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At least 379 records · Page 21Linked to original sources
PubMed1990

Long-term effects of cerebellar pathology on cognitive functions.

Twelve patients with circumscribed chronic neocerebellar lesions but without CT-evidence of forebrain damage (other than the effects of shunting) were investigated for deficits of cognitive functions. Two different mechanisms were considered as possible causes of cognitive impairment: (1) Damage to the dentato-thalamo-cortical projection leading to impairments of cortical functions, and (2) prolonged intracranial pressure resulting in diffuse forebrain damage and subcortical dementia. Patients with lesions in the left neocerebellum showed deficits in cognitive operations in three dimensional space, consistent with the right forebrain dominance for spatial functions. Prolonged intracranial pressure, on the other hand, resulted in a mild overall cognitive impairment.

Brain Damage, Chronic↗
PubMed1985

Conservative and surgical management of focal cerebral infection.

After the introduction of CT-scanning the management of focal cerebral infections has been modified. Based on the data of two patients and on the literature the authors discuss the choice between fully conservative, immediately neurosurgical or delayed neurosurgical treatment. It is the author's opinion that by closely following the infectious process too early neurosurgical intervention can be avoided and thus unnecessary sacrifice of viable neural tissue.

Adolescent↗
PubMed1991

Transient cerebellar mutism after posterior cranial fossa surgery in an adult. Case report and review of the literature.

Transient mutism, without disorders of consciousness or cranial nerve deficits, arising after surgical operations on the posterior cranial fossa is a recently described entity. To date 22 cases have been reported, to which we add the present case (the first report of the syndrome in an adult). We review the salient features of the syndrome in the light of the published cases and speculate on the underlying physiopathology.

Cerebellar Diseases↗
PubMed1995

Immune diagnosis of paraneoplastic neurological disease.

A continuous stream of new information on clinical, pathological and immunological aspects of paraneoplastic neurological syndromes has been published in recent years. In this survey, we will discuss current opinions on the value of anti-neuronal antibody detection for establishing a diagnosis of one of the paraneoplastic syndromes of the central nervous system.

Autoantibodies↗
PubMed1986

Reversible and irreversible neuronal damage caused by excitatory amino acid analogues in rat cerebellar slices.

Slice preparations of the developing rat cerebellum were used to investigate the light and electron microscopic correlates of reversible and irreversible neuronal injury caused by the neurotoxic excitatory amino acid receptor agonists, kainate and N-methyl-D-aspartate. The slices were examined after various periods of exposure to the agonists (up to 30 min) with or without a 90 min recovery period in agonist-free medium. N-Methyl-D-aspartate (100 microM) caused necrosis of deep nuclear neurons and differentiating granule cells, the exposure times necessary to induce non-recoverable damage (leading to necrosis), being, respectively, 10 min and 20-30 min. Exposure periods of only 2-4 min with kainate (100 microM) were needed for Golgi cells to subsequently undergo necrosis. Other cell types (Purkinje, granule and deep nuclear neurons) were altered histologically by kainate but most recovered fully from 30 min exposures. Before the recovery period, the worst affected of these cells (deep nuclear neurons) displayed increased cytoplasmic and nuclear electron density and microvacuolation due to swelling of Golgi cisterns but little or no chromatin clumping or mitochondrial expansion. The neurons which were injured irreversibly by the agonists within 30 min displayed, near the time of lethal injury, increased cytoplasmic and nuclear electron lucency, marked focal aggregation of chromatin and swelling of Golgi apparatus. Mitochondrial swelling did not appear to precede lethal injury and even after exposure times sufficient, or more than sufficient, to lead to necrosis, large numbers of mitochondria remained in a condensed configuration. The significance of the histological changes is discussed and they are compared with those occurring in other pathological conditions. The time scales required for the receptor agonists to induce irreversible cellular lesions would be consistent with this being a process which is responsible for acute neuronal necrosis in the brain.

Animals↗
PubMed1987

Reconstruction of the defective cerebellar circuitry in adult Purkinje cell degeneration mutant mice by Purkinje cell replacement through transplantation of solid embryonic implants.

