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Comparison of predictable smooth ocular and combined eye-head tracking behaviour in patients with lesions affecting the brainstem and cerebellum.

We compared the ability of eight normal subjects and 15 patients with brainstem or cerebellar disease to follow a moving visual stimulus smoothly with either the eyes alone or with combined eye-head tracking. The visual stimulus was either a laser spot (horizontal and vertical planes) or a large rotating disc (torsional plane), which moved at one sinusoidal frequency for each subject. The visually enhanced vestibulo-ocular reflex (VOR) was also measured in each plane. In the horizontal and vertical planes, we found that if tracking gain (gaze velocity/target velocity) for smooth pursuit was close to 1, the gain of combined eye-hand tracking was similar. If the tracking gain during smooth pursuit was less than about 0.7, combined eye-head tracking was usually superior. Most patients, irrespective of diagnosis, showed combined eye-head tracking that was superior to smooth pursuit; only two patients showed the converse. In the torsional plane, in which optokinetic responses were weak, combined eye-head tracking was much superior, and this was the case in both subjects and patients. We found that a linear model, in which an internal ocular tracking signal cancelled the VOR, could account for our findings in most normal subjects in the horizontal and vertical planes, but not in the torsional plane. The model failed to account for tracking behaviour in most patients in any plane, and suggested that the brain may use additional mechanisms to reduce the internal gain of the VOR during combined eye-head tracking. Our results confirm that certain patients who show impairment of smooth-pursuit eye movements preserve their ability to smoothly track a moving target with combined eye-head tracking.

Adult↗

Coeliac disease in patients with cerebellar ataxia of unknown origin.

BACKGROUND: Neurological symptoms of unknown origin are common in coeliac disease (CD). Evidence suggests that CD may also contribute to the development of idiopathic late-onset ataxia. AIM: To evaluate the frequency of CD in patients with cerebellar ataxia of unknown origin. METHODS: The medical files of adult patients with the diagnosis of cerebellar ataxia of unknown origin (n=44) were evaluated. Serum gliadin, endomysial, and serum tissue transglutaminase antibodies were used as screening tests for CD. Subjects with positive results were referred to small-bowel biopsy. RESULTS: The frequency of CD was as high as 9.1% in all patients. A thorough interview and review of the patient files indicated alcohol abuse as a cause for cerebellar disease in almost half (45.5%) of our patients. When the cases with alcohol abuse were omitted, the calculated frequency of CD was 16.7% in patients with ataxia of unknown origin. CONCLUSION: CD is a common association with cerebellar disease and the disease should be considered in all patients with ataxia of unknown origin.

Adult↗

Mutant mice as a model for cerebellar ataxia.

Not later than two synapses after their arrival in the cerebellar cortex all excitatory afferent signals are subsequently transformed into inhibitory ones. Guaranteed by the exceedingly ordered and stereotyped synaptic arrangement of its cellular elements, the cerebellar cortex transmits this inhibitory result of cerebellar integration exclusively via Purkinje cells (PCs) in a precise temporal succession directly onto the target neurons of the deep cerebellar and vestibular nuclei. Thus the cerebellar cortex seems to produce a temporal pattern of inhibitory influence on these target neurons that modifies their excitatory action in such a way that an activation of muscle fibers occurs which progressively integrates the intended motion into the actual condition of the motoric inventory. In consequence, disturbances that affect this cerebellar inhibition will cause uncoordinated, decomposed and ataxic movements, commonly referred to as cerebellar ataxia. Electrophysiological investigations using different cerebellar mouse mutants have shown that alterations in the cerebellar inhibitory input in the target nuclei lead to diverse neuronal responses and to different consequences for the behavioural phenotype. A dependence between the reconstitution of inhibition and the behavioural outcome seems to exist. Obviously two different basic mechanisms are responsible for these observations: (1) ineffective inhibition on target neurons by surviving PCs; and (2) enhancement of intranuclear inhibition in the deep cerebellar and vestibular nuclei. Which of the two strategies evolves is dependent upon the composition of the residual cell types in the cerebellum and on the degree of PC input loss in a given area of the target nuclei. Motor behaviour seems to deteriorate under the first of these mechanisms whereas it may benefit from the second. This is substantiated by stereotaxic removal of the remaining PC input, which eliminates the influence of the first mechanism and is able to induce the second strategy. As a consequence, motor performance improves considerably. In this review, results leading to the above conclusions are presented and links forged to human cerebellar diseases.

