Cervical dystonia associated with tumors of the posterior fossa

Dystonia and Cerebellum: From Bench to Bedside

Dystonia pathogenesis remains unclear; however, findings from basic and clinical research suggest the importance of the interaction between the basal ganglia and cerebellum. After the discovery of disynaptic pathways between the two, much attention has been paid to the cerebellum. Basic research using various dystonia rodent models and clinical studies in dystonia patients continues to provide new pieces of knowledge regarding the role of the cerebellum in dystonia genesis. Herein, we review basic and clinical articles related to dystonia focusing on the cerebellum, and clarify the current understanding of the role of the cerebellum in dystonia pathogenesis. Given the recent evidence providing new hypotheses regarding dystonia pathogenesis, we discuss how the current evidence answers the unsolved clinical questions.

Cervical Dystonia Mimics: A Case Series and Review of the Literature

Background

Cervical dystonia is mostly idiopathic in nature. However, a small subset of cases are mimics, leading to diagnostic pitfalls. There is paucity of literature on pseudodystonias affecting the cervical region.

Method

We performed a retrospective review of patients attending a movement disorders clinic over a period of 7 years (2012–2018). Among them, those who were considered to have mimics of cervical dystonia based upon clinical and supportive investigations were included.

Results

Six out of 2,412 patients (0.24%) were diagnosed as cervical dystonia mimics and the causes included isolated neck extensor myopathy (2), craniovertebral junction anomalies (2), sternocleidomastoid fibrosis (1) and post traumatic sequelae (1). Among these patients, three patients had received various treatments for cervical dystonia, including botulinum toxin injections.

Discussion

Mimics of isolated cervical dystonia are rare. A high degree of suspicion and proper diligent clinical assessment assists management and prognostication.

Neuromodulation: Deep Brain Stimulation for Treatment of Dystonia

Dystonia is a heterogeneous, hyperkinetic movement disorder with sustained or intermittent abnormal postures, hyperkinetic muscle contractions, or repetitive movements. Classification of dystonia involves 2 axes: axis I and axis II, defining relevant clinical features and etiology, respectively. Medical therapy varies based on subtype and includes intramuscular botulinum toxin injections and oral anticholinergic pharmaceuticals. Deep brain stimulation became widely incorporated in 1999 after several landmark studies and has been effectively used in targets of the thalamus, pallidum, and subthalamic nucleus. New insights into pathophysiology of dystonia and genetic analysis continue to guide surgical technique toward ever-effective treatment.

The Use of Botulinum Toxin for Treatment of the Dystonias

Dystonias are characterized by involuntary muscle contractions, twisting movements, abnormal postures, and often tremor in various body regions. However, in the last decade several studies have demonstrated that dystonias are also characterized by sensory abnormalities. While botulinum toxin is the gold standard therapy for focal dystonia, exactly how it improves this disorder is not entirely understood. Neurophysiological studies in animals and humans have clearly demonstrated that botulinum toxin improves dystonic motor manifestations by inducing chemodenervation, therefore weakening the injected muscles. In addition, neurophysiological and neuroimaging evidence also suggests that botulinum toxin modulates the activity of various neural structures in the CNS distant from the injected site, particularly cortical motor and sensory areas. Concordantly, recent studies have shown that in patients with focal dystonias botulinum toxin ameliorates sensory disturbances, including reduced spatial discrimination acuity and pain. Overall, these observations suggest that in these patients botulinum toxin-induced effects encompass complex mechanisms beyond chemodenervation of the injected muscles.

Cervico-shoulder dystonia following lateral medullary infarction: a case report and review of the literature

BACKGROUND

Secondary cervical dystonia is induced by organic brain lesions involving the basal ganglia, thalamus, cerebellum, and brain stem. It is extremely rare to see cervical dystonia induced by a medullary lesion.

CASE PRESENTATION

We report a case of an 86-year-old Japanese woman who developed cervical dystonia following lateral medullary infarction. She developed sudden-onset left upper and lower extremity weakness, right-side numbness, and dysarthria. Brain magnetic resonance imaging revealed an acute ischemic lesion involving the left lateral and dorsal medullae. A few days after her stroke, she complained of a taut sensation in her left neck and body, and cervico-shoulder dystonia toward the contralateral side subsequently appeared. Within a few weeks, it disappeared spontaneously, but her hemiplegia remained residual.

