Delayed-onset cerebellar syndrome

Characteristics of Tremor Induced by Lesions of the Cerebellum

It is a clinical experience that acute lesions of the cerebellum induce pathological tremor, which tends to improve. However, quantitative characteristics, imaging correlates, and recovery of cerebellar tremor have not been systematically investigated. We studied the prevalence, quantitative parameters measured with biaxial accelerometry, and recovery of pathological tremor in 68 patients with lesions affecting the cerebellum. We also investigated the correlation between the occurrence and characteristics of tremor and lesion localization using 3D T1-weighted MRI images which were normalized and segmented according to a spatially unbiased atlas template for the cerebellum. Visual assessment detected pathological tremor in 19% while accelerometry in 47% of the patients. Tremor was present both in postural and intentional positions, but never at rest. Two types of pathological tremor were distinguished: (1) low-frequency tremor in 36.76% of patients (center frequency 2.66 ± 1.17 Hz) and (2) normal frequency-high-intensity tremor in 10.29% (center frequency 8.79 ± 1.43 Hz). The size of the lesion did not correlate with the presence or severity of tremor. Involvement of the anterior lobe and lobule VI was related to high tremor intensity. In all followed up patients with acute cerebellar ischemia, the tremor completely recovered within 8 weeks. Our results indicate that cerebellar lesions might induce pathological postural and intentional tremor of 2-3 Hz frequency. Due to its low frequency and low amplitude, quantitative tremorometry is neccessary to properly identify it. There is no tight correlation between lesion localization and quantitative characteristics of cerebellar tremor.

Electrophysiological Correlates of Blast-Wave Induced Cerebellar Injury

Understanding the mechanisms underlying traumatic neural injury and the sequelae of events in the acute phase is important for deciding on the best window of therapeutic intervention. We hypothesized that evoked potentials (EP) recorded from the cerebellar cortex can detect mild levels of neural trauma and provide a qualitative assessment tool for progression of cerebellar injury in time. The cerebellar local field potentials evoked by a mechanical tap on the hand and collected with chronically implanted micro-ECoG arrays on the rat cerebellar cortex demonstrated substantial changes both in amplitude and timing as a result of blast-wave induced injury. The results revealed that the largest EP changes occurred within the first day of injury, and partial recoveries were observed from day-1 to day-3, followed by a period of gradual improvements (day-7 to day-14). The mossy fiber (MF) and climbing fiber (CF) mediated components of the EPs were affected differentially. The behavioral tests (ladder rung walking) and immunohistological analysis (calbindin and caspase-3) did not reveal any detectable changes at these blast pressures that are typically considered as mild (100-130 kPa). The results demonstrate the sensitivity of the electrophysiological method and its use as a tool to monitor the progression of cerebellar injuries in longitudinal animal studies.

Post-Thalamic Stroke Movement Disorders: A Systematic Review

BACKGROUND

After a stroke, movement disorders are rare manifestations mainly affecting the deep structures of the brain like the basal ganglia (44%) and thalamus (37%), although there have been case studies of movement disorders in strokes affecting the cerebral cortex also.

SUMMARY

This review aims to delineate the various movement disorders seen in association with thalamic strokes and tries to identify the location of the nuclei affected in each of the described movement disorders. Cases were identified through a search of PubMed database using different search terms related to post-thalamic stroke movement disorders and a secondary search of references of identified articles. We reviewed 2,520 research articles and only 86 papers met the inclusion criteria. Cases were included if they met criteria for post-thalamic stroke movement disorders. Case-cohort studies were also reviewed and will be discussed further. Key Messages: The most common post-stroke abnormal movement disorder reported in our review was dystonia followed by hemiataxia. There was a higher association between ischaemic stroke and movement disorder. Acute onset movement disorders were more common than delayed. The posterolateral thalamus was most commonly involved in post-thalamic stroke movement disorders.

The mystery of the cerebellum: clues from experimental and clinical observations

The cerebellum has a striking homogeneous cytoarchitecture and participates in both motor and non-motor domains. Indeed, a wealth of evidence from neuroanatomical, electrophysiological, neuroimaging and clinical studies has substantially modified our traditional view on the cerebellum as a sole calibrator of sensorimotor functions. Despite the major advances of the last four decades of cerebellar research, outstanding questions remain regarding the mechanisms and functions of the cerebellar circuitry. We discuss major clues from both experimental and clinical studies, with a focus on rodent models in fear behaviour, on the role of the cerebellum in motor control, on cerebellar contributions to timing and our appraisal of the pathogenesis of cerebellar tremor. The cerebellum occupies a central position to optimize behaviour, motor control, timing procedures and to prevent body oscillations. More than ever, the cerebellum is now considered as a major actor on the scene of disorders affecting the CNS, extending from motor disorders to cognitive and affective disorders. However, the respective roles of the mossy fibres, the climbing fibres, cerebellar cortex and cerebellar nuclei remains unknown or partially known at best in most cases. Research is now moving towards a better definition of the roles of cerebellar modules and microzones. This will impact on the management of cerebellar disorders.

