Migraine Aura-Catch Me If You Can with EEG and MRI-A Narrative Review

Roughly one-third of migraine patients suffer from migraine with aura, characterized by transient focal neurological symptoms or signs such as visual disturbance, sensory abnormalities, speech problems, or paresis in association with the headache attack. Migraine with aura is associated with an increased risk for stroke, epilepsy, and with anxiety disorder. Diagnosis of migraine with aura sometimes requires exclusion of secondary causes if neurological deficits present for the first time or are atypical. It was the aim of this review to summarize EEG an MRI findings during migraine aura in the context of pathophysiological concepts. This is a narrative review based on a systematic literature search. During visual auras, EEG showed no consistent abnormalities related to aura, although transient focal slowing in occipital regions has been observed in quantitative studies. In contrast, in familial hemiplegic migraine (FHM) and migraine with brain stem aura, significant EEG abnormalities have been described consistently, including slowing over the affected hemisphere or bilaterally or suppression of EEG activity. Epileptiform potentials in FHM are most likely attributable to associated epilepsy. The initial perfusion change during migraine aura is probably a short lasting hyperperfusion. Subsequently, perfusion MRI has consistently demonstrated cerebral hypoperfusion usually not restricted to one vascular territory, sometimes associated with vasoconstriction of peripheral arteries, particularly in pediatric patients, and rebound hyperperfusion in later phases. An emerging potential MRI signature of migraine aura is the appearance of dilated veins in susceptibility-weighted imaging, which may point towards the cortical regions related to aura symptoms ("index vein"). Conclusions: Cortical spreading depression (CSD) cannot be directly visualized but there are probable consequences thereof that can be captured Non-invasive detection of CSD is probably very challenging in migraine. Future perspectives will be elaborated based on the studies summarized.

[A case of suspected migraine with aura: transient cortical venous dilatation visualized by susceptibility-weighted imaging]

A 41-year-old man was admitted with proper name anomia and headache of sudden onset. He had a history of migraine without aura from the age of 35. Neurological examination on admission showed acalculia, proper name anomia, left-right disorientation and severe left-sided headache with nausea. Susceptibility-weighted MRI revealed dilatation of cortical veins of the left hemisphere. MR angiography and contrast CT revealed no cerebral arterial or venous occlusion. The patient's proper name anomia was improved at 5 hours from the onset and acalculia and left-right disorientation were improved at 17 hours from the onset. At 42 hours from the onset, he had recovered from his headache, and the dilatation of cortical veins of the left hemisphere had disappeared. Acalculia and left and right disorientation are rare presentations of migraine with aura. Susceptibility-weighted imaging may be a useful tool to distinguish migraine with aura from stroke and stroke mimics.

Imaging Neurovascular Uncoupling in Acute Migraine with Aura with Susceptibility Weighted Imaging

PURPOSE

Migraine with aura (MwA) in the emergency setting is common and sometimes difficult to distinguish from mimicking conditions. Susceptibility weighted imaging (SWI), a magnet resonance (MR) technique is sensitive to deoxygenated hemoglobin in cerebral veins and depicts these according to their level of oxygenation. Our study aimed at evaluating the frequency of regions of prominent focal veins (PFV) on SWI in the acute phase.

METHODS

Between 2011 and 2018 we evaluated symptoms and MR imaging of adult patients with acute MwA attacks (< 5 days after onset of symptoms). Abnormal imaging was visually scored in 12 ROIs on both hemispheres distributed on 3 slices. The score ranged from 0 to 3.

RESULTS

In all, 638 patients (436 female) mean age 37.39 years (18-89 ± 14.13) were included. Susceptibility weighted imaging was abnormal in 18.8% of patients. The inferior and posterior medial temporal lobe and the occipital lobe were most often affected. Susceptibility weighted imaging was more likely abnormal when MR was performed within 24 hours with an average around 5 hours after symptom onset. The side of aura symptoms and hemispheric imaging alteration in patients with abnormal SWI was highly significant (p < 0.001).