CONCLUSIONS

To date, to the best of our knowledge, there has been only one reported case of cervical dystonia associated with a single medullary lesion. It is interesting to note the similarities in the clinical characteristics of the previously reported case and our patient: the involvement of the dorsal and caudal parts of the medullary and associated ipsilateral hemiplegia. The present case may support the speculation that the lateral and caudal regions of the medulla may be the anatomical sites responsible for inducing cervical dystonia.

The cerebellum and dystonia

Dystonia is a heterogeneous disorder characterized by involuntary muscle contractions, twisting movements, and abnormal postures in various body regions. It is widely accepted that the basal ganglia are involved in the pathogenesis of dystonia. A growing body of evidence, however, is challenging the traditional view and suggest that the cerebellum may also play a role in dystonia. Studies on animals indicate that experimental manipulations of the cerebellum lead to dystonic-like movements. Several clinical observations, including those from secondary dystonia cases as well as neurophysiologic and neuroimaging studies in human patients, provide further evidence in humans of a possible relationship between cerebellar abnormalities and dystonia. Claryfing the role of the cerebellum in dystonia is an important step towards providing alternative treatments based on noninvasive brain stimulation techniques.

Cerebellum: An explanation for dystonia?

Dystonia is a movement disorder that is characterized by involuntary muscle contractions, abnormal movements and postures, as well as by non-motor symptoms, and is due to abnormalities in different brain areas. In this article, we focus on the growing number of experimental studies aimed at explaining the pathophysiological role of the cerebellum in dystonia. Lastly, we highlight gaps in current knowledge and issues that future research studies should focus on as well as some of the potential applications of this research avenue. Clarifying the pathophysiological role of cerebellum in dystonia is an important concern given the increasing availability of invasive and non-invasive stimulation techniques and their potential therapeutic role in this condition.

Using the shared genetics of dystonia and ataxia to unravel their pathogenesis

In this review we explore the similarities between spinocerebellar ataxias and dystonias, and suggest potentially shared molecular pathways using a gene co-expression network approach. The spinocerebellar ataxias are a group of neurodegenerative disorders characterized by coordination problems caused mainly by atrophy of the cerebellum. The dystonias are another group of neurological movement disorders linked to basal ganglia dysfunction, although evidence is now pointing to cerebellar involvement as well. Our gene co-expression network approach identified 99 shared genes and showed the involvement of two major pathways: synaptic transmission and neurodevelopment. These pathways overlapped in the two disorders, with a large role for GABAergic signaling in both. The overlapping pathways may provide novel targets for disease therapies. We need to prioritize variants obtained by whole exome sequencing in the genes associated with these pathways in the search for new pathogenic variants, which can than be used to help in the genetic counseling of patients and their families.

Contribution of TMS and rTMS in the Understanding of the Pathophysiology and in the Treatment of Dystonia

Dystonias represent a heterogeneous group of movement disorders responsible for sustained muscle contraction, abnormal postures, and muscle twists. It can affect focal or segmental body parts or be generalized. Primary dystonia is the most common form of dystonia but it can also be secondary to metabolic or structural dysfunction, the consequence of a drug's side-effect or of genetic origin. The pathophysiology is still not elucidated. Based on lesion studies, dystonia has been regarded as a pure motor dysfunction of the basal ganglia loop. However, basal ganglia lesions do not consistently produce dystonia and lesions outside basal ganglia can lead to dystonia; mild sensory abnormalities have been reported in the dystonic limb and imaging studies have shown involvement of multiple other brain regions including the cerebellum and the cerebral motor, premotor and sensorimotor cortices. Transcranial magnetic stimulation (TMS) is a non-invasive technique of brain stimulation with a magnetic field applied over the cortex allowing investigation of cortical excitability. Hyperexcitability of contralateral motor cortex has been suggested to be the trigger of focal dystonia. High or low frequency repetitive TMS (rTMS) can induce excitatory or inhibitory lasting effects beyond the time of stimulation and protocols have been developed having either a positive or a negative effect on cortical excitability and associated with prevention of cell death, γ-aminobutyric acid (GABA) interneurons mediated inhibition and brain-derived neurotrophic factor modulation. rTMS studies as a therapeutic strategy of dystonia have been conducted to modulate the cerebral areas involved in the disease. Especially, when applied on the contralateral (pre)-motor cortex or supplementary motor area of brains of small cohorts of dystonic patients, rTMS has shown a beneficial transient clinical effect in association with restrained motor cortex excitability. TMS is currently a valuable tool to improve our understanding of the pathophysiology of dystonia but large controlled studies using sham stimulation are still necessary to delineate the place of rTMS in the therapeutic strategy of dystonia. In this review, we will focus successively on the use of TMS as a tool to better understand pathophysiology, and the use of rTMS as a therapeutic strategy.