Cerebellar motor syndrome from children to the elderly

More than a century after the description of its cardinal components, the cerebellar motor syndrome (CMS) remains a cornerstone of daily clinical ataxiology, in both children and adults. Anatomically, motor cerebellum involves lobules I-V, VI, and VIII. CMS is typically associated with errors in the metrics of voluntary movements and a lack of coordination. Symptoms and motor signs consist of speech deficits, impairments of limb movements, and abnormalities of posture/gait. Ataxic dysarthria has a typical scanning (explosive with staccato) feature, voice has a nasal character, and speech is slurred. Cerebellar mutism is most common in children and occurs after resection of a large midline cerebellar tumor. Ataxia of limbs includes at various degrees dysmetria (hypermetria: overshoot, hypometria: undershoot), dysdiadochokinesia, cerebellar tremor (action tremor, postural tremor, kinetic tremor, some forms of orthostatic tremor), isometrataxia, disorders of muscle tone (both hypotonia and cerebellar fits), and impaired check and rebound. Handwriting is irregular and some patients exhibit megalographia. Cerebellar patients show an increased body sway with a broad-based stance (ataxia of stance). Gait is irregular and staggering. Delayed learning of complex motor skills may be a prominent feature in children. CMS is currently explained by the inability of the cerebellum to handle feedback signals during slow movements and to create, store, select, and update internal models during fast movements. The cerebellum is embedded in large-scale brain networks and is essential to perform accurate motor predictions related to body dynamics and environmental stimuli. Overall, the observations in children and adults exhibiting a CMS fit with the hypothesis that the cerebellum contains neural representations reproducing the dynamic properties of body, and generates and calibrates sensorimotor predictions. Therapies aiming at a reinforcement or restoration of internal models should be implemented to cancel CMS in cerebellar ataxias. The developmental trajectory of the cerebellum, the immature motor behavior in children, and the networks implicated in CMS need to be taken into account.

Hypertrophic Olivary Degeneration and Palatal or Oculopalatal Tremor

Hypertrophic degeneration of the inferior olive is mainly observed in patients developing palatal tremor (PT) or oculopalatal tremor (OPT). This syndrome manifests as a synchronous tremor of the palate (PT) and/or eyes (OPT) that may also involve other muscles from the branchial arches. It is associated with hypertrophic inferior olivary degeneration that is characterized by enlarged and vacuolated neurons, increased number and size of astrocytes, severe fibrillary gliosis, and demyelination. It appears on MRI as an increased T2/FLAIR signal intensity and enlargement of the inferior olive. There are two main conditions in which hypertrophic degeneration of the inferior olive occurs. The most frequent, studied, and reported condition is the development of PT/OPT and hypertrophic degeneration of the inferior olive in the weeks or months following a structural brainstem or cerebellar lesion. This “symptomatic” condition requires a destructive lesion in the Guillain–Mollaret pathway, which spans from the contralateral dentate nucleus via the brachium conjunctivum and the ipsilateral central tegmental tract innervating the inferior olive. The most frequent etiologies of destructive lesion are stroke (hemorrhagic more often than ischemic), brain trauma, brainstem tumors, and surgical or gamma knife treatment of brainstem cavernoma. The most accepted explanation for this symptomatic PT/OPT is that denervated olivary neurons released from inhibitory inputs enlarge and develop sustained synchronized oscillations. The cerebellum then modulates/accentuates this signal resulting in abnormal motor output in the branchial arches. In a second condition, PT/OPT and progressive cerebellar ataxia occurs in patients without structural brainstem or cerebellar lesion, other than cerebellar atrophy. This syndrome of progressive ataxia and palatal tremor may be sporadic or familial. In the familial form, where hypertrophic degeneration of the inferior olive may not occur (or not reported), the main reported etiologies are Alexander disease, polymerase gamma mutation, and spinocerebellar ataxia type 20. Whether or not these are associated with specific degeneration of the dentato–olivary pathway remain to be determined. The most symptomatic consequence of OPT is eye oscillations. Therapeutic trials suggest gabapentin or memantine as valuable drugs to treat eye oscillations in OPT.

