Left thalamic hypertensive haemorrhage presenting as transient global amnesia

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.

Transient global amnesia and thalamic hemorrhage

A left rostral thalamic hematoma was found in a 52-year-old hypertensive man who suffered from a 10-h episode of transient global amnesia (TGA). A neuropsychological study revealed no cognitive impairment in a follow-up period for 5 years. The left rostral part of the thalamus appears to be responsible for his TGA, due probably to an interference of the mamillothalamic tract, ventroamygdalofugal pathway or dorsal noradrenergic bundle.

Transient global amnesia

Transient global amnesia (TGA) is a transient, benign neurological syndrome, characterized by global loss of memory, preserved consciousness and self-awareness, associated with some behavioral changes (in particular, repetitive questioning). It generally resolves within 24 h. Mild brain stem symptoms can often be demonstrated during the attack, but major neurological abnormalities never occur. The only sequel is a permanent amnesic gap for the duration of the episode. The episode is often preceded by typical precipitating events, such as physical activity, emotional stress, acute pain, comprising haemodynamic changes of the body. The diagnosis is easy provided one is acquainted with the syndrome. The prevalence of vascular risk factors is low and the risk for stroke is not increased. Although much evidence indicates the possibility of a causative ischaemia in the inferomedial parts of the temporal lobes, an atherothrombo-embolic TIA is not the cause of TGA, and TGA is unrelated to cerebrovascular disease in general. In the author's view, the cause of TGA is a transient ischemic attack (TIA) but a haemodynamic one of the vertebrobasilar system, producing a transient dysfunction of inferomedial parts of the temporal lobes, regions that are particularly sensitive to impaired blood supply. For a full pathogenetic explanation of TGA, clarification of the underlying mechanisms is a prerequisite. This touches on the genesis of migraine and Leao's spreading depression phenomenon. The term 'amnesic TIA' would reflect the pathogenesis more appropriately.

Unilateral amnesic stroke. Six new cases and a review of the literature

BACKGROUND AND PURPOSE

Although persistent amnesia due to bilateral limbic system infarction is well described, reports of amnesic syndromes due to unilateral stroke have appeared infrequently and unsystematically. We report six new cases and review previously published reports to expand and consolidate knowledge regarding amnesic stroke.

CASE DESCRIPTIONS

Six patients developed acute amnesia associated with unilateral stroke. Brain computed tomography or magnetic resonance imaging revealed lesions in limbic structures, which accounted for the memory deficit. Based on these as well as similar cases in the literature, we delineate three distinct syndromes of unilateral amnesic stroke involving the territories of the posterior cerebral, anterior choroidal, and thalamic penetrating arteries. Eighty-five percent of reported cases have involved the left hemisphere.

CONCLUSIONS

Persistent as well as transient amnesia may be the sole or primary manifestation of unilateral hemispheric stroke. The vascular mechanisms of amnesic stroke are diverse. Patients presenting with acute amnesia possibly related to cerebral ischemia should be classified by documented or presumed lesion site as well as the involved vascular territory. Left amygdalohippocampal or diencephalic dysfunction may produce a particular vulnerability to global amnesia.