Role of the parahippocampal cortex in memory for the configuration but not the identity of objects: converging evidence from patients with selective thermal lesions and fMRI.

The parahippocampal cortex and hippocampus are brain structures known to be involved in memory. However, the unique contribution of the parahippocampal cortex remains unclear. The current study investigates memory for object identity and memory of the configuration of objects in patients with small thermo-coagulation lesions to the hippocampus or the parahippocampal cortex. Results showed that in contrast to control participants and patients with damage to the hippocampus leaving the parahippocampal cortex intact, patients with lesions that included the right parahippocampal cortex (RPH) were severely impaired on a task that required learning the spatial configuration of objects on a computer screen; these patients, however, were not impaired at learning the identity of objects. Conversely, we found that patients with lesions to the right hippocampus (RH) or left hippocampus (LH), sparing the parahippocampal cortex, performed just as well as the control participants. Furthermore, they were not impaired on the object identity task. In the functional Magnetic Resonance Imaging (fMRI) experiment, healthy young adults performed the same tasks. Consistent with the findings of the lesion study, the fMRI results showed significant activity in the RPH in the memory for the spatial configuration condition, but not memory for object identity. Furthermore, the pattern of fMRI activity measured in the baseline control conditions decreased specifically in the parahippocampal cortex as a result of the experimental task, providing evidence for task specific repetition suppression. In summary, while our previous studies demonstrated that the hippocampus is critical to the construction of a cognitive map, both the lesion and fMRI studies have shown an involvement of the RPH for learning spatial configurations of objects but not object identity, and that this takes place independent of the hippocampus.

Cognitive outcome after stereotactic amygdalohippocampectomy.

PURPOSE: We sought to determine the neuropsychological outcome after stereotactic radiofrequency amygdalohippocampectomy performed for intractable mesial temporal lobe epilepsy. METHODS: The article describes the cases of 31 patients who were evaluated using the Wechsler Adult Intelligence Scale-Revised and the Wechsler Memory Scale-Revised prior to, and one year after, surgery. KEY FINDINGS: Patients showed increases in their mean Full Scale, Verbal and Performance IQ scores of 4, 3 and 4 IQ points respectively (p<.05). 5 (17.2%), 4 (13.8%) and 4 (13.3%) patients improved in their Full-scale, Verbal and Performance IQ respectively. No significant changes were found in memory performance - with a mean increase of 1, 3 and 0 MQ points in Global, Verbal and Visual memory respectively (p<.05). Global memory improved in 3 (10.3%) patients, verbal memory in 1 (3.4%) and 1 patient (3.3%) showed deterioration in visual memory. SIGNIFICANCE: Our results provide evidence for unchanged memory in patients with MTLE after the procedure. No verbal memory deterioration was detected in any of our patients, while improvements were found in intellectual performance. The results suggest that stereotactic radiofrequency amygdalahippocampectomy could be superior to open surgery in terms of its neurocognitive outcomes. A larger randomised trial of these approaches is justified.

[Temporal lobe epilepsy in adults and possibilities of neurosurgical treatment: the role of magnetic resonance]. / Temporální epilepsie dospelých a moznosti neurochirurgické lécby: úloha magnetické rezonance.

Temporal lobe epilepsy is the most common type of focal epilepsy diagnosed in adult patients. According to the location of seizure generation it is classified as mesial temporal lobe epilepsy and neocortical lateral lobe epilepsy. Diagnosis of temporal lobe epilepsy can be proved by the combination of the clinical manifestation of partial complex seizures, scalp-video EEG monitoring, results of magnetic resonance imaging (MRI) and imaging of interictal fluoro-deoxy-glucose positron emission tomography. Mesial temporal sclerosis is the most common finding on MRI. Temporal lobe epilepsy is the most surgically amenable diagnosis and results of surgery treatments are clearly superior to the prolonged medical therapy; surgical treatment of the mesial temporal epilepsy with mesial temporal sclerosis has the best clinical results. Except for standard microsurgical approaches such as anterior temporal resection and selective amygdalo-hippocampectomy, stereotactic thermocoagulation amygdalo-hippocampectomy is provided in our epilepsy centre. This alternative approach has comparable clinical outcome to the standard surgery approaches in 2 years clinical follow-ups. MRI is important not only in diagnostic procedures, but also in neuronavigation of surgery approaches, per operation control of the extent of resections and postoperative follow-ups, especially in failed epilepsy surgery.

