Unilateral Temporal Lobe Lesions Research Articles

Japanese Encephalitis Presenting with Unilateral Medial Temporal Lobe Lesion

Japanese Encephalitis Presenting with Unilateral Medial Temporal Lobe Lesion

Herpes Simplex Virus Type 1 Encephalitis: A Descriptive, Cross Sectional Study, 2011 - 2016, Iran

Background: Encephalitis may arise from infectious or non-infectious etiologies. Infections, predominantly viruses, are the most common causes of encephalitis. Herpes simplex virus (HSV) is the most prevalent cause of viral encephalitis in the developed countries. HSV encephalitis occurs equally in both genders and most cases are caused by HSV type 1 (HSV-1). Methods: The current descriptive, cross sectional study was conducted on patients admitted with HSV-1 encephalitis from 2011 to 2016 to Imam-Khomeini hospital complex in Tehran, Iran. The patients with clinical diagnosis of encephalitis whose cerebrospinal fluid (CSF) HSV-1 polymerase chain reaction (PCR) was positive were included. All clinical, laboratory, and imaging characteristics of patients along with their outcomes were evaluated and analyzed. Results: In the current study, of 12 cases with encephalitis manifestations and positive CSF HSV-1 PCR results, 5 were male and 7 were female with mean age of 42 years. Fever and headache were the most common complaints. Headache was more common in the cases admitted earlier (P value = 0.001). The patients were studied by brain magnetic resonance imaging (MRI) and the findings confirmed encephalitis in all the cases. Five cases had unilateral temporal lobe lesions and 6 cases had bilateral lesions. There was a clear relationship between bilateral temporal lobe lesions and higher protein level in CSF (P value = 0.001); 25% of patients (3 cases) needed stay in the intensive care unit (ICU). Three patients died and 5 patients developed disabilities. Conclusions: HSV encephalitis is a devastating disease. Clinical findings along CSF analysis and neuroimaging may result in the appropriate diagnosis. Despite appropriate treatment, undesired outcomes are common.

The feeling of familiarity for music in patients with a unilateral temporal lobe lesion: A gating study

Previous research has indicated that the medial temporal lobe (MTL), and more specifically the perirhinal cortex, plays a role in the feeling of familiarity for non-musical stimuli. Here, we examined contribution of the MTL to the feeling of familiarity for music by testing patients with unilateral MTL lesions. We used a gating paradigm: segments of familiar and unfamiliar musical excerpts were played with increasing durations (250, 500, 1000, 2000, 4000ms and complete excerpts), and participants provided familiarity judgments for each segment. Based on the hypothesis that patients might need longer segments than healthy controls (HC) to identify excerpts as familiar, we examined the onset of the emergence of familiarity in HC, patients with a right MTL resection (RTR), and patients with a left MTL resection (LTR). In contrast to our hypothesis, we found that the feeling of familiarity was relatively spared in patients with a right or left MTL lesion, even for short excerpts. All participants were able to differentiate familiar from unfamiliar excerpts as early as 500ms, although the difference between familiar and unfamiliar judgements was greater in HC than in patients. These findings suggest that a unilateral MTL lesion does not impair the emergence of the feeling of familiarity. We also assessed whether the dynamics of the musical excerpt (linked to the type and amount of information contained in the excerpts) modulated the onset of the feeling of familiarity in the three groups. The difference between familiar and unfamiliar judgements was greater for high than for low-dynamic excerpts for HC and RTR patients, but not for LTR patients. This indicates that the LTR group did not benefit in the same way from dynamics. Overall, our results imply that the recognition of previously well-learned musical excerpts does not depend on the integrity of either right or the left MTL structures. Patients with a unilateral MTL resection may compensate for the effects of unilateral damage by using the intact contralateral temporal lobe. Moreover, we suggest that remote semantic memory for music might depend more strongly on neocortical structures rather than the MTL.

