Marco Longoni

Inflammation and excitotoxicity: role in migraine pathogenesis.

The pathogenesis of migraine is still unclear, but much evidence suggests a role of inflammation in pain generation. Calcitonin gene related peptide, nitric oxide and cytokines are all molecules shown to be involved both in animal and human studies. The glutamatergic system is also described as a possible mechanism leading to neuronal hyperexcitability and cortical spreading depression (CSD). Excitotoxic neural death, due to excessive release of the amino acid in the extracellular space, may represent a consequence of protracted CSD and oligaemia and may be involved in migrainous infarction and aspecific lesions seen on T2-weighted NMR imaging.

Increased plasma glutamate in stroke patients might be linked to altered platelet release and uptake

Experimental studies have shown the role of excitotoxicity in the pathogenesis of ischemic brain lesions, and glutamate levels have been found to be elevated in CSF and plasma from patients, early after stroke. In this study, we investigated whether platelets could be involved in the mechanism of altered plasma glutamate levels after stroke. Forty four patients, from 6 hours to 9 months after ischemic stroke, 15 age-related healthy controls and 15 controls with stroke risk factors or previous transient ischemic attack were enrolled. Glutamate plasma levels, platelet glutamate release after aggregation and platelet glutamate uptake were assessed. Plasma glutamate levels were increased up to 15 days after the ischemic event in stroke patients, and the levels at day 3 were inversely correlated with the neurologic improvement between day 3 and 15. Ex vivo platelet glutamate release was decreased by 70% in stroke patients, suggesting previous in vivo platelet activation. Moreover, platelet glutamate uptake in these patients was decreased by 75% up to 15 days and was still reduced 90 days after stroke. Our data show a prolonged increase of glutamate in plasma after stroke, which might presumably be linked to altered platelet functions, such as excessive release of the amino acid or impaired uptake.

Platelet glutamate uptake and release in migraine with and without aura

Glutamate may play an important role in the pathogenesis of migraine: glutamate release in the brain may be involved in the development of spreading depression and increased concentrations of this amino acid have been reported in plasma and platelets from migraine patients. Here we assessed platelet glutamate uptake and release in 25 patients affected by migraine with aura (MA) and 25 patients affected by migraine without aura (MoA), comparing the results with a group of 20 healthy matched controls. Both glutamate release from stimulated platelets and plasma concentrations of the amino acid were assessed by high-performance liquid chromatography, and were increased in both types of migraine, although more markedly in MA. Platelet glutamate uptake, assessed as 3H-glutamate intake, was increased in MA, while it was reduced in MoA with respect to the control group. These results support the view that MA might involve different pathophysiological mechanisms from MoA and, specifically, up-regulation of the glutamatergic metabolism. Understanding these dysfunctional pathways could lead to new, possibly more successful therapeutic approaches to the management of migraine.

Substrate-induced modulation of glutamate uptake in human platelets

1 In the central nervous system (CNS), glutamate rapidly upregulates the activities of different excitatory amino‐acid transporter subtypes (EAATs) in order to help protect neurons from excitotoxicity. Since human platelets display a specific sodium‐dependent glutamate uptake activity, and express the three major glutamate transporters, which may be affected in neurological disorders, we investigated whether platelets are subject to substrate‐induced modulation as described for CNS. 2 A time‐ and dose‐dependent upregulation of [3H]‐glutamate uptake (up to two‐fold) was observed in platelets preincubated with glutamate. There was an increase in maximal velocity rate without affinity changes. Glutamate receptor agonists and antagonists did not modulate this upregulation and preincubation with glutamate analogues failed to mimic the glutamate effect. Only aspartate preincubation increased the uptake, albeit ∼35% less with respect to glutamate. 3 The effect of glutamate preincubation on the expression of the three major transporters was studied by Western blotting, showing an increase of ∼70% in EAAT1 immunoreactivity that was completely blocked by cycloheximide (CEM). However, L‐serine‐O‐sulphate, at a concentration (200 μM) known to block EAAT1/3 selectively, did not completely inhibit the effect of glutamate stimulation, indicating the possible involvement of EAAT2. 4 In fact, glutamate stimulation was completely abolished only when, following CEM pre‐incubation, the experiment was run in the presence of the selective EAAT2 inhibitor dihydrokainic acid. Since surface biotinylation experiments failed to show evidence of EAAT2 translocation, our results suggest the existence of a different way of regulating EAAT2 activity. 5 These findings indicate that human platelets display a substrate‐dependent modulation of glutamate uptake mediated by different molecular mechanisms and confirm that ex vivo platelets are a reliable model to investigate the dysfunction of glutamate uptake regulation in patients affected by neurological disorders.

