Gait features of dystonia in cerebral palsy

Preterm birth is associated with dystonic features and reduced cortical parvalbumin immunoreactivity in mice

BACKGROUND

Preterm birth is a common cause of dystonia. Though dystonia is often associated with striatal dysfunction after neonatal brain injury, cortical dysfunction may best predict dystonia following preterm birth. Furthermore, abnormal sensorimotor cortex inhibition is associated with genetic and idiopathic dystonias. To investigate cortical dysfunction and dystonia following preterm birth, we developed a new model of preterm birth in mice.

METHODS

We induced preterm birth in C57BL/6J mice at embryonic day 18.3, ~24 h early. Leg adduction variability and amplitude, metrics we have shown distinguish between dystonia from spasticity during gait in people with CP, were quantified from gait videos of mice. Parvalbumin-positive interneurons, the largest population of cortical inhibitory interneurons, were quantified in the sensorimotor cortex and striatum.

RESULTS

Mice born preterm demonstrate increased leg adduction amplitude and variability during gait, suggestive of clinically observed dystonic gait features. Mice born preterm also demonstrate fewer parvalbumin-positive interneurons and reduced parvalbumin immunoreactivity in the sensorimotor cortex, but not the striatum, suggesting dysfunction of cortical inhibition.

CONCLUSIONS

These data may suggest an association between cortical dysfunction and dystonic gait features following preterm birth. We propose that our novel mouse model of preterm birth can be used to study this association.

IMPACT

Mouse models of true preterm birth are valuable for studying clinical complications of prematurity. Mice born preterm demonstrate increased leg adduction amplitude and variability during gait, suggestive of clinically observed dystonic gait features. Mice born preterm demonstrate fewer parvalbumin-positive interneurons and reduced parvalbumin immunoreactivity in the sensorimotor cortex, suggesting dysfunction of cortical inhibition. Mice born preterm do not demonstrate changes in parvalbumin immunoreactivity in the striatum. Cortical dysfunction may be associated with dystonic gait features following preterm birth.

Efficacy of Oral Trihexyphenidyl Plus Clonazepam Versus Trihexyphenidyl for the Treatment of Dystonia in Children With Dystonic Cerebral Palsy: An Open-Label Randomized Controlled Trial

BACKGROUND

Trihexyphenidyl and clonazepam are commonly used to treat dystonia in children with cerebral palsy (CP). However, there is a notable gap in the literature when it comes to studies that combine these first-line agents for the management of dystonia.

METHODS

This open-label, randomized controlled trial aimed to compare the efficacy of adding oral clonazepam to trihexyphenidyl (THP + CLZ) versus using trihexyphenidyl alone (THP) in reducing the severity of dystonia, as measured by the Barry-Albright Dystonia (BAD) score. The study was conducted over a 12-week therapy period in children with dystonic CP aged two to 14 years.

RESULTS

Each group enrolled 51 participants. The THP + CLZ group showed significantly better improvement in dystonia severity at 12 weeks compared with the THP group alone (-4.5 ± 2.9 vs -3.4 ± 1.7, P = 0.02). Furthermore, the THP + CLZ group exhibited superior improvement in the severity of choreoathetosis, upper limb function, pain perception by the child, and quality of life, with P values of 0.02, 0.009, 0.01, and 0.01, respectively. The number of participants experiencing treatment-emergent adverse events was comparable in both groups (P = 0.67). Importantly, none of the participants in any of the groups reported any serious adverse events.

CONCLUSION

A combination of oral THP + CLZ proves to be more efficacious than using THP alone for the treatment of dystonic CP in children aged two to 14 years in terms of reducing the severity of dystonia.

Standardized clinical data capture to describe cerebral palsy

Objective

To describe a standardized methodology for capturing clinically valuable information on young people with cerebral palsy (CP) from caregivers and clinicians during routine clinical care.