Role of the left amygdala and right orbital frontal cortex in emotional interference resolution facilitation in working memory

Previous research has shown that emotional information aids conflict resolution in working memory (Levens & Phelps, 2008). Using a Recency-probes working memory (WM) paradigm, Levens and Phelps found that positive and negative emotional stimuli reduced the amount of interference created when information that was once relevant conflicted with currently relevant information, suggesting that emotional information facilitates interference resolution in WM. To determine what regions of the prefrontal cortex (PFC) and temporal lobes are critical to the influence of emotional stimuli on interference resolution, we conducted a Recency-probes emotion paradigm with right and left unilateral frontal and temporal lobe lesion patients. The frontal lobe lesion patient group comprised individuals with unilateral ventral and dorsal PFC lesions. The temporal lobe lesion patient group comprised individuals with lesions of the amygdala and surrounding structures. Results indicate that when the left amygdala is damaged, emotional facilitation of interference resolution is absent (equal emotional and neutral interference levels), when the right orbital frontal cortex (OFC) is damaged, in contrast, emotional interference resolution is impaired (emotional interference levels are higher than neutral levels are). Based on these unique patterns we propose specific contributions for these regions in the emotional facilitation of interference resolution in WM.

Amnesia Following Herpes Simplex Encephalitis: Diffusion-Tensor Imaging Uncovers Reduced Integrity of Normal-appearing White Matter

To explore white matter (WM) and gray matter tissue integrity in the apparently unaffected hemisphere of patients with herpes simplex encephalitis (HSE) who have gross unilateral medial temporal lobe (MTL) lesions and both verbal and visuospatial memory deficits. This study had institutional ethics committee approval and included written informed consent. Magnetic resonance (MR) imaging was performed in five patients who had recovered from HSE (one woman, four men; median age, 32 years; interquartile range, 28.5-37 years) and 51 age-matched controls (30 women, 21 men; median age, 32 years; interquartile range, 28-37 years). As markers of microstructural WM integrity, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity, and radial diffusivity (RD) derived from diffusion-tensor (DT) imaging were used. An automated regional brain segmentation approach yielded estimates of subcortical volumes, including hippocampus, and cortical thickness. Group differences were evaluated by using permutation tests. Examination of standard MR images found unilateral lesions in all patients. The patients with HSE showed reduced FA and increased MD and RD in several WM tracts contralateral to lesions (P < .05, corrected for multiple comparisons). Affected tracts included connections between the MTLs and other parts of the brain. No significant group differences were observed in subcortical volume or cortical thickness. These results suggest that patients with HSE have reduced microstructural integrity of normal-appearing WM contralateral to grossly visible lesions. These subtle lesions, detectable at DT imaging, probably contribute to the memory impairment manifested by these patients. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100179/-/DC1.

To lose the frame of action: A selective deficit in avoiding unpleasant objects following a unilateral temporal lobe lesion

Studies on emotion and its neurobiology have been far more focused on the recognition of emotion than on actions that are caused by emotional states. We investigate the performance of a patient, HS, with a unilateral lesion to the left temporal pole and orbito-frontal cortex (OFC) (including left amygdala), on a well-established approach/avoid task that taps into emotion-driven action. The striking finding of the present study is a remarkable, and selective, slowing of HS's avoidance of unpleasant items in her (impaired) contralesional field. This finding suggests that the left temporal lobe and OFC structures, including the amygdala, appear to be involved in the action component of emotion, specifically in avoiding negative items.

Lexical retrieval and semantic knowledge in patients with left inferior temporal lobe lesions

