Deep Brain Stimulation: Techniques and Practice for Pediatrics Indications

17 Deep Brain Stimulation: Techniques and Practice for Pediatrics Indications


Travis S. Tierney, William S. Anderson, H. Isaac Chen, Shenandoah Robinson


Abstract


Motor dysfunction in childhood usually manifests as spasticity or dystonia. By far the most common cause of motor problems in children is cerebral palsy, and varying degrees of both spasticity and dystonia are usually present. We examine the surgical options for treating either condition. Pallidal deep brain stimulation (DBS) is highly effective for most forms of primary dystonia including DYT1 + , DYT6 + , and DYT11 + genetic subtypes. Pallidal DBS or intrathecal baclofen is moderately effective for secondary dystonia associated with the heredodegenerative dystonias or dystonic cerebral palsy. Spasticity is common and its treatment is individually tailored according to age, severity, and limb distribution. Under the age of 6 years, children with cerebral palsy are best treated with botulinum toxin because spasticity often abates with age. On the other hand, most forms of childhood dystonia usually progress and early surgical intervention may be desirable. Optimal age and selection of the most effective surgical modality has not been well studied for any etiology, but the decision to proceed with most surgery is usually elective. However, two life-threatening conditions associated with movement disorders require urgent medical and often emergent surgical intervention: baclofen withdrawal and status dystonicus. Surgeons need to be aware of early and subtle signs of either condition as these are occasionally overlooked. Finally, selected pediatric neuropsychiatric conditions such as Tourette syndrome and obsessive-compulsive disorder are now being investigated in children, a natural evolution of the field.


Keywords: ablation, baclofen, deep brain stimulation, dystonia, neuromodulation, pediatric, spasticity, surgery


17.1 Introduction


Movement disorders that occur during childhood are mainly hyperkinetic.1 Many of these are transient (e.g., stereotypies, tics, myoclonus), but the few that progress or persist sometimes come to neurosurgical attention (e.g., the dystonias, choreoathetosis). Although spasticity is characterized by motor dysfunction, it is not considered a “movement disorder” by convention2 Nonetheless, spasticity associated with cerebral palsy is by far the most common condition referred to the pediatric movement disorders clinic. Nearly all of these referrals are nonurgent and often involve extensive discussion with an experienced multidisciplinary movement disorders team. On the other hand, two life-threating conditions require rapid recognition and surgical attention: intrathecal baclofen (ITB) withdrawal and status dystonicus. Baclofen overdose, while an emergency when not anticipated, is rarely fatal but often requires ventilator support for a few days and possibly cerebrospinal fluid (CSF) barbotage. This chapter will discuss these emergencies, interventions for primary and secondary dystonia, and briefly touch on Tourette syndrome (TS), a quintessential pediatric neuropsychiatric condition. Surgical management of related conditions such as obsessive-compulsive disorder (OCD) and various other psychiatric disorders that can occur in childhood but have not been well studied in the pediatric population and so remain for future investigation. This chapter emphasizes deep brain stimulation (DBS) therapy for a number of pediatric indications and the differences compared to adult patients.


17.2 Pediatric Movement Disorders: Neurosurgical Emergencies


Some movement disorders in children can present dramatically, and occasionally urgent surgical referrals are made to the clinic or come from the emergency department with concerns about a serious underlying condition. Examples include benign paroxysmal torticollis mimicking rotary subluxation, or Sandifer’s syndrome mimicking seizure or dystonic storm. Often the history and physical exam, together with basic imaging and electrodiagnostic studies are reassuring, and further urgent neurosurgical management can be deferred.


Baclofen overdose is typically iatrogenic and occurs at refilling/reprogramming intervals or after surgical repair of an ITB system without adequate dose adjustment. Overdose can lead rapidly to hypoventilation, flaccid paralysis, and coma. However, baclofen even at high doses is not neurotoxic and complete recovery within a few days with supportive care should be expected. Ventilatory support with intensive care unit (ICU) monitoring is often required. There is no specific pharmacological antidote for baclofen overdose, although some have recommended the acetylcholinesterase inhibitor physostigmine or the benzodiazepine receptor antagonist flumazenil for symptomatic relief.3,4 Neither of these agents have been found to be effective,5,6,7 and a recent consensus statement suggests they should not be used for ITB overdose.8 The most effective therapy seems to be stopping the pump and aspirating 20 to 30 ml of CSF from the access port.


