Ansgar Quiske

Determination of hemisphere dominance for language: comparison of frontal and temporal fMRI activation with intracarotid amytal testing

The reliability of frontal and temporal fMRI activations for the determination of hemisphere language dominance was evaluated in comparison with intracarotid amytal testing (IAT). Twenty-two patients were studied by IAT (bilateral in 13, unilateral in 9 patients) and fMRI using a paradigm requiring semantic decisions. Global and regional (frontal and temporoparietal) lateralisation indices (LI) were calculated from the number of activated (r>0.4) voxels in both hemispheres. Frontolateral activations associated with the language task were seen in all patients, temporoparietal activations in 20 of 22. Regional LI corresponded better with IAT results than global LI. Frontolateral LI were consistent with IAT in all patients with bilateral IAT (including three patients with right dominant and one patient with bilateral language representation) and were not conflicting in any of the patients with unilateral IAT. Temporoparietal LI were discordant with IAT in two patients with atypical language representation. In the determination of hemisphere dominance for language, regional analysis of fMRI activation is superior to global analysis. In cases with clear-cut fMRI lateralisation, i.e. consistent lateralised activation of frontal and temporoparietal language zones, IAT may be unnecessary. FMRI should be performed prior to IAT in all patients going to be operated in brain regions potentially involved in language.

The reliability of fMRI activations in the medial temporal lobes in a verbal episodic memory task.

The test-retest reliability of activation patterns elicited by encoding and recognition of word-pair associates within the whole brain and a predefined medial temporal region of interest (ROI) was investigated. Twenty healthy right-handed subjects were studied within two sessions, either on the same day or 210-308 days later. Three quantitative measures of reliability were calculated for the contrasts encoding and recognition versus a control condition within the ROI and also for the whole brain: A group correlational analysis between the lateralization indices of the first and second session, correlations of the individual SPM(t) maps of the first and the second run, and overlap ratios between both sessions. For the ROI, correlational analysis of lateralization indices during both encoding trials was significant. Eighty percent of the individual positive correlation coefficients of SPM(t) maps during encoding, and 75% during recognition reached significance. The mean percentage of overlapping voxels was 18% during encoding and 19% during recognition. The reproducibility measures evaluated for the whole brain demonstrated significantly higher values compared to the ROI. For the group that stayed inside the scanner, better whole brain test-retest reliability was observed, and no influence of the memory process (encoding or recognition) on reproducibility was found.

Precuneus is involved in allocentric spatial location encoding and recognition

Using a declarative memory paradigm, the anatomical correlates of spatial location encoding and retrieval in the healthy human brain as reflected by BOLD fMRI were investigated. During encoding, subjects were instructed to view and keep in mind different locations of an object on a platform seen from different viewpoints in virtual 3D. In retrieval trials, subjects had to recognize previously learned object locations. Comparing activation patterns associated with encoding and recognition on a voxel-by-voxel basis, we found regions in the precuneus bilaterally activated by both processes. To our knowledge, this is the first study that directly compared human brain activation patterns associated with allocentric encoding and retrieval of spatial locations in virtual 3D. Our results provide further information concerning the role of the precuneus in declarative memory processes, pointing to precuneus involvement in encoding and retrieval of spatial locations.

Cognitive Functions in Juvenile and Adult Patients with Gelastic Epilepsy due to Hypothalamic Hamartoma

Summary:  Purpose: To describe extend and severity of cognitive deficits in juvenile and adult patients with gelastic seizures and hypothalamic hamartoma (HH) and to analyze the impact of epilepsy‐related variables on cognitive performance.

Unsuspected Atypical Hemispheric Dominance for Language as Determined by fMRI

Summary:  Purpose: We sought to illustrate the value of functional magnetic resonance imaging (fMRI) in the presurgical assessment of hemispheric dominance for language by means of an illustrative case report.