Background: It has been proposed that anomia following left inferior temporal lobe lesions may have two different underlying mechanisms with distinct neural substrates. Specifically, naming impairment following damage to more posterior regions (BA 37) has been considered to result from a disconnection between preserved semantic knowledge and phonological word forms (pure anomia), whereas anomia following damage to anterior temporal regions (BAs 38, 20/21) has been attributed to the degradation of semantic representations (semantic anomia). However, the integrity of semantic knowledge in patients with pure anomia has not been demonstrated convincingly, nor were lesions in these cases necessarily confined to BA 37. Furthermore, evidence of semantic anomia often comes from individuals with bilateral temporal lobe damage, so it is unclear whether unilateral temporal lobe lesions are sufficient to produce significant semantic impairment. This research was supported by a Graduate Imaging Fellowship from the University of Arizona and by NIH grants RO1DC008286 and RO1DC07464. Scans were funded through Arizona Alzheimer's Research Consortium, Cognition and NeuroImaging Lab, Arizona Department of Health Services HB2354. Many thanks to Jen Parrott, Kristin Boruff, and Cathy West for their time and assistance. The authors thank Mark Borgstrom, statistical consultant at the University of Arizona, for his assistance with this project. We also thank Chris Rorden for advice regarding lesion analyses. Aims: The main goals of this study were to determine whether anomia following unilateral left inferior temporal lobe damage reflected a loss of semantic knowledge or a post‐semantic deficit in lexical retrieval and to identify the neuroanatomical correlates of the naming impairment. Methods & Procedures: Eight individuals who underwent left anterior temporal lobectomy (L ATL) and eight individuals who sustained left posterior cerebral artery strokes (L PCA) completed a battery of language measures that assessed lexical retrieval and semantic processing, and 16 age‐ and education‐matched controls also completed this battery. High‐resolution structural brain scans were collected to conduct lesion analyses. Outcomes & Results: Performance of L ATL and L PCA patients was strikingly similar, with both groups demonstrating naming performance ranging from moderately impaired to unimpaired. Anomia in both groups occurred in the context of mild deficits to semantic knowledge, which manifested primarily as greater difficulty in naming living things than nonliving things and greater difficulty in processing visual/perceptual as opposed to functional/associative semantic attributes. Lesion analyses indicated that both patient groups sustained damage to anterior inferior temporal lobe regions implicated in semantic processing. Conclusions: These results contribute to a better understanding of the cognitive mechanism of naming impairment in patients with temporal lobe damage and support the notion that pure anomia and semantic anomia represent two endpoints along a continuum of semantic impairment. Unilateral left temporal lobe lesions in our patients resulted in relatively mild semantic deficits that were apparent primarily in lexical production tasks, whereas severe semantic impairment likely requires bilateral temporal lobe damage.

Unilateral hand automatisms in temporal lobe epilepsy

To analyse the lateralising value of unilateral manual automatism (UMA), its relation to contralateral dystonia and the hand by which the UMA was performed. In this retrospective study, we reviewed video recordings of 141 patients (mean age 34.1+/-10) who had consecutively undergone presurgical evaluations with ictal video-EEG recordings and high-resolution MRI, had had epilepsy surgery due to intractable medial temporal lobe epilepsy with complex partial seizures due to unilateral medial temporal lobe lesions. The video recordings were prospectively reviewed by one of the authors blinded to patient's clinical data except the diagnosis of medial temporal lobe epilepsy. Altogether 310 archived seizures were analysed. Hand automatisms occurred in 86.5% of patients. UMA occurred in 53% of patients. If UMA was accompanied by contralateral hand dystonia, it had a high lateralising value to the ipsilateral epileptic focus (EF), it was ipsilateral in 85% of patients. Conversely, if UMA occurred without contralateral dystonia, it had only a limited lateralising value because it was ipsilateral to the EF in only 63% of patients. However, we found that left-sided UMA without dystonia had a high lateralising value to the left hemisphere (ipsilateral to the EF in 82%), while right-sided UMA without dystonia has practically no lateralising value. UMA with contralateral dystonia has a high lateralising value to the ipsilateral hemisphere. Left-sided UMA without contralateral dystonia has a lateralising value to the left hemisphere. Right-sided UMA without contralateral dystonia has no lateralising value.