On the other hand, delayed diagnoses of status dystonicus9,10 or baclofen withdrawal8,11 may be lethal. Suspicion of these two life-threating conditions should prompt an urgent surgical visit and rapid mobilization of combined medical and surgical care. General initial management of either condition usually involves a low threshold for intubation or insertion of an oral airway followed by admission to the pediatric ICU, aggressive hydration to prevent renal compromise from myoglobinuria, rapid correction of electrolytes, and administration of intravenous benzodiazepine. image Table 17.1 presents a simple algorithm to guide initial diagnosis and management of these two closely related conditions.


To avoid progression of baclofen withdrawal, prompt intervention to re-establish ITB therapy is necessary. Even high-dose oral/enteral baclofen cannot be reliably used to temporize definitive care because oral routes do not achieve high enough CSF levels.12,13 Only 1 to 2% of enteral baclofen crosses the blood–brain barrier, and it cannot prevent central nervous system (CNS) signs of withdrawal such as seizures. Enteral baclofen and cyproheptadine can be used to reduce non-CNS symptoms such as pruritis. GABAB receptor modulation with intravenous benzodiazepine (see image Table 17.1 for doses) or propofol14 has been shown to be highly effective against symptomatic progression, and both agents protect against withdrawal seizure. Sustained use of propofol has a risk of propofol infusion syndrome in children so it is not recommended. Like baclofen overdose, withdrawal also tends to occur around refill times. Often, pump interrogation for confirmation of correct drug concentrations and rates together with bolus dosing may be all that is required to resolve the under dose. Pump logs should be checked to exclude pump stall, which is rare, but does occur and can be quickly excluded. There is no test for a pocket refill; to exclude an empty pump, prompt refill of the pump with fresh drug can be performed. A bolus can be programmed to provide faster relief. After human factors, catheter problems are the most common cause of withdrawal. Disconnection and kinking can often be detected on plain films. Occlusion cannot always be detected by a bolus test or aspiration. If a catheter problem is suspected, operative exploration is often the most expeditious route to return of drug delivery. While dye studies were performed in the past, they were often nondiagnostic and simply delayed operative exploration. In unfortunate cases of meningitis or implant infection, device explantation probably will be necessary together with broad-spectrum antibiotics. For complex patients on high ITB doses with pump infection, rapid taper of ITB over a few days, while on broad-spectrum antibiotics, can reduce the overlap of severe infection and withdrawal and improve the overall safety. Here, case reports have suggested that re-establishment of external ITB therapy via lumbar infusion is feasible.15,16 Inflammatory granuloma formation has been observed in patients receiving intrathecal opiate therapy, but has not been reported with ITB infusion.


Table 17.1 1 Initial management steps for treating status dystonicus and ITB withdrawal












































 


Status dystonicus


ITB withdrawal


1. Note mental status


Usually unchanged


Early agitation, delirium, seizures


2. Recognize key clinical features


Rapidly evolving painful spasms, often retrocollis opisthotonos
Hyperthermia without prominent autonomic symptoms
Early bulbar spasm leading to respiratory failure


Pruritis, piloerection (goose bumps), severe rebound spasticity
Hyperthermia with autonomic instability (tachycardia, tachypnea, labile BP)
Early DIC leading to rapid multiple organ failure


3. Initiate acute management (maintenance of airway, respiration, and circulation)


Low threshold for intubation
1.5 X maintenance fluids
A-line, pulse oximetry, cardiac monitor


IV diazepam (or midazolam)
May require intubation Aggressive IV hydration (keeping urine output > 0.5 ml/kg/hour)
A-line, pulse oximetry, cardiac monitor (with initial 12 lead EKG)
Enteral baclofen and cyproheptadine


4. Order preliminary studies


ABG, CXR, CBC, CMP, serum CK, urine myoglobin, blood and urine gram stain and culture


ABG, CXR and Abd X-ray, CBC, CMP, serum CK, urine myoglobin, blood and urine gram stain and culture, LFTs, coagulation profile including fibrinogen and d-dimers