CONCLUSION

In the acute episode of MwA, SWI imaging can show a combination of increased deoxygenation. The results may indicate linking PFV to MwA.

Magnetic resonance imaging of arterial stroke mimics: a pictorial review

Acute ischaemic stroke represents the most common cause of new sudden neurological deficit, but other diseases mimicking stroke happen in about one-third of the cases. Magnetic resonance imaging (MRI) is the best technique to identify those 'stroke mimics'. In this article, we propose a diagnostic approach of those stroke mimics on MRI according to an algorithm based on diffusion-weighted imaging (DWI), which can be abnormal or normal, followed by the results of other common additional MRI sequences, such as T2 with gradient recalled echo weighted imaging (T2-GRE) and fluid-attenuated inversion recovery (FLAIR). Analysis of the signal intensity of the parenchyma, the intracranial arteries and, overall, of the veins, is crucial on T2-GRE, while anatomic distribution of the parenchymal lesions is essential on FLAIR. Among stroke mimics with abnormal DWI, T2-GRE demonstrates obvious abnormalities in case of intracerebral haemorrhage or cerebral amyloid angiopathy, but this sequence also allows to propose alternative diagnoses when DWI is negative, such as in migraine aura or headaches with associated neurological deficits and lymphocytosis (HaNDL), in which cortical venous prominence is observed at the acute phase on T2-GRE. FLAIR is also of major interest when DWI is positive by better showing evocative distribution of cerebral lesions in case of seizure (involving the hippocampus, pulvinar and cortex), hypoglycaemia (bilateral lesions in the posterior limb of the internal capsules, corona radiata, striata or splenium of the corpus callosum) or in posterior reversible encephalopathy syndrome (PRES). Other real stroke mimics such as mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes (MELAS), Susac's syndrome, brain tumour, demyelinating diseases and herpes simplex encephalitis are also included in our detailed and practical algorithm. KEY POINTS: • About 30% of sudden neurological deficits are due to non-ischaemic causes. • MRI is the best technique to identify stroke mimics. • Our practical illustrated algorithm based on DWI helps to recognise stroke mimics.

Magnetic resonance susceptibility weighted imaging in neurosurgery: current applications and future perspectives

Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is still far from consistent in clinical usage. To develop a deeper appreciation for SWI, the authors here review the clinical applications in 4 major fields of neurosurgery: neurooncology, vascular neurosurgery, neurotraumatology, and functional neurosurgery. Finally, they address the limitations of and future perspectives on SWI in neurosurgery.

Changes in (99m)Tc-ECD SPECT and magnetic resonance angiography with sporadic hemiplegic migraine in a child

Sporadic hemiplegic migraine is rare in childhood. We followed a patient with Tc-ECD (Tc-ethyl cysteinate dimer) SPECT and magnetic resonance angiography (MRA). At the age of 8 years, he developed left hemiplegia. The MRA showed vasoconstriction of the posterior right middle cerebral artery. Hemiplegia disappeared in a few hours, and the MRA normalized. At the age of 10 years, right hemiplegia was observed, disappearing completely after a few days. During this second migraine attack, MRA demonstrated left middle cerebral artery vasoconstriction, and SPECT revealed decreased left hemisphere blood flow. Findings normalized as the patient recovered.

Analysis of susceptibility-weighted images of cortico-medullary junction

OBJECTIVE

We qualitatively evaluated the differences among susceptibility-weighted (SWI), magnitude (MAG), and high pass filtered phase (PHA) images in depicting interlobar differences in the appearance of the signal of the corticomedullary junction (CMJ). We conducted quantitative evaluation to validate the qualitative results.

MATERIALS AND METHODS

We obtained SWI images from 25 preoperative brain tumor patients (12 men, 13 women, aged 19 to 82 years, mean, 52 years). Two trained neuroradiologists evaluated MAG, PHA, and SWI images. Qualitative evaluation of the CMJ signal and quantitative calculation of the relative signal ratio (RSR) percentages between the CMJ and deep white matter (WM) were conducted at 3 different slice levels of the brain independently for 4 different lobes (frontal, parietal, temporal, and occipital) and compared among MAG, PHA, and SWI. The extent of the area of the CMJ signal was graded on a 4-point scale (Grade 3, >75%; Grade 2, 50 to 75%; Grade 1, 25 to 50%; Grade 0, <25%). Data were statistically analyzed using a nonparametric Friedman test.

