Clinical Stroke Diagnosis

Information Used for Stroke Diagnosis

Clinicians must first decide on the key questions to be asked. Answers are difficult unless the questions are clearly framed. In neurology, two diagnostic questions always require an answer: (1) what is the disease mechanism—the pathology and pathophysiology? and (2) where is the lesion(s)—the anatomy of the disorder? In stroke patients, the “what” question concerns which of the five stroke mechanisms (hemorrhage—subarachnoid or intracerebral; ischemia—thrombotic, embolic, or decreased global perfusion) is present. Before distinguishing among stroke mechanisms, clinicians should first ask whether the findings could be caused by a nonvascular process, such as a brain tumor, metabolic abnormality, infection, intoxication, seizure disorder, or traumatic injury that mimics stroke ( [CR] is devoted to stroke mimics). The where question concerns the anatomic location of the condition, in the brain and in the vascular system that supplies and drains the brain.

Different data are used to answer these two different questions. In determining stroke mechanism, the what question, the following clinical bedside data are most helpful:

• 1.

  Ecology—the past and present personal and family illnesses

• 2.

  Presence and nature of past strokes or transient ischemic attacks (TIAs)

• 3.

  Activity at the onset of the stroke, such as physical effort

• 4.

  Temporal course and progression of the findings (Was the stroke onset sudden with the deficit maximal at onset? Did the deficit improve, worsen, or remain the same after onset? If it worsened, did this occur in a stepwise, remitting, or gradually progressive fashion? Were there fluctuations between normal and abnormal?)

• 5.

  Accompanying symptoms such as headache, vomiting, seizures, and decreased level of consciousness

Information about these items can all be gleaned from a thorough and thoughtful history from the patient, a review of physicians’ and medical records, and data collected from observers, family members, and friends. The general physical examination, which uncovers disorders not known from the history, adds to the data used for diagnosing the stroke mechanism. Elevated blood pressure, cardiac enlargement, murmurs, arrhythmia, and vascular bruits are examples of physical findings that influence identification of the stroke mechanism.

Diagnosis of stroke location—the where question—is made using very different information:

• 1.

  Analysis of the neurological symptoms and their distribution

• 2.

  Findings on neurological examination

• 3.

  Findings from brain and vascular imaging

Mechanism and anatomic diagnoses are not absolute. More realistic are estimates of probabilities. In one patient, intracerebral hemorrhage may be by far the most likely diagnosis, but embolism and thrombosis are also possible and should not be eliminated from consideration. In another patient, there might be a toss-up between thrombosis and embolism.

The process of diagnosis involves two basic techniques: (1) hypothesis generation and testing and (2) pattern matching.

The Inductive Method—Sequential Hypothesis Generation and Testing and Pattern Matching

Hypothesis generation should begin as soon as the first information about the patient becomes available. As the patient or another individual relates the history, the clinician should be thinking of possible diagnoses. The overview given by the patient or other historian generates hypotheses and queries. The clinician then asks the patient and available other questions whose answers should help confirm or refute the hypotheses about the two questions that should be answered, “What” and “Where.” Anatomic hypotheses are also generated. A left hemiparesis raises the possibility of a right cerebral or brain stem lesion. Ask about accompanying visual, sensory, or brain stem symptoms that would help generate a more specific anatomic localization.

The other technique used by clinicians is pattern matching. Clinicians identify a constellation of findings that match their mental images of patterns of stroke mechanisms and pathology and anatomy.

After the history, the clinician should plan the examination (general and neurological) to test the hypotheses generated from the history. After the examinations the hypotheses and probabilities are revised. The laboratory and imaging testing are planned to further test the hypotheses and to arrive at workable diagnoses.

Impact of Various Findings on the “What” Diagnosis