Kognitive Beeinträchtigungen unter Add-on-Therapie mit Topiramat

ZusammenfassungIn einer offenen Studie wurden 37 Epilepsiepatienten hinsichtlich kognitiver Beeinträchtigungen unter antikonvulsiver Add-on-Therapie mit Topiramat (TPM) untersucht. TPM wurde zusätzlich zu einer bereits bestehenden antikonvulsiven 1- bis 3fach-Kombinationsbehandlung in Schritten von maximal 25 mg/Woche eindosiert. Die Patienten wurden bezüglich kognitiver Nebenwirkungen befragt; subjektiv oder in der Untersuchung auffallende Defizite wurden in standardisierten neuropsychologischen Tests objektiviert. Bei 18/37 Patienten (49%) traten kognitive Beeinträchtigungen in Form von Konzentrationsstörungen, psychomotorischer Verlangsamung, mnestischen Störungen und Dysphasien auf. Die Nebenwirkungen wurden unter TPM-Dosen von 50–575 (Durchschnitt 210) mg/Tag beobachtet. Nach Dosisreduktion von TPM um 25–150 mg/Tag waren sie bei 4 Patienten rückläufig. Bei 8 Patienten führten sie zum Absetzen von TPM. Zusammenfassend zeigte sich trotz langsamer Eindosierung eine höhere Frequenz kognitiver Nebenwirkungen unter TPM als in früheren Studien berichtet. Diese führten z. T. zu erheblichen Beeinträchtigungen im Alltag und am Arbeitsplatz. Zur frühzeitigen Erkennung von Beeinträchigungen empfehlen sich eine neuropsychologische Baseline-Erhebung sowie Follow-up-Untersuchungen von Wortflüssigkeit, kognitiver Verarbeitungsgeschwindigkeit und verbalen Gedächtnisleistungen.SummaryIn an open study, 37 epilepsy patients were investigated with regard to cognitive impairments in anticonvulsant add-on therapy with topiramate (TPM). In addition to a preexisting antiepileptic medication, TPM administration was started and increased by 25 mg/week. Cognitive side effects noted by the patient or doctor were assessed by a neuropsychological test battery. In 18/37 patients (49%), cognitive deficits consisting of impaired concentration, psychomotoric slowing, memory deficits, and dysphasia were observed. The adverse effects became apparent at dosages of 50–575 mg TPM/day (average 210 mg). In four patients, they were reversible after reducing the dose of TPM by 25–150 mg/day. In eight patients, the adverse effects led to withdrawal of TPM. In spite of slow titration, the present study showed a higher frequency of cognitive side effects under TPM than was previously reported. In some patients, these side effects led to substantial impairments in daily life and at work. For early recognition of cognitive impairments, neuropsychological baseline and follow-up investigations of verbal fluency, psychomotor processing speed, and verbal memory are recommended.

Assessment of cognitive functions before and after stereotactic interstitial radiosurgery of hypothalamic hamartomas in patients with gelastic seizures.

We assessed cognitive functions before and 3 months after interstitial radiotherapy in 14 patients with gelastic seizures caused by hypothalamic hamartoma. Cognitive functioning was assessed before temporary implantation of (125)I-seed and 3 months after seed explantation. Performance was compared with that of a selected control group of conservatively treated patients with symptomatic focal epilepsy tested before add-on treatment with a new antiepileptic drug and after reaching steady state. No short-term negative side effects of the interstitial radiosurgery could be observed for the domains of attention and executive functions and verbal and figural memory performance. Cognitive development of the patients treated with seeds was comparable to that of the control group at both assessments. Thus, the stereotactic implantation of (125)I-seeds in this patient group with gelastic seizures caused by hypothalamic hamartoma provides a well-tolerated minimally invasive method in the treatment of this severe epileptic syndrome without negative cognitive side effects.