Stereotactic radiofrequency amygdalohippocampectomy in the treatment of mesial temporal lobe epilepsy.

PURPOSE: Minimally invasive percutaneous single trajectory stereotactic radiofrequency amygdalohippocampectomy was used to treat mesial temporal lobe epilepsy (MTLE). The aim of the study was to evaluate complications and effectiveness of this procedure. MATERIALS AND METHODS: A group of 51 patients with MTLE was treated using stereotactic thermo-lesion of amygdalohippocampal complex under local anaesthesia. The target was reached through the occipital approach with a single trajectory using MRI stereotactic localisation. Thermocoagulation of the amygdalohippocampal complex was planned according to the individual anatomy of each patient. Amygdalohippocampectomy was performed using a string electrode with a 10-mm active tip, and 16-38 lesions (median = 25) were performed in all patients along the 30- to 45-mm trajectory (median = 35) in the amygdalohippocampal complex. RESULTS: The procedure was well tolerated by all patients with no severe permanent morbidity; meningitis was recorded in two patients (4%), hematoma was detected in four patients, clinically insignificant in three of them, and one patient required temporary ventricular drainage (2%). Thirty-two patients were followed up over at least 2 years, and the clinical outcomes were evaluated by Engel's classification; 25 of them (78%) were Engel I, five (16%) were Engel II, and two (6%) were Engel IV. CONCLUSIONS: Stereotactic amygdalohippocampectomy is a minimally invasive procedure with low morbidity and good results that can be the method of choice in selected patients with MTLE.

Microsurgical and stereotactic radiofrequency amygdalohippocampectomy for the treatment of mesial temporal lobe epilepsy: different volume reduction, similar clinical seizure control.

We compared stereotactic radiofrequency amygdalohippocampectomy (SAHE) with microsurgical amygdalohippocampectomy (AHE) in a group of 33 patients with mesial temporal lobe epilepsy in terms of hippocampal and amygdalar volume reductions and clinical outcome. In 23 subjects treated by SAHE, the hippocampal volume decreased by 58.0% (20.0; median, quartile range), with p = 10(-4), and the amygdalar volume decreased by 55.2% (23.8), with p = 10(-4). Two years after SAHE, 74% of patients were classified as class I, 22% as class II and 4% as class III. In 10 subjects treated by AHE, 83.5% (11.2) of the hippocampal and 53.1% (53.9) of the amygdalar volumes were removed (p = 0.05 and p = 0.005, respectively). Two years after the operation, 50% of the subjects were classified as class I, 30% as class II and 10% as class III and IV. To conclude, SAHE leads to a similar reduction of the amygdalar volume but to a significantly lower reduction of the hippocampal volume than AHE. The clinical outcome of SAHE is comparable with that of AHE.

The use of radiosurgery for the treatment of mesial temporal lobe epilepsy and long-term results.

PURPOSE: To determine the efficacy of gamma knife radiosurgery in the treatment of mesial temporal lobe epilepsy due to mesial temporal sclerosis. METHODS: Between November 1995 and May 1999, 14 patients underwent radiosurgical entorhinoamygdalohippocampectomy with a marginal dose of 18, 20, or 25 Gy to the 50% isodose following a standard preoperative epilepsy evaluation. RESULTS: One patient was classified as Engel Class Ib, three were Engel Class IIc, one was Engel Class IIIa, and two were Engel Class IVb in a subgroup of seven patients who were unoperated 2 years prior to the last visit and at least 8 years after irradiation (average 116 months). The insufficient effect of irradiation led us to perform epilepsy surgery on another seven patients an average of 63.5 months after radiosurgery. The average follow-up period was 43.5 months after the operation. Four patients are seizure-free; one is Engel Class IIb and one is Engel Class IId. One patient cannot be classified due to the short period of follow-up. The frequency of seizures tended to rise after irradiation in some patients. Collateral edema was observed in nine patients, which started earlier and was more frequent in those irradiated with higher doses. It had a marked expansive character in three cases and clinical signs of intracranial hypertension were present in three cases. We found partial upper lateral quadrant anopia as a permanent side effect in two patients. Repeated psychotic episodes (two patients) and status epilepticus (two patients) were also seen after treatment. No significant memory changes occurred in the group as a whole. DISCUSSION: Radiosurgery with 25, 20, or 18-Gy marginal dose levels did not lead to seizure control in our patient series, although subsequent epilepsy surgery could stop seizures. Higher doses were associated with the risk of brain edema, intracranial hypertension, and a temporary increase in seizure frequency.