RESULTS

The Kappa coefficients between the qualitative and quantitative grades were 0.002 for MAG, 0.0047 for PHA, and 0.050 for SWI. Qualitatively, on the PHA images and SWI, grades of the occipital lobes were significantly higher than those of the other lobes (P < 0.005). Quantitatively, PHA images showed statistically significant interlobar differences in RSR percentage values of the CMJ (P = 0.025).

CONCLUSION

Qualitatively, the appearance of the CMJ differed significantly among the different lobes of the brain on SWI and underlying PHA images but not on MAG images. Quantitatively, only PHA images showed significant interlobar differences in the RSR. PHA images are most sensitive to the CMJ signal contrast due to local paramagnetic iron content.

Prolonged acute migraine with aura and reversible brain MRI abnormalities after liquid sclerotherapy

Transient visual disturbances constitute the most commonly reported neurological side effect during and immediately after sclerotherapy. A few studies, based on clinical and diffusion-weighted MRI assessments, have suggested that these transient neurological symptoms correspond to migraine with aura. Recently, it has been reported that brain magnetic resonance imaging can reveal transient T2*-weighted abnormalities during the acute phase of migraine with aura. We reported a 36-year-old man who presented with transient neurological symptoms and concomitant T2*-weighted abnormalities on brain magnetic resonance imaging immediately after liquid sclerotherapy. We hypothesize that the reversible nature of the patient's T2*-weighted abnormalities may indicate a relationship with the post-sclerotherapy migraine with aura attack.

Pediatric hemiplegic migraine: role of multiple MRI techniques in evaluation of reversible hypoperfusion

BACKGROUND

Hemiplegic migraine (HM) is a rare type of migraine with aura that involves motor weakness. Data on conventional and advanced neuroimaging findings during prolonged attacks of HM are limited, particularly in children.

CASE

A 13-year-old-female with a history of migraine had a typical attack of HM characterized by right-sided hemiplegia, deterioration of vigilance and paraphasia. MRI performed 3 hours after hemiplegia onset revealed normal diffusion tensor imaging (DTI) sequences, but perfusion weighted imaging (PWI) showed a large area of hypoperfusion within the left cerebral hemisphere and susceptibility weighted imaging (SWI) demonstrated a matching area with prominent, hypointense draining sulcal veins. Magnetic resonance angiography (MRA) revealed subtle narrowing of the left middle cerebral artery. The neuroimaging abnormalities completely resolved 24 hours after the attack onset.

CONCLUSION

Multiple conventional and advanced MRI techniques including SWI play a key role in an HM attack to (1) exclude acute arterial ischemic stroke and (2) further understand the pathophysiology of HM.

Structural and functional neuroimaging in migraine: insights from 3 decades of research

Modern imaging methods provide unprecedented insights into brain structure, perfusion, metabolism, and neurochemistry, both during and between migraine attacks. Neuroimaging investigations conducted in recent decades bring us closer to uncovering migraine as a multifaceted, primarily central nervous system disorder. Three main categories of structural and functional brain changes are described in this review, corresponding to the migrainous aura, ictal headache, and interictal states. These changes greatly advance our understanding of multiple pathophysiologic underpinnings of migraine, from central "migraine generating" loci, to cortical spreading depression, intimate mechanisms underlying activation of neuronal pain pathways in vulnerable patients, central sensitization, and chronification. Structural imaging begins to explain the complex connections between migraine and cerebral vascular events, white matter lesions, grey matter density alterations, iron deposition, and microstructural brain damage. Selected structural and functional alterations of brain structures, as identified with imaging methods, may represent the foundation of new diagnostic strategies and serve as markers of therapeutic efficacy.