Spike frequency is dependent on epilepsy duration and seizure frequency in temporal lobe epilepsy

Objectives We wanted to investigate factors that are associated with frequency of interictal epileptiform discharges by investigating 303 patients with temporal lobe epilepsy (TLE). Methods We included all patients who consecutively underwent the adult presurgical evaluation program at our center and who had intractable, medial TLE with complex partial seizures due to unilateral medial temporal lobe lesions. The interictal EEG samples were automatically recorded and stored on computer. The location and frequency of interictal epileptiform discharges were assessed by visual analysis of interictal EEG samples of 2‐minute duration every hour. Results There were 303 patients (aged 16‐63) who met the inclusion criteria. The median interictal epileptiform discharge frequency was 15 IED/h, the median seizure frequency was 4 seizures/month. According to univariate analyses, we found that age at monitoring, epilepsy duration, and higher seizure frequency were associated with higher interictal epileptiform discharge frequency. In the logistic regression analysis, we found that higher seizure frequency (p &lt; 0.001) and longer epilepsy duration (p = 0.007) were independently associated with higher spike frequency, while the age at monitoring was not. Conclusions Seizure frequency and epilepsy duration (years of patient's life with seizure activity) were independently associated with IED frequency, suggesting that IED are modulated by seizures.

Auditory/visual duration bisection in patients with left or right medial-temporal lobe resection

Patients with unilateral (left or right) medial temporal lobe lesions and normal control (NC) volunteers participated in two experiments, both using a duration bisection procedure. Experiment 1 assessed discrimination of auditory and visual signal durations ranging from 2 to 8 s, in the same test session. Patients and NC participants judged auditory signals as longer than equivalent duration visual signals. The difference between auditory and visual time discrimination was equivalent for the three groups, suggesting that a unilateral temporal lobe resection does not modulate the modality effect. To document interval-timing abilities after temporal lobe resection for different duration ranges, Experiment 2 investigated the discrimination of brief, 50–200 ms, auditory durations in the same patients. Overall, patients with right temporal lobe resection were found to have more variable duration judgments across both signal modality and duration range. These findings suggest the involvement of the right temporal lobe at the level of the decision process in temporal discriminations.

Neuropsychological studies of musical timbre.

Musical timbre is a multidimensional property of sound that allows one to distinguish musical instruments. In this paper, studies that explore the cerebral substrate underlying the processing of musical timbre are discussed. Perceptual asymmetries measured in normal participants, deficits of musical timbre perception obtained in brain-damaged patients, as well as results obtained with various neuroimaging methods are reviewed. The findings obtained in all of these studies generally support the predominant involvement of right temporal lobe areas, and more specifically of its anterior part, in processing spectral and temporal envelopes of musical timbre. However, controversies still exist about the contribution of the left temporal lobe in timbre perception. The necessity of comparing data obtained with different perceptual paradigms (same-different discrimination and similarity judgment) and various types of stimuli (single tones and melodies) was emphasized by reporting lesion studies carried out in patients with unilateral temporal lobe lesions. The few neuroimaging studies published in this domain provided additional and complementary findings. Unlike lesion studies that allow us to infer the cerebral structures that are essential for timbre perception, the latter investigations implicate a more distributed neural network in timbre processing that extends along the superior temporal gyrus to include not only anterior but also posterior temporal regions and possibly frontal areas as well.

Simple partial seizures (isolated auras) in medial temporal lobe epilepsy

We analysed whether the medial temporal lobe epilepsy (MTLE) with isolated auras makes any difference in the clinical picture in comparison with MTLE in which only complex partial seizures (CPS) occur. We included 100 patients (aged 16–59 years) with unilateral medial temporal lobe lesions who consecutively underwent presurgical evaluation due to intractable MTLE and who became completely aura- and seizure-free after the anterior temporal resection. Preoperatively, isolated auras were present in 70 patients. These patients were categorised into the IA group. The remaining 30 patients in whom the auras preceded seizures were categorised into the NIA group. We found no difference between the two groups for the age at onset, epilepsy duration or aura types. Conversely, a right-sided epileptogenic region (61%) occurred more frequently in the IA group than in the NIA group (27%, P=0.001). Conclusively, isolated auras show affinity to the right hemisphere. One explanation may be that seizures stop more quickly in the right hemisphere. Another hypothesis is that consciousness can be disturbed much easier by the ictal activity in left temporal seizures: auras evolve more frequently to CPS due to the disturbance of consciousness.

