Alteration of functional neuroanatomy of simple object memory in medial temporal lobe epilepsy patients

Using H2 15O PET, we examined the neuroanatomy associated with a simple form of episodic memory in patients with right or left medial temporal lobe epilepsy and normal healthy controls. When line drawings of common objects were memorized and tested after a 30 min delay, no behavioral difference was found between the patient groups and the controls. However, the patients with epilepsy showed greater cortical activations than the control group on the side ipsilateral to the epileptic focus. rCBF in the anterior thalamic region was enhanced in patients relative to the control group. The results showed that long-term dysfunction of the medial temporal lobe might reinforce alternative memory pathways and recruit a distributed cortical network ipsilateral to their epilepsy focus.     

Epilepsia partialis continua studied by PET

We report an [18F]fluordeoxyglucose (FDG)-PET study performed in an 11-year-old girl with a 5-month history of epilepsia partialis continua (epc). Visual inspection of PET images showed a hypermetabolic focus in the right central cortex and in the ipsilateral thalamus, which was confirmed by the absolute values of regional cerebral glucose metabolism (rCMRGlu). The thalamic hypermetabolism provides evidence for an involvement of thalamic nuclei in this ictally epileptic process. The scalp EEG revealed a theta-delta and sharp wave focus in the right Rolandic cortex at the same location as the hypermetabolic zone seen in PET. Simultaneously recorded EMG of the left tibialis anterior muscle showed regular jerks, time-locked to the sharp waves at the right central region, and myoclonic 'storms' during focal motor seizures. The results of the brain biopsy and the child's clinical course led us to a diagnosis of 'chronic encephalitis' of Rasmussen.     

Metabolic changes of subcortical structures in intractable focal epilepsy

PURPOSE: Intractable focal epilepsy is commonly associated with cortical glucose hypometabolism on interictal 2-deoxy-2[18F]-fluoro-D-glucose (FDG) positron emission tomography (PET). However, subcortical brain structures also may show hypometabolism on PET and volume changes on magnetic resonance imaging (MRI) studies, and these are less well understood in terms of their pathophysiology and clinical significance. In the present study, we analyzed alterations of glucose metabolism in subcortical nuclei and hippocampus by using FDG-PET in young patients with intractable epilepsy. METHODS: Thirty-seven patients (mean age, 7.5 years; age range, 1-27 years) with intractable frontal (n = 23) and temporal (n = 14) lobe epilepsy underwent FDG-PET scanning as part of their presurgical evaluation. Normalized glucose metabolism was measured in the thalamus and caudate and lentiform nuclei, as well as in hippocampus, both ipsi- and contralateral to the epileptic focus, and correlated with duration and age at onset of epilepsy, presence or absence of secondary generalization, location of the epileptic focus, and extent of cortical glucose hypometabolism. RESULTS: Long duration of epilepsy was associated with lower glucose metabolism in the ipsilateral thalamus and hippocampus. Duration of epilepsy was a significant predictor of ipsilateral thalamic glucose metabolism in both temporal and frontal lobe epilepsy. Presence of secondarily generalized seizures also was associated with lower normalized metabolism in the ipsilateral thalamus and hippocampus. Extent of cortical hypometabolism did not correlate with subcortical metabolism, and glucose metabolism in the caudate and lentiform nuclei did not show any correlation with the clinical variables. CONCLUSIONS: The findings suggest that metabolic dysfunction of the thalamus ipsilateral to the seizure focus may become more severe with long-standing temporal and frontal lobe epilepsy, and also with secondary generalization of seizures.     

Contralateral medial temporal lobe damage in right but not left temporal lobe epilepsy: a (1)H magnetic resonance spectroscopy study

BACKGROUND: Proton magnetic resonance spectroscopy (MRS) of the hippocampus is useful in lateralising the epileptic focus in temporal lobe epilepsy for subsequent surgical resection. Previous studies have reported abnormal contralateral MRS values in up to 50% of the patients. OBJECTIVE: To identify the contributing factors to contralateral damage, as determined by MRS, and its extension in patients with temporal lobe epilepsy. METHODS: Single voxel MRS was carried out in the hippocampus and lateral temporal neocortex of both hemispheres in 13 patients with left temporal lobe epilepsy (LTLE) and 16 patients with right temporal lobe epilepsy (RTLE). All patients had mesial temporal lobe epilepsy with hippocampal sclerosis. Controls were 21 healthy volunteers of comparable age. RESULTS: Consistent with previous studies, the NAA/(Cho+Cr) ratio was abnormally low in the hippocampus ipsilateral to the focus (p < 0.0001), and there were lower values in both patient groups in the ipsilateral temporal neocortex (p < 0.0001). Patients with RTLE had left hippocampal MRS anomalies (p = 0.0018), whereas the right hippocampus seemed to be undamaged in LTLE patients. CONCLUSIONS: Unilateral mesial temporal lobe epilepsy is associated with widespread metabolic abnormalities which involve contralateral mesial and neocortical temporal lobe structures. These abnormalities appear to be more pronounced in patients with RTLE.     

