Training and teaching of vagus nerve stimulation surgery: Worldwide survey and future perspectives.

OBJECTIVE: Vagus nerve stimulation (VNS) therapy has been used for more than two decades to treat drug resistant epilepsy and depression and most recently received FDA approval for stroke rehabilitation. Expanding indications will renew the interest in the technique and increase the number of surgeons to be trained. The aim of this study was to survey surgeons with substantial expertise on optimal teaching and training approaches. METHODS: Anonymous forms comprising 16 questions were sent by e-mail to surgeons with substantial expertise. Statistical analyses were used to compare the answers of the most experienced surgeons (>5 years) with the less experienced ones (<5 years). RESULTS: Fully-completed forms were collected from 57 experts from 20 countries. The placement of the helical coils was deemed to be the most difficult step by 36 (63.2%) experts, and the use of optical magnification during this step was deemed necessary by 39 (68.4%) experts. Vocal cord palsy should be largely avoidable with proper surgical technique according to 44 (77.2%) experts. The teaching tool considered the most useful was mentoring (38, 66.7%). The future of VNS surgery teaching was deemed to be in anatomical workshops (29, 50.9%) and surgical simulation (26, 45.6%). Overall, answers did not vary significantly according to experience. CONCLUSIONS: VNS surgery should be mastered by actively participating in dedicated practical training courses and by individual mentoring during actual surgery, which is still the best way to learn. This study highlights the need for a formal training course and possible specific accreditation.

Basal temporal lobe epilepsy: SEEG electroclinical characteristics.

OBJECTIVE: Temporal lobe epilepsy is the most common type of focal drug-resistant epilepsy. Seizures with predominant involvement of basal temporal regions (BTR) are not well characterized. In this stereo electroencephalography (SEEG) study, we aimed at describing the ictal networks involving BTR and the associated clinical features. METHODS: We studied 24 patients explored with SEEG in our center with BTR sampling. We analyzed their seizures using a quantitative method: the "epileptogenicity index". Then we reported the features of the patients with maximal epileptogenicity within BTR, especially ictal network involved, ictal semiology and post-surgical outcome. RESULTS: We found that rhinal cortex, parahippocampal cortex and posterior fusiform gyrus were the most epileptogenic structures within the BTR (mean EI: 0.57, 0.55, 0.54 respectively). Three main groups of epileptogenic zone organization were found: anterior (23% of total seizures) posterior (30%) and global (47%, both anterior and posterior). Contralateral spread was found in 35% of left seizures and 20% of right seizures. Naming deficit was more prevalent in left BTR (71% vs 29% in right seizures; p = 0.01) whereas automatic speech production was preferentially represented in right seizures (11% vs 54%; p = 0.001). Surgery was proposed for 11 patients (45.8%), leading to seizure freedom in 72% (Engel Class I). One patient presented post-operative permanent functional deficit. CONCLUSION: Basal-temporal lobe epilepsy seems to be a specific entity among the temporal epilepsy spectrum with specific clinical characteristics. Resective surgery can be proposed with good outcomes in a significant proportion of patients and is safe provided that adequate language assessment has been preoperatively made.

The role of the dorsal anterior insula in ecstatic sensation revealed by direct electrical brain stimulation.

BACKGROUND: An ecstatic phenomenon is an altered state of consciousness with a sense of "hyper-reality", and a complete present-moment awareness with a feeling of union with the Universe. A better understanding of the network mechanisms underlying this fascinating subjective experience may help to unravel some mysteries of human consciousness. Insula has been recently proposed to be a key region to elicit these symptoms. OBJECTIVE/HYPOTHESIS: We studied functional connectivity changes in several brain areas during the induction of ecstatic auras by direct electrical stimulation of the dorsal anterior insular cortex in patients with refractory focal epilepsy implanted with intracerebral electrodes (stereotactic-EEG, SEEG) in the context of their pre-surgical evaluation. METHODS: Three patients were selected on the basis of the occurrence of ecstatic symptoms triggered by direct intracerebral electrical stimulation (ES) of the antero-dorsal part of the insula. ES was performed (50 Hz, 1.5-2.1 mA, in a bipolar fashion to each contact in the gray matter during a 3 s period) to map functional cortices and trigger habitual seizures. One stimulation inducing ecstatic changes in each patient was analyzed. Functional connectivity analysis was performed by measuring interdependencies (nonlinear regression analysis based on the h2 coefficient) between SEEG signals before and after stimulations. RESULTS: In all patients, only the stimulation of dorsal anterior insula was able to reproduce an ecstatic aura. We observed a significant increase of functional connectivity values between several brain regions in the immediate period following stimulations. The most commonly implicated region was the dorsal anterior insula. Out-degrees (a measure intended to identify leading structures in a network) identified the dorsal anterior insula as the most common leading region in the induced networks. CONCLUSION(S): Our findings bring additional support in favor of a major role played by the dorsal anterior insula in ecstatic experiences.

