Early false-negative diffusion-weighted imaging in brainstem infarction

Sagittal diffusion-weighted imaging in preventing the false-negative diagnosis of acute brainstem infarction: Confirmation of the benefit by anatomical characterization of false-negative lesions

Background:

In some cases of acute brainstem infarction (BI), standard axial diffusion-weighted imaging (DWI) does not show a lesion, leading to false-negative (FN) diagnoses. It is important to recognize acute BI accurately and promptly to initiate therapy as soon as possible.

Methods:

Of the 171 patients with acute cerebral infarctions in our institution who were examined, 16 were diagnosed with true-positive BI (TP-BI) and six with FN-BI. We evaluated the effectiveness of sagittal DWI in accurately diagnosing acute BI and sought to find the cause of its effectiveness by the anatomical characterization of FN-BIs.

Results:

Considering the direction of the brainstem perforating arteries, we supposed that sagittal DWI might more effectively detect BIs than axial DWI. We found that sagittal DWI detected all FN-BIs more clearly than axial DWI. The mean time between the onset of symptoms and initial DWI was significantly longer in the TP group (17.6 ± 5.5 h) than in the FN group (5.0 ± 1.2 h; P < 0.0001). The lesion volumes were much smaller in FN-BIs (259 ± 82 mm³) than in TP-BIs (2779 ± 767 mm³; P = 0.0007). FN-BIs had a significant inverse correlation with the ventrodorsal length of infarcts (FN 3.5 ± 1.1 mm, TP 11.4 ± 3.6 mm; P < 0.0004) and no correlation with other size parameters such as rostrocaudal thickness and lateral width.

Conclusion:

Anatomical characterization clearly confirmed that the addition of sagittal DWI to the initial axial DWI in suspected cases of BI ensures its accurate diagnosis and improves the patient’s prognosis.

Diagnosis of DWI-negative acute ischemic stroke: A meta-analysis

OBJECTIVE

To determine the prevalence of diffusion-weighted imaging (DWI)-negative acute ischemic stroke (AIS) and to identify clinical characteristics of patients with DWI-negative AIS.

METHODS

We systematically searched PubMed and Ovid/MEDLINE for relevant studies between 1992, the year that the DWI sequence entered clinical practice, and 2016. Studies were included based upon enrollment of consecutive patients presenting with a clinical diagnosis of AIS prior to imaging. Meta-analysis was performed to synthesize study-level data, estimate DWI-negative stroke prevalence, and estimate the odds ratios (ORs) for clinical characteristics associated with DWI-negative stroke.

RESULTS

Twelve articles including 3,236 AIS patients were included. The meta-analytic synthesis yielded a pooled prevalence of DWI-negative AIS of 6.8%, 95% confidence interval (CI) 4.9-9.3. In the 5 studies that reported proportion data for DWI-negative and DWI-positive AIS based on the ischemic vascular territory (n = 1,023 AIS patients), DWI-negative stroke was strongly associated with posterior circulation ischemia, as determined by clinical diagnosis at hospital discharge or repeat imaging (OR 5.1, 95% CI 2.3-11.6, p < 0.001).

CONCLUSIONS

A small but significant percentage of patients with AIS have a negative DWI scan. Patients with neurologic deficits consistent with posterior circulation ischemia have 5 times the odds of having a negative DWI scan compared to patients with anterior circulation ischemia. AIS remains a clinical diagnosis and urgent reperfusion therapy should be considered even when an initial DWI scan is negative.

Using the Physical Examination to Diagnose Patients with Acute Dizziness and Vertigo

BACKGROUND

Emergency department (ED) patients who present with acute dizziness or vertigo can be challenging to diagnose. Roughly half have general medical disorders that are usually apparent from the context, associated symptoms, or initial laboratory tests. The rest include a mix of common inner ear disorders and uncommon neurologic ones, particularly vertebrobasilar strokes or posterior fossa mass lesions. In these latter cases, misdiagnosis can lead to serious adverse consequences for patients.

OBJECTIVE

Our aim was to assist emergency physicians to use the physical examination effectively to make a specific diagnosis in patients with acute dizziness or vertigo.