Movement Disorders Following Cerebrovascular Lesions in Cerebellar Circuits

Cerebellar circuitry is important to controlling and modifying motor activity. It conducts the coordination and correction of errors in muscle contractions during active movements. Therefore, cerebrovascular lesions of the cerebellum or its pathways can cause diverse movement disorders, such as action tremor, Holmes’ tremor, palatal tremor, asterixis, and dystonia. The pathophysiology of abnormal movements after stroke remains poorly understood. However, due to the current advances in functional neuroimaging, it has recently been described as changes in functional brain networks. This review describes the clinical features and pathophysiological mechanisms in different types of movement disorders following cerebrovascular lesions in the cerebellar circuits.

Altered Cerebellar White Matter Integrity in Patients with Mild Traumatic Brain Injury in the Acute Stage

Background and Purpose

Imaging studies of traumatic brain injury demonstrate that the cerebellum is often affected. We aim to examine fractional anisotropy alteration in acute-phase mild traumatic brain injury patients in cerebellum-related white matter tracts.

Materials and Methods

This prospective study included 47 mild traumatic brain injury patients in the acute stage and 37 controls. MR imaging and neurocognitive tests were performed in patients within 7 days of injury. White matter integrity was examined by using diffusion tensor imaging. We used three approaches, tract-based spatial statistics, graphical-model-based multivariate analysis, and region-of-interest analysis, to detect altered cerebellar white matter integrity in mild traumatic brain injury patients.

Results

Results from three analysis methods were in accordance with each other, and suggested fractional anisotropy in the middle cerebellar peduncle and the pontine crossing tract was changed in the acute-phase mild traumatic brain injury patients, relative to controls (adjusted p-value < 0.05). Higher fractional anisotropy in the middle cerebellar peduncle was associated with worse performance in the fluid cognition composite (r = -0.289, p-value = 0.037).

Conclusion

Altered cerebellar fractional anisotropy in acute-phase mild traumatic brain injury patients is localized in specific regions and statistically associated with cognitive deficits detectable on neurocognitive testing.

Effects of traumatic brain injury on locomotor adaptation

BACKGROUND AND PURPOSE

Locomotor adaptation is a form of short-term learning that enables gait modifications and reduces movement errors when the environment changes. This adaptation is critical for community ambulation for example, when walking on different surfaces. While many individuals with traumatic brain injury (TBI) recover basic ambulation, less is known about recovery of more complex locomotor skills, like adaptation. The purpose of this study was to investigate how TBI affects locomotor adaptation.

METHODS

Fourteen adults with TBI and 11 nondisabled comparison participants walked for 15 minutes on a split-belt treadmill with 1 belt moving at 0.7 m/s, and the other at 1.4 m/s. Subsequently, aftereffects were assessed and de-adapted during 15 minutes of tied-belt walking (both belts at 0.7 m/s).

RESULTS

Participants with TBI showed greater asymmetry in interlimb coordination on split-belts than the comparison group. Those with TBI did not adapt back to baseline symmetry, and some individuals did not store significant aftereffects. Greater asymmetry on split-belts and smaller aftereffects were associated with greater ataxia.

DISCUSSION

Participants with TBI were more perturbed by walking on split-belts and showed some impairment in adaptation. This suggests a reduced ability to learn a new form of coordination to compensate for environmental changes. Multiple interacting factors, including cerebellar damage and impairments in higher-level cognitive processes, may influence adaptation post-TBI.

CONCLUSIONS

Gait adaptation to novel environment demands is impaired in persons with chronic TBI and may be an important skill to target in rehabilitation.

VIDEO ABSTRACT AVAILABLE

(See Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A74) for more insights from the authors.

Movement disorders secondary to craniocerebral trauma

Over the past few decades it has been recognized that traumatic brain injury may result in various movement disorders. In survivors of severe head injury, post-traumatic movement disorders were reported in about 20%, and they persisted in about 10% of patients. The most frequent persisting movement disorder in this population is kinetic cerebellar outflow tremor in about 9%, followed by dystonia in about 4%. While tremor is associated most frequently with cerebellar or mesencephalic lesions, patients with dystonia frequently have basal ganglia or thalamic lesions. Moderate or mild traumatic brain injury only rarely causes persistent post-traumatic movement disorders. It appears that the frequency of post-traumatic movement disorders overall has been declining which most likely is secondary to improved treatment of brain injury. In patients with disabling post-traumatic movement disorders which are refractory to medical treatment, stereotactic neurosurgery can provide long-lasting benefit. While in the past the primary option for severe kinetic tremor was thalamotomy and for dystonia thalamotomy or pallidotomy, today deep brain stimulation has become the preferred treatment. Parkinsonism is a rare consequence of single head injury, but repeated head injury such as seen in boxing can result in chronic encephalopathy with parkinsonian features. While there is still controversy whether or not head injury is a risk factor for the development of Parkinson's disease, recent studies indicate that genetic susceptibility might be relevant.