Deep brain activities can be detected with magnetoencephalography.

The hippocampus and amygdala are key brain structures of the medial temporal lobe, involved in cognitive and emotional processes as well as pathological states such as epilepsy. Despite their importance, it is still unclear whether their  neural activity can be recorded non-invasively. Here, using simultaneous intracerebral and magnetoencephalography (MEG) recordings in patients with focal drug-resistant epilepsy, we demonstrate a direct contribution of amygdala and hippocampal activity to surface MEG recordings. In particular, a method of blind source separation, independent component analysis, enabled activity arising from large neocortical networks to be disentangled from that of deeper structures, whose amplitude at the surface was small but significant. This finding is highly relevant for our understanding of hippocampal and amygdala brain activity as it implies that their activity could potentially be measured non-invasively.

EpiTools, A software suite for presurgical brain mapping in epilepsy: Intracerebral EEG.

BACKGROUND: In pharmacoresistant epilepsy, exploration with depth electrodes can be needed to precisely define the epileptogenic zone. Accurate location of these electrodes is thus essential for the interpretation of Stereotaxic EEG (SEEG) signals. As SEEG analysis increasingly relies on signal processing, it is crucial to make a link between these results and patient's anatomy. Our aims were thus to develop a suite of software tools, called "EpiTools", able to i) precisely and automatically localize the position of each SEEG contact and ii) display the results of signal analysis in each patient's anatomy. NEW METHOD: The first tool, GARDEL (GUI for Automatic Registration and Depth Electrode Localization), is able to automatically localize SEEG contacts and to label each contact according to a pre-specified nomenclature (for instance that of FreeSurfer or MarsAtlas). The second tool, 3Dviewer, enables to visualize in the 3D anatomy of the patient the origin of signal processing results such as rate of biomarkers, connectivity graphs or Epileptogenicity Index. RESULTS: GARDEL was validated in 30 patients by clinicians and proved to be highly reliable to determine within the patient's individual anatomy the actual location of contacts. COMPARISON WITH EXISTING METHODS: GARDEL is a fully automatic electrode localization tool needing limited user interaction (only for electrode naming or contact correction). The 3Dviewer is able to read signal processing results and to display them in link with patient's anatomy. CONCLUSION: EpiTools can help speeding up the interpretation of SEEG data and improving its precision.

Long-term results of Gamma-knife stereotactic radiosurgery for vestibular schwannomas in patients with type 2 neurofibromatosis.

INTRODUCTION: The aim of this study was to analyze the long-term results of Gamma-knife radiosurgery treatment of vestibular schwannomas in type 2 neurofibromatosis patients. MATERIALS AND METHODS: A cohort of 129 treatments for vestibular schwannomas in 103 patients was selected from a prospectively-maintained clinical database. Tumor control was assessed by volumetric analysis of the tumor at the last follow-up. Any need of a further procedure such as microsurgical removal or second treatment was regarded as a failure of tumor control. Hearing function was assessed based on Gardner-Robertson classification. Progression-free survival and functional hearing preservation rates were estimated using the Kaplan-Meier method. RESULTS: The median age at treatment was 34 years with no gender predominance. The median tumor volume was 1.5cm3. At a median clinical follow-up of 5.9 years, five patients had died, four underwent a second radiosurgical procedure and eight underwent microsurgical resection. Progression-free survival was 88 and 75% respectively at 5 and 10 years. Hearing was considered serviceable in 70 ears and remained functional in 28 ears. Kaplan-Meier estimates for 5 and 10 years functional hearing was 47 and 34%, respectively. Three patients developed new facial nerve palsy after radiosurgery at 15 days, 6 and 19 months respectively and only one partially recovered. Five patients complained of a subjective instability worsening. Four cases developed trigeminal neuropathy. No predictive factors were found to be statistically correlated with a better hearing outcome or an improved tumor growth control. CONCLUSION: Results prove less satisfying than in sporadic unilateral schwannomas. However, the lower rate of mortality and morbidity compared with microsurgical resection may support a proactive role of Gamma-knife in this pathology.