5. Give initial medications


IV diazepam or midazolam, titrated to muscle relaxation (may require ventilator support)
Clonidine infusion (0.25–2.0 mcg/kg/hour) if not intubated
Antipyretics
Dantrolene and urine alkalization if
rhabdomyolysis develops
Broad-spectrum antibiotics if infection
suspected


IV diazepam or midazolam, titrated to muscle relaxation (may require ventilator support)
IT bolus via lumbar puncture, or infusion via lumbar catheter at pre-withdrawal rate, if severe
Antipyretics
Dantrolene and urine alkalization if rhabdomyolysis develops
Broad-spectrum antibiotics if infection
suspected


6. Search for correctable triggers


Gastroenteritis
Diarrhea
Occult infection
Recent medication adjustment


Catheter discontinuity (40%)
Pump malfunction (check logs)
Reservoir empty (check last refill and replace
drug to exclude pocket fill)
Infection, meningitis


7. Determine disposition


ICU admission


ICU or OR for pump revision


8. Immediate therapeutic goal


Avoid rhabdomyolysis


Re-establish ITB as soon as possible


Abbreviations: ABG, arterial blood gas; BP, blood pressure; CBC, complete blood count; CK, creatine kinase; CMP, complete metabolic panel; CSF, cerebrospinal fluid; CXR, chest X-ray; DIC, disseminated intravascular coagulopathy (aka, death is coming); ICU, intensive care unit; ITB, intrathecal baclofen; LFT, liver function tests; MOR, multi-organ failure; OR, operating room.


Similar to baclofen withdrawal, status dystonicus (also called dystonic storm or crisis) can rapidly escalate into a lifethreating condition in children and may require urgent surgical intervention if it is refractory to medically induced coma.17 The goal of rapid therapeutic escalation is to avoid the development of rhabdomyolysis and respiratory collapse. In most cases, the diagnosis of dystonia is previously known, but in the rare syndrome of glutaric aciduria type I, status dystonicus may be the presenting condition and can be mistaken for status epilepticus.18 The acquired (so-called secondary) dystonias are most likely to develop into dystonic storm,19,20 although any form of dystonia has the potential to escalate. Factors triggering a crisis include infection, fever, dehydration, and DBS or ITB failure.21,22 In these latter triggers, therapeutic failures often occur after depletion of the implanted pulse generator (IPG) or baclofen reservoir. System interrogation and re-establishment of therapy is again urgently indicated. Surgical intervention to place bilateral pallidal leads should be considered when specific medical therapy and paralytic coma fail to control status dystonicus.21,23,24,25,26,27 The youngest patient in the literature so far to have DBS for storm was 4 years of age.28 Attempts to control refractory status dystonicus with ITB have also been made.22,29,30,31 Some centers have reported significantly less success with ITB than DBS,32,33 especially in cases originating from secondary dystonia. However, ITB therapy has been successful in the authors’ experience. Unilateral pallidotomy10,34 or even bilateral staged procedures35,36 are effective, though historical,37,38 treatments for status dystonicus that might still be considered in cases where ongoing infection or other technical complications preclude hardware implantation.39,40


17.3 Dystonia


The dystonias are a heterogeneous group of conditions that share a common formal definition1: “a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both.” Clinically, dystonia manifests as involuntary cocontraction of opposing muscle groups that often causes a smooth lead pipe type rigidity which differs substantially in quality from the so-called knife-clasp rigidity of spasticity (see later). Age-related progression of disability, progressive pain, and social isolation that often accompany the disease in children represent important indications for early surgical intervention. Unlike adult-onset dystonia that tends to remain relatively focal,41 dystonia in childhood usually generalizes shortly after it is diagnosed, especially in cases of primary dystonia.42 The classic but now antiquated term dystonia musculorum deformans is synonymous with the currently used term primary dystonia where genetic analyses have yielded a number of abnormalities leading to various subtypes of primary dystonia.43,44 In general these are rare disorders with prevalence rates ranging from 1 in 10,000 to 1 in 30,000 children. This prevalence is many times higher in the Ashkenazi Jews.


