Seizure Threshold Is Controlled by Brain CO2 and O2

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- Updated on October 29, 2020

Seizure Threshold Is Controlled by Brain CO2 and O2 1By Dr. Artour Rakhimov, Alternative Health Educator and Author

- Medically Reviewed by Naziliya Rakhimova, MD

Epilepsy seizures examination

A proper understanding of epilepsy, seizures, seizure threshold and brain abnormalities during seizures should be based on knowledge of what is going on in the nerve cells during their normal work. In normal conditions, all electrical signals that travel among nerve cells are related to objective and important processes, such as the work of the senses, memory, analysis, logic, decision making, voluntary and involuntary movements of muscles, etc. The electrical signal is transmitted from one nerve cell to another only when the voltage or strength of the signal is high enough. It should be no less than a certain threshold value: the threshold of excitability of the nerve cells that directly relates to the seizure threshold. The normal value for the threshold of excitability in mammals is about 50 microvolts.

Normal brain When this seizure threshold remains normal or high, the electrical signals are transmitted as in the normal computer. Adaptation and self-improvement (learning) are the normal final outcomes of these processes in living creatures. Hence, in order to have a positive effect on the biological system (learning, survival, self-defense, etc.), it is crucial that the transmission of these neuronal signals satisfies 2 criteria:
1) These (real or objective) signals are transmitted and facilitated through the network of the nerve cells so that no important information is lost.
2) Accidental or irrelevant signals get hampered so that they cannot interfere with the normal work of the senses, memory storage, memory retrieval, comparison of experiences, solution making, execution of solutions, feedback, etc.

Brain during epilepsy seizures If for some reason this threshold becomes too low, accidental signals can be amplified causing disruption or even suppression in the normal work of the central and peripheral nervous systems. Consider what happens during abnormal changes in breathing. When the breathing pattern is disturbed (less than 5% of modern people, according to tens of published studies, have normal breathing parameters these days – see Homepage for studies), blood gases become abnormal. The most common abnormality is arterial hypocapnia (low CO2) and cell hypoxia (low O2 in tissues, the brain included), where overbreathing or hyperventilation (breathing more air than the medical norm) is the key cause for both effects. Let us consider how the seizure threshold depends on carbon dioxide and oxygen.

How CO2 and O2 influence threshold for a seizure

Brain hyperventilation effects This excitability threshold of the nerve cells is highly dependent on, and sensitive to, both the O2 and CO2 concentration in nerve tissues. Low oxygen levels create tissue hypoxia and an acidic cellular environment. Low CO2 levels cause abnormal excitability of nerve cells, as discussed on this page CO2: Key Nutrient for Mental Health – Sedative and Tranquilizer. We also found that, according to professional neurologists, hyperventilation or low CO2 in the brain “leads to spontaneous and asynchronous firing of neurons”. Hence, when we overbreathe or hyperventilate, CO2 and O2 levels in cells become abnormally low. As a result, accidental or weak electrical signals can be strengthened and relayed through some parts of the brain interfering with the normal signals. This causes a reduction in the seizure threshold.

Overbreathing and irregular breathing patterns cause seizures

Seizure Threshold What are the medical facts? Depending on particular details of the hyperventilation procedure and individual health state, somewhere between 70 to 100% of epileptics can lower their seizure threshold and trigger their seizures by voluntary hyperventilation (see the abstracts of numerous medical studies below). Many studies found that hyperventilation could cause seizures in all patients. However, modern medical and physiological research has failed to find the exact CO2 threshold that can induce seizures in susceptible individuals. This is logical since, apart from the key role of brain CO2 concentration, there are many other factors that influence the transmission of electrical signals in the brain, including surrounding neuronal activity, distribution of electrical firing within the brain, current metabolic rate (body position, posture, physical exercise, thermoregulation, etc.), oxygen tension, availability and types of calcium and magnesium ions present in tissues, changes in glial cells, concentrations of neurotransmitters, amino acids, and many other substances. Therefore, while hypocapnia is the crucial necessary background for the lowered seizure threshold and appearance of seizures (the prime cause of seizures and epilepsy), many other factors play their roles in experienced symptoms and a clinical picture for some particular seizures.

Indeed, numerous medical studies (see abstracts below) have proven that hyperventilation reliably induces seizures in epileptics and patients suffering from seizures, as an additional indication that seizure threshold is controlled by breathing with some (limited) contribution from other factors (stress, sleep deprivation, low blood sugar, overheating, alcohol, etc.).

