Non-motor associative learning in patients with isolated degenerative cerebellar disease.
In recent decades it has become clear that the cerebellum is involved in associative motor learning, but its exact role in motor learning as such is still controversial. Recently, a contribution of the cerebellum to different cognitive abilities has also been considered, but it remains unclear whether the cerebellum contributes to cognitive associative learning. We compared nine patients with an isolated cerebellar degenerative disease in a cognitive associative learning task with 10 controls. Patients and controls were matched for age, sex, handedness, level of education, intelligence and capabilities of visual memory. The subjects were asked to learn the association between six pairs of colours and numerals by trial and error. Additionally, a simple reaction time and a visual scanning test were conducted in order to control for the influence of motor performance deficits in cerebellar patients. In comparison with the controls, it took the patients significantly longer to learn the correct associations between colours and numerals, and they were impaired in recognizing them later on. Two patients showed no associative learning effect at all. Neither the simple reaction time nor the visual scanning time correlated substantially with the results of associative learning. Therefore, motor-associated disabilities are unlikely to be the reason for the learning deficit in cerebellar patients. Our results suggest that the cerebellum might contribute to motor-independent processes that are generally involved in associative learning. (+info)
Contralateral deafness following unilateral suboccipital brain tumor surgery in a patient with large vestibular aqueduct--case report.
A 68-year-old female developed contralateral deafness following extirpation of a left cerebellopontine angle epidermoid cyst. Computed tomography showed that large vestibular aqueduct was present. This unusual complication may have been caused by an abrupt pressure change after cerebrospinal fluid release, which was transmitted through the large vestibular aqueduct and resulted in cochlear damage. (+info)
Anticonvulsant-induced dyskinesias: a comparison with dyskinesias induced by neuroleptics.
Anticonvulsants cause dyskinesias more commonly than has been appreciated. Diphenylhydantoin (DPH), carbamazepine, primidone, and phenobarbitone may cause asterixis. DPH, but not other anticonvulsants, may cause orofacial dyskinesias, limb chorea, and dystonia in intoxicated patients. These dyskinesias are similar to those caused by neuroleptic drugs and may be related to dopamine antagonistic properties possessed by DPH. (+info)
Intrameatal aneurysm successfully treated by meatal loop trapping--case report.
A 77-year-old female presented with a rare intrameatal aneurysm manifesting as sudden onset of headache, hearing loss, tinnitus, and vertigo associated with subarachnoid hemorrhage. Meatal loop trapping was performed. After surgery, the patient's functions recovered almost completely, probably because of the preservation of the 7th and 8th cranial nerves and the presence of effective collaterals in the area supplied by the anterior inferior cerebellar artery. (+info)
Remote regional cerebral blood flow consequences of focused infarcts of the medulla, pons and cerebellum.
The aim of this study was to evaluate regional and remote diaschisis of inferior brain stem or cerebellar infarcts in 25 patients presenting with relatively limited lesions. Patients presented with medullary, pontine or cerebellar infarction. METHODS: Lesions were evaluated on MRI (0.5 T). Regional cerebral blood flow (rCBF) was assessed by means of SPECT, after injection of 9rmTc-hexamethyl propyleneamine oxime (HMPAO) and, when possible, inhalation of 133Xe in the same session. For each method, asymmetry indices (Als), comparing contralateral to ipsilateral rCBF values, were calculated in four areas of each cerebral hemisphere and in the cerebellum and later compared with values obtained in healthy subjects (P = 0.05). RESULTS: Higher rCBF values were observed in the contralateral cerebellum in 2 of 7 patients with selective lateral medullary lesions, and cerebellar Als were significantly increased. When a cerebellar infarct was associated with a lateral medullary lesion, the cerebellar and contralateral hemispheric asymmetries were more severe. Unilateral paramedian pontine infarcts had more frequent consequences on the cerebellum (2 of 3 cases), with rCBF or tracer uptake being reduced in the ipsilateral or the contralateral lobe. Inverse cerebral hemispheric asymmetry could then be observed. Bilateral pontine lesions were difficult to evaluate. Using 99mTc-HMPAO, discrete cerebellar asymmetry was observed in 3 of 6 cases. Pure cerebellar infarcts in the posterior inferior cerebellar artery territory were always associated with a severe ipsilateral flow drop in the cerebellum, and contralateral hemispheric diaschisis was frequent (3 of 4 patients), predominating in the frontotemporal cortex and subcortical structures. This was also more obvious using 99mTC-HMPAO than 133Xe. Variance analysis showed that hemispheric diaschisis was more severe in mixed brain stem and cerebellar infarcts than in pure cerebellar or brain stem lesions. Furthermore, cerebellar and hemispheric AI values were not correlated with measurements of clinical deficits, disability or handicap. CONCLUSION: Unilateral and limited inferior brain stem lesions can have ipsi- or contralateral consequences on the cerebellum and cerebral hemispheres rCBF. These remote effects are related to lesions of the main pathways joining these structures, resulting in deactivation and, in some cases, overactivation. Contrary to what has been suggested, consequences on cerebral hemispheres are more severe in mixed cerebellar and brain stem infarcts than in pure cerebellar lesions. (+info)
Multiple large and small cerebellar infarcts.
