[Alloesthesia without impairment of consciousness after right putaminal small hemorrhage]

Alloesthesia is a condition in which a sensory stimulus, given on one side of the body, is perceived to be at the corresponding area on the opposite side. In our previous study (Kawamura, Hirayama et al., 1987), we suggested that it may be useful for localization because this phenomenon was observed most frequently in patients with a right putaminal hemorrhage of medium or large size, an average of 42 ml on CT scans, presenting a slight disturbance of consciousness and, in about half of the patients, anosognosia. We also suggested that since alloesthesia is produced not only in cerebral but also in spinal cord lesions, it seems to represent an elementary sensory disturbance of sensory pathways, not a higher cortical dysfunction. We recently observed alloesthesia in two other patients with smaller right putaminal hemorrhages, 7 ml and 6 ml, respectively, who exhibited no disturbance of consciousness, but had impairment not only of superficial but also of proprioceptive sensations. In Patient 1, superficial sensations were intact on admission, except those on the left side of the face. Cortical somatosensory evoked potentials (SEPs) after stimulating the median nerve were measured on Patient 1 on the 11th hospital day when a left hemihypalgesia had developed due to enlargement of the hematoma from 7 to 14 ml. Stimulation of the clinically affected side (left) evoked no N20 from the contralateral scalp. Right-sided stimulation was normal. The fact that both patients showed alloesthesia with no accompanying disturbance of consciousness supported our view of its mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)