OS05.9.A Short-term fasting in glioma patients - Analysis of diet diaries and metabolic parameters of the ERGO2 trial

BACKGROUND

The prospective, randomized ERGO2 trial investigated the effect of fasting / calorie restricted ketogenic diet (KD-IF) on re-irradiation for recurrent brain tumors (Clinicaltrials.gov number: NCT01754350). The study did not meet its primary endpoint of improved progression-free survival in comparison to a standard diet (SD). We here report the results of the quality of life questionnaire, neurocognition testing, detailed analysis of the diet diaries and the alterations of metabolic parameters.

MATERIAL AND METHODS

50 Patients were randomized 1:1 to re-irradiation combined with either SD or KD-IF. The KD-IF schedule included 3 days of ketogenic diet (KD: 21–23 kcal/kg/d, carbohydrate intake limited to 50 g/d), followed by 3 days of fasting and again 3 days of KD. Follow-up included examination of cognition, quality of life and serum samples.

RESULTS

The 20 patients who completed KD-IF met the prespecified goals for calorie and carbohydrate restriction. In these, a decrease in leptin and insulin and an increase in uric acid was observed. The SD group had a lower calorie intake of 21 kcal/kg/d than the expected 30 kcal/kg/d. Neither quality of life nor cognition were affected by the diet. Low glucose emerged as a significant prognostic parameter in a best responder analysis.

CONCLUSION

The strict caloric goals of the ERGO2 trial could be achieved by patients with recurrent brain tumor. The unexpected lower calorie intake of the SD group might have hampered the interpretation of the trial. However, the short diet schedule already led to significant metabolic alterations, suggesting that short-term dietary interventions might be therapeutically useful, possibly combined with other modalities.

Short-term fasting in glioma patients: analysis of diet diaries and metabolic parameters of the ERGO2 trial

Purpose

The prospective, randomized ERGO2 trial investigated the effect of calorie-restricted ketogenic diet and intermittent fasting (KD-IF) on re-irradiation for recurrent brain tumors. The study did not meet its primary endpoint of improved progression-free survival in comparison to standard diet (SD). We here report the results of the quality of life/neurocognition and a detailed analysis of the diet diaries.

Methods

50 patients were randomized 1:1 to re-irradiation combined with either SD or KD-IF. The KD-IF schedule included 3 days of ketogenic diet (KD: 21–23 kcal/kg/d, carbohydrate intake limited to 50 g/d), followed by 3 days of fasting and again 3 days of KD. Follow-up included examination of cognition, quality of life and serum samples.

Results

The 20 patients who completed KD-IF met the prespecified goals for calorie and carbohydrate restriction. Substantial decreases in leptin and insulin and an increase in uric acid were observed. The SD group, of note, had a lower calorie intake than expected (21 kcal/kg/d instead of 30 kcal/kg/d). Neither quality of life nor cognition were affected by the diet. Low glucose emerged as a significant prognostic parameter in a best responder analysis.

Conclusion

The strict caloric goals of the ERGO2 trial were tolerated well by patients with recurrent brain cancer. The short diet schedule led to significant metabolic changes with low glucose emerging as a candidate marker of better prognosis. The unexpected lower calorie intake of the control group complicates the interpretation of the results.

Clinicaltrials.gov number: NCT01754350; Registration: 21.12.2012.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02666-1.

TP3-5 Structural connectivity driven stereoelectroencephalography (SEEG) electrode targeting in suspected pseudotemporal and temporal plus epilepsy

Objectives

One third of patients with drug resistant focal mesial temporal lobe epilepsy (MTLE) fail to achieve long-term seizure freedom following temporal lobe resections. Reasons for failure may include ictal onset outside the temporal lobe (TL), termed ‘pseudotemporal lobe epilepsy’ (pTLE), with propagation from strongly connected neighboring areas or temporal plus (TL+) epilepsy, when the epileptogenic zone primarily involves the temporal lobe and also extends to neighboring regions. In such cases the perisylvian and orbito-frontal (OF) cortices, cingulum and temporo-parieto-occipital junction may be implicated. Stereoelectroencephalography (SEEG) is a procedure in which electrodes are stereotactically placed within predefined brain regions to delineate the SOZ and allows evaluation of deep anatomical structures adjacent to the TL. SEEG electrode contacts sample from a core radius of 3–5 mm. It is unclear which sub-regions of target structures should be preferentially implanted to optimally detect the network involved in seizure onset and rapid propagation. Using normalized average group templates of structural connectivity from patients with hippocampal sclerosis (HS), we determine the greatest connectivity to critical sub-regions and based upon this propose optimal locations for SEEG targeting.

Design

Observational cross-sectional study.

Subjects

Twelve patients with HS (6 right) that had undergone SEEG and pre-operative diffusion imaging were identified from a prospectively maintained database.

Methods

Whole brain connectomes with 10 million tracts were generated using cortical seed regions derived from whole brain GIF parcellations. Normalized group templates were generated separately for right and left HS patients. Orbitofrontal cortex (OF), insula (INS), cingulum (Cing) and temporo-parietal-occipital junction (supramarginal gyrus, angular gyrus, precuneus, fusiform gyrus and lingual gyrus) were segmented into surgically targetable subregions. All subregions had similar volumes. Connectivity of the amygdalohippocampal complex (AHC) was defined based on the number of streamlines terminating in the subregions of interest.

Results

Left HS showed preferential connections to the ipsilateral: posterior part of lateral OF cortex, posterior short gyrus of anterior INS, posterior part of the posterior Cing, middle part of lingual gyrus, posterior part of precuneus and middle part of fusiform gyrus. Right HS showed preferential connections to the ipsilateral: posterior part of the lateral OF cortex, anterior long gyrus of posterior INS, posterior part of posterior Cing, anterior part of lingual gyrus and posterior part of precuneus.

Conclusions

Using whole brain connectomes we determine surgically feasible targets in sub-regions based on greatest connectivity to the AHC. We propose that SEEG targeting utilizing computer-assisted planning may improve the understanding of the overall network connectivity in order to enhance the diagnostic utility of the SEEG implantation. SEEG electrode placement within structures associated with pTLE and TL +may aid in delineating the SOZ if the correct sub-regions are targeted. This should be evaluated prospectively.

