The History of Amnesia-a Review.

PURPOSE OF REVIEW: This review traces amnesia's history from its earliest eighteenth century classification as a medical disorder to the present. Sophisticated depictions in the nineteenth century literature containing elaborate compilations of causal factors, including neurologic, consider pathogenesis, course, duration, durability, and temporal features. RECENT FINDINGS: Severe amnesia, especially anterograde involving new learning, found archetypal expression in the twentieth century, in the case of H.M. The "pure" amnesia confirmed an independent memory disorder distinct from other cognitive disturbances, with functional dissociations illustrating nuanced manifestations and highlighting the role of some discovered structural correlates (e.g., hippocampal and associated MTL regions). Moreover, neural networks and interconnections have also notably been implicated. Although concepts of illness change across cultures and centuries, portrayal of amnesia remained consistent as it spread internationally. Amnesia's groundbreaking original nosology laid a foundation for contemporary paradigms of the multifactorial nature, specificity, and complexity of a poignantly thought-provoking disorder.

The Merging Tracks of Anosognosia and Neglect.

Anosognosia and hemineglect are among the most startling neurological phenomena identified during the 20th century. Though both are associated with right hemisphere cerebral dysfunction, notably stroke, each disorder had its own distinct literature. Anosognosia, as coined by Babinski in 1914, describes patients who seem to have no idea of their paralysis, despite general cognitive preservation. Certain patients seem more than unaware, with apparent resistance to awareness. More extreme, and qualitatively distinct, is denial of hemiplegia. Various interpretations of pathogenesis are still deliberated. As accounts of its captivating manifestations grew, anosognosia was established as a prominent symbol of neurological and psychic disturbance accompanying (right-hemisphere) stroke. Although reports of specific neglect-related symptomatology appeared earlier, not until nearly 2 decades after anosognosia's inaugural definition was neglect formally defined by Brain, paving a path spanning some years, to depict a class of disorder with heterogeneous variants. Disordered awareness of body and extrapersonal space with right parietal lesions, and other symptom variations, were gathered under the canopy of neglect. Viewed as a disorder of corporeal awareness, explanatory interpretations involve mechanisms of extinction and perceptual processing, disturbance of spatial attention, and others. Odd alterations involving apparent concern, attitudes, or belief characterize many right hemisphere conditions. Anosognosia and neglect are re-examined, from the perspective of unawareness, the nature of belief, and its baffling distortions. Conceptual parallels between these 2 distinct disorders emerge, as the major role of the right hemisphere in mental representation of self is highlighted by its most fascinating syndromes of altered awareness.

J.L. Prévost, Eye Deviation, and Early Steps in Space Lateralization: "Looking At or Away".

Conjugate deviation of the eyes toward side of lesion was recognized over a century ago as a manifestation accompanying hemiplegia, usually of apoplectic origin. While working on the services of Alfred Vulpian and Jean-Martin Charcot, Jean-Louis Prévost sparked international interest in the neurologic sign later named after him. His 1868 thesis represents the first systematic case series of patients with this ocular sign, observed in conjunction with head rotation toward the nonparalyzed side, which he called conjugate deviation (CD) of the eyes. Within a decade, it was uniformly reported in both French and English medical literature. Ipsilesional deviation was the rule for cortical or subcortical paralytic lesions. Contralesional deviation, more rarely seen, signaled lesions of lower brain regions, particularly pontine, or indicated irritative, excitatory effects (as in Jacksonian epilepsy). The sign was recognized to be a valuable diagnostic aid in unilateral cerebral lesions. Centralized control of CD by specific cerebral sites, such as frontal, or occipital, or oculomotor centers, was explored, along with the complex relationship with hemineglect, which interestingly was reported only several decades later. The discovery of intricate oculomotor interconnections and self-space relationships, which play an essential role in CD, owes much to Prévost and his followers.

Early History of Amnesia.

Memory and forgetfulness have been viewed since antiquity from perspectives of physical, emotional, and spiritual states of well-being, and conceptualized philosophically. Numerous discussions of memory loss, or case reports, existed, but a fundamental advance in conceptualization of memory loss as a pathological clinical phenomenon originated when Sauvages classified "amnesia" as a medical disorder, in 1763. Originally, amnesia was recognized as a weakening or dissolution of memory, according to a taxonomy that ascribed known causes to the disorder. Etiologic factors included neurological disorders of stroke, hemorrhage, and head injury, metabolic dysregulation, alcohol and substance abuse, toxicity, anoxia, and other acute or chronic (sometimes progressive) brain disorders. Clinical descriptions of amnesia appeared internationally in medical dictionaries and scientific encyclopedias in the early 19th century. The possibility that amnesia could be either idiopathic, or symptomatic of another illness, was proposed based on the wide range of recognized etiologies and associations. Debate ensued regarding the status of amnesia as an illness or a symptom, but regardless, amnesia was soon recognized as an independent disorder of memory, distinguishable from disorders of global intellect, or of consciousness, or of language. Distinctions of amnesia considered its temporal gradient, duration and natural course, nature of onset, severity or depth of memory loss, course, and prognosis. Concepts of retrograde (forgetting knowledge preceding onset) and anterograde (difficulty learning, recalling new information) further specified the nature of amnestic memory difficulty. Alcoholic amnesia in Korsakoff's syndrome generated much attention. Amnesia as a clinical feature was critical to the development of notions of dissociation of conscious from subconscious recall in hysteria, and differentiation of neurogenically-based from psychogenically-based amnesia became central to understanding post-traumatic states. Amnesia studied as a disorder of memory remains an avenue to enrich clinical understanding of a condition that continues to be powerfully challenging to this day.

