Cognitive changes after amygdalotomy

Deep brain stimulation for aggressiveness: long-term follow-up and tractography study of the stimulated brain areas

OBJECTIVE

Initial studies applying deep brain stimulation (DBS) of the posteromedial hypothalamus (PMH) to patients with pathological aggressiveness have yielded encouraging results. However, the anatomical structures involved in its therapeutic effect have not been precisely identified. The authors' objective was to describe the long-term outcome in their 7-patient series, and the tractography analysis of the volumes of tissue activated in 2 of the responders.

METHODS

This was a retrospective study of 7 subjects with pathological aggressiveness. The findings on MRI with diffusion tensor imaging (DTI) in 2 of the responders were analyzed. The authors generated volumes of tissue activated according to the parameters used, and selected those volumes as regions of interest to delineate the tracts affected by stimulation.

RESULTS

The series consisted of 5 men and 2 women. Of the 7 patients, 5 significantly improved with stimulation. The PMH, ventral tegmental area, dorsal longitudinal fasciculus, and medial forebrain bundle seem to be involved in the stimulation field.

CONCLUSIONS

In this series, 5 of 7 medication-resistant patients with severe aggressiveness who were treated with bilateral PMH DBS showed a significant long-lasting improvement. The PMH, ventral tegmental area, dorsal longitudinal fasciculus, and medial forebrain bundle seem to be in the stimulation field and might be responsible for the therapeutic effect of DBS.

Neuropsychological assessment with the Visual Gestalt Test: Psychometric properties and differential diagnostic probabilities

The Visual Gestalt Test is a neuropsychological instrument developed for evaluation of learning and memory of visuo-spatial material. A revised strategy of scoring has motivated the present study, where data from 153 normal persons, 99 epilepsy patients, and 24 depressed patients are presented and compared. The Visual Gestalt Test is observed to discriminate between normal and diagnosed groups in several ways. Additionally it is found to discriminate between depressed and brain damage subgroups of patients. Data are presented in order to supplement previously published ways of scoring and norms. Practical guidelines for the clinical applications of the test are suggested as perspectives.

Clinical relevance of amygdala sclerosis in temporal lobe epilepsy

OBJECT

The goal of this study was to define the incidence and clinical significance of amygdala sclerosis (AS) in patients with temporal lobe epilepsy (TLE).

METHODS

Surgical specimens of the lateral amygdaloid nucleus and the hippocampus excised from 71 patients who were treated for medically intractable TLE were quantitatively evaluated using a computer-assisted image-analysis system and compared with 10 normal autopsy specimens. Densities of neurons and reactive astrocytes in the patients with TLE were correlated with clinical, neuropsychological, and depth-electroencephalography data. The neuron counts of the lateral amygdaloid nucleus did not correlate with various presumed etiological factors of TLE including hereditary seizures, birth complications, febrile convulsions, traumatic brain injury, infections, seizure semiology, and epileptological outcome. However, patient age at surgery was significantly higher (mean difference 10 years) when AS was present, as compared with patients without AS (p < 0.01). Seizure origin, as determined by using amygdalohippocampal depth electrodes, did not correlate with the presence or absence of AS. Neuropsychologically, there was a significant correlation between the neuronal densities of the lateral amygdaloid nucleus and both preoperative visual recognition and postoperative deterioration of short-term verbal memory performance (p < 0.05).

CONCLUSIONS

Except for the relatively long history of epilepsy, the presence of AS is not associated with specific clinical or electrocorticographic features of mesial TLE. However, patients without AS are particularly at risk for deterioration of short-term verbal memory following amygdalohippocampectomy.