Animals↗

Neurologic disease putatively associated with ingestion of Solanum viarum in goats.

Several Nubian-cross goats were evaluated because of chronic progressive neurologic disease. Physical and neurologic examination revealed signs consistent with diffuse cerebellar disease. Neurologic signs included generalized hyperresponsiveness, fine head tremors, wide-based posture, dysmetria, weakness, and horizontal nystagmus. No clinical improvement was noted after removing goats from affected enclosures. Histologic examination of cerebellar tissues revealed extensive vacuolation within the cytoplasm of Purkinje cells. The clinical and histologic lesions resembled closely findings that were associated with ingestion of Solanum spp in cattle and goats. Examination of enclosures revealed Solanum viarum (tropical soda apple) that had been heavily consumed by the goat herd. We hypothesized that ingestion of S. viarum caused the neurologic disorder.

Animals↗

Progressive myoclonus in a child with a deep cerebellar mass.

Myoclonus is often associated with pathology of the cerebellum. However, the site of neurons responsible for the generation of myoclonus in cerebellar disease is not known. The authors report a young child with myoclonus associated with a ganglioglioma in the region of the deep cerebellar white matter and cerebellar nuclei. They hypothesize that abnormal paroxysmal discharge of neurons in the cerebellar nuclei can generate myoclonus.

Cerebellar Ataxia↗

Cerebellar infarction and atrophy in infants and children with a history of premature birth.

BACKGROUND AND OBJECTIVE: We wished to determine the pattern of cerebellar disease in children with a history of premature birth and early ultrasound evidence of intraventricular haemorrhage and/or parenchymal lesions of the cerebral hemispheres. MATERIALS AND METHODS: MRI findings for all premature infants examined in a 3-year period (73 patients) were reviewed to determine the nature and frequency of lesions of the cerebellum and the results were correlated with clinical data. RESULTS: Six cases of unilateral cerebellar infarction were identified. These involved the posterior inferior cerebellar territory in each case (as well as other territories in two cases). A case of generalised cerebellar atrophy and three cases of unilateral cerebellar hemisphere atrophy were identified as well. In nine of these ten cases abnormalities were also seen elsewhere in the brain. CONCLUSION: The literature describes cerebellar infarction in infants and children as rare, but this study shows that it is not unusual following perinatal haemorrhagic/ischaemic anoxic injury. It is suggested that cerebellar atrophy may also occur as a result of vascular disease.

Arteries↗

A case of Charcot-Marie-Tooth disease mimicking Friedreich's ataxia: is there any association between friedreich's ataxia and Charcot-Marie-Tooth disease?

The authors report a case of Charcot-Marie-Tooth disease that mimicked Friedreich's ataxia and featured impaired tendon reflexes in the limbs, incoordination mimicking cerebellar disease in the extremities, extensor plantar responses on both sides, bilateral foot deformity, imparied position sense in the toes, absent vibratory sense in the distal parts of the legs and minimal distal weakness with wasting. Motor conduction velocity in the upper limbs was substantially reduced. Other cases similar in nature reported in the literature resemble spino-cerebellar degeneration in general, and Friedreich's ataxia, in particular. It is emphasized that the natural history, EMG, motor conduction velocity studies and examination of other affected members of the family permit the correct diagnosis to be made in such cases. It is also emphasized that patients similar to the one reported here may also resemble, and should be differentiated from, cases of familial dorsal column ataxia (Biemond type). Stress is put upon the fact that when Charcot-Marie-Tooth disease mimicks spino-cerebellar degeneration, substantial slowing of motor conduction in the upper limbs is generally sufficient to establish the diagnosis. The relation between Friedreich's ataxia an Charcot-Marie-Tooth disease is reviewed and it is concluded that these two disorders are distinct clinical and pathological entities.