Electrophysiological monitoring of injury progression in the rat cerebellar cortex

The changes of excitability in affected neural networks can be used as a marker to study the temporal course of traumatic brain injury (TBI). The cerebellum is an ideal platform to study brain injury mechanisms at the network level using the electrophysiological methods. Within its crystalline morphology, the cerebellar cortex contains highly organized topographical subunits that are defined by two main inputs, the climbing (CFs) and mossy fibers (MFs). Here we demonstrate the use of cerebellar evoked potentials (EPs) mediated through these afferent systems for monitoring the injury progression in a rat model of fluid percussion injury (FPI). A mechanical tap on the dorsal hand was used as a stimulus, and EPs were recorded from the paramedian lobule (PML) of the posterior cerebellum via multi-electrode arrays (MEAs). Post-injury evoked response amplitudes (EPAs) were analyzed on a daily basis for 1 week and compared with pre-injury values. We found a trend of consistently decreasing EPAs in all nine animals, losing as much as 72 ± 4% of baseline amplitudes measured before the injury. Notably, our results highlighted two particular time windows; the first 24 h of injury in the acute period and day-3 to day-7 in the delayed period where the largest drops (~50% and 24%) were observed in the EPAs. In addition, cross-correlations of spontaneous signals between electrode pairs declined (from 0.47 ± 0.1 to 0.35 ± 0.04, p < 0.001) along with the EPAs throughout the week of injury. In support of the electrophysiological findings, immunohistochemical analysis at day-7 post-injury showed detectable Purkinje cell loss at low FPI pressures and more with the largest pressures used. Our results suggest that sensory evoked potentials (SEPs) recorded from the cerebellar surface can be a useful technique to monitor the course of cerebellar injury and identify the phases of injury progression even at mild levels.

Neurostimulation for traumatic brain injury

Traumatic brain injury (TBI) remains a significant public health problem and is a leading cause of death and disability in many countries. Durable treatments for neurological function deficits following TBI have been elusive, as there are currently no FDA-approved therapeutic modalities for mitigating the consequences of TBI. Neurostimulation strategies using various forms of electrical stimulation have recently been applied to treat functional deficits in animal models and clinical stroke trials. The results from these studies suggest that neurostimulation may augment improvements in both motor and cognitive deficits after brain injury. Several studies have taken this approach in animal models of TBI, showing both behavioral enhancement and biological evidence of recovery. There have been only a few studies using deep brain stimulation (DBS) in human TBI patients, and future studies are warranted to validate the feasibility of this technique in the clinical treatment of TBI. In this review, the authors summarize insights from studies employing neurostimulation techniques in the setting of brain injury. Moreover, they relate these findings to the future prospect of using DBS to ameliorate motor and cognitive deficits following TBI.

Unusual delayed presentation of head trauma complicating outcome of facial nerve decompression surgery

Late presentation of head trauma is rare. A young boy presented with a traumatic facial paralysis after head trauma. A CT scan of the head showed temporal bone fracture without intracranial insult. Facial nerve decompression was performed and paralysis started improving. However, he presented with vertigo and sensorineural hearing loss after 2 months. Clinical examination also showed cerebellar sign. We suspected iatrogenic injury to the cochlea; however, brain MRI showed haemorrhage in the area of anterior inferior cerebellar artery. The patient was managed conservatively and the vertigo improved. This case stresses on unusual late presentation of head trauma and cerebellar artery injury that complicated the outcome of facial nerve paralysis.

Movement disorders in cerebrovascular disease

Movement disorders can occur as primary (idiopathic) or genetic disease, as a manifestation of an underlying neurodegenerative disorder, or secondary to a wide range of neurological or systemic diseases. Cerebrovascular diseases represent up to 22% of secondary movement disorders, and involuntary movements develop after 1-4% of strokes. Post-stroke movement disorders can manifest in parkinsonism or a wide range of hyperkinetic movement disorders including chorea, ballism, athetosis, dystonia, tremor, myoclonus, stereotypies, and akathisia. Some of these disorders occur immediately after acute stroke, whereas others can develop later, and yet others represent delayed-onset progressive movement disorders. These movement disorders have been encountered in patients with ischaemic and haemorrhagic strokes, subarachnoid haemorrhage, cerebrovascular malformations, and dural arteriovenous fistula affecting the basal ganglia, their connections, or both.