Neuronal loss and beta-amyloid removal in the amygdala of people with Down syndrome

The decrease in the number of neurons free of neurofibrillary changes, neurons with neurofibrillary degeneration, and the total volume of beta-amyloid (A beta) deposits in the amygdala of people with Down syndrome and in late stages of Alzheimer disease were estimated by using morphometry and regression analysis. This model predicts that the duration of neurofibrillary changes from the pretangle stage to ghost tangles is approximately 4.7 years. The correlation between the decrease in the number of neurons and the decrease in the amount of A beta indicates that amyloid deposition is associated with neurons and that loss of neurons causes decrease in A beta deposition. The presence of neurons only with neurofibrillary tangles, and the absence of the amyloid deposits predicted by regression analysis suggest that neurons with tangles are not engaged in amyloid deposition. The disappearance of amyloid by approximately 2.2 years after loss of neurons free of neurofibrillary changes indicates that A beta deposits are degradable and removable and that even in severely atrophic amygdala, there are mechanisms of amyloid resolution. This study shows that in normal aging in the amygdala, extracellular A beta appears later than neurofibrillary changes.

Contributions of the entorhinal cortex, amygdala and hippocampus to human memory

Recent studies have indicated that, in the monkey, the rhinal cortex (consisting of the entorhinal and perirhinal cortices) is more important to visual recognition memory than the hippocampus or amygdala. The present study investigated the role of the entorhinal cortex in humans using memory scores from surgical epilepsy patients classified according to their mesial temporal lobe pathology. The temporal lobe removals included 4-5 cm of neocortex, amygdala, rhinal cortex and 2-3 cm of the hippocampus and parahippocampal gyrus. Compared to autopsied control subjects, all of the patients showed significant gliosis in the amygdala, but they differed as to whether or not there were entorhinal and/or hippocampal abnormalities. Both preoperatively and one or more years postoperatively, the patients performed tests of verbal recall (Wechsler Memory Scale Logical Memory), visual recall (Rey Figure), verbal recognition and visual recognition (Warrington Recognition Memory Test: Words and Faces, respectively). Preoperatively, patients with hippocampal pathology showed deficits in visual recall. Postoperatively, a significant drop in verbal and visual recall was seen only for patients who lost intact hippocampal tissue, irrespective of the condition of the excised entorhinal cortex. Together, the results argue that the hippocampus is more important than the entorhinal cortex for the recall of newly learned information.

Differential involvement of the right and left amygdalae in expression of memory for aversively motivated training

The present study investigated possible lateralization of amygdala involvement in memory for aversively motivated training. Rats with bilateral cannulae aimed at the amygdalae were trained in a one-trial inhibitory avoidance task. Twenty-four h or 10 days later, animals received bilateral pre-test microinjections of either vehicle, 2% lidocaine, or unilateral infusions of each simultaneously. Five min after the infusions, retention was tested. Retention latencies of rats given bilateral lidocaine or unilateral lidocaine into only the right amygdala were significantly lower than controls. These results suggest that the right and left amygdalae may make differential contributions to the expression of memory, and that the contribution of the right amygdala may be more important to the expression of memory for aversively motivated training.

Neuron loss and shrinkage in the amygdala in Alzheimer's disease

Total neuron numbers in the amygdala and in eight of its subnuclei were determined in 9 cases of Alzheimer's disease (AD) and in 6 age-matched controls (AMC). Total neuron numbers were obtained using the fractionator. A neuron loss of 56.3% for the left amygdala and 50.5% for the right amygdala in AD was found, being more severe than previously reported. The subdivisions showed a differential neuron loss ranging from 35.5% in nucleus lateralis of the right amygdala to 70.4% in the nucleus basalis accessorius of the right amygdala. Moreover, a shift in size distribution to smaller neurons could be demonstrated. No left-right hemispheric differences were detected in total neuron numbers in AD and AMC.

The neuropsychology of paramedian thalamic infarction

A longitudinal study of three patients with CT-scan documented paramedian thalamic infarctions (bilateral, primarily right, unilateral left) is reported and the neuropsychology of human paramedian thalamic infarction is reviewed. The neuropsychological deficits following these selected lesions, the nature of the clinical memory disorder, and the neuroanatomy of memory are discussed. The significance of cortical/subcortical relationship in explaining observed behavioral changes is emphasized. Brain damage with maximum involvement in the dorsomedial nuclei and mamillothalamic tracts appears to cause primarily a memory disorder and frontal-limbic behavioral changes, the severity and profile of deficits depending on lesion extent and location. Both anterograde and remote memory loss may be present. Asymmetry in memory at the level of the thalamus was observed, following the left-verbal, right-nonverbal dichotomy.