Cervical dystonia caused by focal putaminal ischemia

We describe a 48-year-old woman with putaminal gliosis and a sphenoid wing meningioma at the left, who developed dystonia restricted to cervical regions. We propose the following causal chain: the meningioma led to an occlusion of a lenticulo-striatal branch of the middle cerebral artery that caused ventral putaminal ischemia and finally resulting in symptomatic dystonia. The previously reported relevance of the infarcted regions to the pathophysiology of dystonia supports this assumption. Implications for the diagnostic procedure of dystonia will be discussed.

Diffusion tensor imaging in blepharospasm and blepharospasm-oromandibular dystonia

Patterns of white matter (WM) abnormalities and correlation with clinical features in patients with blepharospasm (BSP) and patients with blepharospasm-oromandibular dystonia (BOM) remain unknown. Using voxel-based analysis, diffusion behaviors of WM including fractional anisotropy (FA), mean diffusivity (MD) and eigenvalues were compared between 20 BSP patients vs. 11 healthy controls (HCs) and 11 patients with BOM vs. 11 HCs. Correlation analyses were performed to assess possible association between diffusion behaviors of significantly different areas and clinical measures. Compared with HCs, BSP patients showed significant FA reductions in the left anterior lobe of cerebellum. Significant increases of MD and radial diffusivity (RD) were detected in right lentiform nucleus and thalamus. Significantly decreased FA in the right precuneus of parietal lobe, increased MD in the right lentiform nucleus and insula, and increased axial diffusivity in the right insula were observed in BOM patients. The FA values in the WM of left cerebellum negatively correlated with disease severity in BSP patients measured by JRS (r = -0.655, p = 0.002). The FA values in the right parietal WM negatively correlated with disease duration in BOM patients (r = -0.745, p = 0.008). Both BSP and BOM are related to microstructural abnormalities of WM in the basal ganglia. WM changes outside the basal ganglia may present trait features that are specific for individual dystonia phenotype. The correlation between FA abnormalities and symptom severity suggests that DTI parameters might be of clinical value in assessing and following disability in BSP patients.

Animal models for dystonia

Symptomatic animal models have clinical features consistent with human disorders and are often used to identify the anatomical and physiological processes involved in the expression of symptoms and to experimentally demonstrate causality where it would be infeasible in the patient population. Rodent and primate models of dystonia have identified basal ganglia abnormalities, including alterations in striatal GABAergic (ie, transmitting or secreting γ-aminobutyric acid) and dopaminergic transmission. Symptomatic animal models have also established the critical role of the cerebellum in dystonia, particularly abnormal glutamate signaling and aberrant Purkinje cell activity. Further, experiments suggest that the basal ganglia and cerebellum are nodes in an integrated network that is dysfunctional in dystonia. The knowledge gained from experiments in symptomatic animal models may serve as the foundation for the development of novel therapeutic interventions to treat dystonia. © 2013 Movement Disorder Society.

Dystonia as a network disorder: what is the role of the cerebellum?

The dystonias are a group of disorders defined by sustained or intermittent muscle contractions that result in involuntary posturing or repetitive movements. There are many different clinical manifestations and causes. Although they traditionally have been ascribed to dysfunction of the basal ganglia, recent evidence has suggested dysfunction may originate from other regions, particularly the cerebellum. This recent evidence has led to an emerging view that dystonia is a network disorder that involves multiple brain regions. The new network model for the pathogenesis of dystonia has raised many questions, particularly regarding the role of the cerebellum. For example, if dystonia may arise from cerebellar dysfunction, then why are there no cerebellar signs in dystonia? Why are focal cerebellar lesions or degenerative cerebellar disorders more commonly associated with ataxia rather than dystonia? Why is dystonia more commonly associated with basal ganglia lesions rather than cerebellar lesions? Can answers obtained from animals be extrapolated to humans? Is there any evidence that the cerebellum is not involved? Finally, what is the practical value of this new model of pathogenesis for the neuroscientist and clinician? This article explores potential answers to these questions.