Cerebral venous thrombosis

Cerebral venous thrombosis (CVT) was formerly considered a rare disorder, associated with an unfavorable outcome. More recent data based on modern imaging techniques, however, have changed our perception of this disorder. The use of angiography and, especially, MRI have allowed an early diagnosis and have proved that the incidence of CVT is, in fact, higher than previously thought, approximately 3–4 cases per million people per year, and that the majority of patients have a favorable outcome. At present, the most frequent causes are oral contraceptives assumption and pregnancy/puerperium; as a consequence, 75% of patients are females. CVT may cause isolated intracranial hypertension or lead to an ischemic stroke, which does not follow the distribution of an arterial vessel and has a relevant vasogenic edema. Venous strokes often have a hemorrhagic component, ranging from small petechiae to an actual intracerebral hemorrhage; the latter is associated with a worse clinical course. The clinical presentation of CVT is hihgly variable and includes patients with just a mild headache, others with focal neurological deficits and a few with a dramatic syndrome with coma; seizures are a frequent presenting symptom. The best radiological examination to confirm the suspicion of CVT is MRI of the brain, which can both demonstrate parenchymal lesions and directly show evidence of sinus occlusions. The available evidence suggests that anticoagulants are effective in reducing mortality and dependency in CVT patients; the possible role of systemic or localized thrombolysis is still to be established.

Acute isolated ophthalmoplegia with anti-GQ1b antibodies.

Ophthalmoplegia without ataxia, areflexia or both has been designated as atypical Miller Fisher syndrome (MFS) or acute ophthalmoplegia (AO). This entity, first reported by Chiba et al. is associated with anti-GQ1b IgG antibodies.We report a patient with isolated acute ophthalmoplegia with high titer of anti-GQ1b IgG antibody activity in the acute phase in whom treatment with intravenous immunoglobulin (IVIg) led to the clinical recovery and the decrease in antibody titer.

Dissection of the epiaortic and intracranial arteries

Dissection of epiaortic vessels is a rare event but can have serious clinical consequences such as ischaemic injury to the brain, cerebellum or, more rarely to the retina and is an important cause of stroke in young adults. The main clinical presentation is headache or neck pain, usually but not always associated with Horner syndrome or other local symptoms, followed by an ischemic event in the carotid or vertebral district. Very rarely, the dissection can extend to the intracranial vessels leading to subarachnoid hemorrhage. The time between the headache and the stroke is variable, ranging from a few seconds to weeks. Suspecting an arterial dissection in cases of unexplained head or neck pain in young patients is than crucial to avoid cerebrovascular events; the clinical suspect must be confirmed by ultrasound examination of the epiaortic vessels as a first screening exam, followed by an appropriate neuroimaging study. Treatment with anticoagulants, although not supported by randomized trials, is generally employed to prevent embolic events. The prognosis of stroke caused by arterial dissection does not differ from that of ischaemic events of other origin; the rate of recurrence is low and most patients have only one event in their live. Clinical research with multicenter recruitment is ongoing to provide more solid evidence on the management and prognosis of arterial dissections.

Is elevated post-methionine load homocysteinaemia a risk factor for cervical artery dissection?