Effects of unilateral temporal lobectomy on verbal dichotic listening test

Verbal dichotic listening test was conducted before and after anterior temporal lobectomy on 25 patients who underwent the operation because of their medication-resistant epileptic seizures. Their speech dominance by Wada test was all left sided. 1. Preoperatively, patients having the epileptogenic focus in the right temporal lobe (R-TLE) and those having the focus in the left (L-TLE) were, as expected, all right-ear dominant. The mean number of correct responses was fewer in L-TLE than in R-TLE group. 2. Postoperatively, no detrimental effects for recognition of verbal auditory stimuli by the ear contralateral to the focus was observed both in L-TLE and in R-TLE group. 3. Postoperatively, the ear-dominance shifted: to the left in patients with L-TLE, and to the right more conspicuously in patients with R-TLE compared to the preoperative scores. In other words, the recognition ability by the ears ipsilateral to the side of focus, or of resected temporal lobe, was ameliorated. Summarizing, the unilateral anterior temporal lobectomy did not cause "lesion effect" but yielded improvement of verbal auditory recognition by ears ipsilateral to the epileptogenic focus. Diminished epileptic bombardment resulted in by the resection surgery may be a possible explanation.     

Hippocampal and thalamic diffusion abnormalities in children with temporal lobe epilepsy

PURPOSE: Previous studies using diffusion MRI in patients with temporal lobe epilepsy have shown abnormal water diffusion in the hippocampus. Because thalamus and lentiform nuclei are considered important for the regulation of cortical excitability and seizure propagation, we analyzed diffusion tensor imaging (DTI) abnormalities in these subcortical structures and in hippocampus of children with partial epilepsy with and without secondary generalization. METHODS: Fourteen children with partial epilepsy involving the temporal lobe underwent MRI including a DTI sequence. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were obtained in the hippocampus, thalamus, and lentiform nucleus, and compared with DTI data of 14 control children with no epilepsy, as well as glucose positron emission tomography (PET) findings. RESULTS: Decreased FA (p < 0.001) and increased ADC (p = 0.003) values were found in the hippocampi ipsilateral to the seizure focus. Significant FA decreases (p = 0.002) also were seen in the contralateral hippocampi, despite unilateral seizure onset and excellent surgical outcome in patients who underwent surgery. ADC values showed a trend for increase in the thalami ipsilateral to the epileptic focus in the seven children with secondarily generalized seizures (p = 0.09). No group differences of ADC or FA were found in the lentiform nuclei. The DTI variables did not correlate with regional glucose metabolism in any of the structures analyzed. CONCLUSIONS: Increased ADC values in hippocampus can assist in lateralizing the seizure focus, but decreased FA in the contralateral hippocampus suggests that it too may be dysfunctional despite unilateral seizure onset. Less-robust thalamic abnormalities of water diffusion in patients with secondarily generalized seizures suggest secondary involvement of the thalamus, perhaps due to recruitment of this structure into the epileptic network; however, this must be confirmed in a larger population. DTI appears to be a sensitive method for detection abnormalities in children with partial epilepsy, even in structures without apparent changes on conventional MRI.     

Reduced sensorimotor inhibition in the ipsilesional motor cortex in a patient with chronic stroke of the paramedian thalamus.

