Clinical Implications of Neuroimaging in Stroke

Abstract

Neuroimaging is critical for diagnosing and subsequently managing acute strokes. A variety of neuroimaging studies are used to help differentiate ischemic from hemorrhagic strokes, as well as to rule out other pathologies that could mimic a stroke (i.e., neoplasm, infection). The results of these studies then help determine whether there may be a role for surgical or medical management for our stroke patients. Hemorrhagic strokes can be quickly detected on a noncontrast head CT as a hyperdense lesion. Although the neuroimaging study needed to detect this type of stroke is straightforward, what we do with this information remains controversial. Hemorrhagic strokes can be managed medically or treated surgically by craniotomy for clot evacuation, minimally invasive surgery, endoscopic aspiration, or thrombolytic therapy and clot aspiration [1]. The STICH trial demonstrated that patients with spontaneous supratentorial intracerebral hemorrhages showed no benefit from early surgery when compared to conservative management [2]; however, patients with lobar clots within 1 cm of the surface may benefit from surgical evacuation, and patients with cerebellar hemorrhages greater than 3 cm who are deteriorating neurologically, or have brain stem compression and/or hydrocephalus from ventricular obstruction, should definitely have the clot surgically evacuated as soon as possible [1]. In terms of neuroimaging studies, noncontrast head CTs provide sufficient information about size and location to determine whether a patient with a hemorrhagic stroke would potentially benefit from an intervention. Ischemic strokes, in contrast to hemorrhagic strokes, are not as easily detected on noncontrast head CTs. The sensitivity of noncontrast head CTs for ischemia is 50 % at 3 h and improves to 80–90 % at 6 h [3]. Early CT hypodensity involving more than 50 % of the middle cerebral artery (MCA) territory has been shown to be a predictor of fatal brain edema formation [4]. Therefore, it is critical to rapidly and accurately determine whether a patient has an ischemic stroke as these patients may benefit from different treatment paradigms if detected and treated early enough. Decompressive surgery reduces mortality and increases the number of patients with a favorable functional outcome when treated within 48 h after ischemic stroke onset in patients between 18 and 60 years of age as demonstrated in the DECIMAL [5], DESTINY [6], and HAMLET [7] trials [8]. Approximately 50 % of patients who suffer from malignant middle cerebral artery infarcts are older than 60 years of age, and the DESTINY II trial is currently evaluating whether early decompressive surgery may also benefit these patients [9]. The neuroimaging criteria used in each of the trials differ. The DECIMAL trial used an infarct volume on diffusion-weighted MRI of more than 145 cm, while the DESTINY and HAMLET trials used head CTs affecting at least two thirds of the MCA territory as their criteria for decompressive surgery. Although there is clearly an advantage for decompressive craniectomy for the majority of patients with malignant MCA infarcts, 21 % of patients received conservative treatment and still had a favorable functional outcome (modified Rankin score of less than 3) at 1 year follow-up in the pooled analysis of the three randomized controlled trials [8]. If neuroimaging studies could predict at presentation which patients will not develop life-threatening edema, then this group of patients could potentially forego unnecessary surgery. Transl. Stroke Res. (2012) 3:178–181 DOI 10.1007/s12975-012-0170-0