Compromised pontocerebellar and cerebellothalamocortical systems: speculations on their contributions to cognitive and motor impairment in nonamnesic alcoholism.

BACKGROUND: Corticopontocerebellar and cerebellothalamocortical circuits underlie a wide range of neuropsychological processes compromised by alcoholism. The analyses herein tested whether abnormalities of volumes of brain structures forming nodes of these separate feed-forward and feedback systems are selectively related to each other and whether any of these noncortical regions can account for cognitive and motor deficits occurring as sequelae of chronic alcoholism. METHODS: Regional brain measures originated from our prior neuroimaging studies, showing in alcoholics significant volume deficits in the principal structures of interest: cerebellar hemispheres, vermis, pons, and thalamus as well as prefrontal, frontal, and parietal cortex. Neuropsychological functions targeted for analysis-problem solving, visuospatial ability, and static postural stability-showed 0.6 to 1.6 SD deficits in these alcoholic men. RESULTS: In alcoholics, the patterns of correlations were consistent with dissociation of thalamic and pontine circuitry. Pontine and thalamic volumes were not correlated with each other. Pontine volumes correlated with white matter volumes of anterior superior vermis and gray and white matter volumes of the cerebellar hemispheres but not with cortical regional volumes. Thalamic volumes correlated with gray matter volumes of the cerebellar hemispheres, parietal cortex, and inferior posterior vermian lobule, which itself correlated with parietal, prefrontal, and frontal cortical volumes. Controls did not show these correlational patterns. Brain structure-function relationships in alcoholics examined with multiple regression identified anterior vermian but not prefrontal or parietal volume as a unique predictor of balance scores; vermian and thalamic but not prefrontal cortical volumes as predictors of card sorting scores; and cerebellar hemispheric white matter but not parietal cortical volume as a predictor of visuospatial ability. CONCLUSIONS: Each major node of frontocerebellar circuitry shows volume deficits in alcoholics but can be independently compromised. Disruption of these circuits may underlie alcoholism-related neuropsychological deficits, either by abnormalities present in individual nodes or by disconnection via interruption of selective circuitry.

The relationship between retrograde and anterograde amnesia in patients with typical global amnesia.

An extensive battery of tests of anterograde amnesia and remote memory was given to ten amnesics with lesions either to the medial temporal lobes of the diencephalon. These showed that the patients had anterograde amnesia with deficits in verbal and non-verbal recall and recognition, but preservation of word stem completion and intelligence. Mild impairments on executive tests and digit span performance were largely caused by the poor performance of the Korsakoff patients. The amnesics also showed remote memory deficits for personal and public domain information, and temporal gradients were observed for some of the tests. These deficits probably arose because the patients' anterograde amnesia was more severe than their retrograde amnesia even for the recent pre-morbid past. They were more impaired in the recall of details about famous names in their ability to recognize such names. There was also a suggestion that performance on anterograde tests did not relate strongly to that on tests of retrograde amnesia of the remote pre-morbid past. However, this effect was less apparent with memory for personal information when the format and the information tapped were matched on pre- and post-morbid tests.

Influence of prior events on cognitive judgments in amnesia.

Amnesic patients and control Ss read the names of famous and nonfamous persons. Subsequently, both groups were more likely to designate a name as famous if it had been encountered previously. The facilitatory effect of prior presentation was similar for amnesic patients and control Ss and similar for famous and nonfamous names. For amnesic patients, the effect occurred despite severely impaired recognition memory for the names. In a 2nd experiment, recombining the first and last names that had been presented together did not diminish the facilitatory effect of prior presentation, which indicates that the effect does not depend on forming an association between first and last names. The results show that nondeclarative (implicit) memory can support the acquisition of information that is specific (e.g., names of persons) and that has no preexisting representation (e.g., nonfamous names).

Wernicke's encephalopathy.

Wernicke's encephalopathy should be considered as a possible diagnosis in comatose and hypothermic patients. The classic triad of confusion, ophthalmoplegia (or nystagmus) and ataxia may be absent, and the history of alcohol abuse or other causes of thiamine deficiency may be unknown. Left untreated, acute Wernicke's encephalopathy has a 17 percent mortality rate. Since the morbidity from Wernicke's encephalopathy is potentially reversible with parenteral thiamine, and large doses of thiamine can be given without documented ill effects, it is recommended that all comatose or hypothermic patients, as well as those with more classic presentations of Wernicke's encephalopathy, be given parenteral thiamine before administration of glucose.

[Neuropathology of amnesic syndromes in man]. / Neuropathologie des syndromes amnésiques chez l'homme.

Controversies exist about the type of lesions observed in Korsakoff's syndrome or amnestic syndromes. A review of clinicopathologic data in the literature and findings in a personal series of 31 patients with amnestic syndromes (14 with alcoholism and nutritional deficiency, 8 with tumors including 2 with craniopharyngiomas, 5 with Pick's disease and presbyophrenic manifestations, 2 with vascular affections and one each with anoxia and herpetic encephalitis) were used to determine most frequently responsible lesions. Although it is generally accepted that there must be bilateral lesions divergent opinions are found with regard to the significance of limbic-hippocampomammillary circuit lesions. Some authors refute any specific role for the limbic circuit, and particularly any part played by Ammon's horn, in favor of a role for the temporal isthmus while others reject the possible role of the mammillary bodies and implicate the dorsomedian nucleus of the thalamus. The present study confirmed the importance of the limbic-hippocampomammillocingulus circuit in the maintenance of long-term memory. Involvement of the hippocampus appears obvious, particularly in disorders due to lesions of the subiculum and sommer's field. Mammillary body lesions are a constant finding in amnestic syndromes due to alcoholic nutritional deficiency and may also be present in Korsakoff's syndromes of tumoral origin e.g. a compression due to a craniopharyngioma. The rarely mentioned lesions of the cingular convolution are a further possible cause. The role of a thalamic lesion has not been totally confirmed, findings indicating equally frequent involvement of laterodorsal and dorsomedian nuclei. Clinical evidence, however, points to correlations between fabulation, false recognition and a thalamic lesion. The role of the fornix is debatable, although it is difficult to understand how destruction of the hippocampic formation or of the mammillary bodies can provoke memory disorders while an interruption in the structure that links them would have no consequences, unless it is admitted that as in animals other pathways exist that pass little or not at all through the fornix. Clinical expression of bilateral lesions of these structures differs according to whether they affect the posterior Ammon's horn region or lie more anteriorly in the trigonomammillothalamo-cingular complex. Clinical features of hippocampic amnesia include continuous anterograde amnesia with successive periods of forgetfulness, retrograde deficit of variable duration, parallel alterations of verbal and visuospatial memory and absence of fabulation.(ABSTRACT TRUNCATED AT 400 WORDS)