Transient global amnesia and thalamic hemorrhage

Cerebellar Ischemia Presenting as Transient Global Amnesia

Transient global amnesia (TGA) consists of acute-onset anterograde amnesia and typically resolves within 24 hours. Reported etiologies of TGA include transient ischemia to the hippocampus or thalamus, migraine, venous flow abnormalities, and epilepsy. There are no reports of cerebellar ischemia as an etiology of TGA. A 78-year-old woman with a medical history of diabetes presented to the Ohio State University ER after a period of anterograde amnesia lasting 3 hours. She was alert during the event, but asked the same questions repeatedly. Upon arrival to the ER, she was hypertensive but clinically back to baseline, with no recall of the 3-hour time period. An MRI of her brain revealed an isolated hyperintense signal on diffusion-weighted imaging (DWI) at the junction of the superior cerebellum and vermis, with apparent diffusion coefficient correlation. Vascular imaging of the brain and neck and a routine EEG were unremarkable. We diagnosed her with cerebellar ischemia presenting as TGA. She had no head injury, migraine, or history of epilepsy to suggest alternative etiologies of TGA. An increasing amount of literature has reported that the cerebellum is linked to the limbic system. A case series of SPECT imaging on individuals with TGA revealed transient cerebellar vermis hypoperfusion in addition to hippocampal DWI changes. We present what may be a novel report of isolated cerebellar ischemia presenting as TGA, and we add to the literature for clinicians to consider the possibility that damage to the cerebellum or its circuit to the cerebrum or thalamus can present as TGA.

Value of dynamic susceptibility contrast perfusion MRI in the acute phase of transient global amnesia

PURPOSE

Transient global amnesia (TGA) is a transitory, short-lasting neurological disorder characterized by a sudden onset of antero- and retrograde amnesia. Perfusion abnormalities in TGA have been evaluated mainly by use of positron emission tomography (PET) or single-photon emission computed tomography (SPECT). In the present study we explore the value of dynamic susceptibility contrast perfusion-weighted MRI (PWI) in TGA in the acute phase.

METHODS

From a MRI report database we identified TGA patients who underwent MRI including PWI in the acute phase and compared these to control subjects. Quantitative perfusion maps (cerebral blood flow (CBF) and volume (CBV)) were generated and analyzed by use of Signal Processing In NMR-Software (SPIN). CBF and CBV values in subcortical brain regions were assessed by use of VOI created in FIRST, a model-based segmentation tool in the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FSL).

RESULTS

Five TGA patients were included (2 men, 3 women). On PWI, no relevant perfusion alterations were found by visual inspection in TGA patients. Group comparisons for possible differences between TGA patients and control subjects showed significant lower rCBF values bilaterally in the hippocampus, in the left thalamus and globus pallidus as well as bilaterally in the putamen and the left caudate nucleus. Correspondingly, significant lower rCBV values were observed bilaterally in the hippocampus and the putamen as well as in the left caudate nucleus. Group comparisons for possible side differences in rCBF and rCBV values in TGA patients revealed a significant lower rCBV value in the left caudate nucleus.

CONCLUSIONS

Mere visual inspection of PWI is not sufficient for the assessment of perfusion changes in TGA in the acute phase. Group comparisons with healthy control subjects might be useful to detect subtle perfusion changes on PWI in TGA patients. However, this should be confirmed in larger data sets and serial PWI examinations.

Transient global amnesia associated with an acute infarction at the cingulate gyrus

Background. Transient global amnesia (TGA) is a syndrome of sudden, unexplained isolated short-term memory loss. In the majority of TGA cases, no causes can be identified and neuroimaging, CSF studies and EEG are usually normal. We present a patient with TGA associated with a small acute infarct at the cingulate gyrus. Case Report. The patient, a 62 year-old man, developed two episodes of TGA. He had hypertension and hypercholesterolemia. He was found to have an acute ischemic stroke of small size (15 mm of maximal diameter) at the right cerebral cingulate gyrus diagnosed on brain magnetic resonance imaging. No lesions involving other limbic system structures such as thalamus, fornix, corpus callosum, or hippocampal structures were seen. The remainder of the examination was normal. Conclusion. Unilateral ischemic lesions of limbic system structures may result in TGA. We must bear in mind that TGA can be an associated clinical disorder of cingulate gyrus infarct.

Injury of the mammillothalamic tract in patients with thalamic hemorrhage

Objective: Injury of the mammillothalamic tract (MTT) has been suggested as one of the plausible pathogenic mechanisms of memory impairment in patients with thalamic hemorrhage; however, it has not been clearly demonstrated so far. We attempted to investigate whether injury of the MTT documented by diffusion tensor tractography following thalamic hemorrhage correlates with cognitive impairment.

Methods: We recruited 22 patients with a thalamic hemorrhage and 20 control subjects. MTTs were reconstructed using the probabilistic tractography method. Patients were classified into two subgroups: reconstructed group, patients whose MTT was reconstructed in the affected hemisphere, and non-reconstructed group, patients whose MTT was not reconstructed.