Stellenwert der fMRT zur Bestimmung der zerebralen Sprachdominanz

ZusammenfassungDie Bestimmung der zerebralen Sprachrepräsentation ist wesentlicher Bestandteil der prächirurgischen Diagnostik vor Operationen in potentiell sprachrelevanten Regionen, insbesondere vor elektiven epilepsiechirurgischen Eingriffen. Die etablierten Verfahren Wada-Test und kortikale Stimulation sind invasiv und belastend. Seit ca. 10 Jahren steht die funktionelle Magnetresonanztomographie (fMRT) als nichtinvasive Alternative zur Verfügung. Obwohl in zahlreichen Untersuchungen eine gute Übereinstimmung der Ergebnisse von fMRT und Wada-Test gezeigt werden konnte, gibt es keine allgemein akzeptierten Empfehlungen, in welchen Fällen auf einen Wada-Test verzichtet werden kann. In der vorliegenden Zusammenstellung untersuchten die Autoren, wie sich das diagnostische Procedere seit der klinischen Einführung der Sprach-fMRT an ihrer Institution verändert hat. Seit 1999 wurden in Freiburg 208 Sprach-fMRTs bei 198 Patienten durchgeführt. Im gleichen Zeitraum reduzierte sich der relative Anteil der Patienten der Sektion Prächirurgische Epilepsiediagnostik, bei denen ein Wada-Test durchgeführt wurde, um ca. 50%. Der Anteil der Sprach-fMRTs, der vorwiegend aufgrund mangelhafter Kooperationsfähigkeit der Patienten nicht verwertbar war, lag in den vergangenen 2 Jahren < 10%. Nach Ansicht der Autoren besteht lediglich noch in den Fällen eine zwingende Indikation für einen Wada-Test, in denen keine Sprach-fMRT durchführbar ist oder die fMRT therapeutisch entscheidende Fragen nicht beantworten kann.AbstractDetermination of hemispheric language dominance is an essential step in the diagnostic workup prior to surgery in brain regions potentially involved in language. The established methods Wada test and cortical stimulation are invasive and cumbersome. For a decade, functional magnetic resonance imaging (fMRI) has allowed for the noninvasive determination of cerebral language representation. Numerous studies have shown good correlation between the results of language fMRI and invasive procedures. However, there are no generally accepted proposals in which cases invasive diagnostic procedures might be dispensable. The authors studied how the diagnostic regimen has changed in their institution since the clinical implementation of language fMRI. Since 1999, 208 language fMRIs have been performed in 198 patients in Freiburg. During this period the percentage of patients at the Department of Presurgical Epilepsy Diagnosis receiving a Wada test decreased by 50%. In the last 2 years < 10% of the fMRIs were not utilizable, most often due to motion artifacts. In the authors’ opinion fMRI should be the diagnostic method of first choice in all patients in whom surgery is planned in brain regions potentially involved in language. Only if further questions of therapeutic relevance are present, additional invasive procedures are mandatory.

Selective or Superselective Wada Test for Postoperative Memory Prediction

The authors present a patient with medically intractable left-sided temporal lobe epilepsy and severe memory impairments. After failure of the intracarotid amobarbital procedure for postoperative memory prediction, a superselective Wada test via the anterior choroid artery was carried out. With regard to a sufficient memory performance during this superselective procedure, the patient underwent selective amygdalohippocampectomy. Postoperatively, the patient has become seizure-free with nearly unchanged memory performance. The case demonstrates the usefulness of the superselective Wada test in a patient who failed the memory testing during standard intracarotid amobarbital procedure.ZusammenfassungDie Autoren stellen einen Patienten mit einer pharmakoresistenten linksseitigen Temporallappenepilepsie und hochgradigen Gedächtnisstörungen vor. Nachdem der intrakarotidale Amobarbitaltest zur postoperativen Gedächtnisprognose nicht aussagekräftig war, wurde ein superselektiver Wada-Test über die Arteria chorioidea anterior durchgeführt. Aufgrund der in diesem superselektiven Verfahren gezeigten hinreichenden Gedächtnisleistungen wurde eine selektive Amygdalohippokampektomie durchgeführt. Postoperativ ist der Patient anfallsfrei und zeigt weitgehend unveränderte Gedächtnisleistungen. Der Fall zeigt die Nützlichkeit des superselektiven Wada-Tests in der Vorhersage postoperativer Gedächtnisleistungen.