Technical solutions for simultaneous MEG and SEEG recordings: towards routine clinical use.

OBJECTIVE: The simultaneous recording of intracerebral EEG (stereotaxic EEG, SEEG) and magnetoencephalography (MEG) is a promising strategy that provides both local and global views on brain pathological activity. Yet, acquiring simultaneous signals poses difficult technical issues that hamper their use in clinical routine. Our objective was thus to develop a set of solutions for recording a high number of SEEG channels while preserving signal quality. APPROACH: We recorded data in a patient with drug resistant epilepsy during presurgical evaluation. We used dedicated insertion screws and optically insulated amplifiers. We recorded 137 SEEG contacts on 10 depth electrodes (5-15 contacts each) and 248 MEG channels (magnetometers). Signal quality was assessed by comparing the distribution of RMS values in different frequency bands to a reference set of MEG acquisitions. MAIN RESULTS: The quality of signals was excellent for both MEG and SEEG; for MEG, it was comparable to that of MEG signals without concurrent SEEG. Discharges involving several structures on SEEG were visible on MEG, whereas discharges limited in space were not seen at the surface. SIGNIFICANCE: SEEG can now be recorded simultaneously with whole-head MEG in routine. This opens new avenues, both methodologically for understanding signals and improving signal processing methods, and clinically for future combined analyses.

Survival of melanoma patients treated with targeted therapy and immunotherapy after systematic upfront control of brain metastases by radiosurgery.

BACKGROUND: Targeted therapy (TT) and immunotherapies (ITs) have dramatically improved survival in metastatic melanoma (MM). However, their efficacy on brain metastasis (BM) remains limited and poorly documented. PATIENTS AND METHODS: Retrospective cohort of consecutive MM patients (pts) with BMs, all systematically upfront treated by Gamma-Knife (GK) at first BM and retreated in case of new BMs, from 2010 to 2015 at the time when ipilimumab BRAF ± MEK inhibitors and anti-PD1 were introduced in practice. Survival after 1st GK (OSGK1) according to prognostic factors and treatment. RESULTS: Among 179 consecutive pts treated by GK, 109 received IT and/or TT after the 1st GK. Median OSGK1 was 10.95 months and 1- and 2-year survival rates were 49.5% and 27.4%, respectively, versus a median overall survival (OS) of 2.29 months (p < .001) in those who did not receive IT or TT. In pts who initially had a single BM, median OS and 1- and 2-year survival rates were 14.46 months, 66.7% and 43.4%, respectively; in pts with 2-3 BMs: 8.85 months, 46.4% and 31%, respectively; in pts with >3 BMs: 7.25 months, 37.2% and 11.9%, respectively. Multivariate analysis for OSGK1 confirmed that IT and TT were significantly and highly protective. Best OSGK1 was observed in BRAF-wild-type pts receiving anti-PD1 or in BRAF-mutated pts receiving BRAF-inhibitors and anti-PD1 (12.26 and 14.82 months, respectively). CONCLUSION: In real-life MM pts with BMs, a strategy aiming at controlling BM with GK together with TT and/or TT seems to achieve unprecedented survival rates.

Essential tremor: Update of therapeutic strategies (medical treatment and gamma knife thalamotomy).

Tremor is a highly prevalent movement disorder that markedly reduces quality of life. The management of severe tremor is particularly challenging. Pharmacological treatment is available, but no real breakthrough has emerged recently. Propranolol and primidone are still the two most recommended agents, followed by topiramate. However, surgical treatments for medically refractory tremors are expanding. Gamma knife (GK) thalamotomy is an option particularly suitable for patients who are not candidates for deep brain stimulation. Owing to the fact that it is a non-invasive procedure without craniotomy, GK radiosurgery has almost no contraindications. Since the late 1990s, more than 250 case reports and patient series have been published. Most of these studies show that unilateral GK thalamotomy is well tolerated and reduces tremor disability. A recent study with prospective blinded assessment has confirmed its safety, together with significant improvements in tremor scores and activities of daily living.

On demand Gamma-Knife strategy can be safely combined with BRAF inhibitors for the treatment of melanoma brain metastases.