Alteration in forward model prediction of sensory outcome of motor action in focal hand dystonia

Focal hand dystonia in musicians is a movement disorder affecting highly trained movements. Rather than being a pure motor disorder related to movement execution only, movement planning, error prediction, and sensorimotor integration are also impaired. Internal models (IMs), of which two types, forward and inverse models have been described and most likely processed in the cerebellum, are known to be involved in these tasks. Recent results indicate that the cerebellum may be involved in the pathophysiology of focal dystonia (FD). Thus, the aim of our study was to investigate whether an IM deficit plays a role in FD. We focused on the forward model (FM), which predicts sensory consequences of motor commands and allows the discrimination between external sensory input and input deriving from motor action. We investigated 19 patients, aged 19-59 and 19 healthy musicians aged 19-36 as controls. Tactile stimuli were applied to fingers II-V of both hands by the experimenter or the patient. After each stimulus the participant rated the stimulus intensity on a scale between 0 (no sensation) and 1 (maximal intensity). The difference of perceived intensity between self- and externally applied (EA) stimuli was then calculated for each finger. For assessing differences between patients and controls we performed a cluster analysis of the affected hand and the corresponding hand of the controls using the fingers II-V as variables in a 4-dimensional hyperspace (chance level = 0.5). Using a cluster analysis, we found a correct classification of the affected finger in 78.9-94.7%. There was no difference between patients and healthy controls of the absolute value of the perceived stimulus intensity. Our results suggest an altered FM function in focal hand dystonia. It has the potential of suggesting a neural correlate within the cerebellum and of helping integrate findings with regard to altered sensorimotor processing and altered prediction in FD in a single framework.

Pathologic changes in the brain in cervical dystonia pre- and post-mortem - a commentary with a special focus on the cerebellum

In a recent issue of Experimental Neurology, Prudente et al. (2012) investigated the neuropathology of cervical dystonia in six patients. Their most important finding was a patchy loss of cerebellar Purkinje cells in the cerebellum. In this article we discuss their findings in the context of a review including primary and secondary cervical dystonia. An update is given of the current knowledge on structural and functional brain abnormalities in idiopathic cervical dystonia with a special focus on the cerebellum.

Convergent mechanisms in etiologically-diverse dystonias

INTRODUCTION

Dystonia is a neurological disorder associated with twisting motions and abnormal postures, which compromise normal movements and can be both painful and debilitating. It can affect a single body part (focal), several contiguous regions (segmental), or the entire body (generalized), and can arise as a result of numerous causes, both genetic and acquired. Despite the diversity of causes and manifestations, shared clinical features suggest that common mechanisms of pathogenesis may underlie many dystonias.

AREAS COVERED

Shared themes in etiologically-diverse dystonias exist at several biological levels. At the cellular level, abnormalities in the dopaminergic system, mitochondrial function and calcium regulation are often present. At the anatomical level, the basal ganglia and the cerebellum are frequently implicated. Global CNS dysfunction, specifically aberrant neuronal plasticity, inhibition and sensorimotor integration, are also observed in a number of dystonias. Using clinical data and data from animal models, this article seeks to highlight shared pathways that may be critical in understanding mechanisms and identifying novel therapeutic strategies in dystonia.

EXPERT OPINION

Identifying shared features of pathogenesis can provide insight into the biological processes that underlie etiologically diverse dystonias, and can suggest novel targets for therapeutic intervention that may be effective in a broad group of affected individuals.