Solid pieces of cerebellar primordia taken from 12-day-old C57BL embryos were implanted into the cerebellar parenchyma of 3- to 4-month-old "Purkinje cell degeneration" mutant mice and analysed 2-3 months later. Purkinje cell replacement was followed by means of immunocytochemistry with antisera against either cyclic guanosine monophosphate-dependent protein kinase or vitamin D-dependent calcium-binding protein, which allows the complete staining of these neurons. Although all solid graft implants survived, their fate within the mutant cerebellum varied in three ways: Often, a more or less large fragment of the solid graft remained in the white matter, close to the cortex or even partially replacing it. These remnants contained a few distorted Purkinje cells and a region corresponding to the transplanted deep nuclei, composed of numerous immunostained axons and axon terminals surrounding immunonegative neurons. Less frequently remnants of the graft were extruded to an extracerebellar location, between two adjacent folia. They contained a few Purkinje cells intermixed with granule cells and other neurons. In a few cases corresponding to superficial deposition, the implants developed lobulated and trilaminated minicerebella which were located outside the mutant cerebellum but integrated into it. In all three situations, a large number of grafted Purkinje cells succeeded in moving out of the implants and in invading the host molecular layer. These Purkinje cells develop flattened dendritic trees perpendicular to host bundles of parallel fibres. Ultrastructural examination of the synaptic investment of Purkinje cells which have reached the host molecular layer revealed that they acquire normal synaptic inputs although complex pericellular baskets and pinceau formation do not develop. Axons from molecular layer interneurons synapse on perikaryal and smooth dendritic membranes, climbing fibres synapse on stubby spines emerging from thick dendritic branches, and parallel fibres contact almost exclusively the long-necked spines of the distal spiny branchlets. Finally, Purkinje cells which succeed in migrating to molecular layer regions no further than 0.6 mm from the host deep nuclei are able to grow axons which reach appropriate target areas and establish synaptic connections on nuclear neurons. The results obtained from this series of long-term survival cerebellar transplantations point to the possibility of fulfilling most of the conditions necessary for functional restoration of neural grafts in systems in which neurons are connected in a point-to-point manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

The distributions of Purkinje cell perikaryon and nuclear volume in human and rat cerebellum with the nucleator method.

The Purkinje cells are among the largest cells in the central nervous system and are the output cells of the cerebellar cortex. They are, therefore, of special interest in cerebellar diseases. The estimation of total number and mean perikaryon and nuclear volume of Purkinje cells in five normal human and nine rat cerebella were obtained using unbiased methods based on stereological principles. The average total number of Purkinje cells was 30.5 x 10(6) (Coefficient of variation, CD = S.D./mean = 0.13) in humans and 0.61 x 10(6) (0.21) in rats. Thus the total number of Purkinje cells was 50 times higher in the human cerebellum compared with rats, while numerical density (number/mm3) was 13 times lower in humans (0.81 x 10(3)) compared with rats (10.1 x 10(3)). An unbiased stereological principle, the nucleator, was applied to estimate the volume of Purkinje cell perikarya and nuclei. In humans the average geometric mean volume of Purkinje cell perikaryon is 12,400 microm3 (interindividual coefficient of variation = 0.08), which is about three times larger than in rats, 4900 microm3 (CVi = 0.09). The intraindividual distributional variation (CVd) in perikaryon volume is much larger in humans compared to rats (CVd = 0.72 vs 0.32). One of the differences between the two species is the simple proportionality between perikaryon and nucleus size i humans, whereas larger Purkinje cells have relatively larger nuclei in the rat.

Aged↗
PubMed2005

Speech motor programming in hypokinetic and ataxic dysarthria.