To assess the clinical, topographical, and aetiological features of multiple cerebellar infarcts,18 patients (16.5% of patients with cerebellar infarction) were collected from a prospective acute stroke registry, using a standard investigation protocol including MRI and magnetic resonance angiography. Infarcts in the posterior inferior cerebellar artery (PICA)+superior cerebellar artery (SCA) territory were most common (9/18; 50%), followed by PICA+anterior inferior cerebellar artery (AICA)+SCA territory infarcts (6/18; 33%). One patient had bilateral AICA infarcts. No infarct involved the PICA+AICA combined territory. Other infarcts in the posterior circulation were present in half of the patients and the clinical presentation largely depended on them. Large artery disease was the main aetiology. Our findings emphasised the common occurrence of very small multiple cerebellar infarcts (<2 cm diameter). These very small multiple cerebellar infarcts may occur with (13 patients/18; 72%) or without (3/18; 22%) territorial cerebellar infarcts. Unlike previous series, they could not all be considered junctional infarcts (between two main cerebellar artery territories: 51/91), but also small territorial infarcts (40/91). It is suggested that these very small territorial infarcts may be endzone infarcts, due to the involvement of small distal arterial branches. It is possible that some very small territorial infarcts may be due to a microembolic process, but this hypothesis needs pathological confirmation. (+info)
Failure of cerebellar patients to time finger opening precisely causes ball high-low inaccuracy in overarm throws.
We investigated the idea that the cerebellum is required for precise timing of fast skilled arm movements by studying one situation where timing precision is required, namely finger opening in overarm throwing. Specifically, we tested the hypothesis that in overarm throws made by cerebellar patients, ball high-low inaccuracy is due to disordered timing of finger opening. Six cerebellar patients and six matched control subjects were instructed to throw tennis balls at three different speeds from a seated position while angular positions in three dimensions of five arm segments were recorded at 1,000 Hz with the search-coil technique. Cerebellar patients threw more slowly than controls, were markedly less accurate, had more variable hand trajectories, and showed increased variability in the timing, amplitude, and velocity of finger opening. Ball high-low inaccuracy was not related to variability in the height or direction of the hand trajectory or to variability in finger amplitude or velocity. Instead, the cause was variable timing of finger opening and thereby ball release occurring on a flattened arc hand trajectory. The ranges of finger opening times and ball release times (timing windows) for 95% of the throws were on average four to five times longer for cerebellar patients; e.g., across subjects mean ball release timing windows for throws made under the medium-speed instruction were 11 ms for controls and 55 ms for cerebellar patients. This increased timing variability could not be explained by disorder in control of force at the fingers. Because finger opening in throwing is likely controlled by a central command, the results implicate the cerebellum in timing the central command that initiates finger opening in this fast skilled multijoint arm movement. (+info)
Preserved performance by cerebellar patients on tests of word generation, discrimination learning, and attention.
Recent theories suggest that the human cerebellum may contribute to the performance of cognitive tasks. We tested a group of adult patients with cerebellar damage attributable to stroke, tumor, or atrophy on four experiments involving verbal learning or attention shifting. In experiment 1, a verb generation task, participants produced semantically related verbs when presented with a list of nouns. With successive blocks of practice responding to the same set of stimuli, both groups, including a subset of cerebellar patients with unilateral right hemisphere lesions, improved their response times. In experiment 2, a verbal discrimination task, participants learned by trial and error to pick the target words from a set of word pairs. When age was taken into account, there were no performance differences between cerebellar patients and control subjects. In experiment 3, measures of spatial attention shifting were obtained under both exogenous and endogenous cueing conditions. Cerebellar patients and control subjects showed similar costs and benefits in both cueing conditions and at all SOAs. In experiment 4, intra- and interdimensional shifts of nonspatial attention were elicited by presenting word cues before the appearance of a target. Performance was substantially similar for cerebellar patients and control subjects. These results are presented as a cautionary note. The experiments failed to provide support for current hypotheses regarding the role of the cerebellum in verbal learning or attention. Alternative interpretations of previous results are discussed. (+info)