BACKGROUND: Both Gamma-Knife radiosurgery (GKRS) and BRAF inhibitors (BRAF-I) have been shown to be useful in melanoma patients with brain metastases (BMs), thus suggesting that it could be interesting to combine their respective advantages. However, cases of radiosensitization following conventional radiation therapy in BRAF-I treated patients have raised serious concerns about the real feasibility and risk/benefit ratio of this combination. PATIENTS AND METHODS: Review by two independent observers of brain magnetic resonance imaging (MRI) follow-up pictures, and volume and edema quantifications, and survival assessment in all patients who had been treated by GKRS and BRAF-I at a single institution. RESULTS: Among 53 GKRS carried out in 30 patients who ever received BRAF-I and GKRS, 33 GKRS were carried out in 24 patients while under BRAF-I treatment, from which only 4 with an interruption of BRAF-I. The 20 other GKRS were carried out in 15 patients (including 9 of the 24) before initiation of BRAF-I treatment. No case of radiation-induced necrosis and no scalp radiation dermatitis occurred. A >20% increase in volume was observed in 35 of the 263 BM treated by GKRS (13.3%), but only 3 clear-cut edemas and 3 hemorrhages were detected within 2 months after GKRS, and 4 edemas and 7 hemorrhages later. Neither the MRI features nor the incidence of the volume changes, hemorrhage and edema were deemed unexpected for melanoma BM treated by GKRS. Median survival from first GKRS under BRAF-I and first dose of BRAF-I were 24.8 and 48.8 weeks, respectively. CONCLUSION: This series does not show immediate radiotoxicity nor radiation recall, in melanoma patients with BRAF-I whose BMs are treated by GKRS. Interrupting BRAF-I for stereotactic radiosurgery (SRS) of BM seems useless, although it is still advised for other radiation therapies. The potential benefit of combining SRS and BRAF-I can be safely tested.

[Role of radiosurgery and stereotactic radiotherapy in the management of vestibular schwannomas]. / Radiochirurgie et radiothérapie stéréotaxique des schwannomes vestibulaires.

PURPOSE OF THE STUDY: In order to investigate the role of radiosurgery and stereotactic radiotherapy in the management of vestibular schwannomas, we have reviewed our own prospective cohort and the main series of the modern literature. PATIENTS AND METHODS: Between July 14th 1992 and June 1st 2011, 2991 vestibular schwannomas were operated on the Stereotactic and Functional Neurosurgery Department of Timone University Hospital. All the patients have been evaluated prospectively, with a follow up longer than 3 years for 2336 patients, excluding patients suffering from type 2 neurofibromatosis (148 patients). In 7% of the patients, the vestibular schwannoma had previously been resected. According to Koos classification, in 17.6% of the patients, vestibular schwannomas were stage I, 51.8% stage II, 27% stage III and 3.6% stage IV. The mean tumour volume was 2.63 cm(3). According to Garner Robertson classification, the hearing was still functional at the time of radiosurgery in 46% and subnormal in 20.9% of the patients. RESULTS: Long term tumour control was achieved in 97.5% of the patients. A transient facial palsy was observed in 0.5% of the cases. The rate of trigeminal injury was 0.5%. Useful hearing was preserved at 3 years in 78%. This rate reached 95% in patients with no past history of sudden hearing loss. Other predictors of functional hearing preservation are the young age, the small size of the lesion and a dose to the modiulus of the cochlea lower than 4Gy. We observed no radio-induced tumour. Only large, Koos IV vestibular schwannomas are contraindicated for upfront radiosurgery. In these patients, we propose a combined approach with a deliberately partial microsurgical removal, followed by a radiosurgery of the residue. CONCLUSION: This cohort is unique by the size of the population and the length of the follow up and results demonstrate the efficacy of radiosurgery and its safety, especially its high rate of hearing preservation.

Predilection to deafferentation pain syndrome after radiosurgery in cluster headache.

Cluster-tic syndrome is a rare, disabling disorder. We report the first case of cluster-tic syndrome with a successful response to stereotactic radiosurgery. After failing optimal medical treatment, a 58-year-old woman suffering from cluster-tic syndrome was treated with gamma knife radiosurgery. The trigeminal nerve and sphenopalatine ganglion were targeted with a maximum dose of 85 and 90 Gy respectively. The patient experienced a complete resolution of the initial pain, but developed, as previously described after radiosurgical treatment for cluster headache, a trigeminal nerve dysfunction. This suggests that trigeminal nerve sensitivity to radiosurgery can be extremely different depending on the underlying pathological condition, and that there is an abnormal sensitivity of the trigeminal nerve in cluster headache patients. We do not recommend trigeminal nerve radiosurgery for treatment of cluster headache.