OBJECTIVE: Unilateral or bilateral paramedian infarction in the region of the thalamus and upper midbrain may lead to hypersomnia. To determine whether unilateral infarction of the paramedian thalamus leads to changes in excitability of ipsilesional primary motor hand area (M1). METHODS: We describe a patient with chronic stroke of the right dorsomedian and intralaminar thalamic nuclei, who suffered from mild persistent hypersomnia. We studied the excitability of the right and left M1 with transcranial magnetic stimulation (TMS) in the patient, and in 10 healthy controls. RESULTS: In contrast to healthy controls, contralateral electrical stimulation of the median nerve failed to induce short-latency afferent inhibition (SAI) in the ipsilesional M1. Other measures of corticomotor excitability and somatosensory evoked potentials were normal. CONCLUSIONS: The selective loss of ipsilateral SAI in a patient with paramedian thalamic stroke suggests that during wakefulness, the intact paramedian thalamus facilitates the excitability of intracortical inhibitory circuits, which process thalamocortical sensory inputs in the ipsilateral M1. This preliminary finding suggests that measurements of SAI may provide a means of probing the integrity of some neural pathways, which are involved in the control of wakefulness and arousal. SIGNIFICANCE: In addition to the established role of the paramedian thalamus in arousal and memory, our observation suggests that thalamocortical projections from the paramedian thalamus contribute to the integration of sensory input at the cortical level during wakefulness.     

Asymmetric Gray Matter Volume Changes Associated with Epilepsy Duration and Seizure Frequency in Temporal-Lobe-Epilepsy Patients with Favorable Surgical Outcome

MethodsVBM analysis of brain MRI using statistical parametric mapping 8 (SPM8) was performed for 30 left MTLE (LMTLE) and 30 right MTLE (RMTLE) patients and 30 age- and sex-matched healthy controls. We also analyzed the correlations between GMV changes and clinical features of MTLE patients.ResultsIn SPM8-based analyses, MTLE patients showed significant GMV reductions in the hippocampus ipsilateral to the epileptic focus, bilateral thalamus, and contralateral putamen in LMTLE patients. The GMV reductions were more extensive in the ipsilateral hippocampus, thalamus, caudate, putamen, uncus, insula, inferior temporal gyrus, middle occipital gyrus, cerebellum, and paracentral lobule in RMTLE patients. These patients also exhibited notable reductions of GMV in the contralateral hippocampus, thalamus, caudate, putamen, and inferior frontal gyrus. We observed that GMV reduction was positively correlated with several clinical features (epilepsy duration and seizure frequency in RMTLE, and history of febrile seizure in LMTLE) and negatively correlated with seizure onset age in both the RMTLE and LMTLE groups.ConclusionsOur study revealed GMV decreases in the hippocampus and extrahippocampal regions. Furthermore, the GMV reduction was more extensive in the RMTLE group than in the LMTLE group, since it included the contralateral hemisphere in the former. This difference in the GMV reduction patterns between LMTLE and RMTLE may be related to a longer epilepsy duration and higher seizure frequency in the latter.     

颞叶癫痫放电在颅内外传播模式的研究

目的探索颞叶癫痫放电在颅内外的传播方式。方法对无法通过无创手段定侧、定位而高度怀疑为难治性颞叶癫痫的病人行双颞钻孔颅内电极植入术,同步记录10-20头皮脑电和双侧蝶骨电极。对最终确诊的颞叶癫痫病人,分析其同步记录脑电图,测量颅内癫痫起源传播到颅内外各个电极点的时间间隔。研究发作期放电的颅内外传播方式。结果颞下、海马、颞极和颞叶外侧各部位起源的癫痫在颅内外传播有各自的方式：①颞下→对侧海马或颞下→同侧蝶骨→对侧蝶骨→同侧前或中颞头皮→对侧前或中颞头皮;②海马→同侧蝶骨→对侧海马或颞下→对侧蝶骨→同侧前或中颞头皮→对侧前或中颞头皮;③颞极→对侧海马或颞下→同侧蝶骨→同侧前或中颞头皮→对侧蝶骨→对侧前或中颞头皮;④颞叶外侧→同侧中颞头皮→同侧蝶骨→对侧前颞或颞下→对侧蝶骨→对侧前或中颞头皮。结论了解各部位颞叶癫痫放电的颅内外传播顺序有助于癫痫灶的定侧、定位。     

An optimized voxel‐based morphometric study of gray matter changes in patients with left‐sided and right‐sided mesial temporal lobe epilepsy and hippocampal sclerosis (MTLE/HS)

