITE OF DISORDER
Aspects of the patient’s history may suggest the nature of the disorder; specific symptoms and signs suggest the site of the disorder.
Cerebral disease is implied by seizures or by focal signs that may be attributed to a particular area of the brain; hemiplegia, aphasia, or hemianopia are examples. Generalized manifestations of cerebral disease are seizures, delirium, and dementia.
Brain stem disease is suggested by cranial nerve palsies, cerebellar signs of ataxia of gait or limbs, tremor, or dysarthria. Dysarthria may be the result of incoordination in disorders of the cerebellum itself or its brain stem connections. Cranial nerve palsies or the neuromuscular disorder of myasthenia gravis may also impair speech. Ocular signs have special localizing value. Involuntary movements suggest basal ganglia disease.