When asked for their connotations with the vagus nerve, most medically trained people will think of the parasympathetic efferent tasks of cranial nerve X: heart rate modulation, regulation of ingestion/digestion, effects on lung functioning and so on. And these connotations are what gave this nerve its name: vagus, latin the wanderer. However, the vagus nerve is more a sensory than a motor nerve, since it has about 80% afferent but only 20% efferent fibres (Foley and DuBois, 1937). First reports on the cerebral effects of an electrical stimulation of the vagus were published by Bailey and Bremer in 1938. In the following decades, researchers revealed that vagus nerve stimulation (VNS) may influence surface EEG, suppress epileptic electrical activity in the brain, and even terminate seizures in animal models of epilepsy (Zabara, 1985, 1992). The first single-patient trial on VNS for treatment of epilepsy was set up in 1988 in the USA (Penry and Dean, 1990).
The electrical stimulation of the left vagus nerve trunk by a totally implanted stimulation device (NCPTM-system, Cyberonics Inc.) was approved for treatment of drug-resistant epileptic seizures by the FDA in 1997 and by the European Community in 1994 (Schachter and Saper, 1998). The pulse generator is implanted into the chest wall, in a similar fashion to cardiac pacemakers, while the spiral platinum electrodes are attached to the left vagus nerve trunk below the cardiac branch. The pulse generator may be programmed telemetrically by a programming wand that is held over the generator and connected to a portable computer. At standard settings, the stimulator would deliver electrical pulses to the vagus every 5 minutes for about 30 seconds (pulse frequency: 20-30 Hz, pulse width: 250-500 |xs). Alternatively, rapid cycles with 12 seconds off-stimulation time and 7 seconds on-stimulation time may be programmed.
The treatment usually gets started with an output currency of 0.25 mA after implantation which can be stepwise increased during the next weeks depending on the seizure outcome and adverse side effects (maximum: 3.5 mA). Several studies have shown effectiveness (Amar et al., 1999; Ben-Menachem et al., 1994; DeGiorgio et al., 2000; Handforth et al., 1998), safety (Annegers et al., 1998; Fisher and Handforth, 1999; Ramsay et al., 1994), and sufficient cost-benefit ratios (Boon et al., 1999) of VNS for patients with intractable seizures.
While the antiseizure effect of VNS is usually attributed to the 'afferent', that is, direct cerebral effects, the most common adverse effects such as hoarseness, cough, or throat paraesthesia, are supposed to result from the efferent portion of stimulation which is unavoidable since the entire nerve is stimulated. Regarding the issues reviewed here, one should keep in mind that VNS may achieve its effects by an efferent peripheral mechanism as well.
Anxiety and depressive disorders are common psychiatric conditions in patients with epilepsy (Jacoby et al., 1996; Kohler et al., 1999). About one-third to one-half of patients score high on anxiety and depression self-report scales, but only one-third of the affected patients are recognized by general practitioners to have psychiatric problems (O'Donoghue et al., 1999). Depressive mood states and poor quality of life are part of a complex interplay of clinical measures (e.g. seizure frequency, seizure severity, epilepsy duration, age at onset) and psychosocial parameters (employment, marital status) (Jacoby et al., 1996; Roth et al., 1994; Smith et al., 1991). However, depression in epilepsy patients may not be fully accounted for by either clinical or psychosocial factors since biological mechanisms involved in epi-leptogenesis may also contribute to depression (Hermann et al., 1996; Schmitz et al., 1999). Therefore, seizure outcome is only one - even though leading - outcome measure of epilepsy treatment. Psychiatric aspects of epilepsy have to be considered and new drugs and methods, as for example VNS, have to be evaluated for their benefits regarding mood and quality of life as well as any effect on seizures.
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This guide Don't Panic has tips and additional information on what you should do when you are experiencing an anxiety or panic attack. With so much going on in the world today with taking care of your family, working full time, dealing with office politics and other things, you could experience a serious meltdown. All of these things could at one point cause you to stress out and snap.