Dystonia and tremor secondary to a pediatric thalamic stroke

A previously healthy 10-year-old girl developed a right hemiparesis with sensory loss secondary to a posterolateral thalamic infarct. Despite improvement in strength, three weeks later a 4 Hz kinetic tremor appeared in the right hand accompanied by dystonia in the right upper and lower limbs. Basal ganglia vascular lesions are rare in childhood and movement disorders secondary to such lesions even more so. A thorough work-up failed to disclose the etiology. Our patient illustrates that dystonia and tremor secondary to posterolateral thalamic infarctions are also apt to occur in children and, unlike the adult picture, abnormal movements may develop very soon after the insult.

Animal models of human cerebellar ataxias: a cornerstone for the therapies of the twenty-first century

Cerebellar ataxias represent a group of disabling neurological disorders. Our understanding of the pathogenesis of cerebellar ataxias is continuously expanding. A considerable number of laboratory animals with neurological mutations have been reported and numerous relevant animal models mimicking the phenotype of cerebellar ataxias are becoming available. These models greatly help dissecting the numerous mechanisms of cerebellar dysfunction, a major step for the assessment of therapeutics targeting a given deleterious pathway and for the screening of old or newly synthesized chemical compounds. Nevertheless, differences between animal models and human disorders should not be overlooked and difficulties in terms of characterization should not be occulted. The identification of the mutations of many hereditary ataxias, the development of valuable animal models, and the recent identifications of the molecular mechanisms underlying cerebellar disorders represent a combination of key factors for the development of anti-ataxic innovative therapies. It is anticipated that the twenty-first century will be the century of effective therapies in the field of cerebellar ataxias. The animal models are a cornerstone to reach this goal.

Models of traumatic cerebellar injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. Studies of human TBI demonstrate that the cerebellum is sometimes affected even when the initial mechanical insult is directed to the cerebral cortex. Some of the components of TBI, including ataxia, postural instability, tremor, impairments in balance and fine motor skills, and even cognitive deficits, may be attributed in part to cerebellar damage. Animal models of TBI have begun to explore the vulnerability of the cerebellum. In this paper, we review the clinical presentation, pathogenesis, and putative mechanisms underlying cerebellar damage with an emphasis on experimental models that have been used to further elucidate this poorly understood but important aspect of TBI. Animal models of indirect (supratentorial) trauma to the cerebellum, including fluid percussion, controlled cortical impact, weight drop impact acceleration, and rotational acceleration injuries, are considered. In addition, we describe models that produce direct trauma to the cerebellum as well as those that reproduce specific components of TBI including axotomy, stab injury, in vitro stretch injury, and excitotoxicity. Overall, these models reveal robust characteristics of cerebellar damage including regionally specific Purkinje cell injury or loss, activation of glia in a distinct spatial pattern, and traumatic axonal injury. Further research is needed to better understand the mechanisms underlying the pathogenesis of cerebellar trauma, and the experimental models discussed here offer an important first step toward achieving that objective.

Morphometric MRI findings in the thalamus and brainstem in children after moderate to severe traumatic brain injury

Generalized whole brain volume loss is well documented in moderate to severe traumatic brain injury. Whether this atrophy occurs in the thalamus and brainstem has not been systematically studied in children. Magnetic resonance imaging (MRI) quantitative analysis was used to investigate brain volume loss in the thalamus and brainstem in 16 traumatic brain injury subjects (age range 9-16 years) compared with 16 age and demo-graphically matched controls. Based on multiple analysis of covariance, controlling for age and head size, reduced volume in the thalamus and the midbrain region of the brainstem were found. General linear model analyses revealed a relation between processing speed on a working memory task and midbrain and brain stem volumes. Reduced volume in thalamic and brainstem structures were associated with traumatic brain injury. Reduction in midbrain and thalamic volume is probably a reflection of the secondary effects of diffuse axonal injury and reduction in cortical volume from brain injury.

Development of involuntary movements after ventriculoperitoneal shunting for normal pressure hydrocephalus in a patient with chronic-phase thalamic haemorrhage

BACKGROUND

Delayed-onset involuntary movements have been described after thalamic stroke.

METHODS

We treated a patient with involuntary movements that increased after ventriculoperitoneal shunting (VPS) for normal pressure hydrocephalus (NPH) following thalamic haemorrage. One and one-half years after right thalamic and intraventricular haemorrhage, NPH suggested clinical evaluation and neuroimaging studies in a 56-year-old man.

RESULTS

Hemidystonia and pseudochoreoathetosis were evident in the left arm, leg and trunk. Proprioceptive impairment and mild cerebellar dysfunction affected the left upper and lower extremity. Yet the patient could walk unassisted and carry out activities of daily living (ADL) rated as 90 points according to the Barthel Index (BI). Lumbar puncture lessened both gait disturbance and cognitive impairment. After VPS, cognition and urinary continence improved, but involuntary movements worsened, precluding unaided ambulation and decreasing the BI score to 65 points. Computed tomography after VPS showed resolution of NPH, while single-photon emission computed tomography showed increased cerebral blood flow after VPS.