It is widely accepted that the cerebellar and basal ganglia control circuits contribute to the programming of movement. Converging evidence from neuroimaging, limb control, and neuropsychological studies suggests that (1) people with cerebellar disease have reduced ability to program movement sequences in advance of movement onset and (2) people with Parkinson's disease are unable to maintain a programmed response or to rapidly switch between responses. Despite a substantial supporting literature, no studies have addressed these potential areas of speech programming disruption for speakers with ataxic and hypokinetic dysarthria. Control participants and adults with dysarthria completed speech reaction time protocols designed to capture these aspects of utterance preparation. Results provided initial support for processing deficits in speakers with ataxic and hypokinetic dysarthria that are separable from motor execution impairments.

Acoustic Stimulation↗
PubMed2004

Driven equilibrium (drive) MR imaging of the cranial nerves V-VIII: comparison with the T2-weighted 3D TSE sequence.

PURPOSE: The aim of this study is to evaluate the efficacy of the driven equilibrium radio frequency reset pulse (DRIVE) on image quality and nerve detection when used in adjunction with T2-weighted 3D turbo spin-echo (TSE) sequence. MATERIALS AND METHODS: Forty-five patients with cranial nerve symptoms referable to the cerebellopontine angle (CPA) were examined using a T2-weighted 3D TSE pulse sequence with and without DRIVE. MR imaging was performed on a 1.5-T MRI scanner. In addition to the axial resource images, reformatted oblique sagittal, oblique coronal and maximum intensity projection (MIP) images of the inner ear were evaluated. The nerve identification and image quality were graded for the cranial nerves V-VIII as well as inner ear structures. These structures were chosen because fluid-solid interfaces existed due to the CSF around (the cranial nerves V-VIII) or the endolymph within (the inner ear structures). Statistical analysis was performed using the Wilcoxon test. P < 0.05 was considered significant. RESULTS: The addition of the DRIVE pulse shortens the scan time by 25%. T2-weighted 3D TSE sequence with DRIVE performed slightly better than the T2-weighted 3D TSE sequence without DRIVE in identifying the individual nerves. The image quality was also slightly better with DRIVE. CONCLUSION: The addition of the DRIVE pulse to the T2-weighted 3D TSE sequence is preferable when imaging the cranial nerves surrounded by the CSF, or fluid-filled structures because of shorter scan time and better image quality due to reduced flow artifacts.

Abducens Nerve↗
PubMed2005

Neuroendoscopic anatomy and surgery of the cerebellopontine angle.

To probe the feasibility and utility of neuroendoscopic inspection of the anatomy of the cerebellopontine angle (CPA) and of neuroendoscopic assisted microneurosurgery (NEAMN) for CPA lesions via a retrosigmoid approach, we used retrosigmoid NEAMN in 28 patients with CPA lesions. Prior to this, we undertook anatomical observation of bilateral CPA in two adult cadaver heads using the neuroendoscope. NEAMN tumour resection was performed in eight acoustic neuromas, one meningioma and 14 cholesteatomas and NEAMN vascular decompression was performed in five patients with trigeminal neuralgia. Both the neurovascular structures of the CPA and the ventral surface of the pons, as well as the clivus, can be inspected using the neuroendoscope through a retrosigmoid approach with a 2-3 cm diameter bony opening. Complete excision of the tumour with preservation of the facial nerve was achieved in all eight acoustic neuromas. Likewise, total resection of the tumour was possible in the 14 cholesteatomas and one meningioma. Paroxysmal facial pain resolved after NEAMN vascular decompression in the five patients with trigeminal neuralgia. There were no postoperative complications or deaths in this series. The CPA can be divided into three levels - the cranial, medial, and caudal, and each level contains specific neurovascular structures as seen through the neuroendoscope. Knowledge of these divisions is useful to master the common NEAMN procedures of the CPA. NEAMN for CPA lesions via a retrosigmoid approach is a useful adjunct to standard microneurosurgical techniques effect and may decrease the operative risk.

Adult↗
PubMed2006

Epidermoid cyst with infiltrative malignant melanoma in the cerebellopontine angle.

We report a patient with an intracranial epidermoid cyst associated with malignant melanoma in the cerebellopontine angle. The CT, MRI and histopathological findings showed an intracranial epidermoid cyst with an adjacent infiltrating melanoma. Immunohistochemical staining of the solid tumour was positive for the melanoma marker HMB45 and negative for GFAP and cytokeratin. Both CT and MRI were helpful in this patient but the diagnosis could only be made on histopathology.