Preserved crossmodal association following bilateral amygdalotomy in man

The present study investigated the role of the amygdala in crossmodal association in man. Recent experimental evidence indicates amygdalectomized monkeys show deficits when required to identify, through vision, objects that have been previously examined by touch. We employed a delayed nonmatching to sample task pre- and postoperatively in a patient who underwent bilateral stereotaxic amygdalotomy for intractable aggressivity. Bilateral amygdalotomy did not impair our patient's ability to associate an object from one sensory modality to another, following a short delay. The results suggest that sensory association memory does not depend upon the amygdala in humans. Examination of the neuroanatomic structures affected by the differing surgical procedures in the two species revealed entorhinal and perirhinal cortices were damaged in amygdalectomized monkeys but not in the present case. Because entorhinal cortex is an important structure for the formation of new memory traces, it is possible that damage to the entorhinal and surrounding cortical regions, rather than damage to the amygdala itself, is responsible for the crossmodal association deficit in monkeys.

Disorders of facial recognition, social behaviour and affect after combined bilateral amygdalotomy and subcaudate tractotomy--a clinical and experimental study

A case of a 37-year-old patient, 10 years after bilateral amygdalotomy and subcaudate tractotomy for chronic self-mutilation, is described. The clinical picture revealed a complex mental state, including disorders of facial recognition, social behaviour, affect and elements of the Kluver-Bucy syndrome. Mild selective deficits were demonstrated psychometrically in the recognition of familiar and unfamiliar faces. Certain features have been described in rhesus monkeys, but have not previously been reported in humans. Primate studies are discussed, with particular reference to the role of the amygdala in facial recognition.

Bilateral and limited amygdalohippocampal lesions causing a pure amnesic syndrome

A pure amnesic syndrome of 21 months' duration occurred in a 36-year-old man following a transient confusional state. The patient died of Hodgkin's disease. At postmortem examination, bilateral and symmetrical neuronal loss, without inflammatory changes, was restricted to the hippocampus and amygdaloid bodies.

The amygdala's role in human mnemonic processing

The possible role played by the human amygdaloid complex in the processing of mnemonic information is examined. First, evidence is reviewed from case reports in which amygdaloid damage occurred due to surgical intervention or pathological or age-related changes. Then, studies are evaluated in which the amygdala was stimulated or in which electrical potentials were recorded from it. Based on this survey an hypothesis on the possible involvement of the amygdala in mnemonic information processing is proposed. In essence, it is argued that the human amygdala is responsible for activating or reactivating those mnemonic events which are of an emotional significance for the subjects' life history and that this (re-)activation is performed by charging sensory information with appropriate emotional cues. Supportive evidence for this hypothesis is given based on human case reports, on studies in animals in which information processing was determined following amygdaloid lesions, and on evidence of neuroanatomical connections of the primate amygdala.

The neuropathology of amnesia

Relations between brain damage and memory disturbance are outlined with emphasis on the so-called amnesic syndrome. Following a brief introduction into forms of memory and memory failures, the basic causes of brain damaage (with relevance to amnestic failures) are described. Thereafter, the two best-known forms of brain damage-amnesia relations are reviewed: the consequences of damage to medial temporal lobe structures and to diencephalic regions. For the cases with medial temporal lobe damage, evidence is reported in greater detail for H.M., who has been examined more than any other amnesic patient for more than 30 years now, as a considerable amount of literature has accumulated on his behavior in diverse situations. Other cases with more or less circumscribed damage to medial temporal lobe structures are reviewed so as to outline criteria for or against the hypothesis that there are regions within the medial temporal lobe whose damage might be critical for the amnesic syndrome. Two cases of diencephalic amnesia are summarized in particular (cases of Mair et al., 1979) as they have received extensive neuropsychological and neuropathological investigation. Other cases with, for example, Korsakoff's disease are reviewed, as well as cases with diencephalic, or combined mesencephalic-diencephalic damage without nutritional causes. A third group of patients with massive, but still selective amnesic disturbances are then described: cases of basal forebrain damage, followed by descriptions of Alzheimer's disease which has similarities in the underlying neuropathology. This leads over to cases with more generalized intellectual deteriorations (dementia), which may have developed on the basis of primarily cortical damage or damage principally to basal ganglia structures. After reviewing cases with mainly material-specific memory failures--usually as a consequence of restricted neocortical damage--a separate section follows on patients in whom retrograde amnesia is the prominent symptom. The contribution of animal models of human amnesia is critically reviewed and discrepancies are analyzed between human and animal memory disturbances. This section emphasizes the value of investigating inter-dependencies between brain structures by pointing out that relations between memory disturbances and brain damage may be more complicated than apparent from a simple structure-function assignment. This aspect is further followed up in the conclusions.