Update on the pathology of dystonia

Dystonia is a clinical syndrome with sustained muscle contraction, twisting, and abnormal postures. A number of different genetic forms have been defined, but most cases are sporadic in nature and of uncertain cause. Relatively few cases of dystonia have been studied pathologically. In primary dystonias, where dystonia is the main symptom, most reports describe little or no detectable neuropathology, although changes in brainstem neurons have been described in some cases. Secondary dystonias are associated with degenerative or destructive diseases of the nervous system; the pathology may be located in the basal ganglia, but in some cases the primary pathological changes are found in the cerebellum or cerebellar outflow pathways, suggesting that both regions may be involved in the pathogenesis of dystonic symptoms. Overall the number of well-documented pathological cases available for study is few, and there is an urgent need for additional postmortem studies. This article is part of a Special Issue entitled "Advances in dystonia".

The functional neuroanatomy of dystonia

Dystonia is a neurological disorder characterized by involuntary twisting movements and postures. There are many different clinical manifestations, and many different causes. The neuroanatomical substrates for dystonia are only partly understood. Although the traditional view localizes dystonia to basal ganglia circuits, there is increasing recognition that this view is inadequate for accommodating a substantial portion of available clinical and experimental evidence. A model in which several brain regions play a role in a network better accommodates the evidence. This network model accommodates neuropathological and neuroimaging evidence that dystonia may be associated with abnormalities in multiple different brain regions. It also accommodates animal studies showing that dystonic movements arise with manipulations of different brain regions. It is consistent with neurophysiological evidence suggesting defects in neural inhibitory processes, sensorimotor integration, and maladaptive plasticity. Finally, it may explain neurosurgical experience showing that targeting the basal ganglia is effective only for certain subpopulations of dystonia. Most importantly, the network model provides many new and testable hypotheses with direct relevance for new treatment strategies that go beyond the basal ganglia. This article is part of a Special Issue entitled "Advances in dystonia".

Focal hand dystonia cured by removal of clinoid meningioma-case report-

A 40-year-old Asian female presented with an unusual case of focal hand dystonia caused by contralateral clinoid meningioma. Magnetic resonance imaging showed that the tumor compressed the caudate nucleus, lentiform nucleus, cerebral peduncle, internal capsule, and a large portion of the white matter surrounding the basal ganglia. The tumor was gross totally removed via a frontotemporal approach with zygomatic osteotomy, resulting in cure of the focal hand dystonia. Magnetic resonance imaging after surgery showed that the compression of the surrounding brain was released. This case shows that secondary focal hand dystonia caused by extra-axial brain tumor can be cured by surgical removal.

Dystonia associated with pontomesencephalic lesions

Secondary dystonia is well known subsequent to lesions of the basal ganglia or the thalamus. There is evidence that brainstem lesions may also be associated with dystonia, but little is known about pathoanatomical correlations. Here, we report on a series of four patients with acquired dystonia following brainstem lesions. There were no basal ganglia or thalamic lesions. Three patients suffered tegmental pontomesencephalic hemorrhage and one patient diffuse axonal injury secondary to severe craniocerebral trauma. Dystonia developed with a delay of 1 to 14 months, at a mean delay of 6 months. The patients' mean age at onset was 33 years (range 4-56 years). All patients presented with hemidystonia combined with cervical dystonia, and two patients had craniofacial dystonia in addition. Three patients had postural or kinetic tremors. Dystonia was persistent in three patients, and improved gradually in one. There was little response to medical treatment. One patient with hemidystonia combined with cervical dystonia improved after thalamotomy. Overall, the phenomenology of secondary dystonia due to pontomesencephalic lesions is similar to that caused by basal ganglia or thalamic lesions. Structures involved include the pontomesencephalic tegmentum and the superior cerebellar peduncles. Such lesions are often associated with fatal outcome. While delayed occurrence of severe brainstem dystonia appears to be rare, it is possible that mild manifestations of dystonia might be ignored or not be emphasized in the presence of other disabling deficits.