Other factors influence threshold for a seizure

It is known to many epileptics that seizures can be triggered, prolonged, and worsened by low blood glucose levels. There is even a special category of seizures which has a label “hypoglycemic seizure” or “low blood sugar seizures”. Chronic hyperventilation worsens general blood sugar control increasing symptoms of reactive hypoglycemia. In addition, hypocapnia-induced vasoconstriction (see CO2 vasodilation effect) causes stenosis or spasm of the carotid artery and is an essential aggravating factor. (Fainting due to voluntary hyperventilation is partially based on the same effect: overbreathing decreases glucose availability for the brain.) Whatever the case, low blood sugar level also lowers the seizure threshold.

What about the low brain oxygen effects? Reduced brain oxygenation (due to chest breathing, vasoconstriction, and suppressed Bohr effect) is an additional factor that increases the acidity of brain cells (due to anaerobic cell respiration and elevated lactic acid production). This further intensifies abnormal electrical activity lowering the seizure threshold even more.

This web page (Cause of seizures) provides analysis of information about medical research on how western doctors treated seizures and epilepsy with the application of carbon dioxide and breathing techniques.

In order to prevent approaching seizures (at the onset of the very first signs of seizures), the patient should apply the Emergency Procedure (or reduced breathing exercise), which increases brain CO2 and O2 levels and helps to prevent most seizures that take place during day-time (see How to Stop Seizures Naturally). For prevention of sleep seizures, visit How to Prevent Sleep Seizures: Lifestyle Changes.

Recent research suggests that grounding the human body (also called Earthing) helps to reduce (and often prevent altogether) nearly all types of seizures and normalize the seizure threshold.

Meditation and mindfulness techniques can be useful to normalize the threshold of a seizure too, but more research is needed in these new areas.

How to provoke or stop Seizure Threshold with breathing

There are more than 20 clinical studies (authored by over 80 medical doctors and research scientists from all other the world) that claim that seizures, CO2, and breathing are linked together with a very simple relationship. You can read amazing abstracts of these studies right below here as your bonus content.

Abstracts (Western doctors who treated absence spells and seizures with breathing techniques)

Magarian GJ, Olney RK, Absence spells. Hyperventilation syndrome as a previously unrecognized cause,Am J Med. 1984 May;76(5):905-9.
Absence spells in adults have been recognized in association with disorders of excessive somnolence, transient ischemia of the temporal lobes, and seizure disorders. A 66-year-old man who presented with a history of absence spells for more than 20 years is described. After diagnosis of a hyperventilation syndrome without an associated seizure disorder, educational and behavioral therapy without the use of medication has produced a long, continuing remission of these spells. The hyperventilation syndrome continues to present in many ways, often without recognition by physicians for prolonged periods. The case presented exemplifies this problem and may be the first report of absence spells caused by hyperventilation.

Bruno-Golden B, Holmes GL, Hyperventilation-induced seizures in mentally impaired children, Seizure. 1993 Sep;2(3):229-33.
Boston Neurobehavioral Institute, Harvard Medical School, Children’s Hospital, MA 02115.
Two children with profound development delay and medically intractable seizures were found to have hyperventilation-induced seizures. Following detection of this precipitating factor the parents, teachers and caretakers were taught to modify the childrens’ breathing when they began to hyperventilate. In both patients this technique resulted in a dramatic decrease in seizure frequency.

Fried R, Rubin SR, Carlton RM, Fox MC, Behavioral control of intractable idiopathic seizures: I. Self-regulation of end-tidal carbon dioxide, Psychosom Med. 1984 Jul-Aug;46(4):315-31.
Eleven women and seven men with moderate to severe chronic hyperventilation and idiopathic seizures refractory to therapeutic serum levels of anticonvulsant medication were given diaphragmatic respiration training with percent end-tidal CO2 biofeedback. The training had a rapid correcting effect on their respiration, making it comparable to that of 18 asymptomatic control subjects. Ten of the seizure-group subjects were in the study at least 7 months and following treatment, 8 showed EEG power spectrum “normalization”, restoration of cardio-respiratory synchrony (RSA), and their seizure frequency and severity were significantly reduced.

Medical references for calming CO2 effects on brain cells

“Studies designed to determine the effects produced by hyperventilation on nerve and muscle have been consistent in their finding on increased irritability” Brown EB, Physiological effects of hyperventilation, Physiological Reviews 1953 October, Vol. 33 No. 4; p. 445-471.