CONCLUSION

Increased cerebral blood flow after VPS is suspected to have promoted development of abnormal neuronal circuitry.

Ataxias

Gait disorders in elderly individuals are a major cause of falls and their attendant morbidities. Ataxia is one of the neurologic components of fall risk, as are inattention or confusion, visual impairment, vestibular impairment, subcortical white matter disease, parkinsonism, weakness, sensory loss, orthostasis or arrhythmia with alterations in blood pressure, pain, medication use, and environmental hazards. Ataxia in the geriatric population has many causes. Correctly identifying them can improve clinicians' ability to offer treatment and management strategies to patients and their families. The goals should be safe mobility and preserved activities of daily living.

Injury severity determines Purkinje cell loss and microglial activation in the cerebellum after cortical contusion injury

Clinical evidence suggests that the cerebellum is damaged after traumatic brain injury (TBI) and experimental studies have validated these observations. We have previously shown cerebellar vulnerability, as demonstrated by Purkinje cell loss and microglial activation, after fluid percussion brain injury. In this study, we examine the effect of graded controlled cortical impact (CCI) injury on the cerebellum in the context of physiologic and anatomical parameters that have been shown by others to be sensitive to injury severity. Adult male rats received mild, moderate, or severe CCI and were euthanized 7 days later. We first validated the severity of the initial injury using physiologic criteria, including apnea and blood pressure, during the immediate postinjury period. Increasing injury severity was associated with an increased incidence of apnea and higher mortality. Severe injury also induced transient hypertension followed by hypotension, while lower grade injuries produced an immediate and sustained hypotension. We next evaluated the pattern of subcortical neuronal loss in response to graded injuries. There was significant neuronal loss in the ipsilateral cortex, hippocampal CA2/CA3, and laterodorsal thalamus that was injury severity-dependent and that paralleled microglial activation. Similarly, there was a distinctive pattern of Purkinje cell loss and microglial activation in the cerebellar vermis that varied with injury severity. Together, these findings emphasize the vulnerability of the cerebellum to TBI. That a selective pattern of Purkinje cell loss occurs regardless of the type of injury suggests a generalized response that is a likely determinant of recovery and a target for therapeutic intervention.

Acute transient cerebellar dysfunction and stuttering following mild closed head injury

INTRODUCTION

A wide range of pathologies can cause cerebellar dysfunction but there have been few reports of transient dysfunction after mild head injury. There are none describing stuttering as an acute symptom after such injuries.

CASE REPORT

We report a 12-year-old boy who presented with headache, stuttering speech and truncal and bilateral peripheral cerebellar dysfunction after falling prone from his skateboard. Computed tomographic brain imaging showed normal results. All clinical symptoms and signs had resolved within 24 h obviating further investigation. A follow up clinical interview and examination 4 weeks later revealed no recurrence of cerebellar or speech dysfunction.

CONCLUSION

This is the first reported case of acute transient cerebellar dysfunction and stuttering after mild closed head injury. Neurogenic causes for stuttering are increasingly being recognised.

Isolated continuous rhythmic involuntary tongue movements following a pontine infarct

Isolated involuntary tongue movements are rare and poorly understood. The anatomical substrate and pathogenesis underlying involuntary tongue movements remain elusive. We describe a patient who developed isolated continuous rhythmic involuntary tongue movements after pontine infarct without evidence of hypertrophy of inferior olivary nucleus on follow-up magnetic resonance image. We discuss the rhythmic involuntary tongue movements as a prototype of involuntary hyperkinetic movement released by a central pacemaker.

Atypical parkinsonism and motor neuron syndrome in a Biosphere 2 participant: A possible complication of chronic hypoxia and carbon monoxide toxicity?

Exogenous toxins and chronic hypoxia have been implicated in the etiopathogenesis of a variety of neurological disorders, but it is not always possible to establish a cause-effect relationships. We describe a patient who presented with an unusual gait disorder and progressive motor neuron disease after residing for 2 years within Biosphere 2, a scientifically engineered dome, tightly sealed to allow miniscule exchange of air between its atmosphere and the earth's atmosphere. We postulate that this unusual syndrome resulted from chronic hypoxia possibly coupled with carbon monoxide and nitrous oxide exposure.