The basal ganglia and cerebellum interact in the expression of dystonic movement

Dystonia is a neurological disorder characterized by excessive involuntary muscle contractions that lead to twisting movements or abnormal posturing. Traditional views place responsibility for dystonia with dysfunction of basal ganglia circuits, yet recent evidence has pointed towards cerebellar circuits as well. In the current studies we used two strategies to explore the hypothesis that the expression of dystonic movements depends on influences from a motor network that includes both the basal ganglia and cerebellum. The first strategy was to evaluate the consequences of subthreshold lesions of the striatum in two different animal models where dystonic movements are thought to originate from abnormal cerebellar function. The second strategy employed microdialysis to search for changes in striatal dopamine release in these two animal models where the cerebellum has been already implicated. One of the animal models involved tottering mice, which exhibit paroxysmal dystonia due to an inherited defect affecting calcium channels. In keeping with prior results implicating the cerebellum in this model, surgical removal of the cerebellum eliminated their dystonic attacks. In contrast, subclinical lesions of the striatum with either 6-hydroxydopamine (6OHDA) or quinolinic acid (QA) exaggerated their dystonic attacks. Microdialysis of the striatum revealed dystonic attacks in tottering mice to be associated with a significant reduction in extracellular striatal dopamine. The other animal model involved the induction of dystonia via pharmacological excitation of the cerebellar cortex by local application of kainic acid in normal mice. In this model the site of stimulation determines the origin of dystonia in the cerebellum. However, subclinical striatal lesions with either 6OHDA or QA again exaggerated their generalized dystonia. When dystonic movements were triggered by pharmacological stimulation of the cerebellum, microdialysis revealed significant reductions in striatal dopamine release. These results demonstrate important functional relationships between cerebellar and basal ganglia circuits in two different animal models of dystonia. They suggest that expression of dystonic movements depends on influences from both basal ganglia and cerebellum in both models. These results support the hypothesis that dystonia may result from disruption of a motor network involving both the basal ganglia and cerebellum, rather than isolated dysfunction of only one motor system.

Secondary cervical dystonia following stereotactic radiosurgery in a patient with thalamic glioma

BACKGROUND

Cervical dystonia associated with structural lesion is uncommon. We report the first patient with secondary CD after stereotactic radiosurgery for thalamic glioma. Possible network abnormalities relevant to manifestation of CD were discussed.

CASE DESCRIPTION

A 27-year-old woman complaining of headache and left motor weakness was found to have a thalamic tumor on the right side. The lesion was totally removed using transventricular approach. Histopathologically, tumor samples manifested features of anaplastic astrocytoma. She underwent stereotactic radiosurgery in addition to the conventional radiation and chemotherapy. Afterward, she returned to her usual life without any neurological deficits. Sixteen months postoperatively, the patient developed forced head tilting to the left side combined with chin lift. On the TWSTRS, she registered 15 for torticollis severity. The abnormal head posturing was alleviated by the sensory trick of touching her face with her right hand. Irregular-shaped lesion involving the thalamus, lenticular nuclei, midbrain, pons, and cerebellum was presented on magnetic resonance images. Steroid therapy effectively diminished the lesion size, and her abnormal head posturing was gradually ameliorated (TWSTRS severity scale = 3).

CONCLUSION

The clinical-neuroradiological course of the present case strongly suggested that the lesion detected long after the surgery was due to radiation necrosis. The present study may provide a critical information in understanding pathophysiological mechanisms of CD that may involve substantial interactions between olivocerebellar and basal ganglia-thalamocortical circuits.

Torticollis secondary to posterior fossa and cervical spinal cord tumors: report of five cases and literature review

Torticollis is either congenital or acquired in childhood. Acquired torticollis is not a diagnosis but rather a sign of an underlying disorder. The causes of acquired torticollis include ligamentous, muscular, osseous, ocular, psychiatric, and neurologic disorders and may be a symptom of significant abnormalities of the spinal cord and brain, such as spinal syrinx or central nervous system neoplasia. Torticollis is rarely considered to be an initial clinical presentation of posterior fossa and cervical spinal cord tumors. We report five cases of pediatric tumors with torticollis at the onset: an astrocytoma originating from the medulla oblongata, another presumptive astrocytoma of the spinal cord located between C1 and C6 cervical vertebrae (not operated), an ependymoma located throughout the whole cervical spinal cord extending into the bulbomedullary junction, an astrocytoma originating from the bulbus and extending into the posterior fossa, and another case of a eosinophilic granuloma located extradurally through the anterior and posterior portions of the vertebral bodies from C3 to C7 producing the collapse of the sixth cervical vertebra. All five cases were seen in children, aged between 3 and 12 years. All these cases reflect the misinterpretation of this neurological sign and the lack of association with the possibility of spinal or posterior fossa tumor. This delay in the diagnosis of these diseases led to progressive neurological deterioration and to the increase in the tumor size, which made surgical intervention difficult and the prognosis unfavorable. Although torticollis secondary to tumors is rarely seen, it is necessary to be kept in mind in the differential diagnosis.