Preoperative evaluation for temporal lobe surgery.

Temporal lobe epilepsy (TLE), the most common form of partial epilepsy in adults is often refractory to medical treatment and in these patients epilepsy surgery is considered. Successful surgery is dependent on accurate localisation and lateralisation of the epileptogenic zone. The preoperative evaluation involves a series of assessments and investigations including detailed clinical history, interictal EEG, video-EEG monitoring, MRI, PET, SPECT, and neuropsychology and neuropsychiatric assessment. The role of each of these investigations and assessments in the preoperative evaluation is discussed. Advanced MR techniques including magnetic resonance spectroscopy, MR diffusion and MR perfusion have recently been assessed and are likely to enhance the pre-surgical evaluation of patients with TLE.The surgical outcome and preoperative investigations performed of 80 consecutive patients who underwent temporal lobe surgery between 1993 and 2002 at Royal Melbourne Hospital were reviewed. All patients had MRI, video-EEG monitoring and neuropsychology assessment and 56% a PET scan. During a mean follow-up of 5.9 years 75% had Class 1 outcome, 22% non-Class 1 outcome and 3% were lost to follow-up. The results of preoperative investigations were correlated with outcome. For interictal EEG, seizure semiology, ictal EEG, PET and neuropsychology assessment the surgical outcome of patients in whom results were concordant to side of surgery was compared with those discordant or non-lateralising. There was no significant difference. In 78 of 80 patients MRI revealed mesial temporal sclerosis or a foreign tissue lesion. The outcome was no different between these two groups. Results suggest that in patients with unilateral temporal lobe lesion on MRI and where ictal EEG is either concordant or non-lateralising, other investigations including PET, provide little additional prognostic information.

Severe amnesia following a unilateral temporal lobe stroke

A 60 year old right-handed man developed severe amnesia following a left medial temporal stroke as documented by cerebral MRI, MRA and SPECT scans. Neuropsychological evaluation 13 weeks after the stroke showed a profound retrograde amnesia characterised by memory loss for public facts and events over the previous four decades. In addition, autobiographical memory showed selective loss of personal episodic memory with relative preservation of personal semantic memory. The development of this degree of amnesia with these features following a unilateral temporal lobe lesion is unusual. The possible neuroanatomical mechanisms underlying the amnesia and how they relate to current theories of memory loss are discussed.

Changes in Lateralized Memory Performance in Subjects with Epilepsy Following Neurofeedback Training

Both seizure reduction and neuropsychological improvements have been reported following neurofeedback training directed to normalization of the sensorimotor EEG. These findings could be interpreted as nonspecific effects rather than specific changes brought about by EEG training. The present study demonstrated neuropsychological changes of a selective nature that would be difficult to interpret as nonspecific. Epileptic subjects with unilateral temporal lobe lesions were administered memory tests prior to EEG training, after control training, and after sensorimotor EEG normalization training. Successfully trained subjects showed exclusive improvement on memory tasks specific to the hemisphere contralateral to their lesion, and no improvement on memory tasks specific to the hemisphere with the lesion. Such selective changes are difficult to interpret as nonspecific effects of participating in a study, and would seem to require genuine alteration of neural substrates as a result of EEG training.

Musical Function and Temporal Lobe Structures: A review of Brain Lesion Studies

This paper reviews several studies examining the contribution of different temporal lobe structures in musical function. Findings that yield important clues to the understanding of the auditory function of temporal lobes are initially reported. Then, the functional asymmetry of the temporal lobes as well as the role of different temporal lobe areas in musical tasks are described by presenting results obtained in epileptic patients with unilateral temporal lobe lesion. Evidence suggesting the predominant contribution of the right temporal lobe in musical perception revealed a functional asymmetry in low-level processing of musical information. The role of the primary auditory cortex in melodic discrimination was also discussed. Additional results indicating the predominant contribution of the secondary association areas of the anterior right temporal lobe in short-term retention of pitch were reported. Arguments in favor of bilateral contribution of both temporal lobes in higher level of melodic processing were then presented. Finally, recent data obtained in patients with hippocampal damage support the idea that medial temporal lobe structures may also be involved in supra-span learning as well as long-term retention of unfamiliar tunes.

