[Allesthesia].

Allesthesia is a peculiar symptom in which sensory stimulation to one side of the body is perceived on the opposite side. This was first described by Obersteiner1) in patients with spinal cord lesions in 1881. Thereafter, it has occasionally been reported for brain lesions and was classified into higher cortical dysfunction as a right parietal lobe symptom. No detailed studies on this symptom have long been reported in association with lesions of either the brain or spinal cord, partly because of difficulties in its pathological evaluation. Being scarcely mentioned in recent books on neurology, allesthesia has virtually become a forgotten neural symptom. The author identified allesthesia in some patients with hypertensive intracerebral hemorrhage and three patients with spinal cord lesions, and studied its clinical signs and mechanism of pathogenesis2). The following sections discuss allesthesia in light of its definition, cases and responsible lesions, clinical signs, and mechanism of pathogenesis.

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.