Flexible enzymatic activation of artificial polyketide extender units by Streptomyces cinnamonensis into the monensin biosynthetic pathway

Streptomyces cinnamonensis A495 is a variant of the monensin producer which instead of the native polyether antibiotic gives rise to antibiotic and anti-tumour shunt-product premonensin. Through the supplementation of the fermentation medium with suitable precursors, premonensin can be derivatized via the incorporation of new-to-nature extender units into the biosynthetic machinery. Polyketide extender units require activation, typically in form of coenzyme A-thioesters. These are membrane impermeable and thus in the past an artificial mimic was employed. Here, we show the use and preliminary characterization of a highly substrate promiscuous new enzyme for the endogenous thioester formation in a Streptomyces strain. These intracellularly activated alternative extender units are significantly better incorporated into premonensin than the synthetically activated counterparts.

SIGNIFICANCE AND IMPACT OF THE STUDY

Polyketide natural products are of enormous relevance in medicine. The hit-rate in finding active compounds for the potential treatment of various diseases among this substance family of microbial origin is high. However, most polyketides require derivatization to render them suitable for the application. Of relevance in this field is the incorporation of artificial substances into the biogenesis of polyketides, hampered by both the microbial metabolism and the complexity of the enzymes involved. This manuscript describes the straightforward and selective biosynthetic incorporation of synthetic substances into a reduced polyketide and showcases a promising new enzyme to aid this purpose.

Standardisierter Computer-basiert-organisierter Report des EEG (SCORE) – Eine strukturierende Form der EEG-Befundung

Eine 2013 von der „International Federation of Clinical Neurophysiology“ gegründete Taskforce hat eine international konsensfähige EEG-Terminologie entwickelt. Im Folgenden soll das Resultat – die 2. Version des Standardized Computer-based Organized Reporting of EEG (SCORE) - vorgestellt werden. Die Terminologie wurde im Rahmen eines Softwarepaketes (SCORE-EEG) in der klinischen Praxis an über 12.000 EEGs getestet. Die Auswahl der Begriffe ist kontextabhängig: die initiale Auswahl bestimmt, welche weiteren Auswahlmöglichkeiten zur Verfügung stehen. Im Verlauf wird automatisch ein Befund erstellt und dessen Einzelmerkmale in eine Datenbank eingespeist. SCORE verfügt über Module spezifisch für die Befundung epileptischer Anfälle, sowie charakteristischer neonataler und intensivmedizinische EEG-Merkmale. SCORE ist nicht nur ein nützliches Werkzeug im ambulanten, klinischen und wissenschaftlichen Setting, es erleichtert auch Qualitätssicherung, Datenaustausch und die EEG-Aus und Weiterbildung.

Measurement of Temporal Asymmetries of Glucose Consumption Using Linear Profiles: Reproducibility and Comparison with Visual Analysis

Aim: One approach to regionally analyze temporal glucose consumption consists in drawing linear profiles over the maximal values measured in the temporal cortical ribbon. The aim of our study was to test the reproducibility of this method and to compare its diagnostic performance to that of visual analysis in patients with complex partial seizures (CPS). Methods: Regional cerebral glucose consumption (rCMRGIc) was measured interictally in 25 CPS patients and 10 controls using F-18-deoxyglucose and the positron emission tomography (PET) camera ECAT EXACT 47. The PET scans were visually analyzed for the occurrence of unilateral temporal hypermetabolism. Furthermore, rCMRGIc was quantified on six contiguous coronal planes by manually tracing maximal values of temporal glucose consumption, thus creating line profiles of temporal glucose consumption for each side. Indices of asymmetry (ASY) were then calculated from these line profiles in four temporal regions and compared to the corresponding 95% confidence intervals of the control data. All analyses were performed by two observers independently from each other and without knowledge of the clinical findings. Results: The agreement between the two observers with regard to focus lateralization was 96% (κ = 0.93) on visual analysis and 100% (κ = 1) on quantitative analysis. There was an excellent agreement with regard to focus lateralization between visual and quantitative evaluation (κ = 0.8). Conclusion: Quantitation of local temporal rCMRGIc by using linear profile analysis is highly reproducible; for the lateralization of epileptogenic foci, however, this method does not possess significant advantages over the visual evaluation of the scans.

Role of cortisol in mood and memory in patients with intractable temporal lobe epilepsy

OBJECTIVE

This study prospectively examined the relationships among late night salivary cortisol (NSC) levels and depressive symptoms, memory performance, and hippocampal volumes in patients with medically intractable temporal lobe epilepsy (TLE) and the potential mediating effects of cortisol in the relationships between these variables.

METHODS

Participants included 24 adults with well-characterized medically refractory TLE (right = 11; left = 12; bitemporal = 1). All patients provided saliva samples and completed measures of mood, anxiety, and memory (objective and subjective). MRI-based volumetric analyses of the hippocampi were also conducted.

RESULTS

As hypothesized, cortisol was found to be negatively related to several memory measures such that patients with higher cortisol levels demonstrated lower memory performance. However, unexpectedly, cortisol was not related to current symptoms of depression or anxiety, subjective memory ratings, or hippocampal volumes. Consistent with previous findings in the literature, a number of other relationships among the study variables were observed (objective memory and hippocampal volume; subjective memory and mood/anxiety). Results of mediator analyses suggested that cortisol does not mediate the relationship between depression and memory dysfunction or the relationship between depression and hippocampal atrophy.

CONCLUSIONS

While cortisol may play a role in memory performance in patients with TLE, it does not fully explain the relationship between depression and mesial temporal dysfunction, likely reflecting the complex and multifactorial relationships among these variables. Results confirm the relationship between memory performance and structural brain integrity and provide further support for a role of depression in subjective memory complaints.

Differences in corpus callosum volume and diffusivity between temporal and frontal lobe epilepsy

We analyzed volume and diffusivity measures of the corpus callosum (CC) in patients with temporal (TLE) and frontal (FLE) lobe epilepsy in comparison with healthy subjects. On high-resolution T1-weighted scans of 18 controls and 44 patients the volumes (cm(3)) of Witelson regions (WRs) and the entire CC were measured. The apparent diffusion coefficients (ADCs, 10(-5)mm(2)s(-1)) for the entire CC and three areas of interest were measured from co-registered ADC maps. The CC of patients with TLE and FLE, corrected for total brain volume, was smaller than that of controls. Patients' ADC values were higher than those of controls. Findings were significant for WR1, WR2, and WR6, the CC regions connecting the frontal and temporal lobes. Patients with FLE had smaller WR1 and higher ADC values; in patients with TLE, the findings were similar for WR6. Atrophy and increased diffusivity in subregions of the CC connecting homotopic contralateral cortical regions indicate anatomical abnormalities extending beyond the epileptogenic zone in FLE and TLE.