“Conclusions. Many cells clearly reacted to even small changes in Pco2 (e.g. 4 mm Hg). Moderate doses of CO2 led to both excitation and depression; typically there was an initial phase of excitation during the rise in PCO2, a subsequent longer period of depression, and some sharp excitation during the fall of PCO2.” Krnjevic K, Randic M and Siesjo B, Cortical CO2 tension and neuronal excitability, Journal of Physiology 1965, No. 176: p.105-122.

Orthodromically evoked compound action potentials (‘population spikes’) were depressed in hypercapnia and increased in hypocapnia.” Balestrino M, Somjen GG, Concentration of carbon dioxide, interstitial pH and synaptic transmission in hippocampal formation of the rat, Journal of Physiology, 1988, No. 396: p. 247-266.

“Hyperventilation leads to spontaneous and asynchronous firing of neurons” Huttunen J, Tolvanen H, Heinonen E, Voipio J, Wikstrom H, Ilmoniemi RJ, Hari R, Kaila K, Effects of voluntary hyperventilation on cortical sensory responses. Electroencephalographic and magnetoencephalographic studies, Experimental Brain Research 1999, Vol. 125 No. 3: p. 248-254.

Neuron. 2005 Dec 22;48(6):1011-23.
Adenosine and ATP link PCO2 to cortical excitability via pH.
Dulla CG, Dobelis P, Pearson T, Frenguelli BG, Staley KJ, Masino SA.
Neuroscience Program, Department of Neurology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
In addition to affecting respiration and vascular tone, deviations from normal CO(2) alter pH, consciousness, and seizure propensity. Outside the brainstem, however, the mechanisms by which CO(2) levels modify neuronal function are unknown. In the hippocampal slice preparation, increasing CO(2), and thus decreasing pH, increased the extracellular concentration of the endogenous neuromodulator adenosine and inhibited excitatory synaptic transmission. These effects involve adenosine A(1) and ATP receptors and depend on decreased extracellular pH. In contrast, decreasing CO(2) levels reduced extracellular adenosine concentration and increased neuronal excitability via adenosine A(1) receptors, ATP receptors, and ecto-ATPase. Based on these studies, we propose that CO(2)-induced changes in neuronal function arise from a pH-dependent modulation of adenosine and ATP levels. These findings demonstrate a mechanism for the bidirectional effects of CO(2) on neuronal excitability in the forebrain.

Br J Anaesth. 1972 Nov;44(11):1128-32.
Effects of acute hypocapnia and hypercapnia on neuromuscular transmission and on monosynaptic spinal reflex in wakeful man.
Higashi H, Kano T, Shimoji K, Morioka T, Sances A.
The effects of both acute hypocapnia and hypercapnia on neuromuscular transmission (NMT) and monosynaptic spinal reflex (MSR) in conscious subjects were studied by observing the averaged evoked electromyogram. The M-wave amplitude increased to 165 ± 25 % (mean ± standard error) during acute hypocapnia with an end expiratory carbon dioxide concentration of 2.5 ± 0.2 vol.% and decreased to 73 + 7% during acute hypercapnia with an expiratory concentration of 6.8 ± 0 . 1 vol.%, in comparison with the control value. The H-wave amplitude increased to 226 ± 8 2% during acute hypocapnia and decreased to 85 ± 9% during acute hypercapnia in comparison with the control value. These results indicate that both NMT and MSR in conscious man are facilitated by acute hypocapnia, and that NMT is inhibited by acute hypercapnia. However, the effect of acute hypercapnia on MSR could not be ascertained only by the observation of the H reflex in these conditions.

References and quotes (Overbreathing and irregular breathing triggerseizures)

