Sign language aphasia following right hemisphere damage in a left-hander: a case of reversed cerebral dominance in a deaf signer?

Recent lesion studies have shown that left hemisphere lesions often give rise to frank sign language aphasias in deaf signers, whereas right hemisphere lesions do not, suggesting similar patterns of hemispheric asymmetry for signed and spoken language. We present here a case of a left-handed, deaf, life-long signer who became aphasic after a right-hemisphere lesion. The subject exhibits deficits in sign language comprehension and production typically associated with left hemisphere damaged signers.

Functional amnesia: clinical description and neuropsychological profile of 10 cases.

We carried out the first neuropsychological study of a series of patients with functional amnesia. We evaluated 10 patients, first with a neurological examination and then with three tests of anterograde amnesia and four tests of retrograde amnesia. Excluding one patient who later admitted to malingering, all patients had a significant premorbid psychiatric history and one or more possible precipitating factors for their amnesia.

Discourse deficits following right hemisphere damage in deaf signers.

Previous findings have demonstrated that hemispheric organization in deaf users of American Sign Language (ASL) parallels that of the hearing population, with the left hemisphere showing dominance for grammatical linguistic functions and the right hemisphere showing specialization for non-linguistic spatial functions. The present study addresses two further questions: first, do extra-grammatical discourse functions in deaf signers show the same right-hemisphere dominance observed for discourse functions in hearing subjects; and second, do discourse functions in ASL that employ spatial relations depend upon more general intact spatial cognitive abilities? We report findings from two right-hemisphere damaged deaf signers, both of whom show disruption of discourse functions in absence of any disruption of grammatical functions. The exact nature of the disruption differs for the two subjects, however.

Transient global amnesia: a complication of incremental exercise testing.

Incremental exercise testing is routinely used for diagnosis, rehabilitation, health screening, and research. We report the case of a 71-yr-old patient with chronic obstructive pulmonary disease (COPD) who suffered an episode of transient global amnesia (TGA) several minutes after successfully completing an incremental exercise test on a cycle ergometer. TGA, which is known to be precipitated by physical or emotional stress in about one-third of cases, is a transient neurological disorder in which memory impairment is the prominent deficit.

Transient global amnesia and functional retrograde amnesia: contrasting examples of episodic memory loss.

We studied 11 patients with transient global amnesia (TGA) and ten patients with functional retrograde amnesia (FRA). Patients with TGA had a uniform clinical picture: a severe, relatively isolated amnesic syndrome that started suddenly, persisted for 4-12 h, and then gradually improved to essentially normal over the next 12-24 h. During the episode, the patients had severe anterograde amnesia for verbal and non-verbal material and retrograde amnesia that typically covered at least two decades.

A case of 'sign blindness' following left occipital damage in a deaf signer.

We report on a right-handed, deaf, life long signer who suffered a left posterior cerebral artery (PCA) stroke. The patient presented with right homonymous hemianopia, alexia and a severe sign comprehension deficit. Her production of sign language was, however, virtually normal.

Permanent global amnesia with unknown etiology.

Three patients developed severe and selective memory impairment with no known cause, one during a period of a few days and two others during a period of 1 to 2 years. In two of these patients, the amnesia has been stable and circumscribed for 5 to 6 years. The third patient appears to have declined in cognitive functions during the past year, at the age of 78, after 6 years of stable, circumscribed amnesia.

Three-dimensional trajectory analysis of congenital mirror movements in a single subject.

Mirror movements are involuntary movements executed by one side of the body that occur with voluntary activation of homologous muscles of the other side. Although such movements have been described qualitatively and with surface EMG recordings, the spatial and temporal characteristics of these movements remain relatively unexplored. We studied selected simple and complex upper limb movements in a 20-yr.

Neuropsychological presentation of Ganser symptoms.

We describe a patient with memory complaints whose history of head injury, polysubstance abuse and positive neurological findings suggested the presence of dementia. Neuropsychological testing revealed inconsistent performance plus multiple verbal and visuospatial approximate answers leading to the diagnosis of a Ganser episode. This case illustrates the importance of neuropsychological assessment in diagnosing Ganser symptoms and in differentiating this disorder from organic conditions and malingering.

Description of brain injury in the amnesic patient N.A. based on magnetic resonance imaging.

N.A. has been amnesic since 1960 when at the age of 22 years he sustained a penetrating brain injury with a miniature fencing foil.

Cognitive impairment following frontal lobe damage and its relevance to human amnesia.

Whether frontal lobe pathology can account for some of the cognitive impairment observed in amnesic patients with Korsakoff's syndrome was investigated. Various cognitive and memory tests were given to patients with circumscribed frontal lobe lesions, patients with Korsakoff's syndrome, non-Korsakoff amnesic patients, and control Ss. Patients with frontal lobe lesions were not amnesic.

Transient global amnesia: evidence for extensive, temporally graded retrograde amnesia.

We gave six patients with transient global amnesia (TGA) neuropsychological tests during and after their episodes. During TGA, all patients had severe anterograde amnesia for verbal and nonverbal material and a patchy but temporally graded retrograde amnesia for personal and public events dating back to at least 1960. In addition, they were unusually passive during TGA, had impaired ability to copy a complex figure, and possibly had mild impairment of confrontation naming.

Transient global amnesia: characterization of anterograde and retrograde amnesia.

Five patients with transient global amnesia (TGA) were given neuropsychological tests during and after their episode. During TGA, all patients were impaired on tests of new learning ability for both verbal and nonverbal material. Retrograde amnesia was patchy and covered a variable period of time before the onset of the episode: from about 36 hours in one case to 4 years in two cases.

Normal memory after damage to medial thalamus.

We studied two patients with nonhemorrhagic infarcts of the thalamus and assessed their cognitive functions comprehensively using standardized neuropsychological probes. Neither patient had any discernible memory impairment for verbal or nonverbal material. Analysis of magnetic resonance images with a stereotaxic method revealed that one subject had a right-sided lesion involving about 15% of the dorsomedial nucleus (DM).

Transient global amnesia. When memory temporarily disappears.

Transient global amnesia is a benign condition of sudden onset that resolves spontaneously. Retrograde amnesia prevents recall of events antedating the episode by hours to years, and anterograde amnesia produces the characteristic features of inability to learn new material and repetitious questioning. Laboratory investigation of these patients is generally unrewarding.

Short-latency somatosensory evoked potentials.

Short-latency components of the somatosensory evoked potential (SEP) were studied in 20 subjects who had median nerve stimulation using knee, forehead, and ear reference recordings. Six potentials were identified (P10, P12, P14, N19, P20, P23). Potential P10 seems to originate in the brachial plexus, P12 most likely is generated in dorsal column nuclei and medial lemniscus, P14 is probably thalamic in origin but is frequently bilobed and may have a second generator source, and N19 may originate in sensory radiation or cortex.