Sleep apnea in carotid stenosis.

OBJECTIVES: Sleep apnea is associated with advanced atherosclerosis. This study was focused on sleep breathing in patients with hemodynamically significant carotid stenosis, currently free from clinical symptoms. DESIGN AND SETTINGS: 17 patients with carotid artery stenosis of 70% and more in the absence of actual neurological symptoms indicated for non-acute endarterectomy, and 17 age- and sex-matched controls were examined using sleep polygraphy. 12 patients had a follow-up sleep polygraphy a month after the surgery. RESULTS: The criteria of obstructive sleep apnea (OSA) were met by 4 patients prior to operation, by 2 patients after the operation, and by 2 control subjects. The pre-surgery apnea/hypopnea index (AHI) was 14 (+/-SD=17.0), post-surgery 8.3 (+/-9.0) and in the controls 6.7(+/-6.7). The pre-surgery oxygen desaturation index was 20.1 (+/-17.7), post-surgery 15.0 (+/-12.0) and in the controls 11.6 (+/-6.1). A comparison between the pre-surgery results seen in the patients and in controls after adjustment for BMI revealed no significant difference. The only significant difference between the pre-surgery and post-surgery values was found in the AHI (P=0.045). CONCLUSION: According to this study there exists an association between carotid stenosis and OSA, however this association is explainable by a higher BMI. The study also found a tendency toward OSA alleviation in response to endarterectomy.

Stereotactic radiofrequency amygdalohippocampectomy for the treatment of mesial temporal lobe epilepsy: correlation of MRI with clinical seizure outcome.

SUMMARY: Stereotactic radiofrequency amygdalohippocampectomy (AHE) has been reintroduced as an alternative treatment of mesial temporal lobe epilepsy. The aim of this study was to describe MRI changes after stereotactic AHE and to correlate the hippocampal and amygdalar volumes reduction with the clinical seizure outcome. Eighteen patients after stereotactic AHE were included. Volumetry was calculated from pre-operative MRI and from MRI obtained 1 year after the operation. The clinical outcome was examined 1 and 2 years after the treatment. Hippocampal volume decreased by 54+/-19%, and amygdalar volume decreased by 49+/-18%. One year after the procedure, 13 (72%) patients were classified as Engel's Class I (9 as Class IA), 4 (22%) patients as Class II and 1 (6%) patient as Class III. Two years after the operation, 14 patients (82%) were classified as Class I (7 as Class IA) and 3 patients (18%) as Class II. We found 3 surgical complications after the procedure: one small subdural hematoma, and twice a small electrode tip left in operation field (these patients were excluded from the study). In 3 patients, temporary meningeal syndrome developed. Results of radiofrequency AHE are promising. The volume reduction of target structures after AHE is significantly related to the clinical outcome.

Vagus nerve stimulation: longitudinal follow-up of patients treated for 5 years.

We performed a retrospective, multicenter, open-label study to evaluate the efficacy of vagus nerve stimulation (VNS) in all patients in the Czech Republic who have received this treatment for at least 5 years (n=90). The mean last follow-up was 6.6+/-1.1 years (79+/-13 months). The median number of seizures among all patients decreased from 41.2 seizures/month in the prestimulation period to 14.9 seizures/month at 5 years follow-up visit. The mean percentage of seizure reduction was 55.9%. The responder rate in these patients is in concordance with the decrease of overall seizure frequency. At 1 year after beginning the stimulation, 44.4% of patients were responders; this percentage increased to 58.7% after 2 years. At the 5 years last follow-up 64.4% of patients were responders, 15.5% experienced > or = 90% seizure reduction, and 5.5% were seizure-free. A separate analysis of patients younger than 16 years of age showed lower efficacy rates of VNS in comparison to the whole group. Complications and chronic adverse effects occurred in 13.3% of patients. VNS is an effective and safe method to refractory epilepsy in common clinical practice.

