Acute Stroke
This chapter describes the initial evaluation and management of acute stroke, with an emphasis on the use of thrombolytic therapy, and the recommendations in the current clinical practice guidelines on acute stroke (1).
I. Definitions
Stroke is defined as “an acute brain disorder of vascular origin accompanied by neurological dysfunction that persists for longer than 24 hours” (2).
Stroke is classified according to the underlying mechanism:
Ischemic stroke accounts for 87% of all strokes (3): 80% of ischemic strokes are thrombotic strokes, and 20% are embolic strokes. Most emboli originate from thrombi in the left side of the heart, but some originate from venous thrombi in the legs that reach the brain through a patent foramen ovale (4).
A transient ischemic attack (TIA) is an acute episode of ischemia with focal loss of brain function that lasts less than 24 hours (2). The feature that distinguishes TIA from stroke is the reversibility of clinical symptoms. This
does not apply to reversibility of cerebral injury, because one-third of TIAs are associated with cerebral infarction (5,6).
II. Initial Evaluation
The evaluation of a patient with suspected acute stroke must proceed quickly; i.e., each minute of cerebral infarction results in the destruction of 1.9 million neurons and 7.5 miles of myelinated nerves (7).
A. Bedside Evaluation
The clinical presentation of acute stroke is determined by the area of brain that is injured, as demonstrated in Figure 42.1.
1. Mental Status
Most cerebral infarctions are unilateral, and do not result in loss of consciousness (8).
When focal neurological deficits are accompanied by coma, the most likely conditions are intracerebral hemorrhage, brainstem infarction, or nonconvulsive seizures.
2. Aphasia
Injury in the left cerebral hemisphere (the dominant hemisphere for speech in 90% of the population) produces aphasia, which is a disturbance in the comprehension and/or formulation of language. There can be difficulty with verbal comprehension (receptive aphasia), difficulty with verbal expression (expressive aphasia), or both (global aphasia).
3. Sensorimotor Loss
Injury involving one cerebral hemisphere results in weakness on the opposite or contralateral side of the body (i.e.,
hemiparesis). Hemiparesis has also been reported in patients with hepatic and septic encephalopathy (9,10).
hemiparesis). Hemiparesis has also been reported in patients with hepatic and septic encephalopathy (9,10).
 FIGURE 42.1 Areas of brain injury and corresponding neurological abnormalities. ‡Indicates deficits involving the same side of the face and the opposite side of the body. |
4. Stroke Mimics
5. NIH Stroke Scale
The use of a clinical scoring system is recommended to standardize the evaluation of acute stroke (1), and the most validated scoring system is the NIH Stroke Scale (NIHSS). The NIHSS evaluates 11 different aspects of performance, and the total score ranges from zero (best performance) to 41 (worst performance); a score of 22 or higher generally indicates a poor prognosis. (The NIHSS can be downloaded from http://stroke.nih.gov.easyaccess1.lib.cuhk.edu.hk/documents.)
B. Computed Tomography
Noncontrast computed tomography (NCCT) is typically the first diagnostic test that is obtained in suspected acute stroke.
 FIGURE 42.2 Noncontrast CT images from the first and third day following an ischemic stroke. The image on day 1 is unrevealing, but the image on day 3 shows a large hypodense area (outlined by the dotted line) with mass effect, representing extensive tissue destruction with intracerebral edema. Images from Reference 13. |
NCCT has a sensitivity close to 100% for detecting intra-cranial hemorrhage (5), and the results of NCCT are essential for decisions regarding thrombolytic therapy.
NCCT is not reliable for visualizing ischemic changes. One-half of ischemic strokes are not apparent on NCCT (12), and the diagnostic yield is even lower in the first 24 hours after an acute stroke (13). The nonvalue of CT imaging in the early post-infarct period is shown in Figure 42.2 (13). The CT image on day 3 shows a large area of infarction with mass effect, which is not apparent in the CT image on day 1 (the day of the stroke).
C. Magnetic Resonance Imaging
MRI with diffusion-weighted imaging is the most sensitive and specific technique for the detection of ischemic stroke (1). This technique (which is based on water movement through tissues) can detect ischemic changes within 5–10 minutes after onset (14), and it has a sensitivity of 90% for the detection of ischemic stroke in the early period after stroke onset (5).Related posts:
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