Patients with neurologic symptoms are approached in a stepwise manner termed the neurologic method, which consists of the following:
- Identifying the anatomic location of the lesion or lesions causing symptoms
- Identifying the pathophysiology involved
- Generating a differential diagnosis
- Selecting specific, appropriate tests
Identifying the anatomy and pathophysiology of the lesion through careful history taking and an accurate neurologic examination markedly narrows the differential diagnosis and thus the number of tests needed. This approach should not be replaced by reflex ordering of CT, MRI, and other laboratory testing; doing so leads to error and unnecessary cost.
To identify the anatomic location, the examiner considers questions such as
- Is the lesion in one or multiple locations?
- Is the lesion confined to the nervous system, or is it part of a systemic disorder?
- What part of the nervous system is affected?
Specific parts of the nervous system to be considered include the cerebral cortex, subcortical white matter, basal ganglia, thalamus, cerebellum, brain stem, spinal cord, brachial or lumbosacral plexus, peripheral nerves, neuromuscular junction, and muscle.
Once the location of the lesion is identified, categories of pathophysiologic causes are considered; they include
When appropriately applied, the neurologic method provides an orderly approach to even the most complex case, and clinicians are far less likely to be fooled by neurologic mimicry—eg, when symptoms of an acute stroke are actually due to a brain tumor or when rapidly ascending paralysis suggesting Guillain-Barré syndrome is actually due to spinal cord compression.
The history is the most important part of the neurologic evaluation. Patients should be put at ease and allowed to tell their story in their own words. Usually, a clinician can quickly determine whether a reliable history is forthcoming or whether a family member should be interviewed instead.
History of present illness should include the following:
- Specific questions clarify the quality, intensity, distribution, duration, and frequency of each symptom.
- What aggravates and attenuates the symptom and whether past treatment was effective should be determined.
- Asking the patient to describe the order in which symptoms occur can help identify the cause.
- Specific disabilities should be described quantitatively (eg, walks at most 25 feet before stopping to rest), and their effect on the patient’s daily routine noted.
Past medical history and a complete review of systems are essential because neurologic complications are common in other disorders, especially alcoholism, diabetes, cancer, vascular disorders, and HIV infection.
Family history is important because migraine and many metabolic, muscle, nerve, and neurodegenerative disorders are inherited.
Social, occupational, and travel history provides information about unusual infections and exposure to toxins and parasites.
Sometimes neurologic symptoms and signs are functional or hysterical, reflecting a psychiatric disorder. Typically, such symptoms and signs do not conform to the rules of anatomy and physiology, and the patient is often depressed or unusually frightened. However, functional and physical disorders sometimes coexist, and distinguishing them can be challenging.
Physical Examination and Testing
A physical examination to evaluate all body systems is done, but the focus is on the nervous system (neurologic examination). The neurologic examination, discussed in detail elsewhere in The Manual, includes the following:
- Mental status
- Cranial nerves
- Motor system
- Muscle strength
- Gait, stance, and coordination
- Autonomic nervous system
In many situations, a cerebrovascular examination also is done.
Diagnostic tests may be needed to confirm a diagnosis or exclude other possible disorders.