Parkinson's disease and exposure to infectious agents and pesticides and the occurrence of brain injuries: role of neuroinflammation

Idiopathic Parkinson's disease (PD) is a devastating movement disorder characterized by selective degeneration of the nigrostriatal dopaminergic pathway. Neurodegeneration usually starts in the fifth decade of life and progresses over 5-10 years before reaching the fully symptomatic disease state. Despite decades of intense research, the etiology of sporadic PD and the mechanism underlying the selective neuronal loss remain unknown. However, the late onset and slow-progressing nature of the disease has prompted the consideration of environmental exposure to agrochemicals, including pesticides, as a risk factor. Moreover, increasing evidence suggests that early-life occurrence of inflammation in the brain, as a consequence of either brain injury or exposure to infectious agents, may play a role in the pathogenesis of PD. Most important, there may be a self-propelling cycle of inflammatory process involving brain immune cells (microglia and astrocytes) that drives the slow yet progressive neurodegenerative process. Deciphering the molecular and cellular mechanisms governing those intricate interactions would significantly advance our understanding of the etiology and pathogenesis of PD and aid the development of therapeutic strategies for the treatment of the disease.

Head injury and posttraumatic movement disorders

WE REVIEW THE phenomenology, pathophysiology, pathological anatomy, and therapy of posttraumatic movement disorders with special emphasis on neurosurgical treatment options. We also explore possible links between craniocerebral trauma and parkinsonism. The cause-effect relationship between head injury and subsequent movement disorder is not fully appreciated. This may be related partially to the delayed appearance of the movement disorder. Movement disorders after severe head injury have been reported in 13 to 66% of patients. Although movement disorders after mild or moderate head injury are frequently transient and, in general, do not result in additional disability, kinetic tremors and dystonia may be a source of marked disability in survivors of severe head injury. Functional stereotactic surgery provides long-term symptomatic and functional benefits in the majority of patients. Thalamic radiofrequency lesioning, although beneficial in some patients, frequently is associated with side effects such as increased dysarthria or gait disturbance, particularly in patients with kinetic tremor secondary to diffuse axonal injury. Deep brain stimulation is used increasingly as an option in such patients. It remains unclear whether pallidal or thalamic targets are more beneficial for treatment of posttraumatic dystonia. Trauma to the central nervous system is an important causative factor in a variety of movement disorders. The mediation of the effects of trauma and the pathophysiology of the development of posttraumatic movement disorders require further study. Functional stereotactic surgery should be considered in patients with disabling movement disorders refractory to medical treatment.

Oculopalatal tremor with tardive ataxia

Oculopalatal tremor consists of palatal tremor and pendular nystagmus and may develop in a delayed fashion after an acute brainstem lesion. Delayed sequelae are generally restricted to the eyes and branchial-derived muscles, such as those of the palate. We report three cases of oculopalatal tremor that subsequently developed disabling delayed-onset ataxia and emphasize the potential for this significant complication after larger bilateral acute brainstem lesions with sparing of the inferior olive.

Delayed onset mixed involuntary movements after thalamic stroke: clinical, radiological and pathophysiological findings

Although occurrence of involuntary movements after thalamic stroke has occasionally been reported, studies using a sufficiently large number of patients and a control population are not available. Between 1995 and 1999, the author prospectively identified 35 patients with post-thalamic stroke delayed-onset involuntary movements, which included all or some degree of dystonia-athetosis-chorea-action tremor, occasionally associated with jerky, myoclonic components. A control group included 58 patients examined by the author during the same period who had lateral thalamic stroke but no involuntary movements. Demography, clinical features and imaging study results were compared. There were no differences in gender, age, risk factors, side of the lesion and follow-up periods. During the acute stage of stroke, the patients who had involuntary movements significantly more often had severe (< or = III/V) hemiparesis (50 versus 20%, P < 0.05) and severe sensory loss (in all modalities, P < 0.01) than the control group. At the time of assessment of involuntary movements, the patients with involuntary movements significantly more often had severe sensory deficit (in all modalities, P < 0.01) and severe limb ataxia (60 versus 5%, P < 0.01) than the control patients, but neither more severe motor dysfunction (7 versus 0%) nor more painful sensory symptoms (57 versus 57%). The patients with involuntary movements had a higher frequency of haemorrhagic (versus ischaemic) stroke (63 versus 31%, P < 0.05). Further analysis showed that dystonia-athetosis-chorea was closely associated with position sensory loss, whereas the tremor/myoclonic movements were related to cerebellar ataxia. Recovery of severe limb weakness seemed to augment the instability of the involuntary movements. Persistent failure of the proprioceptive sensory and cerebellar inputs in addition to successful, but unbalanced, recovery of the motor dysfunction seemed to result in a pathological motor integrative system and consequent involuntary movements in patients with relatively severe lateral-posterior thalamic strokes simultaneously damaging the lemniscal sensory pathway, the cerebellar-rubrothalamic tract and, relatively less severely, the pyramidal tract.