Methods

We developed a caregiver-facing intake form and clinician-facing standardized note template and integrated both into routine clinical care at a tertiary care CP center ( https://bit.ly/CP-Intake-Methodology ). We extracted this caregiver and clinician-entered data on people with an ICD10 diagnosis of CP seen between 3/22/23 and 12/28/23. We used this data to describe how CP manifests in this group and which medical features affected the odds of walking, oral feeding, and speech by age 5.

Results

Of 686 visits, 663 (97%) had caregiver- and clinician-entered data and 633 had a clinician-confirmed CP diagnosis (mean age 9.1, 53.4% Male, 78.5% White). It was common to have quadriplegia (288/613, 47.0%), both spasticity and dystonia (257/632, 40.7%), walk independently (368/633, 58.1%), eat all food and drink safely by mouth (288/578, 55.9%), and produce understandable speech (249/584, 42.6%). Cortical grey matter injury and duration of initial critical care unit stay affected the odds of walking, oral feeding, and speech (binary logistic regression, p<0.001).

Conclusions

We comprehensively captured caregiver and clinician-entered data on 97% of people seen in a tertiary care CP Center and used this data to determine medical features affecting the odds of three functional outcomes. By sharing our methodology, we aim to facilitate replication of this dataset at other sites and grow our understanding of how CP manifests in the US.

Article summary

Using caregiver and clinician-entered data on people seen in a tertiary-care CP center, we determined medical features affecting the odds of three functional outcomes.

What’s known on this subject

Detailed CP characterization can be limited if using population-based registries and retrospective chart review alone, including limited data on recently validated functional classification systems for CP.

What this study adds

We comprehensively captured caregiver and clinician-entered data on 97% of people seen in our CP Center to describe how CP manifests and show that cortical injury and initial ICU stay duration affect the odds of walking, oral feeding, and speech.

Contributors Statement

Susie Kim helped design the study, aggregated data, carried out data analyses, and critically reviewed and revised the manuscript.Kelsey Steffen helped conceptualize and design the study and critically reviewed and revised the manuscript.Lauren Gottschalk, Jennifer Miros, Katie Leger, Amy Viehoever, and Karen Taca helped design the study and critically reviewed and revised the manuscript.Bhooma Aravamuthan conceptualized and designed the study, supervised data collection and analysis, drafted the initial manuscript, and critically reviewed and revised the manuscript.

Clinician Knowledge, Confidence, and Practice Patterns Defining, Identifying, and Quantifying Dystonia in Children: A Cross-Sectional Survey Study

A survey was completed by 183 clinicians at a pediatric hospital to investigate knowledge, confidence, and practice patterns defining, identifying, and quantifying dystonia in children. The definition of dystonia was correctly identified by 86% of participants. While 88% reported identifying dystonia, only 42% of physicians and therapists reported quantifying dystonia. A weak, significant correlation, rs =.339, p ≤ .001, was found between years of pediatric experience and confidence identifying dystonia. Clinician reported higher confidence levels identifying and quantifying dystonia if they perform a neurological exam. Clinical training initiatives are needed to improve standardization and build confidence in defining, identifying, and quantifying dystonia.

Mice born preterm develop gait dystonia and reduced cortical parvalbumin immunoreactivity

Preterm birth leading to cerebral palsy (CP) is the most common cause of childhood dystonia, a movement disorder that is debilitating and often treatment refractory. Dystonia has been typically associated with dysfunction of striatal cholinergic interneurons, but clinical imaging data suggests that cortical injury may best predict dystonia following preterm birth. Furthermore, abnormal sensorimotor cortex inhibition has been found in many studies of non-CP dystonias. To assess the potential for a cortical etiology of dystonia following preterm birth, we developed a new model of preterm birth in mice. Noting that term delivery in mice on a C57BL/6J background is embryonic day 19.1 (E19.1), we induced preterm birth at the limits of pup viability at embryonic day (E) 18.3, equivalent to human 22 weeks gestation. Mice born preterm demonstrate display clinically validated metrics of dystonia during gait (leg adduction amplitude and variability) and also demonstrate reduced parvalbumin immunoreactivity in the sensorimotor cortex, suggesting dysfunction of cortical parvalbumin-positive inhibitory interneurons. Notably, reduced parvalbumin immunoreactivity or changes in parvalbumin-positive neuronal number were not observed in the striatum. These data support the association between cortical dysfunction and dystonia following preterm birth. We propose that our mouse model of preterm birth can be used to study this association and potentially also study other sequelae of extreme prematurity.