Adolescent↗

Prolonged postexcitatory inhibition after transcranial magnetic stimulation of the motor cortex in patients with cerebellar ataxia.

Postexcitatory inhibition after transcranial magnetic stimulation of the motor cortex (silent period, SP) is supposed to be predominantly mediated by the activation of inhibitory cortical interneurons. Cortical excitability seems to be reduced in patients with cerebellar ataxia. Motor threshold, central motor conduction time and the duration of the silent period after a single magnetic stimulus to the motor cortex on both sides were measured in five patients with cerebellar ataxia of different origin and 18 healthy controls. Duration of SP was highly significantly prolonged in patients compared with controls (P<0.001) while motor threshold and central motor conduction times were not different. Fifteen of 18 control subjects showed late EMG responses after magnetic stimulation but none of the patients did (P<0.001). These findings support the hypothesis that cerebellar lesions activate inhibitory cortical interneurons or cause a disruption of a normally tonic cerebellar excitation to the motor cortex. Silent period measurement appears to be a sensitive diagnostic tool in the neurophysiological examination of cerebellar diseases.

Adult↗

Free and conjugated GABA in human cerebrospinal fluid: effect of degenerative neurologic diseases and isoniazid.

gamma-Aminobutyric acid (GABA) was measured in CSF as such and following acid hydrolysis by the ion-exchange/fluorometric method. The conjugated GABA level was obtained by subtracting the free GABA level from the total GABA level. Results showed that at room temperature, while the free GABA level increased, the level of conjugated GABA decreased in a linear fashion during the first 24 h (r = -0.974; P less than 0.001). Aging and CSF conjugated GABA levels were inversely correlated (r = -0.613; P less than 0.05). Unlike free GABA levels, the levels of conjugated GABA were not altered in Huntington's disease, Parkinson's disease, cerebellar ataxias, dementias, epilepsy and multiple sclerosis compared to controls. In patients with Huntington's disease, on administration of isoniazid at 900 mg/day, along with pyridoxine at 100 mg/day, a 4-fold increase of both free (P less than 0.005) and conjugated GABA (P less than 0.0025) was seen. The results indicate that while total GABAergic peptides are not altered in several of the neurologic diseases studied, drugs such as isoniazid and/or pyridoxine can significantly elevate both free and conjugated GABA levels in human CSF.

Adult↗

Tay-Sachs disease and normal cerebellar cells in culture: elevated levels of lysosomal enzymes in Tay-Sachs disease cells.

Tay-Sachs disease and normal fetal cerebellar cells were maintained in culture for up to four weeks. Elevated levels of the lysosomal enzymes hexosaminidase B, beta-galactosidase, and acid phosphatase were observed in the Tay-Sachs cells in long term cultures although elevated lysosomal enzyme levels were not observed in the normal cultures. Similarly, elevated lysosomal enzyme activities were observed in Tay-Sachs cultures which had been treated with Concanavalin A.

Acid Phosphatase↗

Objective evaluation of manual performance deficits in neurological movement disorders.

Impaired hand function is a frequent finding in movement disorders. The skilled control of prehensile finger forces is an essential feature of tool use in daily life. In healthy subjects, grip force is precisely adjusted to the mechanical object properties, such as weight and surface friction. Grip force is accurately scaled to be only a small amount higher than the minimum necessary to prevent a hand-held object from slipping. When an object is lifted and moved around in space, grip force is modulated in parallel with the movement-induced fluctuations in load. The absence of a temporal delay between grip and load force profiles implies that the central nervous system is able to predict the load variations before the intended manipulation. Sensory information is used to adjust the level of applied finger forces efficiently to the requirements of the mechanical object properties and the task at hand. The characteristics of impaired finger force control include inefficient grip force scaling and imprecision of the temporal coupling between grip and load force profiles. Here, we review the characteristics of deficient grip force behavior in movement disorders, e.g. Parkinson's disease, task-specific dystonia, Gille de la Tourette's syndrome and cerebellar disease. Grip force analysis is a highly sensitive method to document even subtle impairments of finger force control and may be used both as a diagnostic tool and for the objective evaluation of treatment in neurological movement disorders.

Fingers↗