Hemineglect and Attentional Dysfunction.

Tracing the history of neglect is intriguing, as diverse terminologies have been used to characterize a multi-factorial disorder with rather startling manifestations. In part, heterogeneous terms may have hinted at distinct subtypes. Thus, different variants of hemi-inattention and neglect relate conceptually, but may be functionally dissociable. Patients with neglect, acting as if the world-space they perceive is full, do not phenomenally experience the omissions or absences so patently obvious to an observer. From the late 19th century, hemi-inattention was described according to its prominent manifestations, visual, bodily or spatial. Since then, diverse terms including imperception, inattention, unilateral visual inattention, unilateral spatial agnosia, and neglect, among others, reflected proposed underlying mechanisms. Major theories presented to account for this curious, even astonishing, neurological disorder, included disruption of body-scheme, perceptual rivalry and extinction, forgetting or amnesia for half the body, and highly nuanced models of distribution of directed spatial attention, and of disrupted perceptual processes. Unlike neurological counterparts, already designated as hemi-syndromes by the first part of the 20th century, not until about 1970 did neglect become so broadly recognized as a syndrome. Earlier, commonalities were identified, features conceptually clustered, and then subtypes were distinguished. Neglect was designated as an overarching term for a class of disorder with distinct subtypes, including visual, motor, extrapersonal, bodily or personal, other somatosensory, and representational. Specificity for modality, chronology, material, and symptom severity was noted. Remarkable clinical, neuropsychological, and behavioral manifestations of hemi-inattention and neglect may involve varying proposed mechanisms of higher cognitive functions, all within a spectrum of clinical disorder. Concepts of connectivity and interaction, neural networks, and functional integration enhance understanding of dysfunction, recovery, and compensation in neglect and inattention. Focus on distinct manifestations clustered under the umbrella of neglect offers a vantage point for examining historical trends in approach to the phenomenon.

Unawareness of disability in CVA: a comparison study with musculoskeletal patients.

OBJECTIVE: Unawareness in cerebrovascular accident (CVA) was investigated employing a multiple rater, multimodal assessment approach and by comparison with demographically matched musculoskeletal patients. BACKGROUND: Unawareness is a phenomenon often reported in CVA that poses challenges in neurorehabilitation settings, but debate exists regarding processes involved. METHOD: Three techniques for rating awareness were used: independent clinical rating, comparison of structured interview with medical information, and discrepancies in performance estimation. Association with neurocognitive and psychogenic factors was also explored. RESULTS: The specific association of unawareness with CVA was confirmed; CVA patients had less awareness of disability than musculoskeletal patients and underestimated performance difficulties relative to staff. Awareness measures showed convergent validity, yet were not redundant, perhaps tapping different aspects of awareness. Cognition, emotion, and group diagnostic classification successfully predict awareness when combined in multiple regression analyses. Unawareness had variable associations with cognition and emotion individually. Awareness was more consistently associated with cognition in musculoskeletal patients. Results suggested that unawareness is complex and multidimensional. Findings support some concurrence of cognitive and emotional factors in patients with unawareness of disability, yet suggest that unawareness may also have some distinct and independent status beyond contributions from associated factors.

The philosopher's swoon--the concussion of Michel de Montaigne: a historical vignette.

The French philosopher Michel Eyquem de Montaigne (1533-1592) sustained a transient loss of consciousness due to a head injury. Montaigne described his concussion as a "swoon," with astutely illustrative details of the symptoms he experienced, including brief loss of consciousness, with apparent (temporary) confusion, and post-traumatic amnesia. His vivid portrayal of the recovery period lends understanding of the process of conscious awakening after his near-death experience. Thanks to his power of introspection and literary talent we may gain insight into the feelings and perceptions of some patients during their recovery from concussion.

Babinski's anosognosia for hemiplegia in early twentieth-century French neurology.

In 1914, Babinski first described "anosognosia"; a term he coined for a phenomenon involving unawareness of disability in hemiplegia. Historical roots of contemporary perspectives on anosognosia after stroke may be found in early discussions among French neurologists. Current notions and debate regarding the roles played by cognition, emotional factors, sensory loss and somatosensory neglect in anosognosia, and the distinctness of anosognosia as a symptom echo the theoretical dilemmas of an earlier past. Historical overview of the development of perspectives on anosognosia enriches our understanding of unawareness of disability.