Neuromodulation in Childhood Onset Dystonia: Evolving Role of Deep Brain Stimulation

Stereotactic Awake Basal Ganglia Electrophysiological Recording and Stimulation (SABERS): A Novel Staged Procedure for Personalized Targeting of Deep Brain Stimulation in Pediatric Movement and Neuropsychiatric Disorders

Selection of targets for deep brain stimulation (DBS) has been based on clinical experience, but inconsistent and unpredictable outcomes have limited its use in patients with heterogeneous or rare disorders. In this large case series, a novel staged procedure for neurophysiological assessment from 8 to 12 temporary depth electrodes is used to select targets for neuromodulation that are tailored to each patient's functional needs. Thirty children and young adults underwent deep brain stimulation target evaluation with the new procedure: Stereotactic Awake Basal ganglia Electrophysiological Recording and Stimulation (SABERS). Testing is performed in an inpatient neuromodulation monitoring unit over 5-7 days, and results guide the decision to proceed and the choice of targets for permanent deep brain stimulation implantation. Results were evaluated 3-6 months postoperatively with the Burke-Fahn-Marsden Dystonia Rating Scale and the Barry-Albright Dystonia Scale. Stereotactic Awake Basal ganglia Electrophysiological Recording and Stimulation testing allowed modulation to be tailored to specific neurologic deficits in a heterogeneous population, including subjects with primary dystonia, secondary dystonia, and Tourette syndrome. All but one subject were implanted with 4 permanent deep brain stimulation leads. Results showed significant improvement on both scales at postoperative follow-up. No significant adverse events occurred. Use of the Stereotactic Awake Basal ganglia Electrophysiological Recording and Stimulation protocol with evaluation in the neuromodulation monitoring unit is feasible and results in significant patient benefit compared with previously published results in these populations. This new technique supports a significant expansion of functional neurosurgery to predict effective stimulation targets in a wide range of disorders of brain function, including those for which the optimal target is not yet known.

Elective and Emergency Deep Brain Stimulation in Refractory Pediatric Monogenetic Movement Disorders Presenting with Dystonia: Current Practice Illustrated by Two Cases

BACKGROUND

Dystonia is characterized by sustained or intermittent muscle contractions, leading to abnormal posturing and twisting movements. In pediatric patients, dystonia often negatively influences quality of life. Pharmacological treatment for dystonia is often inadequate and causes adverse effects. Deep brain stimulation (DBS) appears to be a valid therapeutic option for pharmacoresistant dystonia in children.

METHODS

To illustrate the current clinical practice, we hereby describe two pediatric cases of monogenetic movement disorders presenting with dystonia and treated with DBS. We provide a literature review of similar previously described cases and on different clinical aspects of DBS in pediatric dystonia.

RESULTS

The first patient, a 6-year-old girl with severe dystonia, chorea, and myoclonus due to an ADCY5 gene mutation, received DBS in an elective setting. The second patient, an 8-year-old boy with GNAO1-related dystonia and chorea, underwent emergency DBS due to a pharmacoresistant status dystonicus. A significant amelioration of motor symptoms (65% on the Burke-Fahn-Marsden Dystonia Rating Scale) was observed postoperatively in the first patient and her personal therapeutic goals were achieved. DBS was previously reported in five patients with ADCY5-related movement disorders, of which three showed objective improvement. Emergency DBS in our second patient resulted in the successful termination of his GNAO1-related status dystonicus, this being the eighth case reported in the literature.

CONCLUSION

DBS can be effective in monogenetic pediatric dystonia and should be considered early in the disease course. To better evaluate the effects of DBS on patients' functioning, patient-centered therapeutic goals should be discussed in a multidisciplinary approach.

Long-Term Outcomes of Deep Brain Stimulation for Pediatric Dystonia

BACKGROUND

Deep brain stimulation (DBS) has been utilized for over two decades to treat medication-refractory dystonia in children. Short-term benefit has been demonstrated for inherited, isolated, and idiopathic cases, with less efficacy in heredodegenerative and acquired dystonia. The ongoing publication of long-term outcomes warrants a critical assessment of available information as pediatric patients are expected to live most of their lives with these implants.

SUMMARY

We performed a review of the literature for data describing motor and neuropsychiatric outcomes, in addition to complications, 5 or more years after DBS placement in patients undergoing DBS surgery for dystonia at an age younger than 21. We identified 20 articles including individual data on long-term motor outcomes after DBS for a total of 78 patients. In addition, we found five articles reporting long-term outcomes after DBS in 9 patients with status dystonicus. Most patients were implanted within the globus pallidus internus, with only a few cases targeting the subthalamic nucleus and ventrolateral posterior nucleus of the thalamus. The average follow-up was 8.5 years, with a range of up to 22 years. Long-term outcomes showed a sustained motor benefit, with median Burke-Fahn-Marsden dystonia rating score improvement ranging from 2.5% to 93.2% in different dystonia subtypes. Patients with inherited, isolated, and idiopathic dystonias had greater improvement than those with heredodegenerative and acquired dystonias. Sustained improvements in quality of life were also reported, without the development of significant cognitive or psychiatric comorbidities. Late adverse events tended to be hardware-related, with minimal stimulation-induced effects.

KEY MESSAGES

While data regarding long-term outcomes is somewhat limited, particularly with regards to neuropsychiatric outcomes and adverse events, improvement in motor outcomes appears to be preserved more than 5 years after DBS placement.

Deep Brain Stimulation for Pediatric Dystonia

Dystonia is one of the most common pediatric movement disorders and can have a profound impact on the lives of children and their caregivers. Response to pharmacologic treatment is often unsatisfactory. Deep brain stimulation (DBS) has emerged as a promising treatment option for children with medically refractory dystonia. In this review we highlight the relevant literature related to DBS for pediatric dystonia, with emphasis on the background, indications, prognostic factors, challenges, and future directions of pediatric DBS.