Purpose: To determine whether changes in gray matter volume (GMV) differ according to the affected side in mesial temporal lobe epilepsy/hippocampal sclerosis (MTLE/HS) syndrome, and moreover to test the hypothesis of more pronounced structural changes in right‐sided MTLE/HS. This hypothesis (especially that the contralateral thalamus is more affected in right‐sided MTLE/HS) arose from the results of our recent study, wherein more expressed structural and functional changes were observed in a small sample of patients with right‐sided MTLE/HS ( Brázdil et al., 2009 ). Methods: Twenty patients with left‐sided and 20 with right‐sided MTLE/HS and 40 sex‐ and age‐matched healthy controls were included in the study. Voxel‐based morphometry (VBM) with a modulation step was applied to magnetic resonance imaging (MRI) brain images. Statistical parametric maps were used to compare structural changes between patients and controls separately for the left‐ and right‐sided MTLE/HS subgroups. We also compared the local GMV of the brain structures (insula and thalamus) between the subgroups of patients. Results: In the subgroup with right‐sided MTLE/HS, a reduction of GMV was detected in the mesiotemporal structures and the ipsilateral thalamus (as in left‐sided MTLE/HS), but also notably in the ipsilateral insula and contralateral thalamus. A statistical analysis revealed a significantly more extensive reduction of GMV in the ipsilateral/contralateral insula and the contralateral thalamus in the subgroup with right‐sided compared to left‐sided MTLE/HS. Conclusion: We found asymmetrical morphologic changes in patients with left‐ and right‐sided MTLE/HS syndrome (more pronounced in right‐sided MTLE/HS). These differences could be theoretically explained by different neuronal networks and pathophysiologic changes in temporolimbic structures.     

Thalamic hypometabolism on 18FDG-positron emission tomography in medial temporal lobe epilepsy

OBJECTIVES: Degree of hypometabolism in the thalamus on (18)Fluorodeoxyglucose-positron emission tomography (FDG-PET) was compared with those of medial and lateral temporal lobes in patients with medial temporal lobe epilepsy (mTLE), and its relationship with post-operative seizure outcomes was investigated. METHODS: Twenty-six patients with mTLE who underwent anterior temporal lobectomy were included. Post-operatively, 13 patients became completely seizure-free and 13 showed residual seizure, regardless of frequency (five patients became almost seizure-free, six had rare seizures and two showed significant improvements). Degrees of hypometabolism in bilateral thalamus, ipsilateral medial and lateral temporal lobes were evaluated visually and semi-quantitatively by determining the asymmetry index (AI), a value indicating 100 x (ipsilateral - contralateral)/[1/2 x (ipsilateral + contralateral)] and the region-to-cerebral hemisphere ratio (R/C ratio) being the ratio between averaged counts in each area and those in the cerebral hemisphere of the same side. RESULTS: Hypometabolism in the medial temporal lobe was visually observed in all patients. Hypometabolism in the lateral temporal lobe was observed in 20 patients and was semi-quantitatively more prominent than that of the medial temporal lobe. Pathologically, hippocampal sclerosis and prominent astrogliosis of the lateral temporal lobe were present in all cases. However, while thalamic hypometabolism was visually observed in nine patients (in the ipsilateral side of four cases, contralateral side of three and on both sides of two), no significant thalamic hypometabolism was semi-quantitatively observed. No significant differences in metabolic rate in any area except for the lateral temporal lobe between seizure-free patients and residual seizure patients were seen semi-quantitatively. DISCUSSION: Data indicated that metabolism in the lateral temporal lobe of patients with mTLE significantly decreased and revealed pathologic glial changes. Thalamic hypometabolism was quite mild and did not correlate with post-operative seizure outcome.     

Hemichorea and hemiballism associated with contralateral hemiparesis and ipsilateral basal ganglia lesions.

We report on two patients with unilateral hyperkinetic movement disorders associated with contralateral hemiparesis and ipsilateral basal ganglia lesions. The first patient, a 47-year-old woman, had a low-grade astrocytoma located in the right basal ganglia extending into the subthalamic area and the cerebral peduncle. She presented with left hemiparesis, right hemichorea, and intermittent right-sided tremor at rest. The second patient, a 85-year-old woman, had hypertensive hemorrhage to the right posterior basal ganglia, the posterior limb of the internal capsule, the lateral thalamus, and the subthalamic region with accompanying intraventricular bleeding. She developed right-sided transient hemichorea-hemiballism. A videotape illustration of one of the patients is provided. The literature on the rare occurrence of ipsilateral hemichorea-hemiballism is discussed and possible pathomechanisms are reviewed. We postulate that hemiparesis contralateral to basal ganglia lesions might have a conditioning effect on the appearance of ipsilateral dyskinetic movement disorders.     

