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Background Migraine is a well-known feature of mitochondrial disorders (MDs). However, no systematic epidemiological data are available in large populations of patients. Aims The aim of this cross-sectional cohort study was to describe the prevalence and migraine characteristics in a large cohort of patients with mitochondrial encephalomyopathies. Methods We studied 93 consecutive patients with characterised MDs referred to our Neuromuscular Unit during a 12-month period. All patients (age range = 16-78 years; 31 men; 58 progressive external ophthalmoplegia [PEO], 12 myoclonic epilepsy with ragged red fibres [MERRF], eight mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes [MELAS], two mitochondrial neurogastrointestinal encephalomyopathy [MNGIE] and 13 other MDs) underwent a structured diagnostic headache interview using an operational diagnostic tool following the IHS criteria. If they met the criteria for migraine, they were included in the 'Migraine Group'. The other patients were counted in the 'No Migraine Group'. Patient demographic and migraine characteristics were examined. Clinical, neuroradiological and neurophysiological data were compared between groups. Results Migraine was reported in 35.5% of patients. Migraine without aura was the most common headache (81.8%). The migraine group showed younger age ( P < 0.01), increased prevalence of epilepsy ( P = 0.01), myoclonus ( P = 0.03), stroke-like episodes ( P = 0.03) and decreased prevalence of muscle weakness ( P < 0.01). Multivariate analysis showed that migraine was positively associated with absence of muscle weakness ( P = 0.04) and presence of EEG abnormalities ( P = 0.02). Conclusion Migraine has a higher prevalence in MDs compared with general population-based data, independently from genotype or phenotype. Migraine is not merely a phenotypic aspect of specific MDs but is rather the expression of vulnerability of the central nervous system, probably directly related with defects of the respiratory chain.

Background: Habituation deficit, suggesting a deregulation of cortical excitability, represents a typical hallmark of interictal stages of migraine. We previously demonstrated that several neurophysiological markers of altered cortical excitability are significantly correlated to spontaneous clinical fluctuations of migraine. We therefore aimed at verifying whether clinical fluctuations are correlated to specific patterns of somatosensory evoked potential (SEP) habituation., Methods: We analyzed habituation after median nerve stimulation of both high-frequency oscillations (HFOs) and N20 SEP in 25 migraine patients and 18 healthy volunteers. Subjects underwent six consecutive series of 500 stimuli., Results: Migraine patients as a whole showed a significant habituation deficit of the N20 response. Moreover, spontaneously worsening patients show a clear potentiation of this wave in the last block of stimuli, whereas in spontaneously improving patients the N20 amplitude remained stable. Presynaptic HFOs were smaller in worsening patients and larger in improving ones, but they did not undergo habituation in patients as well as in healthy subjects., Conclusions: Potentiation of the N20 response in spontaneously worsening migraineurs confirms that the reduction of the thalamocortical drive plays a major role in migraine pathogenesis. Moreover, the stable pattern we observed in spontaneously improving patients suggests that compensatory mechanisms can also play an important role. The normal response to repeated stimuli of HFOs in migraineurs might indicate that, although its initial amount depends on clinical conditions, high-frequency thalamocortical drive remains stable during the stimulation and probably reflects the activity of a buffer mechanism.

Background: In a previous study we demonstrated that high-frequency oscillations (HFOs) elicited by median nerve stimulation are significantly correlated to clinical fluctuations of migraine. We aimed at verifying whether clinical fluctuations and HFO changes are correlated to N20 somatosensory evoked potential (SEP) recovery cycle, which is likely to reflect the functional refractoriness of primary somatosensory cortex neurons., Methods: We analysed both HFOs and N20 SEP recovery cycle to paired stimulation in 21 migraine patients and 18 healthy volunteers., Results: Shortened recovery cycle correlated with low-amplitude HFOs as well as with clinical worsening. By contrast, prolonged recovery cycle correlated with enhanced HFOs, as well as with spontaneous clinical improvement., Conclusions: In our migraine patients the strict relationship between presynaptic HFO amplitude and N20 recovery function suggests that changes of both parameters might be caused by modifications of the thalamo-cortical drive. Our findings suggest that the thalamo-cortical drive during interictal stages could fluctuate from abnormally high to abnormally low levels, depending on mechanisms which reduce cortical excitability in spontaneously improving patients, and increase cortical excitability in spontaneously worsening ones.

The aim of this study was to compare the recovery cycle of somatosensory evoked potentials (SEPs) in children with migraine without aura before and after treatment with topiramate. Eleven migraine children were studied before and after a 3-month treatment with topiramate at the average dose of 1.3 mg/kg/day. We calculated the SEP latency and amplitude modifications after paired electrical stimuli at 5, 20 and 40 ms interstimulus intervals, comparing them with a single stimulus condition assumed as baseline. In nine patients, who had a significant reduction in headache frequency after treatment, the recovery cycles of the P24 (P = 0.03) and N30 (P < 0.005) potentials were longer after than before topiramate treatment. In two migraineurs who did not show any improvement, the recovery cycles of the cortical SEP components were even shorter after treatment. Our results suggest that topiramate efficacy in paediatric migraine prophylaxis is probably related to restored cortical excitability.

Primary headaches are closely related to sleep. Modifications in the patterns of arousal during sleep have been reported in migraine, especially in the nights preceding a headache attack. We aimed at evaluating the pattern of arousal from sleep in a group of patients affected by sleep-related migraine. We enrolled 10 consecutive patients, three males and seven females, aged between 20 and 62 years, who presented frequent attacks of migraine without aura (more than five per month), closely related to sleep (more than one-half of the attacks occurred during sleep, causing an awakening). A control group was studied, matched for age and sex. Patients and controls underwent a full-night polysomnographic study, following adaptation; arousal pattern was studied by the scoring of the high-frequency EEG arousal and by the cyclic alternating pattern (CAP). Migraineurs showed a lower CAP rate in non-rapid eye movement (NREM) sleep and, in particular, a lower number of A1 phases (low-frequency, high-amplitude EEG bursts) compared with the controls. Migraineurs also showed a lower index of high-frequency EEG arousals during rapid eye movement (REM) sleep. The reduction in the CAP rate indicates a lower level of arousal fluctuation in NREM sleep. The reduced arousal index in REM suggests a dysfunction in neural structures involved in both the control of REM sleep and the pathophysiology of migraine, such as the hypothalamus and the brainstem.

Cluster headache (CH) is a primary headache with a close relation to sleep. CH presents a circa-annual rhythmicity; attacks occur preferably during the night, in rapid eye movement (REM) sleep, and they are associated with autonomic and neuroendocrine modifications. The posterior hypothalamus is the key structure for the biological phenomenon of CH. Our aim is to describe a 55-year-old man presenting a typical episodic CH, in whom we performed a prolonged sleep study, consisting of a 9-week actigraphic recording and repeated polysomnography, with evaluation of both sleep macrostructure and microstructure. During the acute bout of the cluster we observed an irregular sleep-wake pattern and abnormalities of REM sleep. After the cluster phase these alterations remitted. We conclude that CH was associated, in this patient, with sleep dysregulation involving the biological clock and the arousal mechanisms, particularly in REM. All these abnormalities are consistent with posterior hypothalamic dysfunction.