[Mechanisms of action of high-frequency deep brain stimulation. A review of the literature and current concepts]. / Les mécanismes d'action de la stimulation cérébrale à haute fréquence. Revue de la littérature et concepts actuels.

High-frequency deep brain stimulation (HF-DBS) has become a widely used therapeutic method in the field of movement disorders for the treatment of Parkinson's disease, essential tremor or dystonia. New targets and indications are under evaluation in several other conditions such as cluster headache, obesity, epilepsy or psychiatric diseases (depression, OCD). However, the mechanisms of action of HF-DBS remain poorly understood. Herein we present a review of the literature and our current view of the question. The first part deals with the effects of stimulation itself on the different parts of the neuron and tries to answer the question of what is actually stimulated by DBS (cell bodies, dendrites or axons). The second part is devoted to the ortho- and antidromic effects of the stimulation. The third part more specifically focuses on the case of subthalamic nucleus stimulation. The target axons in the subthalamic area are discussed in the light of recent optogenetic studies. In conclusion, HF-DBS leads to a kind of functional deafferentation of the stimulated structure and to the modulation of cortical activity (both ortho and antidromically). Which effects are relevant to the therapeutic effects of DBS is still unclear. Further investigations are required especially regarding the corticosubthalamic pathways.

High frequency deep brain stimulation of the subthalamic nucleus versus continuous subcutaneous apomorphine infusion therapy: a review.

In advanced Parkinson's disease, several therapeutical option including not only lesional surgery (VIM, GPi) and deep brain stimulation (STN, GPi, VIM) but also continuous subcutaneous apomorphine infusion therapy can be proposed to the patient. The choice depends on the hope of the patient, patient's general health condition and the experience and choice of the neurosurgical and neurologist team. Here we report our experience based on 400 STN-DBS cases and we discuss, on the basis of our experience and on the literature, the advantage and disadvantage of DBS strategy as compared with non-surgical option such as continuous subcutaneous apomorphine infusion therapy.

Cardiovascular changes in spontaneously hypertensive rats are improved by chronic treatment with zofenopril.

BACKGROUND AND PURPOSE: The aim of this study was to investigate the effect of chronic treatment with antihypertensive and non-antihypertensive doses of zofenopril on cardiovascular changes in spontaneously hypertensive rats (SHR). EXPERIMENTAL APPROACH: Male SHR were treated with 0.5 or 10 mg kg(-1) per day of zofenopril (Z(0.5) and Z(10)) for 3 months. SHR and Wistar-Kyoto rats (WKY) receiving vehicle were used as controls. Systolic blood pressure was measured using the tail cuff method. Left ventricular weight/body weight ratio was calculated as cardiac hypertrophy index. Angiotensin converting enzyme (ACE) activity was determined in plasma and tissues by a fluorimetric method. Vascular reactivity was evaluated on aortic rings by acetylcholine and sodium nitroprusside relaxations. Effects on vascular structure were assessed by lumen diameter, wall thickness and medial cross-sectional area determination. Superoxide anion generation was quantified using lucigenin-amplified chemiluminescence in aorta. RESULTS: Long-term daily administration of zofenopril (10 mg kg(-1)) to SHR reduced blood pressure to WKY values, decreased cardiac hypertrophy, improved the acetylcholine-induced relaxant response and reversed the vascular remodelling. ACE inhibition and antioxidant activity were involved in these effects. 0.5 mg kg(-1) per day of zofenopril slightly modified blood pressure and the other effects were weaker. CONCLUSIONS AND IMPLICATIONS: Antihypertensive effects of chronic treatment with zofenopril were accompanied by recovery of endothelial function and improvement of cardiovascular structure. Low-dose zofenopril had little effect on blood pressure, with some benefits on cardiovascular structure and function. Inhibition of ACE and antioxidant activity were involved in these effects.

[Basal ganglia deep-brain stimulation for treatment of drug-resistant epilepsy: review and current data]. / La stimulation cérébrale profonde des ganglions de la base comme traitement des épilepsies pharmacorésistantes: revue et données actuelles.