Cerebellar Diseases↗
PubMed2006

Extinction of conditioned eyeblink responses in patients with cerebellar disorders.

Extinction of conditioned eyeblink responses (CRs) was analyzed in sixteen patients with pure cortical cerebellar degeneration, 14 patients with lesions within the territory of the superior cerebellar artery (SCA), 13 patients with infarctions within the territory of the posterior inferior cerebellar artery (PICA) and 45 age-matched controls. Three-dimensional (3D) magnetic resonance (MRI) data sets were acquired in patients with focal lesions to identify affected cerebellar lobules and possible involvement of nuclei. Eyeblink conditioning was performed using a standard delay protocol. At the end of the experiment 10 CS-alone trials were presented as extinction trials. Controls showed significant effects of extinction that is a significant decline comparing CR-incidences in the extinction trials and the last block of 10 trials of the paired trials. In the group of all cerebellar patients, however, no significant effects of extinction were observed. In patients with unilateral lesions effects of extinction were present on the unaffected, but not on the affected side. Deficits of extinction were observed in PICA and SCA patients both with and without involvement of cerebellar nuclei. Extending previous reports in cerebellar patients the present findings show that the ipsilateral cerebellar hemisphere contributes to extinction of conditioned eyeblink responses in humans. It cannot be ruled out, however, that impaired acquisition affected the extinction results.

Adult↗
PubMed2006

Adjustable primitive pattern generator: a novel cerebellar model for reaching movements.

Cerebellum has been assumed as an array of adjustable pattern generators (APGs). In recent years, electrophysiological researches have suggested the existence of modular structures in spinal cord called motor primitives. In our proposed model, each "adjustable primitive pattern generator" (APPG) module in the cerebellum is consisted of a large number of parallel APGs, the output of each module being the weighted sum of the outputs of these APGs. Each spinal field is tuned by a coefficient, representing a descending supraspinal command, which is modulated by ith APPG correspondingly. According to this model, motor control can be interpreted in terms of the modification of these coefficients. Vector summation of force fields implies that the complex nonlinearities in neuronal behavior are eliminated, causing our model to be simple and linear. The force field vectors, derived from motor primitives, depend on the state of movement and its derivative and the time that causes different repertoire of movement. This is physiologically plausible. Our model agrees with virtual trajectory hypothesis, stating that dynamics are not computed explicitly in central nervous system, but the desired trajectory, is fed into the spinal cord. We think that the dysmetria and the ataxia seen in some cerebellar diseases may be the result of local disruption of some APPGs. Accordingly, determining the exact location of related motor primitives in human spinal cord and stimulating them by functional neurostimulation may provide a good management for these clinical signs. Surely, experimental researches and clinical trials are needed to validate our hypothesis.

Animals↗
PubMed2005

Functional localization in the human cerebellum based on voxelwise statistical analysis: a study of 90 patients.

The aim of the present study was to examine somatotopy in the cerebellar cortex and a possible differential role of the cerebellar cortex and nuclei in functional outcome. Clinical findings and 3D MRI-based cerebellar lesions site were compared in a group of 90 patients with focal cerebellar lesion using International Cooperative Ataxia Rating Scale (ICARS) and voxel-based lesion-symptom mapping (VLSM). Separate analysis was performed in patients with acute and chronic ischemic lesions (n=43) and patients with acute and chronic surgical lesions (n=47). Thirty-eight patients were included after resection of a cerebellar tumor in childhood or adolescence. The most significant lesion symptom correlations were observed in the subgroup with acute ischemic lesions. Limb ataxia was significantly correlated with lesions of the interposed (NI) and part of the dentate nuclei (ND), ataxia of posture and gait with lesions of the fastigial nuclei (NF) including NI. Correlations with cortical lesions were less significant and present in the superior cerebellum only. Upper limb ataxia was correlated with lesions of vermal, paravermal and hemispheral lobules IV-V and VI, lower limb ataxia with lesions of vermal, paravermal and hemispheral lobules III and VI, dysarthria with lesions of paravermal and hemispheral lobules V and VI and ataxia of posture and gait with lesions of vermal and paravermal lobules II, III and IV. In the subgroups with chronic focal lesions, similar correlations were observed with lesions of the cerebellar nuclei, but significantly less correlations with lesions of the cerebellar cortex. Functional localization based on VLSM backs findings in previous animal and functional brain images studies in healthy human subjects. The lesion site appears to be critical for motor recovery. Lesions affecting the cerebellar nuclei are not fully compensated at any age and independent of the pathology in humans.