Wirrell EC, Camfield PR, Gordon KE, Camfield CS, Dooley JM, Hanna BD, Will a critical level of hyperventilation-induced hypocapnia always induce an absence seizure? Epilepsia. 1996 May;37(5):459-62.
Department of Paediatrics, Dalhousie University Medical School, Izaak Walton Killam Hospital for Children, Halifax, Nova Scotia, Canada.
We wished to determine if the degree of hypocapnia correlates with increased frequency of absence seizures and if there is a critical pCO2 at which absence seizures are reliably provoked. Twelve untreated children with newly diagnosed absence epilepsy were continuously monitored by EEG and end-expiratory CO2 recording during quiet respiration and hyperventilation (to absence seizure or exhaustion) while breathing four gas mixtures: (a) room air, (b) 100% O2, (c) 4% CO2 in room air, or (d) 4% CO2 + 96% O2). In quiet respiration, a reduction in number of spike and wave bursts and total seconds of spike and wave was noted in children breathing supplemental CO2 (gases c and d vs. gases a and b), p < 0.05. Supplemental O2 had no effect. Eight subjects had absence seizures elicited with each trial of hyperventilation. All subjects had their own critical pCO2, ranging from 19 to 28 mmHg. Three children had no seizures, two despite hypocapnia to pCO2 of 19 and 21 and 1 who achieved a pCO2 of only 25. In 1, absence seizures were provoked in only six of nine hyperventilation trials to pCO2 of 17-23. In 67% of subjects, absence seizures were reliably provoked by hypocapnia. Critical pCO2 varied among children with absence. Determination of whether variation in sensitivity to hypocapnia may be helpful in determining response to antiepileptic drugs (AEDs) or remission of seizures will require further study.

Jonas J, Vignal JP, Baumann C, Anxionnat JF, Muresan M, Vespignani H, Maillard L, Effect of hyperventilation on seizure activation: potentiation by antiepileptic drug tapering, J Neurol Neurosurg Psychiatry. 2010 Jun 20. [Epub ahead of print]
Service de Neurologie, Centre Hospitalier Universitaire de Nancy, Nancy, France.
… Discussion. The findings confirm that hyperventilation is efficient to activate epileptic seizures in epileptic patients referred for long-term video-EEG monitoring and that this activating effect is mainly related to the potentiating effect of AED tapering…

Ma X, Zhang Y, Yang Z, Liu X, Sun H, Qin J, Wu X, Liang J, Childhood absence epilepsy: Electroclinical features and diagnostic criteria, Brain Dev. 2010 Apr 6. [Epub ahead of print]
Department of Pediatrics, Peking University First Hospital, No. 1, of Xian Men Street, Xicheng District, Beijing 100034, PR China; Bayi Children’s Hospital Affiliated to General Hospital of Beijing District, PLA 100710, PR China.
Objective: To analyze the electroclinical features of children with childhood absence epilepsy (CAE) and discuss the diagnostic criteria for CAE. Methods: The video-electroencephalogram (VEEG) database in our hospital was searched using “absence seizures” and “3-Hz generalized spike and waves (GSW)” as key-words. Other epileptic syndromes with typical absence seizures were carefully excluded. Children meeting the CAE diagnostic criteria of the International League Against Epilepsy (ILAE) in 1989 were further evaluated with the diagnostic criteria proposed by Panayiotopoulos in 2005. Results: Totally 37 children met the 1989 ILAE criteria of CAE. The onset age of absence seizures ranged from 3 to 11 years. All patients had frequent absence seizures (5-60 times per day). Two patients (5.4%) had generalized tonic-clonic seizures. Hyperventilation induced absences in all patients…

Yang ZX, Liu XY, Qin J, Zhang YH, Wu Y, Jiang YW, [Clinical and electroencephalographic characteristics of epilepsy with myoclonic absences] [Article in Chinese], Zhonghua Er Ke Za Zhi. 2009 Nov;47(11):862-6.
Department of Pediatrics, Peking University First Hospital, Beijing 100034, China.
OBJECTIVE: Epilepsy with myoclonic absences (EMA) is a type of childhood epilepsy characterized by a specific seizure type, i.e. myoclonic absences (MA). This study aimed to investigate the clinical and electrophysiological characteristics of EMA. METHOD: Video-EEG monitoring was carried out in 6 patients with EMA, and 2 of them were examined with simultaneous deltoid muscle surface electromyogram (EMG). The clinical and EEG characteristics, treatment and prognoses of EMA were analyzed. RESULT: Of the 6 patients, 3 were female, and 3 were male. The age of onset was from 2 years and 3 months to 11 years (average 5 years and 2 months). MA was the sole seizure type in 5 patients. One patient presented generalized tonic clonic seizures (GTCS) at the onset and then switched to MA. The manifestations of MA included an impairment of consciousness of variable intensity, rhythmic myoclonic jerks with evident tonic contraction mainly involving the upper extremities, a deviation of head and body to one side or asymmetrical jerks observed in some cases, a duration ranging from 2 to 30 s, an abrupt onset and termination, a high frequency of attacks, at least several times to over 30 times per day, and easily provoked by hyperventilation…