The value of interictal diffusion-weighted imaging in lateralizing temporal lobe epilepsy

BACKGROUND

A subgroup of patients with nonlesional temporal lobe epilepsy (TLE) has no evidence of hippocampal sclerosis on standard temporal lobe protocol MRI.

OBJECTIVE

To investigate whether interictal diffusion-weighted imaging adds lateralizing information in patients with TLE with and without lateralizing conventional MRI.

METHODS

We studied 22 patients (9 right, 13 left TLE) who had undergone temporal lobectomy and 18 control subjects. We measured hippocampal volumes on high- resolution coronal magnetization-prepared rapid gradient echo scans. Apparent diffusion coefficients (ADCs) for the entire hippocampus and three arbitrarily defined areas of interest within the hippocampal head, body, and tail were measured from the coregistered ADC map. Pathology was reviewed and correlated with imaging findings.

RESULTS

Fourteen of 22 patients had hippocampal atrophy on MRI (defined as volume asymmetry greater than 2 SDs compared with asymmetry in the control group). Overall, resected hippocampi (n = 22) were significantly smaller than contralateral hippocampi as well as ipsilateral hippocampi in controls. ADCs were significantly higher in resected hippocampi than contralateral hippocampi as well as ipsilateral hippocampi in controls. These differences were also observed within the three areas of interest. ADCs in the hippocampi contralateral to the epileptogenic zone (n = 22) were also higher than in ipsilateral hippocampi in controls. In the subgroup of eight patients with nonlateralizing conventional MRIs, ADCs of resected hippocampi were not significantly different compared with the contralateral side. Pathology in these patients revealed gliosis only without apparent neuron loss.

CONCLUSION

Interictal apparent diffusion coefficients confirm lateralization in patients with hippocampal atrophy on standard temporal lobe protocol MRI. However, they do not provide lateralizing information in patients with nonlateralizing conventional MRI.

Vorschlag für eine neue patientenorientierte Epilepsieklassifikation

The recent proposal by the ILAE Task Force for Epilepsy Classification is a multiaxial, syndrome-oriented approach. Epilepsy syndromes--at least as defined by the ILAE Task Force--group patients according to multiple, usually poorly defined parameters. As a result, these syndromes frequently show significant overlap and may change with patient age. We propose a five-dimensional and patient-oriented approach to epilepsy classification. This approach shifts away from syndrome orientation, using independent criteria in each of the five dimensions similarly to the diagnostic process in general neurology. The main dimensions of this new classification consist of (1) localizing the epileptogenic zone, (2) semiology of the seizure, (3) etiology, (4) seizure frequency, and (5) related medical conditions. These dimensions characterize all information necessary for patient management, are independent parameters, and include information more pertinent than the ILAE axes with regard to patient management. All cases can be classified according to this five-dimensional system, even at initial encounter when no detailed test results are available. Information from clinical tests such as MRI and EEG are translated into the best possible working hypothesis at the time of classification, allowing increased precision of the classification as additional information becomes available.

Temporal lobe volumes in patients with hippocampal sclerosis with or without cortical dysplasia

BACKGROUND

Recent MRI-based volume reconstruction studies in intractable temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) suggested atrophy that extends to the adjacent neocortical areas.

OBJECTIVE

To study the extent of temporal lobe volume (TLV) abnormalities in patients with pathologically confirmed HS (with or without cortical dysplasia [CD]) who underwent anterior temporal lobectomy for the treatment of drug-resistant TLE.

METHODS

Fifty patients (right TLE: n = 24; left TLE: n = 26) were found to have HS (hippocampal cell loss of >30%). Associated neocortical CD was seen in 20 patients (43%). MRI-based TLVs and hippocampal and hemispheric volume reconstructions in all patients were compared between pathologic groups and with volumes acquired from 10 age-matched control subjects.

RESULTS

TLVs ipsilateral to the epileptogenic zone in patients with TLE were smaller than TLVs in control subjects (p < 0.01). In patients with left TLE, TLVs ipsilateral to the epileptogenic zone were smaller than contralateral TLVs (left: 66.6 +/- 8.3 cm3, right: 74.9 +/- 10.0 cm3; p < 0.001). In patients with right TLE, there were no significant asymmetries. The contralateral TLVs (regardless of the side of surgery) were smaller in the HS + CD group than the HS group (HS + CD group: 74.9 +/- 8.6 cm3, HS group: 79.7 +/- 6.6 cm3; p < 0.05). Patients with HS + CD had a tendency to have less hippocampal atrophy and slightly smaller TLVs ipsilateral to the epileptogenic zone, accounting for significantly smaller TLV/hippocampal volume ratios compared with patients with HS alone.

CONCLUSIONS

Drug-resistant TLE due to HS is associated with extrahippocampal temporal lobe atrophy. The presence of bilateral temporal lobe atrophy is suggestive of a more widespread (bilateral) temporal lobe involvement in patients with HS and CD.

Hamartomas and epilepsy: clinical and imaging characteristics

PURPOSE

Cerebral hamartomas are lesions marked by a disorganized arrangement of mature neural elements and represent a rare cause of medically intractable focal epilepsy. We present the clinical presentation and imaging findings of this rare entity.

METHODS

History and neurophysiological studies of 14 patients with pathologically confirmed hamartomas who had surgery for intractable focal epilepsy were reviewed. MRIs were available for review in 10 patients.

RESULTS

The lesions were most commonly located in the temporal and frontal lobes. Seizure semiology was concordant with the anatomic location of the hamartoma in all patients. Nine of the thirteen patients (69%) with the hamartoma confined to one lobe had interictal spikes and sharp waves at the corresponding electrodes. The ictal pattern was confined to the same lobe of the hamartoma in five of nine patients with ictal recordings. Although imaging characteristics were variable, all patients had signal increase on T2-weighted images and 50% of them had mild mass effect. Neocortical involvement was present in the majority of patients (7/10), blurring of the gray/white matter interface was seen in seven patients. Five of those seven patients were found to have associated cortical dysplasia by pathology.

CONCLUSION

Hamartomas represent a rare entity and may cause devastating epilepsy. Imaging characteristics are difficult to distinguish from those of some other developmental tumors. Hamartomas are frequently associated with microscopic cortical dysplasia (CD), thus underlining their malformative etiology.