The surgical treatment of intractable epilepsies involving eloquent areas of the cortex is still challenging. Deep-brain stimulation could be an alternative to resective surgery because it can modulate the remote control systems of epilepsy, such as the thalamus and basal ganglia. The surgical experience acquired in the field of movement disorder surgery and the low morbidity of this technic could allow one to apply DBS to intractable epilepsies, such as generalized, motor and bitemporal epilepsies. Here we discuss the main experimental and clinical data reported so far in the literature and taken from our own experience.

[Temporal disconnection as an alternative treatment for intractable temporal lobe epilepsy: techniques, complications and results]. / Déconnexion du lobe temporal dans les épilepsies temporales pharmacorésistantes: techniques, complications et résultats.

Temporal lobe epilepsy (TLE) is the most common form of intractable partial epilepsy in adults. Surgery (lobectomy or amygdalohippocampectomy) is effective in most patients. However, some complications can occur and brain shift, hematoma into the post operative cavity and occulomotor nerve palsy have been reported due to the surgical technic. We report the technique, safety and efficacy of temporal disconnection in nonlesional TLE. Forty-seven patients (18 males, 29 females; handedness: 12 left, 33 right; aged 35 years+/-10; mean duration of epilepsy: 24+/-10 years) underwent temporal disconnection (20 left, 27 right) guided by neuronavigation. Sixteen patients (35 %) underwent additional presurgical evaluation with SEEG. The outcome was assessed using Engel's classification. At the two-year follow-up, 85 % of the patients were seizure-free (Engel I), 26 (58 %) of whom were Ia. Postoperative persistent morbidity included mild hemiparesis (n=1), mild facial paresis (n=1), quadranopsia (n=23) and hemianopia (n=1). Verbal memory worsened in 13 % of cases when the disconnection was performed in the dominant lobe. MRI follow-up showed two cases of nonsymptomatic thalamic or pallidal limited ischemias, two cases of temporal horn-cystic dilatation, one requiring surgical reintervention without sequelae. There was one case of postoperative phlebitis. In the seizure-free patient group, postoperative EEG showed interictal temporal spikes at three months, one year and two years located in the anterior temporal region. Temporal disconnection is effective, prevents the occurrence of subdural cyst and hematomas in the temporal cavity, prevents the occurrence of oculomotor palsy, and limits the occurrence of quadranopsia. However, comparative studies are required to evaluate temporal disconnection as an alternative to lobectomy in nonlesional TLE.

Synthesis of a new series of 4-aryl-1,4-dihydropyridines with calcium channel blocking and vasodilatory activity.

Synthesis of a new series of 4-aryl-1,4-dihydropyridines possessing potential calcium channel blocking activity along with good vasodilatory profile is reported. The compounds were synthesized using modified Hantzsch condensation of various aldehydes with methyl 3-aminocrotonate in the presence of a catalytic amount of trifluoroacetic acid and subsequent alkylation with various hydrochlorides of dialkylaminoalkyl chlorides. In vitro calcium channel blocking activity has been evaluated in cultures of neonatal rat cortical neurons by measuring the inhibitory response at L-type calcium channels activated by veratridine. Many compounds exhibited moderate to significant calcium channel blockade around 1 microM. The vasodilatory activity was assessed on isolated rat thoracic aortic rings precontracted by phenylephrine/KCl (30 mM). Most of the compounds produced a concentration-dependent inhibition of the contractile response.

Vasorelaxant effect of new neo-clerodane diterpenoids isolated from Croton schiedeanus.

The vasorelaxant effect of two new neo-clerodane diterpenoids, (12R)-12-hydroxycascarillone and 5beta-hydroxy-cis-dehydrocrotonin, in addition to the known cis-dehydrocrotonin and trans-dehydrocrotonin, all them previously isolated by us from Croton schiedeanus Schlecht, was studied in isolated aorta rings contracted by high K+ (80 mM) or phenylephrine (1 microM). According to their IC50 values to KCl induced contraction, the potency order was (12R)-12-hydroxycascarillone > cis-dehydrocrotonin > 5beta-hydroxy-cis-dehydrocrotonin > trans-dehydrocrotonin (0.3, 1.5, 96 and >100 mM, respectively). The possible cooperativity between diterpenoid compounds and the predominant flavonoid (ayanin) was studied. The vasorelaxant activity of cis-dehydrocrotonin and ayanin was increased when both compounds were incorporated simultaneously to the aortic rings precontracted with phenylephrine. These results suggest that Croton schiedeanus induces its effects via the synergistic actions of several vasodilator substances, among which neo-clerodane diterpenoids play an important role.