Ipsilateral thalamic MRI abnormality in an epilepsy patient

In a 19-year-old patient with status epilepticus arising in the right parietal neocortex, unenhanced ictal MRI showed abnormalities mainly in the right cerebral cortex, contralateral cerebellum, and ipsilateral thalamus. The thalamus is considered a key site of functional abnormality in this patient.     

Glucose and [11C]flumazenil positron emission tomography abnormalities of thalamic nuclei in temporal lobe epilepsy

OBJECTIVES: To analyze interictal patterns of thalamic nuclei glucose metabolism and benzodiazepine receptor binding in patients with medically intractable temporal lobe epilepsy (TLE) using high-resolution 2-deoxy-2-[18F]fluoro-D-glucose (FDG) and [11C]flumazenil (FMZ) PET. BACKGROUND: Structural and glucose metabolic abnormalities of the thalamus are considered important in the pathophysiology of TLE. The differential involvement of various thalamic nuclei in humans is not known. METHODS: Twelve patients with TLE underwent volumetric MRI, FDG and FMZ PET, and prolonged video-EEG monitoring. Normalized values and asymmetries of glucose metabolism and FMZ binding were obtained in three thalamic regions (dorsomedial nucleus [DMN], pulvinar, and lateral thalamus [LAT]) defined on MRI and copied to coregistered, partial-volume-corrected FDG and FMZ PET images. Hippocampal and amygdaloid FMZ binding asymmetries and thalamic volumes also were measured. RESULTS: The DMN showed significantly lower glucose metabolism and FMZ binding on the side of the epileptic focus. The LAT showed bilateral hypermetabolism and increased FMZ binding. There was a significant correlation between the FMZ binding asymmetries of the DMN and amygdala. The PET abnormalities were associated with a significant volume loss of the thalamus ipsilateral to the seizure focus. CONCLUSIONS: Decreased [11C]flumazenil (FMZ) binding and glucose metabolism of the dorsomedial nucleus (DMN) are common and have strong lateralization value for the seizure focus in human temporal lobe epilepsy. Decreased benzodiazepine receptor binding can be due to neuronal loss, as suggested by volume loss, but also may indicate impaired gamma-aminobutyric acid (GABA)ergic transmission in the DMN, which has strong reciprocal connections with other parts of the limbic system. Increased glucose metabolism and FMZ binding in the lateral thalamus could represent an upregulation of GABA-mediated inhibitory circuits.     

Autonomic phenomena of temperature regulation in temporal lobe epilepsy

Cold shiver and piloerection are rare ictal signs in focal epilepsies. They are often associated with an epileptic seizure focus within the temporal lobe. In rare cases the phenomenon of piloerection has been reported to be confined to body parts ipsilateral to the seizure focus. In this multicentric study epilepsy patients with ictal cold shiver and/or piloerection were retrospectively asked to describe exactly location and spreading patterns of these signs as well as their temporal sequence in relation to other ictal signs. Clinical data, etiology of epilepsy, and seizure focus location were also assessed. In our patient group there was a high relationship to an epileptic focus within the left temporal lobe. Distinct spreading patterns or unilateral piloerection was not indicative of a focus in the ipsilateral temporal lobe as described previously. Our results suggest that phenomena of temperature dysregulation during epileptic seizures may be of value in the presurgical evaluation as they may be indicative of a left temporal lobe seizure focus.     

Contraversive shift of conjugate eye deviation in hemispheric stroke indicates emerging mass effect

Conjugate eye deviation (CED) towards the ipsilateral or the contralateral side of the brain lesion can occur as a result of acute hemispheric stroke. To our knowledge, there have been no reports of CED shifting from the lesional side to the contralateral side in acute hemispheric stroke in the literature. We present four patients with right hemispheric stroke with a forced CED shift from the right to the left side during the acute stage with corresponding mass effect on the right internal capsule and right thalamus, as shown on brain imaging. Mass effect on thalamic mediated circuits and the corticopontine projection within the internal capsule probably underlies this CED shift via the dynamic balance of oculomotor control between the two hemispheres. Contraversive CED shift is a potentially useful early predictor of emerging mass effect in acute hemispheric stroke.     