Fluid-attenuated inversion recovery: correlations of hippocampal cell densities with signal abnormalities

BACKGROUND

Hippocampal sclerosis (HS) is characterized by hippocampal atrophy and increased signal on T2-weighted images and on fluid-attenuated inversion recovery (FLAIR) images.

OBJECTIVE

To quantitate cell loss and compare it with signal abnormalities on FLAIR images.

METHODS

Thirty-one patients with temporal lobe resection, pathologically proven HS, and Engel class I and II outcome were included: 20 with HS only and 11 with HS associated with pathologically proven cortical dysplasia (dual pathology). The signal intensity on FLAIR was rated as present or absent in the hippocampus and correlated with the neuronal losses in the hippocampus.

RESULTS

FLAIR signal increases were present in 77% (24/31) of all patients studied. In patients with isolated HS, 90% (18/20) had ipsilateral signal increases, but in patients with dual pathology, only 55% (6/11; p < 0.02) showed FLAIR signal increase. Hippocampal cell losses were significantly higher in the isolated HS group. The average cell loss in patients with FLAIR signal abnormalities was 64.8 +/- 8.0% as compared with only 32.7 +/- 5.1% in patients with no FLAIR signal abnormalities. There was a significant positive correlation between the presence of signal abnormality and average hippocampal cell loss in both pathologic groups.

CONCLUSIONS

Ipsilateral FLAIR signal abnormalities occur in the majority of patients with isolated HS but are less frequent in those with dual pathology. The presence of increased FLAIR signal is correlated with higher hippocampal cell loss.

Disturbed benzodiazepine receptor function at the onset of temporal lobe epilepsy--lomanzenil-binding in de-novo TLE

PURPOSE

Epileptogenic foci exhibit disturbed function at the level of the benzodiazepine receptor. The aim of our study was to investigate the incidence of focal reductions of temporal benzodiazepine receptor binding (BRB) as assessed by scintigraphy with 123I-iomazenil in patients with denovo temporal lobe epilepsy (TLE).

METHODS

Forty adult patients (age: 34+/-12 years) with cryptogenic denovo TLE underwent scintigraphy with 123I-iomazenil. In all patients, symptomatic epilepsy was excluded by clinical investigation and MRI. The median duration of TLE was seven months, and the patients had a median of three documented seizures in their history of disease. BRB was quantified in four temporal regions covering the whole temporal lobe. Temporal asymmetry values (ASY) were compared with data determined in 13 age-matched controls yielding Z-scores for global and regional temporal BRB.

RESULTS

A significant reduction of temporal BRB was found in 19 of the 40 patients (48 %), mainly in mesial temporal regions; temporal BRB asymmetries were also found in patients with a short history of seizures and low seizure frequency (< or = 1 year; n = 32, 13/32 (41 %)). Only in the entire cohort did the magnitude of temporal reduction of BRB correlate with the duration of TLE as well as with the number of previous partial seizures (r = 0.40 and r = 0.36; p < 0.03, respectively).

CONCLUSIONS

Foci of decreased BRB can already be detected at the onset of TLE; their magnitude is related to ongoing epileptic activity.

Temporal hypometabolism at the onset of cryptogenic temporal lobe epilepsy

Most patients with intractable temporal lobe epilepsy (TLE) exhibit temporal glucose hypometabolism. The reasons for the development of this abnormality are as yet unclear. The current notion is that an initial injury causes seizures, which in turn give rise to hypometabolism. The aim of this study was to assess whether temporal reductions in glucose metabolism in non-lesional TLE are the result of repeated seizures or whether hypometabolism represents an initial disturbance at the onset of disease. Glucose consumption was assessed with fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) in 62 patients with cryptogenic non-refractory TLE in different stages of disease. Twelve subjects without neurological illness served as controls. Patients with onset of epilepsy at least 3 years prior to the PET scan were defined as having chronic TLE. Using this criterion, the whole patient cohort included 27 patients with de novo TLE and 35 patients with chronic TLE. The groups were matched for age and sex. The appearance of high-resolution magnetic resonance images of the brain was unremarkable in all patients. In the total cohort, number, duration and frequency of seizures had a significant relation to the magnitude of hypometabolism. Temporal hypometabolism was exhibited by 26 of the 62 patients (42%), including 8 out of 27 (30%) with newly diagnosed TLE and 18 out of 35 (51%) with chronic TLE. The disturbances were more extensive and more severe in patients with chronic TLE. It is concluded that temporal hypometabolism may already be present at the onset of TLE, but is less frequent and less severe in newly diagnosed than in chronic TLE. The metabolic disturbance correlates with the number of seizures. These findings suggest that an initial dysfunction is present in a considerable number of patients and that hypometabolism is worsened by continuing epileptic activity.

Postictal diffusion-weighted imaging for the localization of focal epileptic areas in temporal lobe epilepsy

PURPOSE

Diffusion-weighted MR imaging (DWI) is a novel technique to delineate focal areas of cytotoxic edema of various etiologies. We hypothesized that DWI may also detect the epileptogenic region and adjacent areas during the ictal and early postictal periods in patients with temporal lobe epilepsy (TLE).

METHODS

We studied patients with intractable TLE (n = 9), due to hippocampal sclerosis (HS, n = 7), left mesial temporal lobe tumor (n = 1), and of unknown etiology (n = 1). Informed consent was obtained before inclusion in the study. All patients with single short seizures were scanned immediately after EEG-documented seizures (between 45 and 150 min); one of two patients in status was scanned 14 h after cessation of seizures. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) maps.

RESULTS

We found significant decreases in ADC postictally in one of six patients with TLE due to HS and single short seizures. One patient with an incompletely resected temporal lobe tumor also exhibited ADC abnormalities. One patient in focal status epilepticus revealed a decrease in ADC, and one patient with a continuous aura had no DWI abnormality.

CONCLUSIONS

Postictal DWI technique may occasionally help delineate epileptic areas in some patients with TLE. Yield is low in patients with HS and single short seizures: it may be higher in patients with tumor or status epilepticus.

Temporal lobe epilepsy: when are invasive recordings needed?