Magnetic resonance imaging in the evaluation of infantile torticollis

This retrospective study assessed the use of magnetic resonance imaging (MRI) in 58 infants with infantile torticollis. Eighteen patients had nonmuscular causes of torticollis (group 1); MRI identified lesions in 16 patients. Of 40 patients with a diagnosis of congenital muscular torticollis (group 2), 28 had a normal MRI. Five patients had asymmetry of the sternocleidomastoid without noticeable signal changes. Seven patients showd evidence of fibromatosis colli. Asymmetry of the posterolateral skull consistent with plagiocephaly was common. Magnetic resonance imaging did not alter treatment of group 2. Findings of compartment syndrome of sternocleidomastoid were inconsistent. Magnetic resonance imaging is not recommended for asymptomatic patients with infantile torticollis.

Secondary cervical dystonia associated with structural lesions of the central nervous system

We tested the hypothesis that structural lesions of the central nervous system (CNS) associated with cervical dystonia more commonly involve the cerebellum and its primary afferent pathways than basal ganglia structures. Cervical dystonia is the most common focal dystonia, the majority of cases are idiopathic, and only a small percentage of patients have a family history of dystonia or other movement disorders. Pathophysiological mechanisms operative in solely or predominantly appendicular dystonias such as writer's cramp and Oppenheim's dystonia, respectively, may not be directly applicable to axial dystonias. The localization of structural lesions of the CNS associated with secondary cervical dystonia may provide some insight into the neural structures potentially involved in primary cervical dystonia. The National Library of Medicine Gateway (from 1960) and a clinical database maintained by the senior author (from 1999) were searched for cases of secondary cervical dystonia associated with structural lesions of the CNS. Search terms included one or more of the following: dystonia, torticollis, cervical, secondary, and symptomatic. Lesion localization and type, patient age, patient gender, head position, occurrence of sensory tricks, and associated neurological findings were tabulated for each case. Structural lesions associated with cervical dystonia were most commonly localized to the brainstem and cerebellum. The remaining cases were equally divided between the cervical spinal cord and basal ganglia. Although inconsistent, head rotation tended to be contralateral to lesion localization. Additional neurological abnormalities were present in the majority of patients with secondary cervical dystonia. The relative paucity of basal ganglia pathology and concentration of lesions in the brainstem, cerebellum, and cervical spinal cord in patients with secondary cervical dystonia suggests that dysfunction of cerebellar afferent pathways may be important to the pathophysiology of primary cervical dystonia.

[Diagnosis of cerebellum-pontine angle tumors using artificial intelligence techniques]

We are concerned in this paper with learning classification procedures from known cases. More precisely, we provide a diagnostic model that discriminate between cerebellum-pontine angle (CPA) tumors and otorhinolaryngological (ENT) disorders. Usually, in order to distinguish between CPA tumors and ENT disorders one must perform clinical-neurological examination together with expensive radiological imagery (CT and MRI). The proposed model was obtained through artificial intelligence methods and presented a good accuracy level (88.4%) when tested against new cases, considering only clinical examination without radiological imagery results.

Parkinsonism in children resulting from mesencephalic tumors

Parkinsonism secondary to intrinsic brain stem mass lesions is rare. Two children with parkinsonism caused by mesencephalic tumors are reported. The pathophysiological mechanisms of this association are discussed and the literature describing similar cases is reviewed.

Dystonia

Many different disorders have dystonia as the only or primary sign. The list of causes for dystonia increases yearly and now includes three mapped loci for primary torsion dystonia, although other susceptibility genes are suspected. Study of one of these primary torsion dystonia loci (DYT1) has culminated in the cloning of a gene which codes for a novel protein, torsin A. Physiological and positron emission tomography analyses suggest that dystonia results from impaired inhibition at cortical and subcortical levels; these physiological changes may in turn be due to striatal dysfunction and a mismatch or imbalance between the direct and indirect pathways. Future study of normal and mutant torsin A, as well as the identification of other primary torsion dystonia genes, should help elucidate the mechanisms underlying dystonia.