Yang Z, Liu X, Qin J, Jiang Y, Neck myoclonia with absence seizures: report of 3 cases, J Child Neurol. 2009 Aug;24(8):1026-9.
Department of Pediatrics, Peking University First Hospital, Beijing, People’s Republic of China.
Absence seizures associated with myoclonic phenomena can be seen in typical absences, myoclonic absences, eyelid myoclonia, and perior al myoclonia, all of which have diagnostic electroclinical features. The authors report 3 patients who encountered prominently rhythmic neck myoclonias with and without absences (loss of awareness). The descriptive symptoms of attacks by witnesses were head shaking or turning repeatedly instead of absences. The seizures were induced by hyperventilation in all 3 cases…

Arain AM, Arbogast PG, Abou-Khalil BW, Utility of daily supervised hyperventilation during long-term video-EEG monitoring, J Clin Neurophysiol. 2009 Feb;26(1):17-20.
Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
Hyperventilation (HV) is most effective in activation of generalized absence seizures during routine EEG studies…

J ECT. 2008 Sep;24(3):195-8.
Moderate hyperventilation prolongs electroencephalogram seizure duration of the first electroconvulsive therapy.
Sawayama E, Takahashi M, Inoue A, Nakajima K, Kano A, Sawayama T, Okutomi T, Miyaoka H.
Department of Psychiatry, Kitasato University School of Medicine, Sagamihara, Japan.
Although it is controversial that seizure duration can influence the efficacy of electroconvulsive therapy (ECT), a missed or brief seizure is considered less effective ECT. Of the background in the practice of ECT, hyperventilation may augment the seizure duration. To elucidate these hypotheses, we performed double-blind randomized controlled trial for 19 patients. They were divided into 2 groups, according to the end-tidal pressure of carbon dioxide (ETCO2): The moderate hyperventilation group with ETCO2 of 30 mm Hg and the normal ventilation group with ETCO2 of 40 mm Hg. ECT was performed under general anesthesia with propofol and suxamethonium. During ECT electroencephalogram (EEG) and electromyogram were recorded. The Global Assessment of Functioning scores were also analyzed before and after 6 sequential ECT. The moderate hyperventilation group showed a significant increase in EEG seizure duration in the first treatment compared with the normal ventilation group (P < 0.05)

Silva W, Giagante B, Saizar R, D’Alessio L, Oddo S, Consalvo D, Saidón P, Kochen S, Clinical features and prognosis of nonepileptic seizures in a developing country, Epilepsia. 2001 Mar;42(3):398-401.
Municipal Epilepsy Center, Department of Neurology, Ramos Mejía Hospital, and CONICET, Buenos Aires, Argentina.
PURPOSE: To determine the predictive value of clinical features and medical history in patients with nonepileptic seizures (NESs). METHODS: One hundred sixty-one consecutive ictal video-EEGs were reviewed, and 17 patients with 41 NESs identified. NES diagnosis was defined as paroxysmal behavioral changes suggestive of epileptic seizures recorded during video-EEC without any electrographic ictal activity. Clinical features, age, sex, coexisting epilepsy, associated psychiatric disorder, social and economic factors, delay in reaching the diagnosis of NES, previous treatment, and correlation with outcome on follow-up were examined. RESULTS: The study population included 70% female patients with a mean age of 33 years. Mean duration of NESs before diagnosis was 9 years. Forty-one percent had coexisting epilepsy. The most frequent NES clinical features were tonic-clonic mimicking movements and fear/ anxiety/ hyperventilation…

Paediatr Drugs. 2001;3(5):379-403.
Treatment of typical absence seizures and related epileptic syndromes.
Panayiotopoulos CP.
Department of Clinical Neurophysiology and Epilepsies, St Thomas’ Hospital, London, England.
Typical absences are brief (seconds) generalised seizures of sudden onset and termination. They have 2 essential components: clinically, the impairment of consciousness (absence) and, generalised 3 to 4Hz spike/polyspike and slow wave discharges on electroencephalogram (EEG). They differ fundamentally from other seizures and are pharmacologically unique. Their clinical and EEG manifestations are syndrome-related. Impairment of consciousness may be severe, moderate, mild or inconspicuous. This is often associated with motor manifestations, automatisms and autonomic disturbances. Clonic, tonic and atonic components alone or in combination are motor symptoms; myoclonia, mainly of facial muscles, is the most common. The ictal EEG discharge may be consistently brief (2 to 5 seconds) or long (15 to 30 seconds), continuous or fragmented, with single or multiple spikes associated with the slow wave. The intradischarge frequency may be constant or may vary (2.5 to 5Hz). Typical absences are easily precipitated by hyperventilation in about 90% of untreated patients…

