Cervical dystonia as a probable consequence of focal cerebral lesion

The functional anatomy of dystonia: Recent developments

While dystonia has traditionally been viewed as a disorder of the basal ganglia, the involvement of other key brain structures is now accepted. However, just what these structures are remains to be defined. Neuroimaging has been an especially valuable tool in dystonia, yet traditional cross-sectional designs have not been able to separate causal from compensatory brain activity. Therefore, this chapter discusses recent studies using causal brain lesions, and animal models, to converge upon the brain regions responsible for dystonia with increasing precision. This evidence strongly implicates the basal ganglia, thalamus, brainstem, cerebellum, and somatosensory cortex, yet shows that different types of dystonia involve different nodes of this brain network. Nearly all of these nodes fall within the recently identified two-way networks connecting the basal ganglia and cerebellum, suggesting dysfunction of these specific pathways. Localisation of the functional anatomy of dystonia has strong implications for targeted treatment options, such as deep brain stimulation, and non-invasive brain stimulation.

Network localization of cervical dystonia based on causal brain lesions

Cervical dystonia is a neurological disorder characterized by sustained, involuntary movements of the head and neck. Most cases of cervical dystonia are idiopathic, with no obvious cause, yet some cases are acquired, secondary to focal brain lesions. These latter cases are valuable as they establish a causal link between neuroanatomy and resultant symptoms, lending insight into the brain regions causing cervical dystonia and possible treatment targets. However, lesions causing cervical dystonia can occur in multiple different brain locations, leaving localization unclear. Here, we use a technique termed 'lesion network mapping', which uses connectome data from a large cohort of healthy subjects (resting state functional MRI, n = 1000) to test whether lesion locations causing cervical dystonia map to a common brain network. We then test whether this network, derived from brain lesions, is abnormal in patients with idiopathic cervical dystonia (n = 39) versus matched controls (n = 37). A systematic literature search identified 25 cases of lesion-induced cervical dystonia. Lesion locations were heterogeneous, with lesions scattered throughout the cerebellum, brainstem, and basal ganglia. However, these heterogeneous lesion locations were all part of a single functionally connected brain network. Positive connectivity to the cerebellum and negative connectivity to the somatosensory cortex were specific markers for cervical dystonia compared to lesions causing other neurological symptoms. Connectivity with these two regions defined a single brain network that encompassed the heterogeneous lesion locations causing cervical dystonia. These cerebellar and somatosensory regions also showed abnormal connectivity in patients with idiopathic cervical dystonia. Finally, the most effective deep brain stimulation sites for treating dystonia were connected to these same cerebellar and somatosensory regions identified using lesion network mapping. These results lend insight into the causal neuroanatomical substrate of cervical dystonia, demonstrate convergence across idiopathic and acquired dystonia, and identify a network target for dystonia treatment.

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.

Systemic diseases that cause movement disorders

The present review is aimed at providing practical assistance to the clinical neurologist in reaching a diagnosis, understanding the pathogenic mechanisms of movement disorders associated with systemic diseases, and determining appropriate therapy. Infectious disease by direct effect or as an acquired autoimmune neurological disease, stroke, hypoxia-ischemia, paraneoplastic syndromes, collagen disorders, endocrine, liver and kidney diseases that may cause hypokinetic or hyperkinetic abnormal movement are considered separately. The type and evolution of abnormal movement caused by systemic disease vary with age and underlying pathology. Therapy for abnormal movements should include a primary treatment for the systemic disease.

Post-stroke movement disorders: report of 56 patients

BACKGROUND

Although movement disorders that occur following a stroke have long been recognised in short series of patients, their frequency and clinical and imaging features have not been reported in large series of patients with stroke.

METHODS

We reviewed consecutive patients with involuntary abnormal movements (IAMs) following a stroke who were included in the Eugenio Espejo Hospital Stroke Registry and they were followed up for at least one year after the onset of the IAM. We determined the clinical features, topographical correlations, and pathophysiological implications of the IAMs.

RESULTS

Of 1500 patients with stroke 56 developed movement disorders up to one year after the stroke. Patients with chorea were older and the patients with dystonia were younger than the patients with other IAMs. In patients with isolated vascular lesions without IAMs, surface lesions prevailed but patients with deep vascular lesions showed a higher probability of developing abnormal movements. One year after onset of the IAMs, 12 patients (21.4%) completely improved their abnormal movements, 38 patients (67.8%) partially improved, four did not improve (7.1%), and two patients with chorea died. In the nested case-control analysis, the patients with IAMs displayed a higher frequency of deep lesions (63% v 33%; OR 3.38, 95% CI 1.64 to 6.99, p<0.001). Patients with deep haemorrhagic lesions showed a higher probability of developing IAMs (OR 4.8, 95% CI 0.8 to 36.6).

CONCLUSIONS

Chorea is the commonest movement disorder following stroke and appears in older patients. Involuntary movements tend to persist despite the functional recovery of motor deficit. Deep vascular lesions are more frequent in patients with movement disorders.

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.

Mosaic pattern of gliosis in the neostriatum of a North American man with craniocervical dystonia and parkinsonism

We present the case of a 51-year-old patient with a 31-year history of psychiatric symptoms, craniocervical dystonia, bulbar dysfunction, and parkinsonism. His dystonic movements included blepharospasm, jaw opening and lingual dystonia, and spasmodic retrocollis. Psychiatric symptoms included psychosis and depression, with onset years before the movement disorder. After his death by aspiration, examination of his brain revealed abnormalities limited to the neostriatum. Staining of brain sections, including Holzer, glial fibrillary acidic protein, and immunohistochemical stain for calbindin D28k, revealed the presence of a mosaic pattern of gliosis with neuronal loss (sparing large neurons) within this region. The islands of tissue between stands of gliosis had a normal appearance. This patient represents only the fourth case (and first North American born) with a mosaic pattern of gliosis in the neostriatum. The clinical and pathologic features were similar in all four cases except that our patient was the first with prominent psychiatric symptoms and a more stable, less progressive course. Mosaicism has been described in the X-linked Filipino disorder Lubag. Occurrence in non-Filipino patients, such as ours, suggest that either Lubag can develop in non-Filipino families or that mosaicism is a nonspecific pathologic finding in some patients with idiopathic dystonia. Finally, our case reports the notion that craniocervical dystonia may result from neostriatal dysfunction.