The secondary dystonias are differentiated from the primary dystonia when a structural lesion within the brain (usually involving the internal segment of the pallidum) is evident on magnetic resonance imaging (MRI)20 (image Fig. 17.1). They also have a broad spectrum of causes including both genetic and acquired etiologies, but by far the most common is cerebral palsy-associated dystonia with a prevalence of 2 to 3 per 1,000 or about 15 to 25% of all children with cerebral palsy.45 In general, the secondary dystonias are thought to be less responsive to DBS compared with the primary dystonia, however open-label studies and case reports indicate that tardive dystonia,46,47,48 well-selected cases of dystonic cerebral palsy49,50 and certain heredodegenerative disease including pantothenate kinase-associated neurodegeneration (PKAN)51,52 may respond to bilateral pallidal stimulation. ITB can improve the comfort and function of many, but not all, patients with secondary dystonia.


The initial clinical presentation of dystonia in children is usually subtle, but in rare instances noted above, dystonic storm is the first indication of disease where rapid surgical intervention may be required. Often the forme fruste of the condition is intermittently present and usually involves torsion of a limb. Here, home videos are helpful. An experienced childhood movement disorders specialist is even more helpful. From guiding the initial genetic diagnoses of the primary and heredodegenerative dystonias to coordinating ongoing medical management, multidisciplinary teams are essential. To follow these patients over the long-term and to ensure a smooth transition to adult providers, a dedicated multidisciplinary pediatric team that includes neurology, physiatry, and/or developmental pediatrics is essential for successful care of these complex patients.


Although full consideration of the diagnosis of dystonia lies outside the scope of this chapter, the neurosurgeon should be aware of a few pitfalls in the diagnosis of dystonia, recognize those genetic subtypes that seem to respond best to DBS, or ITB therapy, and be familiar with the basic rating scales. Rating scales for primary dystonia (Burke–Fahn–Marsden Dystonia Rating Scale, BFMDRS) and secondary dystonia (Barry–Albright Dystonic Scale, BAD) have been validated in children.53,54,55,56 These scales can serve as a benchmarks to gauge treatment effects and compare outcomes between centers.



Segawa syndrome,57 also called dopa-responsive dystonia (DYT5 +), has features of spasticity and parkinsonism with childhood onset and is occasionally misdiagnosed as dystonic cerebral palsy.58,59 Most experts recommend a trial of levodopa in all children who develop dystonic posturing since Segawa syndrome, as well as a number of other dystonias, responds dramatically to a low dose of levodopa.43 In cases where the diagnosis of dystonic cerebral palsy is not unequivocally supported by historical and radiographic data, delaying surgical interventions for a trial of levodopa over several weeks is warranted to avoid an error in diagnosis and unnecessary surgery.


In general, the primary dystonias are thought to be more responsive to DBS than the secondary dystonias.47 There are now a number of genetically identified etiologies of the primary dystonias, making the once synonymous term idiopathic generalized dystonia now somewhat of a misnomer. Genetic screening for the 20 or so various subtypes of torsion dystonia (DTY) is available, as is genetic testing for the heredodegenerative secondary dystonias.60 Once the diagnosis of dystonia is suspected and high-resolution images have excluded various forms of secondary dystonia (e.g., dystonic cerebral palsy, Rett syndrome, Leigh’s disease, metal accumulation diseases, trauma, tumors, and stroke), this testing is usually undertaken in conjunction with a medical geneticist. Fortunately, the most common form of early-onset primary dystonia is also among the most responsive dystonias to bilateral pallidal stimulation. Dystonia with DYT1 gene mutation, caused by TOR1A gene CAG deletion on chromosome 9q, accounts for 40 to 60% of childhood-onset primary dystonia.61 Autosomal dominant dystonia with cranio-cervical predilection (DYT6 +) and myoclonic dystonia (DYT11 +) have also been noted in open-label studies to be similarly responsive to DBS.62,63 Several studies have also shown that genetically undetermined causes of primary dystonia, so called non-DYT cases, may also respond well to pallidal stimulation.64