Amnesic syndrome: a lesion-specific disorder?

This paper reviews various lines of evidence which suggest that organic amnesia stemming from lesions of the temporal lobe region produce an amnesia that is qualitatively different from that produced by diencephalic lesions. Differences between these two classes of amnesia were found within five dimensions of performance; (a) insight, concern and confabulation, (b) retrograde amnesia, (c) forgetting rate, (d) frontal lobe symptoms, (e) sensitivity to interference in short term memory. The range of differences found suggest that temporal lobe and diencephalic amnesics should not be considered as suffering from the same type of "amnesic syndrome". It is proposed that future experimental work on amnesia should take full account of neuropathological differences between amnesic patients.

The neuroanatomy of amnesia: amygdala-hippocampus versus temporal stem

Using a task known to be sensitive to human amnesia, we have evaluated two current hypotheses about which brain regions must be damaged to produce the disorder. Monkeys with bilateral transections of the white matter of the temporal stem were unimpaired, but monkeys with conjoint amygdala-hippocampal lesions exhibited a severe memory deficit. The results indicate that the hippocampus, amygdala, or both, but not the temporal stem, are involved in memory in the monkey and suggest that a rapprochement between the findings for the human and the nonhuman primate may be close at hand.

Intellectual function in patients with transient ischaemic attacks (TIA) or minor stroke. Long-term improvement after carotid endarterectomy

Psychological testing was performed in 25 patients (mean age 56 years) with transient ischaemic attacks and/or minor strokes and with angiographically verified internal carotid artery stenosis. The effects of carotid endarterectomy on intellectual functions were evaluated postoperatively at 2 weeks and 8 months respectively. Preoperatively the mean test values were below the normal level for all tests indicating a general intellectual impairment for the group as a whole. This may reflect multi-infarct dementia in statu nascendi. At the early postoperative test session some test results were statistically significantly worse than the preoperative. 8 months postoperatively the mean values for all tests had improved as compared with the preoperative values. This improvement reached a statistically significant level in 6 tests. When the side of operation was considered a pattern emerged: in the 12 patients with left-sided endarterectomies improvement was significant for tests mainly related to left-hemisphere function (Word Pairs Test, Story Recall, Trail Making B, Similarities) and in the 13 patients with right-sided endarterectomies significant improvement occurred in the functions mainly related to the right hemisphere (Visual Gestalts, Block Design, Digit Span backwards). This relationship between side of operation and improvement in lateralized functions cannot be explained by retest effects. It is concluded that TIA's and minor strokes per se may impair intellectual function, and that reversal of deterioration and even improved mental state may follow carotid endarterectomy.

Neurotoxic effects of heavy lead exposure determined with psychological tests

Nine men exposed to high concentrations of lead in their work at a battery plant were examined with the aid of psychological tests. Intelligence tests indicated normal intellectual potential, but memory, attention, concentration and psychomotor performance were severely impaired. The clinical picture indicated an organic mental syndrome. Psychological tests are recommended for clinical evaluation of neurotoxic effects of lead exposure.

Memory and learning in epileptic patients treated by amygdalotomy and anterior hippocampotomy

The memory and learning capacity in patients treated for temporal epilepsy was studied. The study was performed in 55 patients, observed before and after stereotaxic amygdalotomy and hippocampotomy. Very often disturbances in memory and learning capability were present before surgery. After surgery their learning efficiency increased. Disturbances in memory tracing, as provoked by distraction, remained at the same level after neurosurgery. No decrease in general intelligence was noted.