Current neurology and neuroscience reports
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Curr Neurol Neurosci Rep · Feb 2012
ReviewPain disorders and erythromelalgia caused by voltage-gated sodium channel mutations.
Voltage-gated sodium channels play a pivotal role in pain transmission. They are widely expressed in nociceptive neurons, and participate in the generation of action potentials. Alteration in ionic conduction of these channels causes abnormal electrical firing, thus renders neurons hyperexcitable. ⋯ These syndromes are inherited in a dominant trait; they usually begin in childhood or infancy, and are characterized by attacks of severe neuropathic pain accompanied with autonomic symptoms. Recently, small fiber neuropathy and chronic nonparoxysmal pain have been described in patients harboring gain-of-function mutations in Na(v)1.7 channel. Loss-of-function mutations in Na(v)1.7 are extremely rare, and invariably cause congenital inability to perceive pain.
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The mainstay of epilepsy surgery is the resection of a presumed seizure focus or disruption of seizure propagation pathways. These approaches cannot be applied to all patients with medically refractory epilepsy (MRE). Since 1997, vagus nerve stimulation has been a palliative adjunct to the care of MRE patients. ⋯ Recently published results from the SANTE (Stimulation of the Anterior Nuclei of Thalamus for Epilepsy) trial-the first large-scale, randomized, double-blind trial of bilateral anterior thalamus DBS for MRE-demonstrate a significant reduction in seizure frequency with programmed stimulation. Another surgical alternative is the RNS™ System (NeuroPace, Mountain View, CA), which uses a closed-loop system termed responsive neurostimulation to both detect apparent seizure onsets and deliver stimulation. Recently presented results from the RNS™ pivotal trial demonstrate a sustained reduction in seizure frequency with stimulation, although comprehensive trial results are pending.
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N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis is a recently described immunotherapy-responsive panencephalitis with characteristic features that include a psychiatric onset and a later movement disorder. This entity was first described as a paraneoplastic phenomenon in young women with ovarian teratomata. ⋯ Early diagnosis followed by immunotherapies and tumor removal, when relevant, expedite recovery from the condition. Antibody levels correlate with the clinical severity of the disease in individual patients, and the antibodies have been shown to substantially reduce NMDA receptors on hippocampal neurons both in vitro and in vivo, supporting the likely direct pathogenicity of the NMDAR antibodies.
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Migraine is a disorder with variable natural history. In some sufferers, migraine evolves over time into a state of headaches on more days than not. This process of migraine chronification is poorly understood, but risk factors have been clearly identified. ⋯ We follow with a discussion of the role of comorbid conditions and environmental exposures. We suggest that clinicians consider risk factor modification as part of migraine management, aspiring to not just relieve current pain and disability, but to avoid migraine progression. Reducing attack frequency, avoiding medication overuse, appropriately using preventive drugs and behavioral therapies, and encouraging weight loss should be part of migraine therapy to improve current pain and disability and also to avoid future pain and disability by preventing chronification.