Clustering and switching on verbal fluency: the effects of focal frontal- and temporal-lobe lesions

We examined the hypothesis that, on verbal fluency, clustering (i.e. generating words within subcategories) is related to temporal-lobe functioning, whereas switching (i.e. shifting between subcategories) is related to frontal-lobe functioning. Tests of phonemic and semantic fluency were administered to 53 patients with focal frontal-lobe lesions (FL), 23 patients with unilateral temporal-lobe lesions (TL) and 55 matched controls. Performance by FL patients was consistent with our hypothesis: in comparison to controls, patients with left-dorsolateral or superior-medial frontal lesions switched less frequently and produced normal cluster sizes on both phonemic and semantic fluency. Performance by TL patients was not consistent across fluency tasks and provided partial support for our hypothesis. On phonemic fluency, TL patients were unimpaired on both switching and clustering. On semantic fluency, TL patients were impaired on switching in comparison to controls and left TL patients produced smaller clusters than right TL patients. The best indices for discriminating the patient groups, therefore, were phonemic-fluency switching (impaired only with frontal lesions) and semantic-fluency clustering (impaired only with temporal-lobe lesions).

Comparison of Interaural Time and Intensity Difference Discrimination in Patients with Temporal Lobe Lesions

We studied the sound lateralization in 15 patients with left (12 patients) or bilateral (3 patients) temporal lobe cerebrovascular lesions. The lesions included the auditory cortex. Interaural time difference (ITD) and interaural intensity difference (IID) discriminations were separately measured by using a self-recording apparatus. All 12 patients with left temporal lobe lesions could discriminate ITD, and their ITD thresholds were significantly higher than those in healthy volunteers. None of the 3 patients with bilateral temporal lobe lesions could discriminate ITD. On the other hand, all patients with either unilateral or bilateral temporal lobe lesions could discriminate IID and their IID thresholds were significantly higher than those in healthy volunteers. The present findings indicate that the auditory cortex plays an important role in discriminating both cues, but that the role may not be essential for IID.

Sound lateralization in patients with lesions including the auditory cortex: comparison of interaural time difference (ITD) discrimination and interaural intensity difference (IID) discrimination

We examined sound lateralization using dichotic presentation of noises in 15 patients with left unilateral (12 patients) or bilateral (3 patients) temporal lobe lesions, that included the auditory cortex, and evaluated their abilities to discriminate interaural time and intensity difference (ITD, IID) separately. On the ITD discrimination test, discrimination thresholds in patients with left unilateral lesions were significantly higher than those in normal subjects, but all patients with left unilateral lesions could detect ITD. However, none of 3 patients with bilateral lesions could detect ITD. On the 1113 discrimination test, all patients with either unilateral or bilateral lesions could detect IID. IID discrimination thresholds in these patients were significantly higher than those in normal subjects. The auditory cortex plays an important role in discriminating both cues, but appears to be necessary for discriminating ITD.

Topographical disorientation following unilateral temporal lobe lesions in humans

Studies of the non-human temporal lobe, particularly the hippocampus, confirm its significant role in learning and memory, particularly allocentric spatial mapping of the environment. The role of the human temporal lobes in topographical orientation was investigated by examining the formation of representations of a large-scale real-world environment after unilateral left and right temporal lobe surgery. Patients and normal control subjects viewed videotape presentations of overlapping routes through a novel urban area. Topographical orientation was then assessed across a range of parameters. Right temporal lobe lesions alone gave rise to deficits in making proximity judgements. However, on all other topographical orientation tasks both right and left temporal lobe lesion groups were impaired relative to the normal control group, but the two patient groups did not differ significantly from each other. These findings suggest that such is the nature of remembering and way-finding in the environment that the integrity of both human temporal lobes is required. Copyright © 1996 Elsevier Science Ltd