DISCUSSION

Recent evidence indicates that the physical examination can help physicians accurately discriminate between benign inner ear conditions and dangerous central ones, enabling correct management of peripheral vestibular disease and avoiding dangerous misdiagnoses of central ones. Patients with the acute vestibular syndrome mostly have vestibular neuritis, but some have stroke. Data suggest that focused eye movement examinations, at least when performed by specialists, are more sensitive for detecting early stroke than brain imaging, including diffusion-weighted magnetic resonance imaging. Patients with the triggered episodic vestibular syndrome mostly have benign paroxysmal positional vertigo (BPPV), but some have posterior fossa mass lesions. Specific positional tests to provoke nystagmus can confirm a BPPV diagnosis at the bedside, enabling immediate curative therapy, or indicate the need for imaging.

CONCLUSIONS

Emergency physicians can effectively use the physical examination to make a specific diagnosis in patients with acute dizziness or vertigo. They must understand the limitations of brain imaging. This may reduce misdiagnosis of serious central causes of dizziness, including posterior circulation stroke and posterior fossa mass lesions, and improve resource utilization.

"Invisible" brain stem infarction at the first day

BACKGROUND

In specific stroke cases, serial diffusion-weighted magnetic resonance imaging (DW MRI) on day 1 was unable to show a lesion, whereas that on day 4 and later clearly revealed a lesion. However, clinical features of this phenomenon ("invisible" brain stem infarction [IBI] at the first day) have not been fully delineated.

METHODS

We retrospectively recruited 212 stroke patients in the Emergency Unit and Neurology Department. Among these, we studied patients with IBI. Definition of IBI is that acute and clear brain stem symptoms/signs on arrival were ameliorated at discharge and appearance of high signal intensity on serial DW images with low apparent diffusion coefficient (ADC) by 1.5 T MRI with 2-mm slices.

RESULTS

IBI were found in only 6 patients. Day 1 invisible stroke was found only in the brain stem (17%, 6 of 35) but none (0 of 177) in the hemispheric infarction (P < .05). In most patients with IBI, DW MRI turned out visible at the third/fourth day. Before the fourth day, DW/ADC signal changes in patients with IBI were minimal. In IBI, lesion size (mean 2.7 mm(2)) was smaller than that of visible cases (mean 7.3 mm(2)). In IBI, lesion location was mostly at the dorsolateral medulla. In IBI, sensory disturbance was significantly more common (67%) than visible cases (24%; P < .05), whereas dysarthria was less common (0%; P < .01) than visible cases (66%; P < .01).

CONCLUSIONS

It is likely that patients with smaller stroke volume, sensory disturbance, and medullary location are prone to develop IBI. When evaluating stroke using MRI criteria, recognition of IBI is important to start early management.

Differential diagnosis of T2 hyperintense brainstem lesions: Part 1. Focal lesions

Brainstem lesions can be classified as focal or diffuse. Magnetic resonance imaging is the most suitable imaging modality for evaluating these lesions. As a rule, focal lesions are not large and have well-defined margins. Causes include tumors, vascular malformations, demyelinating diseases, brain abscesses, hypertrophic olivary degeneration, and dilated Virchow-Robin spaces. Differential diagnoses of these numerous entities mandates a review of magnetic resonance imaging findings in conjunction with epidemiologic aspects, clinical features, and other medical test results.

Acute ischemic stroke lasting for 5 days without definite lesions on diffusion-weighted magnetic resonance imaging in a patient with severe leukoaraiosis

The reported frequency of false-negative diffusion-weighted magnetic resonance imaging (DWI) cases is 3.5%-25%. However, territorial stroke (eg, middle cerebral artery territory) with negative DWI is very rare. We report a case of territorial ischemic stroke persisting for 5 days without identification of a definite lesion on DWI but with decreased perfusion on perfusion computed tomography in a patient with underlying severe leukoaraiosis. This case suggests that severe leukoaraiosis might be responsible for the negative finding on DWI in acute ischemic stroke.