Hemisphere memory differences in Sodium Amytal testing of epileptic patients

Material-specific memory performance was studied by a Sodium Amytal testing procedure in order to diagnose hemispheric memory functions in 27 patients with unilateral temporal or frontal epileptic lesions who were under consideration for surgical therapy. Memory was tested for concrete and abstract words, pictures of common objects, figures, and faces, presented pre- and post-inactivation of the hemisphere contralateral or ipsilateral to the epileptic focus. The results showed that tests involving words and pictures of common objects were conclusive about hemispheric memory functions, in showing cross-over interactions between side of lesion and side of injection. Figures and faces were hemisphere discriminative to a much lesser degree (only a minor preference for the right hemisphere was found) and are presumably more dependent on the functional integrity of both hemispheres. The present findings demonstrate that hemispheric memory functions can be studied in more detail with the Amytal technique than has been shown hitherto in the literature.     

Influence of the ipsilateral hemisphere upon somatosensory evoked potential in cats

Somatosensory evoked potentials (SEPs) were recorded on the skull corresponding to the (left) SI area by (right) superficial radial nerve stimulation. Amongst the various components of the SEP, special attention was directed to the negative component (N15) with a latency of approximately 15 ms. Changes in this potential followed by conditioning stimulation of the ipsilateral (right) hemisphere were observed and the following results were obtained: (i) when conditioning stimuli were applied to the contralateral (left) superficial radial nerve, the ipsilateral (right) thalamic VPL nucleus and the ipsilateral (right) sensory cortex, the amplitude of N15 decreased to 65-80% of the control level at C-T intervals less than 100 ms and (ii) following functional elimination of the unilateral sensory cortex by KCl application, the amplitude of N15 recorded at the opposite side significantly increased. In this condition, the inhibitory effects of the ipsilateral thalamus and contralateral peripheral nerve disappeared. From these observations, ipsilateral homologous cortex may well have an inhibitory influence upon the near field potential (N15) of the SEP.     

Patterns of cerebral glucose metabolism in patients with partial seizures

We analyzed local cerebral metabolic rates of glucose (LCMRglu) in 20 regions from 22 patients with complex partial seizures, who were taking neither phenytoin nor phenobarbital and who had normal CTs. Results were compared with data from 19 normal controls. Ten patients had left temporal, eight right temporal, and four bitemporal or generalized EEG discharges. There were no significant differences between patient and control values in any of 20 regions of interest. LCMRglu was depressed at the site of the epileptic focus: L/R ratio was 0.85 +/- 0.12 (p less than 0.003 compared with control), 0.92 +/- 0.08 (p less than 0.05), and 0.84 +/- 0.1 (p less than 0.001), respectively, in mesial, superior, and inferior temporal regions for patients with left temporal foci; 1.7 +/- 0.96 (p less than 0.04), 1.1 +/- 0.1 (NS), and 1.15 +/- 0.04 (p less than 0.001) for patients with right temporal foci. Patients with left temporal EEG foci had significantly lower values than patients with right temporal foci in left superior frontal and thalamic as well as left temporal regions, while patients with right-sided EEG foci had depressed LCMRglu (compared with patients with left temporal EEG foci) restricted to right mesial temporal lobe. The patients with left temporal foci tended to have longer seizure histories (22.7 +/- 5.4 versus 11 +/- 5.6 years; p less than 0.001). There was an inverse correlation between length of seizure history and mean LCMRglu (r = 0.38; 0.1 greater than p greater than 0.05). Our study suggests that LCMRglu is not depressed in regions beyond the epileptic focus when patients are not taking drugs known to decrease cerebral glucose metabolism.     

Pure amnesia after unilateral left polar thalamic infarct: topographic and sequential neuropsychological and metabolic (PET) correlations.

A 54-year-old patient who had an isolated small polar thalamic infarct and acute global amnesia with slight frontal type dysfunction but without other neurological dysfunction was studied. Memory improved partially within 8 months. At all stages the impairment was more severe for verbal than non-verbal memory. Autobiographic recollections and newly acquired information tended to be disorganised with respect to temporal order. Procedural memory was unaffected. Both emotional involvement and pleasure in reading were lost. On MRI, the infarct was limited to the left anterior thalamic nuclei and the adjacent mamillothalamic tract. The regional cerebral metabolic rate of glucose (measured with PET) was decreased on the left in the thalamus, amygdala, and posterior cingulate cortex 2 weeks after the infarct, and in the thalamus and posterior cingulate cortex 9 months later. These findings stress the specific role of the left anterior thalamic region in memory and confirm that longlasting amnesia from a thalamic lesion can occur without significant structural damage to the dorsomedial nucleus. Furthermore, they suggest that the anterior thalamic nuclei and possibly their connections with the posterior cingulate cortex play a role in emotional involvement linked to ipsilateral hemispheric functions.