Classification and definition of disorders causing hypertonia in childhood

Misdiagnoses in children with dopa-responsive dystonia

Dystonia is a state of continuous contraction of groups of agonist and antagonist muscles resulting in a sustained abnormal posture. Dopa-responsive dystonia was first described in 1976 by Segawa. Patients typically have diurnal variation of their symptoms with worsening at the end of the day and a dramatic response to low-dose L-dopa. This report presents five consecutive children with dopa-responsive dystonia who were misdiagnosed initially as spastic diplegic cerebral palsy, intractable epilepsy, hereditary spastic paraplegia, or a neurodegenerative disorder. There were two males and three females aged 3-13 years (mean 8.6 years). They were monitored for up to 2 years (mean 14.8 months). One had focal, one axial, one segmental, and two generalized dystonia. The dystonia was paroxysmal in two (tiptoe walking and opisthotonus), and all had a progressive course. All children responded dramatically to L-dopa (mean 200 mg/day), including three who were wheelchair-bound for several years. The difficulties in early diagnosis, variability of clinical presentation, and dramatic response to L-dopa will be illustrated. To conclude, dopa-responsive dystonia should be considered in any child who presents with paroxysmal or progressive hypertonia of unknown etiology, because it responds so dramatically to L-dopa.

Evaluation of a child with cerebral palsy

Evaluation of a child with cerebral palsy (CP) requires a multidisciplinary approach with a team of professionals comprising of a pediatrician or pediatric neurologist, occupational therapist, a physiotherapist, child psychologist, and a social worker. The assessment is necessary to confirm the diagnosis, determine the cause, assess the motor function and associated problems. The diagnosis of CP is clinical but selected investigations may be required for ascertaining the cause. Evaluation includes assessment for common medical problems of childhood particularly nutritional disorders and assessment of family functioning. Additional disabilities are common. Routine assessment of vision and hearing is required in children with CP. Since CP is a changing disorder, some limitations may not be evident early in life but manifest in the school age or later. The evaluation of a child with CP is an ongoing process and should be a part of continuing care as the child grows from infancy to adolescence.

Biomechanic characteristics of patients with spastic and dystonic hypertonia in cerebral palsy11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated

OBJECTIVE

To determine what biomechanic characteristics of knee joint motion and walking show potential to quantitatively differentiate spasticity and dystonia in cerebral palsy (CP).

DESIGN

Descriptive measurement study.

SETTING

University hospital.

PARTICIPANTS

Seventeen pediatric and adult patients with CP.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We measured the resistance of the knee joint at different velocities and positions, maximum muscle activation during external motion, amplitude of knee tendon reflexes, maximum isometric flexion and extension torques, velocity of walking, and knee kinematics during the gait cycle. Patients were classified into 2 groups (dystonia or spasticity) if at least 2 of 3 physicians agreed that a prominent component of dystonia was present.

RESULTS

Patients with dystonia had a greater degree of co-contraction and an increased resistance to external motion at slow velocities. The tendon reflexes were almost normal in patients with dystonia, whereas they were increased in patients with spasticity. Muscle strength was more impaired in patients with dystonia, probably as a result of greater muscle co-contraction. They also walked slower, with smaller knee ranges of motion, during the stance phase of walking.

CONCLUSIONS

The measurement of resistance and of muscle activation during passive motion and tendon reflexes shows potential to differentiate dystonia from spasticity in CP patients with a mixed form of hypertonia. More studies are needed to confirm these results.

Cerebral palsy

Cerebral palsy, a range of non-progressive syndromes of posture and motor impairment, is a common cause of disability in childhood. The disorder results from various insults to different areas within the developing nervous system, which partly explains the variability of clinical findings. Management options include physiotherapy, occupational and speech therapy, orthotics, device-assisted modalities, pharmacological intervention, and orthopaedic and neurosurgical procedures. Since 1980, modification of spasticity by means of orally administered drugs, intramuscular chemodenervation agents (alcohol, phenol, botulinum toxin A), intrathecally administered drugs (baclofen), and surgery (neurectomy, rhizotomy) has become more frequent. Family-directed use of holistic approaches for their children with cerebral palsy includes the widespread adoption of complementary and alternative therapies; however, the prevalence of their use and the cost of these options are unknown. Traditional medical techniques (physiotherapy, bracing, and orthopaedic musculoskeletal surgery) remain the mainstay of treatment strategies at this time. This seminar addresses only the musculoskeletal issues associated with cerebral palsy and only indirectly discusses the cognitive, medical, and social issues associated with this diagnosis.