Caregiver descriptions of dystonia in cerebral palsy

OBJECTIVE

To determine how caregivers describe dystonia in people with cerebral palsy (CP).

METHODS

In this prospective cohort study, paper surveys were administered to caregivers between September 7, 2021 and October 28, 2021 during CP Center visits at a large tertiary care center. Caregivers were asked to describe involuntary movements triggered by voluntary movement or triggered by tactile stimulation in the people with CP they cared for. Their CP Center medical provider separately assessed people with CP for dystonia. Movement features described exclusively by caregivers of people with CP and dystonia were determined using conventional content analysis.

RESULTS

113 caregivers responded on behalf of 56 people with and 57 people without dystonia. If caregivers noted that both voluntary movement and tactile stimulation triggered involuntary movements, that had a 92% positive predictive value for a dystonia diagnosis. Movement features exclusively described in people with CP and dystonia included: (1) stiffening, tensing, or tightening (15% of respondents); (2) involvement of the head (10%), torso (5%), or feet (5%); and (3) triggers of stretching (12.5%), excitement (5%), or transfers (5%).

INTERPRETATION

In addition to a thorough exam, asking caregivers of people with CP to describe involuntary movements triggered by voluntary movement or tactile stimulation may inform clinical dystonia diagnosis.

Upper Extremity Dystonia Features in People With Spastic Cerebral Palsy

Background and Objectives

Dystonia in cerebral palsy (CP) is debilitating and common, but underdiagnosed, especially when coexistent with spasticity. With dedicated research-based assessment, dystonia is found in most people with spastic CP but is only clinically diagnosed in the minority. To begin addressing the high rates of dystonia underdiagnosis in this population, we determined the key feature experts use to assess upper extremity dystonia in people with spastic CP.

Methods

In this prospective cohort study, 3 pediatric movement disorder specialists assessed upper extremity dystonia in neurologic examination videos of people with spastic CP and isolated periventricular leukomalacia (PVL) on brain MRI (i.e., those with a brain injury pattern typical for spastic CP). Dystonia severity was rated using the 10-point Global Dystonia Severity Rating Scale, first by each expert independently and then again after consensus-building discussion. Conventional content analysis of these discussions revealed salient features ("codes") that experts used to assess upper extremity dystonia. Code frequency distributions were compared between dystonia severity categories using χ2 tests.

Results

We identified 96 people with spastic CP with isolated PVL on brain MRI seen in the St. Louis Children's Hospital CP Center between 2005 and 2018. Of them, 26 people were able and willing to be recorded while doing a standardized set of upper extremity examination maneuvers (age 4-25 years; 28% nonambulatory, 77% White). When assessing their videos, experts cited the "hand" less often and "shoulder" more often with increasing dystonia severity (p < 0.005, χ2 test). "Mirror movements" and the "hand open/close" examination maneuver were cited significantly more frequently in videos when experts were attempting to distinguish between no dystonia and mild dystonia (p < 0.005).

Discussion

Expert clinicians use distinct movement features to assess upper extremity dystonia in people with spastic CP and PVL. Attention to involuntary shoulder (vs hand) movements can help gauge dystonia severity. Differentiation between mirror movements and dystonia, particularly during the hand open/close examination maneuver, may help identify mild dystonia. These results can help guide upper extremity dystonia assessment in people with spastic CP, thus potentially helping mitigate dystonia underdiagnosis.