Temporal lobe epilepsy (TLE) is the most common type of medically intractable partial epilepsy amenable to surgery. In the majority of cases, the underlying pathology in temporal lobe epilepsy is mesial temporal sclerosis (MTS). Whereas historically invasive recordings were required for most epilepsy surgeries, indications have dramatically changed since the introduction of high-resolution MRI, which uncovers structural lesions in a high percentage of cases. No invasive recordings are required to perform a temporal lobectomy in patients with intractable epilepsy who have structural imaging suggesting unilateral MTS and concordant interictal and ictal surface EEG recordings, functional imaging, and clinical findings. Invasive testing is needed if there is evidence of bitemporal MTS on structural imaging and/or electrophysiologically, and additional information from functional imaging, neuropsychology, and the intracarotid amobarbital (Wada) test also does not help to lateralize the epileptogenic zone. Depth electrodes can be particularly helpful in this setting. However, no surgery is indicated, even without invasive recordings, if bitemporal-independent seizures are recorded by surface EEG and all additional testing is inconclusive. Other etiologies of TLE such as a tumor, vascular malformation, encephalomalacia, or congenital developmental abnormality account for about 30% of all patients who undergo epilepsy surgery. Epilepsy surgery is indicated after limited electrophysiologic investigations if neuroimaging and electrophysiology converge. However, approaches for resection in lesional temporal lobe epilepsy vary among centers. Completeness of resection is crucial and invasive recordings may be needed to guide the resection by mapping eloquent cortex and/or to determine the extent of the non-MRI-visible epileptogenic area. Specific approaches for the different pathologies are discussed because there is evidence that the relationship between the lesions visible on MRI and the epileptogenic zone varies among lesions of different pathologies, and therefore variable surgical strategies must be applied.

Evidence of cingulate motor representation in humans

A 44-year-old man with a right frontal lobe tumor and intractable seizures underwent subdural grid evaluation before resection. The electrode locations were identified on a three-dimensional surface-reconstructed image of the brain after subdural grid placement. Electrical stimulation of electrodes placed over the right cingulate gyrus revealed evidence of tonic posturing of the left forearm and wrist and tonic extension of the left leg. This finding provides further evidence of a motor area in the cingulate gyrus in humans.

Periictal diffusion-weighted imaging in a case of lesional epilepsy

PURPOSE

Diffusion-weighted MR imaging (DWI) has been used for the early diagnosis of acute ischemic lesions in humans and in animal models of focal status epilepticus. We hypothesized that DWI may be a sensitive, noninvasive tool for the localization of the epileptogenic area during the periictal period.

METHODS

A periictal DWI study was performed on a 35-year-old patient during focal status epilepticus with repetitive prolonged focal motor seizures originating from a lesion in the right frontal lobe. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) maps.

RESULTS

On DWI, a single area of signal increase (decrease in ADC) was found in the region of focal electrocorticographic seizures that was mapped intraoperatively.

CONCLUSIONS

Ictal/postictal DWI may be a useful technique for seizure localization in patients with lesional epilepsy.

5'-hydroxycotinine-N-oxide, a new nicotine metabolite isolated from rat urine

1. 5'-Hydroxycotinine-N-oxide, 5-(3-pyridyl-N-oxide)-5-hydroxy-1-methyl-pyrrolidone-2, was identified as a new in vivo metabolite of nicotine. 2. The new metabolite was isolated from the urine of rats treated with S-nicotine and characterized using chemical and spectrometric methods. 3. 5'-Hydroxycotinine-N-oxide was synthesized and characterized by MS and by infrared as well as 1H- and 13C-NMR spectroscopy. 4. Identity of the new metabolite with synthetic 5'-hydroxycotinine-N-oxide was demonstrated by comparing the MS and 1H-NMR spectroscopy data as well as by co-chromatography of a spiked urine sample.

Cerebral hemodynamic response to generalized spike-wave discharges

PURPOSE

Data in the literature concerning metabolic demand during generalized spike-wave activity (gSW) are conflicting. We investigated instantaneous changes in cerebral blood flow velocities (CBFV) in both middle cerebral arteries (MCAs) by transcranial Doppler sonography (TCD) during gSW paroxysms recorded by scalp EEG.

METHODS

In 13 patients, CBFVs in both MCAs were averaged, time-locked to the occurrence of the gSW; respiratory rate (RR) and end-expiratory pco2 were measured in one patient.

RESULTS

Nine patients showed significant changes in CBFV during gSW. Four had biphasic flow changes with an initial increase (p < 0.05) and a subsequent decrease (p < 0.01). This was partially paralleled by an increase in RR (p < 0.01) and a decrease in pco2 (p < 0.01). In three patients, an increase in CBFV that preceded the onset of gSW by several seconds was observed, followed by a decrease in CBFV. Two patients showed a significant decrease only of CBFV. Only gSWs of a median duration of >0.8 s were associated with significant changes in CBFV.

CONCLUSIONS

We were able to demonstrate that gSWs of several seconds duration lead to cortical perfusion changes. We suggest that the initial increase of CBFV demonstrated in some patients reflects neuronal activation, whereas the subsequent decrease might in part be due to hyperventilation-induced hypocapnia.

PET and SPECT in medically non-refractory complex partial seizures. Temporal asymmetries of glucose consumption, benzodiazepine receptor density, and blood flow

AIM

In contrast to medically refractory complex partial seizures (CPS), only limited knowledge exists on cerebral perfusion and metabolism in medically non-refractory CPS. The aim of this study was to investigate the frequency of temporal asymmetries in regional cerebral glucose consumption (rCMRGlc), regional cerebral blood flow (rCBF), and regional cerebral benzodiazepine receptor density (BRD) in this group of patients.

METHODS

The study included 49 patients with medically non-refractory cryptogenic CPS (age: 36.0 +/- 16.1 years). rCMRGlc was studied with F-18-FDG-PET (FDG), rCBF with Tc-99m-ECD-SPECT (ECD), and BRD with l-123-iomazenil-SPECT (IMZ). All studies were performed interictally and within four weeks in each patient. Duration of epilepsy ranged from 0.1 to 42 years (median 4.0 years). SPECT was performed with the triple-headed SPECT camera Multispect 3, PET with the PET camera ECAT EXACT 47. Using linear profiles, glucose consumption, as well as uptake of ECD and IMZ, were measured in four temporal regions of interest (ROIs), and asymmetry indices were calculated (ASY). The results were compared to 95% confidence intervals determined in control subjects.

RESULTS

Thirty-five of the 49 (71%) patients had at least one significantly elevated ASY; temporal rCMRGlc was asymmetrical in 41% of the patients, temporal BRD in 29%, and temporal rCBF in 24%. One patient had an asymmetry of all three variables, two of temporal rCMRGlc and BRD, three of temporal rCMRGlc and rCBF, and another four of rCBF and BRD. Fourteen patients had an isolated temporal asymmetry in rCMRGlc, seven in BRD, and four in rCBF. A discrepancy in lateralization between the three modalities was not observed.