Management of spasticity in children with cerebral palsy

As one component of the upper motor neuron syndrome, spasticity can have a significant functional impact on the child with cerebral palsy. Treatment planning requires the determination that excess tone interferes with some aspect of function, comfort, or care, and takes into consideration carefully devised goals that meet the needs of the patient and the caregiver. Treatment options include physical therapy, oral medications, chemodenervation with botulinum toxin or phenol, rhizotomy, intrathecal baclofen, and orthopedic surgery. The uses and limitations of each is discussed, and evidence for efficacy in cerebral palsy is reviewed.

Preterm fetal hypoxia-ischemia causes hypertonia and motor deficits in the neonatal rabbit: a model for human cerebral palsy?

Prenatal hypoxia-ischemia to the developing brain has been strongly implicated in the subsequent development of the hypertonic motor deficits of cerebral palsy (CP) in premature and full-term infants who present with neonatal encephalopathy. Despite the enormous impact of CP, there is no animal model that reproduces the hypertonia and motor disturbances of this disorder. We report a rabbit model of in utero placental insufficiency, in which hypertonia is accompanied by marked abnormalities in motor control. Preterm fetuses (67-70% gestation) were subjected to sustained global hypoxia. The dams survived and gave spontaneous birth. At postnatal day 1, the pups that survived were subjected to a battery of neurobehavioral tests developed specifically for these animals, and the tests were videotaped and scored in a masked manner. Newborn pups of hypoxic groups displayed significant impairment in multiple tests of spontaneous locomotion, reflex motor activity, and the coordination of suck and swallow. Increased tone of the limbs at rest and with active flexion and extension were observed in the survivors of the preterm insult. Histopathological studies identified a distinct pattern of acute injury to subcortical motor pathways that involved the basal ganglia and thalamus. Persistent injury to the caudate putamen and thalamus at P1 was significantly correlated with hypertonic motor deficits in the hypoxic group. Antenatal hypoxia-ischemia at preterm gestation results in hypertonia and abnormalities in motor control. These findings provide a unique behavioral model to define mechanisms and sequelae of perinatal brain injury from antenatal hypoxia-ischemia.

Motor disturbances in mice with deficiency of the sodium channel gene Scn8a show features of human dystonia

The med(J) mouse with twisting movements related to deficiency of the sodium channel Scn8a has been proposed as a model of kinesiogenic dystonia. This prompted us to examine the phenotype of these mice in more detail. By cortical electroencephalographic (EEG) recordings, we could not detect any changes, demonstrating that the motor disturbances are not epileptic in nature, an important similarity to human dystonia. The significantly decreased body weight of med(J) mice was related to reduced food intake. Observations in the open field and by video recordings revealed that the mice exhibit sustained abnormal postures and movements of limbs, trunk and tail not only during locomotor activity but also at rest. With the exception of the head tremor, the other motor impairments were persistent rather than paroxysmal. When several neurological reflexes were tested, alterations were restricted to the posture and righting reflexes. Results of the wire hang test confirmed the greatly reduced muscle strength in the med(J) mouse. In agreement with different types of human dystonia, biperiden, haloperidol and diazepam moderately reduced the severity of motor disturbances in med(J) mice. In view of the sodium channel deficiency in med(J) mice, the beneficial effects of the sodium channel blocker phenytoin was an unexpected finding. By immunohistochemical examinations, the density of nigral dopaminergic neurons was found to be unaltered, substantiating the absence of pathomorphological abnormalities within the brain of med(J) mice shown by previous studies. With the exception of muscle weakness, many of the features of the med(J) mouse are similar to human idiopathic dystonia.

Pharmacologic management of the spastic and dystonic upper limb in children with cerebral palsy

Spasticity or dystonia of the upper limb in children with CP commonly is seen as part of a more involved clinical picture. Each can cause functional problems in and can interfere with the quality of life of children with CP. Pharmacologic manipulation of the spasticity and dystonia requires a patient and ordered approach. Treatment often is performed using an open trial method, with medications introduced slowly but often being limited in their usefulness by significant side effects. Despite multiple medications being available for spasticity and dystonia management, few of the oral treatments have been assessed systematically in children with CP. Specific evaluation of the use of enteral medications in upper limb management is even rarer.

Movement disorders in children: definitions, classifications, and grading systems

Disorders that affect movement in children are relatively common. However, they have received little attention, especially when compared with epilepsy and neuromuscular disorders. In this review article, we address the major types of movement disorders that affect children, their clinical characteristics and etiologies, and, when available, the scales used to grade them. A discussion on spasticity, which traditionally is not addressed in reviews of "movement disorders," is also included.

Pathophysiology of pediatric movement disorders

Pediatric movement disorders constitute a relatively small cluster of symptoms that can be associated with many different underlying diseases. To provide effective treatment, it is essential to understand the relationship between etiology and clinical expression. This article reviews the recent literature on several common pediatric movement disorders, including spasticity, dystonia, chorea, myoclonus, bradykinesia, and tics, and it discusses current models of physiology that may help link the cellular pathology of specific diseases to the expression of clinical symptoms.