Consideration of nonpallidal targets, for example, the ventrolateral thalamus and the subthalamic nucleus, has been suggested in childhood dystonia,65 but these nuclei are generally reserved for cases where optimally placed pallidal electrodes are ineffective or cause hypokinetic side effects.66 Although the United States Food and Drug Administration (FDA) Humanitarian Device Exemption does allow for placement of electrodes at the subthalamic nucleus (STN), the posteroventral pallidum remains, by far, the most commonly selected target for both pediatric primary67 and secondary dystonia.68 Note that secondary dystonia is an off- label use and it does not require applications to the FDA or approval by an institutional review board if conducted on a case-by-case basis. No comparative studies in children exist to guide selection of an optimal target in childhood dystonia, but it seems intuitive that the STN might be a favorable site in children with damaged pallidum that commonly accompanies the secondary dystonias.20 However, for primary dystonias, the posteroventral pallidum should remain the favored site. Secondary dystonias are often responsive to ITB treatment.69 In some patients, ITB therapy can significantly improve function and comfort. Those with severe dystonia may benefit from ITB therapy supplemented by DBS.


17.4 Spasticity


Compared with dystonia, spasticity is much more common, affecting about 300,000 people under 18 years of age in the United States alone. Paradoxically perhaps, advances in perinatal care seem to be increasing the incidence of cerebral spasticity as the survival of at-risk low birth weight infants, who go on to develop cerebral palsy, increases.70,71 Defined as velocity-dependent increase in muscle resistance to passive stretch, limb spasticity can be clinically classified into four useful groups based on location: quadriparesis (also called tetraplegia), para-paresis (also called diplegia), hemiparesis, and monoparesis. The extent of limb function disruption largely guides the selection of therapy. For example, monoparesis may respond well to botulinum toxin injections, whereas quadriparesis might be best treated with ITB therapy. In well-selected cases of spastic diplegia, selective dorsal rhizotomy is often ideal. It is important to note that spasticity is not always harmful. Many patients use their spasticity to maintain trunk support and supplement weak leg muscles. While the initial insult that precipitates spasticity was likely a static injury, the impact of spasticity on function and comfort can change with time.72 On one hand, “worsening spasticity” may be a red flag for a missed diagnosis of hypertonicity associated with dystonia or hereditary spastic paraparesis (also called familial spastic paraplegia or Strumpell–Lorrain disease).73 The pattern of severity of cerebral palsy is changing in the United States over time,74 which likely reflects the improvements in obstetrical and neonatal care. With these improvements in care, some infants are left with fewer deficits, while others who previously may not have survived now experience significant deficits.


Spasticity can be graded clinically and treatment effects may be followed using one of two rating scales: the simpler and validated Modified Ashworth Scale75,76 or the more comprehensive but less studied Tardieu Scale77 (image Table 17.2). Both provide a method for assessing the degree of spasticity across limb joints and are an important criterion in patient selection.


The child is usually tested lying down and each joint is evaluated methodically with particular attention being paid to flexors and internal rotators of the lower extremities. It is also important to test muscle strength in the legs and trunk as some children may supplement weakened muscles with involuntary spastic contractions to improve their gait and pivot transfers. In these cases, interventions to improve spasticity may actually reduce overall functional mobility. When a joint has been subjected to severe spasticity for many months, the muscle and tendon tend to progressively shorten into a fixed contracture that does not improve with treatment of the spasticity. Commonly, this occurs at the plantar flexors, knee flexors, and hip adductors, the latter of which often leads to progressive hip subluxation and acetabular deformity. The goal of treating spastic diplegia, in particular, is to avoid the development of this painful condition. Orthopedic treatment of fixed contractures is not discussed in detail in this chapter but consists of various surgeries for musculoskeletal release followed by extensive rehabilitative therapy to maintain enhanced mobility.78,79


Table 17.2 Two common rating scales for pediatric dystonia: Burke–Fahn–Marsden Dystonia Rating Scale motor subscale (BFMDRS-M) for primary dystonia and the Barry-Albright Dystonia (BAD) scale for secondary dystonia








































Region and description


BFMDRS-M (score range 0–120a)


BADS (score range 0–32b)


Eyes—signs of dystonia of the eyes include: prolonged eyelid spasms and/or forced eye deviations


0 No dystonia present


1 Slight: occasional blinking


2 Mild: frequent blinking without prolonged spasms of eye closure


3 Moderate: prolonged spasms of eyelid closure, but eyes open most of the time


4 Severe: prolonged spasms of eyelid closure, with eyes closed at least 30% of the time


0 Absent


1 Slight: dystonia less than 10% of the time and does not interfere with tracking


2 Mild: frequent blinking without prolonged spasms of eyelid closure, and/or eye movements less than 50% of the time


3 Moderate: prolonged spasms of eyelid closure, but eyes open most of the time, and/or eye movements more than 50% of the time that interfere with tracking, but able to resume tracking