CONCLUSION

The majority of patients with medically non-refractory CPS have focal abnormalities of blood flow and metabolism in their temporal lobe. In this group of patients, FDG-PET demonstrates abnormalities with the highest frequency of the three modalities studied, followed by IMZ-SPECT, and ECD-SPECT.

Worsening seizures after surgery for focal epilepsy due to emergence of primary generalized epilepsy

Our patient underwent right anteromesial temporal resection at 17 years of age for intractable complex partial seizures due to hippocampal sclerosis, and then developed juvenile myoclonic epilepsy after a change in medication. Postoperative seizures ceased after a change to valproate monotherapy. Our patient reminds us to remain aware that generalized and focal epilepsy may coexist as an unusual cause for surgical failure. We feel that these patients may still be favorable candidates for epileptic surgery, as long as the focal epileptogenic zone is amenable to resection and the generalized epilepsy appears to be readily controllable.

The photic driving EEG response and photoreactive cerebral blood flow in the posterior cerebral artery in controls and in patients with epilepsy

OBJECTIVES

Instantaneous changes in blood flow velocities during visual stimulation can be assessed by transcranial Doppler sonography (TCD).

METHODS

We investigated the possible relationship between the characteristics of photic driving in the EEG elicited by repetitive intermittent photic stimulation and the photoreactive flow changes in the posterior and middle cerebral artery (PCA, MCA) of 25 normal controls and 25 patients with focal epilepsy. Cerebral blood flow velocities (CBFV) of the right PCA (P2 segment) and the left middle cerebral artery (MCA) were measured using a 2 Hz transcranial Doppler device. Simultaneously, scalp EEGs were recorded.

RESULTS

During photic stimulation the mean CBFV increase was 20.4 +/- 9.5% in the PCA of the controls (n = 132 stimulations) and 16.0 +/- 10.8% in epileptic patients (n = 150 stimulations, P < 0.01). During those stimulation series with a good EEG driving response (n = 203), the mean increase of CBFV in the PCA was 19.7 +/- 10.0%, as opposed to 14.4 +/- 10.5% during the stimulations with a poor EEG response (n = 79, P < 0.01). A good photic driving response was associated with a higher increase of CBFV in the PCA than a poor one. The increase in CBFV of the PCA in normal controls was higher than in patients with focal epilepsy.

CONCLUSIONS

This may indicate that epileptic patients have a reduced coupling between neuronal activation and blood flow.

[Routine electroencephalogram in follow-up of patients with HIV infections of different stages. A long-term study]

Electroencephalography (EEG) is a well-tolerated non-invasive method and is therefore well suited for repetitive examinations. We performed serial EEG's on 117 HIV patients without any clinical signs of secondary neuromanifestation in order to document electroencephalographic changes in the course of HIV infection. Clinical signs of HIV-associated encephalopathy presented 18 patients at the first examination and 23 at reexamination. EEGs were analyzed visually; there was a mean interval of 20.3 +/- 13.7 months between the first and the second examination. Significant slowing of background activity occurred in the course of the disease; the alpha rhythm decreased from 10.7 +/- 2.3 Hz to 10.0 +/- 2.4 Hz (P < 0.05) with an increase in amplitudes from 60.9 +/- 24.6 microV to 69.5 +/- 33.7 microV (p < 0.05). The percentage of spontaneous dysrhythmias also increased from 30.7% to 41.8% (P < 0.05); pathological findings provoked by hyperventilation increased from 13.6% to 18.2%. Foci occurred rarely and did not increase in frequency with time. CD4 cell counts decreased from 294.2 +/- 209.5/microliter to 188.7 +/- 208.3/microliter (P < 0.01). The results of this study indicate progressive CNS dysfunction with worsening of the immunostatus.

Measurement of temporal asymmetries of glucose consumption using linear profiles: reproducibility and comparison with visual analysis

AIM

One approach to regionally analyze temporal glucose consumption consists in drawing linear profiles over the maximal values measured in the temporal cortical ribbon. The aim of our study was to test the reproducibility of this method and to compare its diagnostic performance to that of visual analysis in patients with complex partial seizures (CPS).

METHODS

Regional cerebral glucose consumption (rCMRGIc) was measured interictally in 25 CPS patients and 10 controls using F-18-deoxyglucose and the positron emission tomography (PET) camera ECAT EXACT 47. The PET scans were visually analyzed for the occurrence of unilateral temporal hypometabolism. Furthermore, rCMRGIc was quantified on six contiguous coronal planes by manually tracing maximal values of temporal glucose consumption, thus creating line profiles of temporal glucose consumption for each side. Indices of asymmetry (ASY) were then calculated from these line profiles in four temporal regions and compared to the corresponding 95% confidence intervals of the control data. All analyses were performed by two observers independently from each other and without knowledge of the clinical findings.

RESULTS

The agreement between the two observers with regard to focus lateralization was 96% (kappa = 0.93) on visual analysis and 100% (kappa = 1) on quantitative analysis. There was an excellent agreement with regard to focus lateralization between visual and quantitative evaluation (kappa = 0.8).

CONCLUSION

Quantitation of local temporal rCMRGIc by using linear profile analysis is highly reproducible; for the lateralization of epileptogenic foci, however, this method does not possess significant advantages over the visual evaluation of the scans.

Spontaneous oscillations in cerebral blood flow velocities in middle cerebral arteries in control subjects and patients with epilepsy

BACKGROUND AND PURPOSE

Cardiac arrhythmias mediated by the sympathetic nervous system have been implicated in sudden, unexplained deaths in patients with epilepsy. Cerebral blood flow velocities (CBFV) as measured by transcranial Doppler are characterized by slow spontaneous oscillations in part attributed to changes in sympathetic activity (M waves, 3 to 9 cycles per minute) and to discharges of monoaminergic neurons in the brain stem (B waves, 0.5 to 2 cycles per minute). This study was designed to compare spontaneous fluctuations of CBFV in patients with epilepsy with those in normal control subjects.

METHODS

Simultaneous registrations of scalp electroencephalograms, with electrodes placed according to the 10-20 System, and transcranial Doppler recordings of both middle cerebral arteries were performed in 27 patients (9 with primary generalized epilepsy, 18 with focal epilepsy). Data analysis of CBFV was based on the envelope curves of the Doppler spectrum. A fast Fourier transformation over the 20-minute CBFV curve was performed, and the amplitudes of B and M waves were calculated and compared with those in 20 normal, age-matched control subjects.