Chronic striatal cholinergic interneuron excitation induces clinically-relevant dystonic behavior in mice

Dystonia is common, debilitating, often medically refractory, and difficult to diagnose. The gold standard for both clinical and mouse model dystonia evaluation is subjective assessment, ideally by expert consensus. However, this subjectivity makes translational quantification of clinically-relevant dystonia metrics across species nearly impossible. Many mouse models of genetic dystonias display abnormal striatal cholinergic interneuron excitation, but few display subjectively dystonic features. Therefore, whether striatal cholinergic interneuron pathology causes dystonia remains unknown. To address these critical limitations, we first demonstrate that objectively quantifiable leg adduction variability correlates with leg dystonia severity in people. We then show that chemogenetic excitation of striatal cholinergic interneurons in mice causes comparable leg adduction variability in mice. This clinically-relevant dystonic behavior in mice does not occur with acute excitation, but rather develops after 14 days of ongoing striatal cholinergic interneuron excitation. This requirement for prolonged excitation recapitulates the clinically observed phenomena of a delay between an inciting brain injury and subsequent dystonia manifestation and demonstrates a causative link between chronic striatal cholinergic interneuron excitation and clinically-relevant dystonic behavior in mice. Therefore, these results support targeting striatal ChIs for dystonia drug development and suggests early treatment in the window following injury but prior to dystonia onset.

One Sentence Summary

Chronic excitation of dorsal striatal cholinergic interneuron causes clinically-relevant dystonic phenotypes in mice.

Neurophysiology of cerebellar ataxias and gait disorders

There are numerous forms of cerebellar disorders from sporadic to genetic diseases. The aim of this chapter is to provide an overview of the advances and emerging techniques during these last 2 decades in the neurophysiological tests useful in cerebellar patients for clinical and research purposes. Clinically, patients exhibit various combinations of a vestibulocerebellar syndrome, a cerebellar cognitive affective syndrome and a cerebellar motor syndrome which will be discussed throughout this chapter. Cerebellar patients show abnormal Bereitschaftpotentials (BPs) and mismatch negativity. Cerebellar EEG is now being applied in cerebellar disorders to unravel impaired electrophysiological patterns associated within disorders of the cerebellar cortex. Eyeblink conditioning is significantly impaired in cerebellar disorders: the ability to acquire conditioned eyeblink responses is reduced in hereditary ataxias, in cerebellar stroke and after tumor surgery of the cerebellum. Furthermore, impaired eyeblink conditioning is an early marker of cerebellar degenerative disease. General rules of motor control suggest that optimal strategies are needed to execute voluntary movements in the complex environment of daily life. A high degree of adaptability is required for learning procedures underlying motor control as sensorimotor adaptation is essential to perform accurate goal-directed movements. Cerebellar patients show impairments during online visuomotor adaptation tasks. Cerebellum-motor cortex inhibition (CBI) is a neurophysiological biomarker showing an inverse association between cerebellothalamocortical tract integrity and ataxia severity. Ataxic gait is characterized by increased step width, reduced ankle joint range of motion, increased gait variability, lack of intra-limb inter-joint and inter-segmental coordination, impaired foot ground placement and loss of trunk control. Taken together, these techniques provide a neurophysiological framework for a better appraisal of cerebellar disorders.

Determinants of gait dystonia severity in cerebral palsy

AIM

To determine the movement features governing expert assessment of gait dystonia severity in individuals with cerebral palsy (CP).

METHOD

In this prospective cohort study, three movement disorder neurologists graded lower extremity dystonia severity in gait videos of individuals with CP using a 10-point Likert-like scale. Using conventional content analysis, we determined the features experts cited when grading dystonia severity. Then, using open-source pose estimation techniques, we determined gait variable analogs of these expert-cited features correlating with their assessments of dystonia severity.