Cervical artery dissection (CAD) represents one of the most frequent causes of stroke in young adults. Although traumas are known to be main risk factors for developing CAD, spontaneous idiopathic forms, probably related to arterial wall diseases, have been described as well, actually representing the major quota. Interestingly, recent studies indicate that even mild elevation of basal plasma homocysteine (Hcy) levels might be a risk factor for spontaneous CAD [1–3], possibly by favouring the damage and/or the dysfunction of the endothelium [4]. However, plasma levels of post-methionine load Hcy have never been investigated in spontaneous CAD patients. As a matter of fact, increased Hcy plasma levels after methionine load has been reported to be a risk factor for stroke in young adults, while no differences were shown for basal levels with respect to healthy agematched controls [5]. Notably, some authors suggest that the post-methionine load test might help identifying those patients harbouring a putative state of “methionine intolerance” that might be clinically relevant, although not associated to elevated basal Hcy plasma levels [6]. Here we report the case of a patient who came to our attention for a sudden orbito-frontal pain unresponsive to non-steroid anti-inflammatory drugs. A brain MRI suggested a CAD, which was subsequently confirmed by conventional angiography. No known risk factors for CAD were present, leading to the diagnosis of spontaneous CAD. Basal Hcy plasma level was measured 10 days after admission and was normal (11.5 μmol/l; normal range: 10–15 μmol/l), while post-methionine load Hcy plasma level (240 min following oral administration of 0.1 g/kg methionine) was 37.2 ?mol/l (normal range: up to 30 μmol/l). Although it is not possible to rule out that elevated basal and/or post-load Hcy plasma levels might be a consequence of the acute event, one study reported elevated basal levels up to 10 years following CAD [2]. Therefore, the present, purely anecdotal, case report, if replicated, might prompt to design a clinical study for specifically addressing the role of elevated post-methionine load Hcy plasma levels as an independent risk factor for CAD. In conclusion, we would like to suggest that postmethionine load Hcy and, possibly, folate supplementation for secondary prevention, as previously suggested for hyperhomocysteinaemia states [7], might deserve further clinical investigation in CAD patients, possibly helping to shed more light on the still unknown pathogenesis of this disease.

Cytokine network in acute stroke

inflammatory mechanisms in the pathophysiology of ischemic brain damage [1]. Central and peripheral activation of a cytokine network, with proor anti-inflammatory activity, has been widely demonstrated; various cytokine release events in the central nervous system (CNS) or in peripheral blood have been correlated to stroke severity and outcome [2]. In this issue, Perini and colleagues [3] provide further evidence for peripheral immune involvement in stroke. They found increased interleukin (IL)–6 serum levels during the first two weeks after onset, with a significant correlation with severity and outcome, assessed on the Scandinavian stroke scale, the Rankin scale and the Barthel index. Serum IL-6 correlated also with cell count and with neutrophils at different times after the event. On the other hand, IL-10 was decreased in stroke patients during all considered times. Most interestingly, in control subjects the authors found a significant inverse correlation between serum levels of these two cytokines, which seem to display opposite activities (IL6 is mainly pro-inflammatory, while IL-10 is anti-inflammatory). However, this correlaton was lost in stroke patients, although IL-6 increase and IL-10 decrease should virtually enforce this inverse trend. Supposing that the inverse correlation described in healthy subjects reflects a reciprocal regulation of the two cytokines, the stroke event may then trigger the release of other mediators, which disrupt the physiological cytokine network. Interestingly, in a similar cohort of stroke patients in which we previously demonstrated increased peripheral release of IL-6 [4], we recently observed a significant direct correlation between serum levels of transforming growth factor (TGF)-β and nerve growth factor (NGF). This correlation was present only in stroke patients and was absent in controls, suggesting a common or reciprocal regulation of the two neurotrophins, triggered by stroke [5]. All together, data from the literature show the existence of a complex network of interactions between proand antiinflammatory mediators and trophic factors, whose meaning is still to be determined. Cytokine pathways may be differentially regulated in physiological conditions and after stroke, which perturbs such regulation and triggers a new cascade of cytokine interactions. Altered cytokine networks may work as putative risk factors for stroke, and are involved in the pathogenesis of brain damage after stroke. Although the role of each cytokine in stroke is still difficult to define, the value of these studies is not only for a better understanding of the pathophysiology of stroke, but also for future clinical implications: therapeutic trials with drugs that prevent leukocyte infiltration in ischemic brain and neutralize the subsequent cytokine production are already in progress [6].

Cerebrovascular Interactions in Cerebral Disorders (Stroke, Transient Ischaemic Attacks, Microvascular Disease, Migraine)

The complexity of the interaction between the blood and brain is well known since the hemato-encephalic barrier (BEE) was firstly described. Most of the neurological diseases lead to BEE disruption. In this chapter, we will focus the attention on the neurological deficits due to vascular impairment.