RESULTS

While the amplitudes of the B waves in both groups were similar, patients with epilepsy showed significantly increased M waves. Patients with focal epilepsy did not present asymmetries between the normal hemisphere and the side of the epileptic focus with respect to both M and B waves.

CONCLUSIONS

Enhanced M waves in epileptic patients may reflect increased sympathetic activity even in the absence of seizures. This study provides further evidence for an autonomic dysfunction as a possible mechanism for sudden unexplained death in patients with epilepsy.

Persistent unihemispheric perceptual impairments in humans following focal seizures

Perception has been linked to a highly coordinated activation of cortical regions whose functional organization and performance is subject to plastic changes. We tested whether chronic repetitive disturbances of the brain by focal epileptic activity have a long-standing detrimental effect on the perceptual performance in the affected hemisphere. Nine patients were examined who had a history of complex partial seizures but no structural cerebral damage on magnetic resonance imaging and no evidence of ongoing epileptic activity on scalp electroencephalography and who had clinically been without seizures for at least 3 days. The side of primary epileptic involvement was determined by seizure semiology (n = 2), focal electroencephalographic slowing (n = 3) or focal abnormality during single photon emission topography (SPECT) (n = 4). The computer controlled psychometric assessment of the somesthetic frequency discrimination revealed that the perception in the hand corresponding to the affected hemisphere was impaired relative to the contralateral hand (P < 0.01), and to the performance of a group of normal controls (P < 0.01). We conclude that mechanisms related to focal epileptic activity can result in regional perceptual decrements even when there is no clinical or surface-electroencephalographic evidence of epileptic discharges. This in turn suggests that somatosensory testing may be of help in localizing, or at least lateralizing an epileptic focus.

Reduced GABAA receptor density contralateral to a potentially epileptogenic MRI abnormality in a patient with complex partial seizures

Imaging cerebral GABAA receptor density (GRD) with single-photon emission tomography (SPET) and iodine-123 iomazenil is highly accurate in lateralizing epileptogenic foci in patients with complex partial seizures of temporal origin. Limited knowledge exists on how iomazenil SPET compares with magnetic resonance imaging (MRI) in this regard. We present a patient with complex partial seizures in whom MRI had identified an arachnoid cyst anterior to the tip of the left temporal lobe. Contralaterally to this structural abnormality, interictal electroencephalography (EEG) performed after sleep deprivation disclosed an intermittent frontotemporal dysrhythmic focus with slow and sharp waves. On iomazenil SPET images GRD was significantly reduced in the right temporal lobe and thus contralaterally to the MRI abnormality, but ipsilaterally to the pathological EEG findings. These data suggest that iomazenil SPET may significantly contribute to the presurgical evaluation of epileptic patients even when MRI identifies potentially epileptogenic structural lesions.

A credentialing program for nursing staff caring for pediatric patients with an ilizarov apparatus

The purpose of this article is to provide an overview of an educational program that was implemented at a postacute pediatric rehabilitation facility to prepare the nursing staff to provide quality care for patients undergoing limb lengthening. Patients undergoing limb lengthening and limb reconstruction by the Ilizarov orthopedic method wear a highly complex external fixation device that has numerous variations. As such, it is a type of apparatus that pediatric rehabilitation nurses are unaccustomed to dealing with in the clinical arena. The nursing department at the facility described in this article undertook an intensive educational and credentialing program to ensure staff competency, parent satisfaction, and quality patient care for cases involving limb lengthening and reconstruction.

Variability of Doppler microembolic signal counts in patients with prosthetic cardiac valves

BACKGROUND AND PURPOSE

The purpose of this study was the evaluation of intraobserver, interobserver, and intrasubject variability in the Doppler detection of microembolic signals in patients with mechanical prosthetic valves. Simultaneously, the feasibility of automated embolus detection by means of a neuronal network was investigated.

METHODS

From 25 patients with mechanical prosthetic heart valves, single transcranial Doppler monitoring sessions of 30 minutes' duration were recorded on videotape, randomized, and subsequently analyzed by eight independent trained observers from three centers. Three observers evaluated these tapes on three separate occasions, blinded to their previous results. An additional 48 patients with prosthetic heart valves were repetitively monitored with transcranial Doppler ultrasonography for 30 minutes three times within 1 year to examine the long-term variability in the occurrence of microembolic signals. Finally, in an effort to assess the short-term intrasubject variability, 20 patients were examined for 90 minutes, and the results of the three 30-minute periods were compared. The interobserver, intraobserver, and intrasubject (both short- and long-term) variability was evaluated.

RESULTS

No significant differences in microembolic signal counts were found among the different observers, between the human observers and the neuronal network, or among the three separate evaluations of stored data by the same observer. The same was true for repeat examinations of the same patient (P > .05, Student's two-paired t test and Friedman's test).

CONCLUSIONS

The detection of microembolic signals in patients with prosthetic cardiac valves is a reproducible technique. The reliable performance of the neuronal network argues for a broader use of this device. The intrasubject stability of the microembolic rate over 1 year supports the concept that the underlying emboligenic process is associated with intrinsic mechanical properties of the valve implant and not due to a thromboembolic process in the heart.

Variability of Doppler Microembolic Signal Counts in Patients With Prosthetic Cardiac Valves

Background and Purpose The purpose of this study was the evaluation of intraobserver, interobserver, and intrasubject variability in the Doppler detection of microembolic signals in patients with mechanical prosthetic valves. Simultaneously, the feasibility of automated embolus detection by means of a neuronal network was investigated.

Methods From 25 patients with mechanical prosthetic heart valves, single transcranial Doppler monitoring sessions of 30 minutes’ duration were recorded on videotape, randomized, and subsequently analyzed by eight independent trained observers from three centers. Three observers evaluated these tapes on three separate occasions, blinded to their previous results. An additional 48 patients with prosthetic heart valves were repetitively monitored with transcranial Doppler ultrasonography for 30 minutes three times within 1 year to examine the long-term variability in the occurrence of microembolic signals. Finally, in an effort to assess the short-term intrasubject variability, 20 patients were examined for 90 minutes, and the results of the three 30-minute periods were compared. The interobserver, intraobserver, and intrasubject (both short- and long-term) variability was evaluated.