Results: Mammillothalamic tract was reconstructed in 5 (22.7%, reconstructed group) patients in the affected hemisphere and was not reconstructed in the remaining 17 patients (77.3%, non-reconstructed group). In addition, the MTT was not reconstructed even in the unaffected hemisphere in four patients (23.5%) in non-reconstructed group. Fractional anisotropy and mean diffusivity values of the affected hemisphere in reconstructed group also did not show significant differences from those in the unaffected hemisphere of reconstructed group and the control group (p > 0.05). However, the tract volume of the affected hemisphere in reconstructed group was significantly lower than that of the unaffected hemisphere in reconstructed group and the control group (p < 0.05).

Conclusion: A large portion of patients with thalamic hemorrhage appeared to suffer severe injury of the ipsilesional MTT (77.3%) and 18.2% of them appeared to suffer severe injury even in the contralesional MTT. In addition, the remaining 22.7% of patients who had preserved integrity of the ipsilesional MTT appeared to suffer partial injury of the ipsilesional MTT.

Cognitive, affective and behavioural disturbances following vascular thalamic lesions: a review

During the last decades, many studies have shown that the thalamus is crucially involved in language and cognition. We critically reviewed a study corpus of 465 patients with vascular thalamic lesions published in the literature since 1980. 42 out of 465 (9%) cases with isolated thalamic lesions allowed further neurocognitive analysis. On the neurolinguistic level, fluent output (=31/33; 93.9%), normal to mild impairment of repetition (=33/35; 94.3%), mild dysarthria (=8/9; 88.9%) and normal to mild impairment of auditory comprehension (=27/34; 79.4%) were most commonly found in the group of patients with left and bilateral thalamic lesions. The taxonomic label of thalamic aphasia applied to the majority of the patients with left thalamic damage (=7/11; 63.6%) and to one patient with bithalamic lesions (=1/1). On the neuropsychological level, almost 90% of the left thalamic and bithalamic patient group presented with amnestic problems, executive dysfunctions and behaviour and/or mood alterations. In addition, two thirds (2/3) of the patients with bilateral thalamic damage presented with a typical cluster of neurocognitive disturbances consisting of constructional apraxia, anosognosia, desorientation, global intellectual dysfunctioning, amnesia, and executive dysfunctions associated with behaviour and/or mood alterations. Our study supports the long-standing view of a 'lateralised linguistic thalamus' but restates the issue of a 'lateralised cognitive thalamus'. In addition, critical analysis of the available literature supports the view that aphasia following left or bithalamic damage constitutes a prototypical linguistic syndrome.

Vascular syndromes of the thalamus

BACKGROUND

This article reviews the anatomy, connections, and functions of the thalamic nuclei, their vascular supply, and the clinical syndromes that result from thalamic infarction.

SUMMARY OF REVIEW

Thalamic nuclei are composed of 5 major functional classes: reticular and intralaminar nuclei that subserve arousal and nociception; sensory nuclei in all major domains; effector nuclei concerned with motor function and aspects of language; associative nuclei that participate in high-level cognitive functions; and limbic nuclei concerned with mood and motivation. Vascular lesions destroy these nuclei in different combinations and produce sensorimotor and behavioral syndromes depending on which nuclei are involved. Tuberothalamic territory strokes produce impairments of arousal and orientation, learning and memory, personality, and executive function; superimposition of temporally unrelated information; and emotional facial paresis. Paramedian infarcts cause decreased arousal, particularly if the lesion is bilateral, and impaired learning and memory. Autobiographical memory impairment and executive failure result from lesions in either of these vascular territories. Language deficits result from left paramedian lesions and from left tuberothalamic lesions that include the ventrolateral nucleus. Right thalamic lesions in both these vascular territories produce visual-spatial deficits, including hemispatial neglect. Inferolateral territory strokes produce contralateral hemisensory loss, hemiparesis and hemiataxia, and pain syndromes that are more common after right thalamic lesions. Posterior choroidal lesions result in visual field deficits, variable sensory loss, weakness, dystonia, tremors, and occasionally amnesia and language impairment.

CONCLUSIONS

These vascular syndromes reflect the reciprocal cerebral cortical-thalamic connections that have been interrupted and provide insights into the functional properties of the thalamus.

The importance of identifying intracranial haemorrhage as a cause of transient focal neurological symptoms

Until recently, there have been no reports of intracerebral haemorrhage presenting with transient neurological symptoms. We present two cases of intracerebral haemorrhage presenting as transient ischaemic attacks and discuss the radiological changes on early and late CT scans. It would seem justified to scan most patients presenting with TIA early to institute appropriate secondary prevention measures.

Prolonged reversible amnesia: A case report

A 55-year-old woman sustained an acute amnesia that lasted for 8 days. The results of a cerebral magnetic resonance imaging scan and an electroencephalogram were normal. A Wechsler Memory Scale-Revised (WMS-R) test performed 6 days after the event showed global impairment in every domain, except for attention/concentration. A single photon emission computed tomography (SPECT) scan taken 8 days after the event showed hypoperfusion in the left temporal and frontal areas. The results of a follow-up SPECT scan on the 40th day after the episode were normal. A second WMS-R test showed some improvement on the 40th day after the event and considerable improvement on the 176th day. The clinical feature of the patient meets the criteria of transient global amnesia (TGA), except for her protracted course. It was not amnesic stroke, however, because of its reversibility and because there were no accompanying neurological signs. This case raises some implications of the pathogenesis of TGA and the clinical applicability of research criteria.