Adult↗
PubMed2006

The pathophysiologic mechanism of cerebellar mutism.

OBJECTIVE: Cerebellar mutism (CM) is a postoperative complication of mainly pediatric posterior fossa surgery. Multiple theories exist for explaining this phenomenon. We have made an attempt to further understand this entity given a particularly interesting case as it relates to multiple pathophysiologic pathways. METHODS: We have reviewed the details surrounding a particularly interesting case of CM. A retrospective analysis of this patient's clinical history and recovery is described. An extensive literature review has been performed in conjunction with an attempt to help elucidate details and a better understanding of CM. RESULTS: A thorough analysis of existing theories as to the pathophysiologic mechanism of CM has been performed as it relates to the details of this particular case. A case is described in which a child exhibiting CM abruptly improved and made a relatively quick recovery after the triggering of the melodic speech pathway by way of watching and beginning to sing along with a video. It appears that this incident involving a familiar song catalyzed various speech pathways, which apparently were in some state of shock. This phenomenon seems to be a temporary entity involving not only the mechanical coordination of speech production, but also the initiation of speech itself. CONCLUSIONS: Evidence exists for a pathophysiologic pathway for speech by way of coordinating phonation and articulation. In addition, there seems to exist a pathway by which the initiation of speech may be altered or halted by posterior fossa pathology, namely, vermian or dentate nuclear injury. In particular to this case, we found that the incidental appreciation of other forms of speech, melodic in this instance, may be the key to help stimulate and accelerate the recovery from CM.

Acoustic Stimulation↗
PubMed2005

Irrepressible saccades from a tectal lesion in a Rhesus monkey.

We present a case of spontaneously occurring irrepressible saccades in an experimental Rhesus monkey. Though eye jerks are sometimes associated with cerebellar disease, central demyelination or brainstem lesions, there is little consensus on their neurological mechanisms. From neurological and anatomical investigation we report that these irrepressible saccades were caused by a discrete cerebrovascular accident that involved the rostral superior colliculus along with its commissure, and with minor invasion of periaqueductal gray and adjacent mesencephalic reticular formation. Other suspected structures, like the raphe interpositus, substantia nigra and the cerebellum, were unaffected.

Animals↗
PubMed2000

The human cerebellum and associative learning: dissociation between the acquisition, retention and extinction of conditioned eyeblinks.

The present paper is part of a systematic exploration of the neural substrates of conditioned eyeblink responses in humans. Normal subjects and patients with lesions restricted to the cerebellum were examined for their ability to acquire new classically conditioned eyeblinks to an auditory conditioned stimulus and whether they were able to perform and extinguish a previously learned natural anticipatory eyeblink response - the kinesthetic threat eyeblink response (KTER). In classical conditioning to an auditory conditioned stimulus, cerebellar patients failed to acquire new conditioned responses. In contrast to this impairment, in the KTER task both cerebellar patients and control subjects exhibited a high incidence of anticipatory eyeblinks which were initiated before the forehead tap. These results indicate that the cerebellar circuits, which are critical for the acquisition of new conditioned responses, are not essential for the storage and expression of naturally acquired conditioned responses. In the extinction experiment, cerebellar patients failed to extinguish their KTERs. This finding suggests that in humans, the acquisition of new and the extinction of previously learned conditioned responses depends on a similar set of cerebellar circuits.

Animals↗