4 Severe: prolonged spasms of eyelid closure, with eyelids closed at least 30% of the time, and/or eye movements more than 50% of the time that prevent tracking


Mouth—signs of dystonia of the mouth include grimacing, clenched or deviated jaw, forced open mouth, and/or forceful tongue thrusting


0 No dystonia present


1 Slight: occasional grimacing or other mouth movements (e.g., jaw open or clenched, tongue movement)


2 Mild: movement present less than 50% of the time


3 Moderate: dystonic moderate movements or contractions present most of the time


4 Severe: severe dystonic movements or contractions present most of the time


0 Absent


1 Slight: dystonia less than 10% of the time and does not interfere with speech and/or feeding


2 Mild: dystonia less than 50% of the time and does not interfere with speech and/or feeding


3 Moderate: dystonia more than 50% of the time and/or dystonia that interferes with speech and/or feeding


4 Severe: dystonia more than 50% of the time and/or dystonia that prevents speech and/or feeding


Speech and swallowing


0 Normal


1 Slightly involved; speech easily understood or occasional choking


2 Some difficulty in understanding speech or frequent choking


3 Marked difficulty in understanding speech or inability to swallow firm foods


4 Complete or almost complete anarthria, or marked difficulty swallowing soft foods or liquids


 


Neck—signs of dystonia of the neck include pulling of the neck into any plane of motion: extension, flexion, lateral flexion or rotation


0 No dystonia present


1 Slight: occasional pulling


2 Obvious torticollis, but mild


3 Moderate pulling


4 Extreme pulling


0 Absent


1 Slight: pulling less than 10% of the time and does not interfere with lying, sitting, standing and/or walking


2 Mild: pulling less than 50% of the time and does not interfere with lying, sitting, standing and/or walking


3 Moderate: pulling more than 50% of the time and/or dystonia that interferes with lying, sitting, standing and/or walking


4 Severe: pulling more than 50% of the time and dystonia that prevents sitting in a standard wheelchair (e.g., requires special head rest), standing and/or walking


Arm—signs of dystonia of the upper extremities include sustained muscle contractions causing abnormal postures, score each limb separately


0 No dystonia present


1 Slight: clinically insignificant


2 Mild: obvious dystonia but not disabling


3 Moderate: able to grasp, with some manual function


4 Severe: no useful grasp


0 Absent


1 Slight: dystonia less than 10% of the time and does not interfere with normal positioning and/or functional activities


2 Mild: dystonia less than 50% of the time and does not interfere with normal positioning and/or functional activities


3 Moderate: dystonia more than 50% of the time and/or dystonia that interferes with normal positioning and/or upper extremity function


4 Severe: dystonia more than 50% of the time and/or dystonia that prevents normal positioning and/or upper extremity function (e.g., arms restrained to prevent injury)


Trunk—signs of dystonia of the trunk include pulling of the trunk into any plane of motion: extension, flexion, lateral flexion or rotation


0 No dystonia present


1 Slight bending; clinically insignificant


2 Definite bending but not interfering with standing or walking


3 Moderate bending; interfering with standing or walking


4 Extreme bending of trunk preventing standing or walking


0 Absent


1 Slight: pulling less than 10% of the time and does not interfere with lying, sitting, standing and/or walking


2 Mild: pulling less than 50% of the time and does not interfere with lying, sitting, standing and/or walking


3 Moderate: pulling more than 50% of the time and/or dystonia that interferes with lying, sitting, standing and/or walking


4 Severe: pulling more than 50% of the time and dystonia that prevents sitting in a standard wheelchair (e.g., requires adapted seating system), standing and/or walking


Leg—signs of dystonia of the lower extremities include sustained muscle contractions causing abnormal postures, Score each limb separately