Results No significant differences in microembolic signal counts were found among the different observers, between the human observers and the neuronal network, or among the three separate evaluations of stored data by the same observer. The same was true for repeat examinations of the same patient ( P >.05, Student’s two-paired t test and Friedman’s test).

Conclusions The detection of microembolic signals in patients with prosthetic cardiac valves is a reproducible technique. The reliable performance of the neuronal network argues for a broader use of this device. The intrasubject stability of the microembolic rate over 1 year supports the concept that the underlying emboligenic process is associated with intrinsic mechanical properties of the valve implant and not due to a thromboembolic process in the heart.

A double-blind comparison of amitriptylinoxide versus doxepine in the treatment of severe depression

In a double-blind parallel group study the efficacy and safety of amitriptylinoxide were evaluated vs. doxepine in the treatment of in-patients with severe depression. Two groups of 22 patients each received amitriptylinoxide and doxepine respectively at a daily dosage of 120-360 mg for a period of 4 weeks. The total score on the Hamilton Depression Scale (HAMD) was reduced with amitriptylinoxide on an average from 28 +/- 5 before treatment to 12 +/- 8 at the end of treatment, with doxepine from 29 +/- 8 to 13 +/- 11. Of the amitriptylinoxide-treated patients, 12 showed a more than 50% reduction in this score compared with 15 under doxepine. The difference was not statistically significant. Twenty patients in each group experienced adverse drug reactions, the percentage of anticholinergic side effects being equal in the two groups.

The influence of mechanical stimuli and of acetylsalicylic acid on the discharges of slowly conducting afferent units from normal and inflamed muscle in the rat

In anaesthetized rats, the influence of an experimental inflammation and of acetylsalicylic acid (ASA) on the discharge properties of muscle receptors with slowly conducting afferent fibres was studied using a single-fibre recording technique. Following the induction of a myositis with carrageenan, the proportion of units having background activity and the frequency of the background discharge were significantly increased. The latter change was particularly prominent in high-threshold mechanosensitive (HTM) units. There was evidence for an inflammation-induced lowering of mechanical threshold in HTM units, but the change was not statistically significant. Administration of ASA intravenously led to a decrease in the frequency of background discharge in some units while others were unaffected, although they appeared to be sensitized by the inflammation. If one assumes that at least some of the HTM receptors fulfil nociceptive functions, the results suggest that the pain and tenderness of an inflamed muscle is largely due to a sensitization and hence increased activity of nociceptive muscle receptors. The sensitization is only partially abolished by ASA.

Spontaneous oscillations in cerebral blood flow velocity in normal humans and in patients with carotid artery disease

Spontaneous oscillations in cerebral blood flow velocity (CBFV) in normals and in patients with stenoses or occlusions of the internal cerebral artery were measured using transcranial Doppler sonography. In normal subjects, large oscillations of up to +/- 30% from the mean CBFV were found with low frequencies between 0.4 and 9 cycles/min. No correlations between CBFV oscillations and systemic circulatory parameters were detected. In patients with carotid artery obstructions the CBFV oscillations were significantly reduced in the middle cerebral artery ipsilaterally to a hemodynamically significant lesion, but not contralaterally. Our results support the hypothesis that spontaneous oscillations (B-waves) of small pial vessels are responsible for the CBFV fluctuations.

Histological and neurophysiological changes induced by carrageenan in skeletal muscle of cat and rat

Infiltration of the rat gastrocnemius-soleus (GS) muscle with carrageenan induced a myositis which was characterized histologically by an accumulation of polymorphonuclear leukocytes around capillaries and small arterioles. In chloralose-anaesthetized cats having an inflamed GS-muscle, the discharge behaviour of single muscle receptors with group III and IV afferent fibres was recorded. Concerning background activity, only group III receptors showed a significant increase, whereas a significant lowering in mechanical threshold was present only among group IV receptors. Both high- and low-threshold mechanosensitive receptors showed signs of a sensitization. In contrast to group IV receptors in the cat, rat group IV receptors showed a significantly higher level of background activity in inflamed muscle but no increased responsiveness to mechanical stimuli. Acetylsalicylic acid (ASA) influenced only some of the receptors in the inflamed tissue. Leukotriene D4 did not act as a sensitizing substance but depressed the activity of group IV muscle receptors.

Cerebral blood flow in autogenic training and hypnosis

In 12 healthy volunteers with at least an experience of six months in autogenic training (AT), the cerebral blood flow (CBF) was measured at rest, in AT and in hypnosis (H). The results were correlated with individual test profiles. The cortical flow pattern at rest of our AT trained volunteers did not show the hyperfrontality which is described in the literature. This may be interpreted as an effect of better and habitualized relaxation in long trained AT practitioners. This flow pattern corresponds to the low grades of neuroticism and aggressivity found in the tests. Furthermore an activation in central cortical areas and a deactivation in regions which are associated with acoustic and autonomous functions occur. Possible explanations for these phenomena as well as for the relatively low perfusion of the left hemisphere at rest and activation in AT are discussed. The global rise of CBF in H may be an activation effect caused by resistance against the hypnotizer: the deeper the trance, the smaller the CBF increase in the motor cortical area needed for maintaining catalepsy of the right arm and in temporal cortical fields processing acoustic inputs.

Single base-pair mutations in centromere element III cause aberrant chromosome segregation in Saccharomyces cerevisiae

In this paper we show that a 211-base pair segment of CEN3 DNA is sufficient to confer wild-type centromere function in the yeast Saccharomyces cerevisiae. We used site-directed mutagenesis of the 211-base pair fragment to examine the sequence-specific functional requirements of a conserved 11-base pair segment of centromere DNA, element III (5'-TGATTTATCCGAA-3'). Element III is the most highly conserved of the centromeric DNA sequences, differing by only a single adenine X thymine base pair among the four centromere DNAs sequenced thus far. All of the element III sequences contain specific cytosine X guanine base pairs, including a 5'-CCG-3' arrangement, which we targeted for single cytosine-to-thymine mutations by using sodium bisulfite. The effects of element III mutations on plasmid and chromosome segregation were determined by mitotic stability assays. Conversion of CCG to CTG completely abolished centromere function both in plasmids and in chromosome III, whereas conversion of CCG to TCG decreased plasmid and chromosome stability moderately. The other two guanine X cytosine base pairs in element III could be independently converted to adenine X thymine base pairs without affecting plasmid or chromosome stability. We concluded that while some specific nucleotides within the conserved element III sequence are essential for proper centromere function, other conserved nucleotides can be changed.