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. The history is important in identifying the likely site of neurologic dysfunction, and the neurologic examination is used to corroborate the suspected location. 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
Are all the symptoms and signs referable to a single lesion in the nervous system or to multiple lesions?
Is the central or peripheral nervous system involved, or are both involved?
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 those originating primarily in the nervous system and those originating elsewhere in the body and affecting the nervous system secondarily (eg, vascular, infectious, immune-mediated). General categories of causes for neurologic disorders include the following:
Vascular
Infectious
Neoplastic
Degenerative
Traumatic
Toxic-metabolic
Congenital
Immune-mediated
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.
History
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 can be obtained or whether a family member should be interviewed instead.
History of present illness should include asking the patient about the following:
The quality, intensity, distribution, duration, and frequency of each symptom (questions should be specific)
The duration of symptoms to differentiate between acute, subacute, and chronic (including congenital) conditions
The circumstances that aggravate and attenuate the symptom
The effectiveness of past treatments
The order in which symptoms occur to help identify the cause
Symptoms not directly related to the nervous system, which suggest a generalized or systemic condition
Specific disabilities, described quantitatively (eg, walking at most 7.6 meters [25 feet] before needing to stop to rest) and their effect on the patient's daily routine.
Past medical history and a complete review of systems are essential because neurologic complications are common in other disorders, especially alcohol use disorder, 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, reflecting a psychiatric disorder. Typically, such symptoms and signs do not conform to the rules of anatomy and physiology, and the patient may be 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:
In many situations, a cerebrovascular examination also is done.
Diagnostic tests may be needed to confirm a diagnosis or exclude other possible disorders.