Temporary inactivation in the primate motor thalamus during visually triggered and internally generated limb movements

To better understand the contribution of cerebellar- and basal ganglia-receiving areas of the thalamus [ventral posterolateral nucleus, pars oralis (VPLo), area X, ventral lateral nucleus, pars oralis (VLo), or ventral anterior nucleus, pars parvicellularis (VApc)] to movements based on external versus internal cues, we temporarily inactivated these individual nuclei in two monkeys trained to make visually triggered (VT) and internally generated (IG) limb movements. Infusions of lignocaine centered within VPLo caused hemiplegia during which movements of the contralateral arm rarely were performed in either task for a short period of time ( approximately 5-30 min). When VT responses were produced, they had prolonged reaction times and movement times and a higher incidence of trajectory abnormalities compared with responses produced during the preinfusion baseline period. In contrast, those IG responses that were produced remained relatively normal. Infusions centered within area X never caused hemiplegia. The only deficits observed were an increase in reaction time and movement amplitude variability and a higher incidence of trajectory abnormalities during VT trials. Every other aspect of both the VT and IG movements remained unchanged. Infusions centered within VLo reduced the number of movements attempted during each block of trials. This did not appear to be due to hemiplegia, however, as voluntary movements easily could be elicited outside of the trained tasks. The other main deficit resulting from inactivation of VLo was an increased reaction time in the VT task. Finally, infusions centered within VApc caused IG movements to become slower and smaller in amplitude, whereas VT movements remained unchanged. Control infusions with saline did not cause any consistent deficits. This pattern of results implies that VPLo and VLo play a role in the production of movements in general regardless of the context under which they are performed. They also suggest that VPLo contributes more specifically to the execution of movements that are visually triggered and guided, whereas area X contributes specifically to the initiation of such movements. In contrast, VApc appears to play a role in the execution of movements based on internal cues. These results are consistent with the hypothesis that specific subcircuits within the cerebello- and basal ganglio-thalamo-cortical systems preferentially contribute to movements based on external versus internal cues.

Pathology of symptomatic tremors

Symptomatic tremors are labeled in the literature under different names including rubral tremor, midbrain tremor, thalamic tremor, myorhythmia, Holmes' tremor, cerebellar tremor, and goal-directed tremor. The most common tremor is a delayed-onset postural and action tremor with a low frequency of 3 Hz and a proximal distribution. Resting irregular tremor is sometimes present. Mild cerebellar dysmetria is often detected. The lesions are mainly located in the thalamus, the brain stem, and the cerebellum, with secondary interruption and degeneration of various pathways and olivary hypertrophy. The more consistent lesions are found in the cerebello-thalamo-cortical and dentato-rubro-olivary pathways. The role of superimposed dysfunction of the nigrostriatal system may account for the rest component. The role of the basal ganglia in the emergence and control of tremor is poorly understood.

Hyperkinetic movement disorders during and after acute stroke: the Lausanne Stroke Registry

BACKGROUND AND OBJECTIVE

To study consecutive patients with acute or delayed hyperkinetic movement disorders in the Lausanne Stroke Registry.

METHODS

We have identified 29 patients with acute or delayed movement disorders among 2500 patients who had their first-ever acute stroke in the Lausanne Stroke Registry.

SETTING

Department of Neurology, Lausanne University Hospital.

RESULTS

Our patients presented with hemichorea-hemiballism (11 patients), hemidystonia (5 patients), stereotypias (2 patients), jerky dystonic unsteady hand (3 patients), asterixis (2 patients), initial limb-shaking (2 patients), bilateral tremor (1 patients), bilateral jaw myoclonus (1 patient), hemiakathisia (1 patient) and dysarthria-dyskinetic hand (1 patient). On neuroimaging a lesion was found in 25 of the 29 cases in the territory of the middle cerebral artery (7 deep, 2 superficial and 2 complete), the posterior cerebral artery (11 patients), both middle and posterior cerebral arteries (2 patients) or the anterior cerebral artery (1 patient). The jerky dystonic unsteady hand syndrome was associated with a specific lesion, an infarct in the territory of the posterior choroidal artery. Presumed small-vessel disease was the commonest cause of stroke (15 patients). Only 3 patients had persistent movements (> 6 months).

CONCLUSION

Hyperkinetic movement disorders are uncommon in acute stroke (1%), the commonest types being hemichorea-hemiballism and hemidystonia. These movement disorders are associated with stroke involving the basal ganglia and adjacent white matter in the territory of the middle or the posterior cerebral artery. The jerky dystonic unsteady hand syndrome is specifically associated with a small infarct in the territory of the posterior choroidal artery. The abnormal movements usually regress spontaneously.