eLetters

6 e-Letters

  • RE: RE: Migraine and stroke

    The role of CSD in migraine is actually generally accepted as one of the pathophysiological process. In fact several novel CGRP targeted migraine medications are showing that CGRP-mAb can prevent the activation and sensitization of high-threshold (central) trigeminovascular neurons by cortical spreading depression. Some of them are currently under review by FDA and expect to be on the market in late 2018. The research in rodents may not always be applicable to human with migraine and this theory has been in existence for over a decade. On your view of posterior cerebral circulation vulnerability to stroke, that was not quite relevant to the theme of current paper, which was about the association of migraine and stroke, not why stroke occurs more in posterior circulation. One fact of interest is that migraine sequelae related white matter changes would involve the entire brain, not limited to posterior circulation.

  • RE: RE: The efficacy and safety of endovascular recanalization of occluded large cerebral arteries during the subacute phase of cerebral infarction: a case series report

    By Shugui Shi, MD & Kangning Chen, MD.

     

    To the Reader,

     

    We have reviewed your comments on our paper. For your opinion on the issue of penumbra not to be present in subacute phase of stroke, there are literature reporting its presence days after the initial stroke. Penumbra is a dynamic phenomenon without clear demarcation. For example, there is a zone of benign misery perfusion outside of penumbra with its CBF between 15 to 30ml/100g/min (1). This zone may not be viable if perfusion is not re-established. That is to say with a major cerebral arterial occlusion, even with the help of collaterals, brain tissue may die slowly over a period of time. In clinical practice and proven by imaging studies, the side of brain with a large arterial occlusion will significantly atrophy, a process perhaps related to cell apoptosis from chronic hypoxic state (2). Hence, re-opening the occluded artery may or may not help the immediate stroke, but likely help the large ipsilateral brain tissue in a long run. More longitudinal study is certainly needed to examine this issue.

     

    You have questioned our equipment on its ability to detect penumbra. We have had over 10 years of experience in performing MR perfusion with MRI scanner manufactured by Siemens.

     

    All of our patients have received guideline recommended best medical management including dual antiplatelet and statin therapy plus life style modificat...

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  • RE: The efficacy and safety of endovascular recanalization of occluded large cerebral arteries during the subacute phase of cerebral infarction: a case series report

    The article by Dr. Chen and his colleagues1 raises an important issue of managing intracranial stenosis or occlusion during the subacute phase of ischemic stroke. The authors concluded that selective percutaneous transluminal angioplasty (PTA) or percutaneous transluminal angioplasty and stenting (PTAS) for intracranial severe stenosis or occlusion is safe and effective in patients with subacute or subacute/chronic stroke. It should be extremely precaution while applying this conclusion into clinical practice. A couple of concerns need to be addressed: (1) there is large body of evidences and publications demonstrated that the ischemic penumbra can exist for only few hours 2. The authors provided the perfusion study in case 1 and commended that there is large area of low perfusion which might be salvageable. However, the authors did not mention which vendor and software have been utilized in the perfusion study. A different vendor and/or software can have significant variability on the result of cerebral perfusion study. I doubt the penumbra (aka, the mismatch on a perfusion study) can last for days in patients with ischemic stroke. (2) American Heart Association/American Stroke Association recommended3 aggressive medical management including dual antiplatelets of aspirin and clopidogrel as well as high-intensity Statin (Class IIB; level of Evidence B) for patients with ischemic stroke caused by 50% to 99% stenosis of a major intracranial artery. Intracranial artery angiop...

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  • RESPONSE to: RE: Artificial intelligence in healthcare: past, present and future

    Dear Reader:

     

    Thanks so much for notifying us about the figure misalignment issue in the original article - “Artificial Intelligence in Healthcare: Past, Present and Future.”

     

    We have now investigated the issue. The misalignment originated from a glitch during the production stage. We now have fixed the issue and updated the online version of the paper. The latest publication is attached for your reference. Please accept our sincere apology for the mistake.

     

    Yours sincerely,

    Haipeng Shen

    Professor and Area Coordinator

    Innovation and Information Management

    Faculty of Business and Economics

    University of Hong Kong

  • RE: Migraine and stroke

    I read with interest the article by Zhang et al., (SVN, 2017, 2: e000077) [1] about "Migraine and stroke". At a time when the pathophysiology of migraine is poorly understood and the pathogenetic role of cortical spreading depression (CSD) is far from being generally accepted (Gupta, 2009) [2], Zhang et al. underscore the link between migraine with aura and ischemic stroke. With nosological splitting having been taken to the extreme end of the spectrum, Zhang et al., believe that migraine with aura (MwA) and migraine without aura (MwoA) are distinct entities.1 With the same epidemiology, the same clinical features (except the aura), and the same migraine preventive agents like propranolol, we have split wide the classification of the primary headache disorders, and maintain the belief-in-belief strategy at the cost of remaining confused at several levels, including the pathophysiology of primary headache disorders.

    The concept of CSD is maintained by key omissions and assumptions (see Box 1, p. 1601, reference No. 2). The fact that atenolol, a hydrophilic pharmacologic agent, that does not cross the blood-brain barrier and does not influence any brain neuronal function including the CSD in unconscious experimental animals and prevents both MwA and MwoA equally efficiently is a pharmacologic absolute known since 1980, [3,4,] that is by itself sufficient to eliminate the concept of CSD from migraine pathophysiology.

    The rodent model of...

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  • RE: Artificial intelligence in healthcare: past, present and future

    It appears that the figures to not match their descriptive text: Figure 8 is not a stylised representation of an neural network - it is a stylised representation of a support vector machine and figure 9 is not a stylised representation of a deep learning network, the authors illustration is more of a conventional neural network with only one hidden layer.