Stereotactic amygdalohippocampectomy for temporal lobe epilepsy: promising results in 16 patients.

OBJECTIVES: Minimally invasive procedures for treating temporal lobe epilepsy have been investigated recently, namely stereotactic and gamma knife amygdalohippocampectomy (AHE). However, the results are not fully satisfactory. Our aim was to evaluate efficacy and side-effects of stereotactic AHE mimicking the neurosurgical procedure in terms of extent of the lesion. METHODS: 16 consecutive patients were assessed using VEEG, MRI, FDG-PET and WADA test. All had definite pharmacoresistant medial temporal lobe epilepsy. The stereotactic AHE was performed on the Leksell stereotactic system. All lesions exceeded 40 mm along the long axis of the hippocamus. RESULTS: Seizure outcome was favourable on one year follow-up: 12 patients (75%) were seizure-free (Engel I), three (19%) were Engel II, and one (6%) was Engel III. Side-effects were mild, lasting up to 7 days: cephalea, meningeal syndrome with sterile CSF in three subjects, and CSF leak lasting up to 3 days in seven subjects. CONCLUSION: Stereotactic AHE encompassing sufficient volume of the amygdalohippocampal complex appears to be safe, effective, and free from long-term side-effects.

Object-location memory impairment in patients with thermal lesions to the right or left hippocampus.

Memory for object-location was investigated by testing subjects with small unilateral thermolesions to the medial temporal lobe using small-scale 2D (Abstract) or large-scale 3D (Real) recall conditions. Four patients with lesions of the left hippocampus (LH), 10 patients with damage to the right hippocampus (RH) and 9 matched normal controls (NC) were tested. Six task levels were presented in a pseudorandom order. During each level, subjects viewed one to six different objects on the floor of a circular curtained arena 2.90 m in diameter for 10 s. Recall was tested by marking the locations of objects on a map of the arena (Abstract recall) and then by replacing the objects in the arena (Real recall). Two component errors were studied by calculating the Location Error (LE), independent of the object identity and the configuration error by finding the best match to the presented configuration. The RH group was impaired relative to the NC for nearly all combinations of recall and error types. An impairment was observed in this group even for one object and it deepened sharply with an increasing object number. Damage to the right perirhinal or parahippocampal cortices did not add to the impairment. Deficits in the LH group were also observed, but less consistently. The data indicate that spatial memory is strongly but not exclusively lateralised to the right medial temporal lobe.

A battery of tests for quantitative examination of idiothetic and allothetic place navigation modes in humans.

Research into the neural mechanisms of place navigation in laboratory animals has led to the definition of allothetic and idiothetic navigation modes that can be examined by quantitative analysis of the generated tracks. In an attempt to use this approach in the study of human navigation behavior, 10 young subjects were examined in an enclosed arena (2.9 m in diameter, 3 m high) equipped with a computerized tracking system. Idiothetic navigation was studied in blindfolded subjects performing the following tasks-Simple Homing, Complex Homing and Idiothesis Supported by Floor-Related Signals. Allothetic navigation was examined in sighted subjects instructed to find in an empty arena the acoustically signaled unmarked goal region and later to retrieve its position using tasks (Natural Navigation, Cue-Controlled Navigation, Snapshot Memory, Map Reading) that evaluated different aspects of allothesis. The results indicate that allothetic navigation is more accurate than idiothetic, that the poor accuracy of idiothesis is due to angular rather than to distance errors, and that navigation performance is best when both allothetic and idiothetic modes contribute to the solution of the task. The proposed test battery may contribute to better understanding of the navigation disturbances accompanying various neurological disorders and to objective evaluation of the results of drug therapy and of rehabilitation procedures.