RESULTS

Experts assessed videos from 116 participants (46 with dystonia aged 15 years [SD 3] and 70 without dystonia aged 15 years [SD 2], both groups ranging 10-20 years old and 50% male). Variable limb adduction was most commonly cited by experts when identifying dystonia, comprising 60% of expert statements. Effect on gait (regularity, stability, trajectory, speed) and dystonia amplitude were common features experts used to determine dystonia severity, comprising 19% and 13% of statements respectively. Gait variables assessing adduction variability and amplitude (inter-ankle distance variance and foot adduction amplitude) were significantly correlated with expert assessment of dystonia severity (multiple linear regression, p < 0.001).

INTERPRETATION

Adduction variability and amplitude are quantifiable gait features that correlate with expert-determined gait dystonia severity in individuals with CP. Consideration of these features could help optimize and standardize the clinical assessment of gait dystonia severity in individuals with CP.

Dystonia in individuals with spastic cerebral palsy and isolated periventricular leukomalacia

AIM

To determine the prevalence of dystonia in individuals with periventricular leukomalacia (PVL) and spastic cerebral palsy (CP), but without basal ganglia and thalamic injury (BGTI) on brain magnetic resonance imaging (MRI).

METHOD

This was a retrospective study of individuals with spastic CP and PVL on MRI evaluated between 2005 and 2018 in a CP center. Individuals with non-PVL brain lesions on MRI, including BGTI, were excluded. Dystonia was assessed via blinded review of neurological exam videos by pediatric movement disorders specialists.

RESULTS

Eighty-five participants (45 males, 40 females; mean age at videotaping 12 years [standard deviation 5 years 6 months], range 4-26 years) met inclusion and exclusion criteria. Of these participants, 50 (59%) displayed dystonia in their exam videos. The most common locations of dystonia were the fingers and hip adductors. The prevalence of dystonia was unaffected by the gestational age or severity of PVL, and was affected by Gross Motor Function Classification System level.

INTERPRETATION

Dystonia is common in individuals with spastic CP and PVL, even without BGTI on MRI. Our findings suggest vigilance for dystonia in individuals with spastic CP should remain high, even without MRI evidence of BGTI.

WHAT THIS PAPER ADDS

Individuals with spastic cerebral palsy and isolated periventricular leukomalacia on magnetic resonance imaging commonly display dystonia. Common sites of dystonia are in the fingers and hip adductors.

Top 10 Research Themes for Dystonia in Cerebral Palsy: A Community-Driven Research Agenda

Dystonia in cerebral palsy (DCP) is a common, debilitating, but understudied condition. The CP community (people with CP and caregivers) is uniquely equipped to help determine the research questions that best address their needs. We developed a community-driven DCP research agenda using the well-established James Lind Alliance methodology. CP community members, researchers, and clinicians were recruited through multiple advocacy, research, and professional organizations. To ensure shared baseline knowledge, participants watched webinars outlining our current knowledge on DCP prepared by a Steering Group of field experts (cprn.org/research-cp-dystonia-edition). Participants next submitted their remaining uncertainties about DCP. These were vetted by the Steering Group and consolidated to eliminate redundancy to generate a list of unique uncertainties, which were then prioritized by the participants. The top-prioritized uncertainties were aggregated into themes through iterative consensus-building discussions within the Steering Group. 166 webinar viewers generated 67 unique uncertainties. 29 uncertainties (17 generated by community members) were prioritized higher than their randomly matched pairs. These were coalesced into the following top 10 DCP research themes: (1) develop new treatments; (2) assess rehabilitation, psychological, and environmental management approaches; (3) compare effectiveness of current treatments; (4) improve diagnosis and severity assessments; (5) assess the effect of mixed tone (spasticity and dystonia) in outcomes and approaches; (6) assess predictors of treatment responsiveness; (7) identify pathophysiologic mechanisms; (8) characterize the natural history; (9) determine the best treatments for pain; and (10) increase family awareness. This community-driven research agenda reflects the concerns most important to the community, both in perception and in practice. We therefore encourage future DCP research to center around these themes. Furthermore, noting that community members (not clinicians or researchers) generated the majority of top-prioritized uncertainties, our results highlight the important contributions community members can make to research agendas, even beyond DCP.