0 No dystonia present


1 Slight: dystonia but not causing impairment; clinically insignificant


2 Mild: walks briskly and unaided


3 Moderate: severely impairs walking or requires assistance.


4 Severe: unable to stand or walk on involved leg


0 Absent


1 Slight: dystonia less than 10% of the time and does not interfere with normal positioning and/or functional activities


2 Mild: dystonia less than 50% of the time and does not interfere with normal positioning and/or functional activities


3 Moderate: dystonia more than 50% of the time and/or dystonia that interferes with normal positioning and/or lower extremity weight bearing and/or function


4 Severe: dystonia more than 50% of the time and/or dystonia that prevents normal positioning and/or lower extremity weight bearing and/or function


a The above severity score in each region of the BFMDRS is multiplied by a provoking factor score as follows: 0: No dystonia at rest or with action, 1: dystonia on a particular action, 2: dystonia on many actions, 3: dystonia on action of distant part of body, or intermittently at rest 4: dystonia at rest. For speech and swallowing the provoking factor score is 0: none, 1 occasional speech and/or swallow difficulty, 2: frequent speech or swallow difficulty, 3: frequent speech or swallow difficulty, and occasional speech or/and swallow difficulty, 4: frequent speech and swallowing difficulty. Additionally, a weight of ½ is given for severity and provoking products of eye, mouth and neck. The total summed adjusted maximum score is 120.
b The BADS score is simply the sum of severity scores in each of the 8 body regions for a maximum of 32.


Before any surgical therapy, a candid discussion with the child, parents, and associated care givers should clearly establish postoperative expectations and set a few common goals. In general, the therapeutic goal should include: (1) reduction of pain, (2) facilitation of routine care such as bathing and feeding, (3) prevention of contractures, and (4) some degree of functional improvement. Often high expectations on the part of the patient with regard to functional improvement must be tempered in order to offer realistic hope. In general, this last goal encompasses greater ease in activities of daily living such as dressing, transfers, and ambulation. No studies have yielded more specific predictors of improvements in fine motor or mid-line control required for improved handwriting or augmented speech intelligibility or swallowing capability. No screening trial has been developed to accurately predict functional improvement after selective dorsal rhizotomy or ITB therapy. Current clinical selection criteria for surgical intervention depend heavily on severity and distribution of spasticity as well as the child’s age (image Table 17.3).


17.5 Tourette Syndrome


TS is a quintessential pediatric neuropsychiatric condition in the sense that tics and urges phenomenologically bridge neurology and childhood psychiatry. Characterized by prepubertal onset of motor and vocal tics, TS is often associated with attention deficit hyperactivity disorder and OCD, but its relationship to these comorbid conditions remains controversial.24,80,81 Like spasticity, tic severity tends to decrease during adolescence, and by early adulthood as many as one-third of children with TS become tic free.82,83 Despite this regressive natural history, a number of centers have now treated pediatric patients with severely disabling motor/vocal tics with surgery.84,85,86,87 The most common procedures involve bilateral placement of thalamic (centromedian-parafascicular and ventralis oralis complex) or pallidal (pars internus) DBS leads. In general, the results of DBS for the treatment of TS in children from these studies seem to be on par with those outcomes from the adult cohort. Some have offered important ethical as well as biological reasons to remain cautious in treating pediatric neuropsychiatric disease surgically.88 On the other hand, children with medically intractable TS may be considered an extremely vulnerable group, in which surgical interventions shown to be safe and effective in adults should be studied in small-scale trials at dedicated pediatric research centers. A cautious but timely approach to childhood psychiatric conditions naturally follows from the many historical successes of DBS in treatment of pediatric movement disorders.89,90 Still, no governmental regulatory agency has approved DBS for the treatment of tics associated with TS in children or adults. Some possible explanations include the paucity of cases referred for DBS even at larger academic medical centers, the lack of a major multisite randomized trial, and the diversity of surgical targets and outcomes observed in various studies (see Chapter 14, DBS in Tourette Syndrome). To this end, an international registry under the aegis of the Tourette Association of America has recently been established in the hope of systematically capturing all adverse events and efficacy data from a large number of cases worldwide.91 Similar data was used to achieve a Humanitarian Device Exemption from the US FDA in 2009 for the treatment of OCD in adults, another developmental psychiatric condition with pediatric origins.80


Mar 23, 2020 | Posted by in NEUROLOGY | Comments Off on Deep Brain Stimulation: Techniques and Practice for Pediatrics Indications
Premium Wordpress Themes by UFO Themes