Marrosu F, Puligheddu M, Giagheddu M, Cossu G, Piga M, Correlation between cerebral perfusion and hyperventilation enhanced focal spiking activity, Epilepsy Res. 2000 Jun;40(1):79-86.
Institute of Neurology and Department of Nuclear Medicine, Faculty of Medicine, University of Cagliari, Via Ospedale, 54 09100, Cagliari, Italy.
Hyperventilation (HPV) represents a well established EEG activation procedure aimed at enhancing epileptiform discharges

Clin Electroencephalogr. 1993 Jan;24(1):1-5.
Transcranial magnetic stimulation (TMS) of the brain in patients with mesiotemporal epileptic foci.
Steinhoff BJ, Stodieck SR, Zivcec Z, Schreiner R, von Maffei C, Plendl H, Paulus W.
Department of Neurology, Ludwig-Maximilians-Universität, Munich, Germany.
Transcranial magnetic stimulation (TMS) of the human brain is mainly used for the diagnosis of diseases with disturbed central motor conduction. Recent studies revealed controversial results concerning the possibility of a TMS-induced specific activation of epileptogenic foci in patients with localization-related epilepsies, which would make TMS an additional diagnostic tool for the presurgical localization of the primary epileptogenic zone. We applied TMS to 19 patients with complex-partial seizures and investigated its effects and safety. In 12 patients we performed TMS during scalp electroencephalogram (EEG) recordings. The remaining 7 patients with localization-related epilepsies of mesiobasal limbic seizure origin underwent EEG with additionally implanted foramen-ovale-electrodes (FOE). We did not notice any significant spike activation and even observed bilateral reduction of epileptic activity in some patients. On the contrary, hyperventilation induced a marked activation of the epileptic focus. Our findings support that TMS is safe since adverse effects did not occur. However, due to possible safety hazards, TMS in epileptic patients still requires cautious application until more data will be available.

Bergsholm P, Gran L, Bleie H, Seizure duration in unilateral electroconvulsive therapy. The effect of hypocapnia induced by hyperventilation and the effect of ventilation with oxygen, Acta Psychiatr Scand. 1984 Feb;69(2):121-8.
Seizure duration in unilateral electroconvulsive therapy (ECT) was recorded by means of EEG in an intraindividual comparison under different alveolar O2- and CO2-concentrations. Hypocapnia induced by hyperventilation to an alveolar CO2-concentration of 2% (2 kPa) resulted in a highly significant increase in seizure duration compared to a normal CO2 of 5%, when the alveolar O2-concentration was constant at 92%. Oxygen ventilation to an alveolar O2-concentration of 92% gave no significant increase in seizure duration compared to 15%, obtained by ventilation with air, when the CO2-concentration was kept constant at 5%. Seizure duration seems to augment progressively with decreasing alveolar CO2-concentration.

Neurol Neurochir Pol. 1981 Sep-Dec;15(5-6):545-52.
[Effect of physical exertion on seizure discharges in the EEG of epilepsy patients]
[Article in Polish]
Horyd W, Gryziak J, Niedzielska K, Zielinski JJ.
The purpose of this study was establishing the effect of moderate exercise on EEG tracings in young epileptics. The model of graded exercise was 15-minute work on a cycle ergometer. The effect of the exercise on the pattern of simultaneously recorded EEG was compared with the effect of 3-minute hyperventilation. After testing a control group of 20 young subjects without evidence of organic brain damage or with this damage causing no epilepsy another group of 43 epileptics was studied. In none of these patients the intensity of changes in EEG increased during the exercise but evident EEG differences could be detected during different stages of the exercise in 28 patients with significant generalized discharges. It was found that during the exercise in nearly all patients the number of discharges decreased while during hyperventilation it increased. In 10 patients in this group a repeated rise in the number of discharges was observed immediately after the exercise which was connected usually with greater fatigue after the exercise. In the light of these results the authors conclude that moderate exercise inhibits rather seizure activity in EEG contrary to hyperventilation which increases these changes.


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