Diffusion-Weighted MRI Findings in Patients with Capsular Warning Syndrome

Abstract

Background and Purpose: The ‘capsular warning syndrome’ (CWS) of recurrent stereotyped episodes of motor or sensory dysfunction is clinically well recognized, and is associated with a high risk of imminent lacunar infarction with permanent deficits resembling those of CWS. However, the pathophysiology of CWS has not been well characterized. We report a clinicoanatomic correlation with MR imaging studies in the acute and chronic phases in patients with CWS. Material and Methods: Between April 1997 and March 2001, we prospectively studied 8 patients, mean age 73.3 years, presenting with 4–17 motor or sensorimotor transient ischemic attacks (TIAs; duration 2–90 min) up to 3 days after onset of the first episode. Four patients were free of symptoms between the attacks and had no residua, whereas 4 patients developed a pure motor or sensorimotor stroke within 1–3 days after symptom onset. Diffusion-weighted echoplanar MRI (DWI) and T₂-weighted MRI studies were performed within 1 week after symptom onset and were repeated 1–2 months later. Results: Seven of the 8 patients had an appropriate lesion on DWI in the acute phase. DWI abnormalities in the 3 patients with TIAs were 4–10 mm in diameter and confined to the lateral thalamus or medial globus pallidus without involving the internal capsule, whereas 4 patients who developed a stroke had abnormalities localized to the putamen extending to corona radiata (3 patients), or the pontomesencephalic junction (1 patient). All 6 patients who underwent follow-up MRI had an infarct on T₂-weighted images corresponding to, but usually smaller than, the acute phase DWI abnormality. Conclusions: Small infarcts in the basal ganglia or the pons, close to central motor pathways, appear to be the primary lesion in CWS. The pathophysiology of CWS is complex, and may involve hemodynamic mechanisms in penetrating arterial territories, as well as molecular mechanisms, such as peri-infarct depolarizations affecting adjacent motor pathways.

Thrombolysis in Capsular Warning Syndrome

“…Another theory suggests the role of an intermittent peri-infarct depolarization, which affects motor pathways adjacent to the infarct due to metabolic alterations. This has been demonstrated in animals but not in humans [6] . Anticoagulant treatment with heparin has also been used [1,6] .…”

“…This has been demonstrated in animals but not in humans [6] . Anticoagulant treatment with heparin has also been used [1,6] . One article reported the effect of a loading dose of clopidogrel plus acetylsalicylic acid in 2 patients with aspirinresistant CWS [7] .…”

“…In this situation, rt-PA action could prevent the final established stroke. This possibility may be supported by the fact that thrombolysis-treated patients which remained asymptomatic did not show any acute lesion in MRI-DWI after treatment [6] .…”

Callosal warning syndrome

“…Stroke warning syndrome refers to a cerebrovascular syndrome that is characterized by recurrent, stereotyped episodes of transient neurological symptoms and signs leading up to infarction in the corresponding anatomical site [1][2][3][4]. Based on the neuroanatomical location of the final infarction, the syndrome has been given the corresponding name.…”

“…Based on the neuroanatomical location of the final infarction, the syndrome has been given the corresponding name. For instance, when the recurrent episodes of transient hemiparesis are followed by infarction in the internal capsule, it is called capsular warning syndrome [1,2]. On the other hand, when the corresponding infarction heralded by transient events occurs in the region of the pontine tegmentum, it is termed as pontine warning syndrome [3,4].…”