What is involved in Deep Brain Stimulation (DBS) treatment?

Deep Brain Stimulation (DBS): Overview and Clinical Application

Deep Brain Stimulation is an implanted neurosurgical device that delivers precise electrical signals to specific brain targets to modulate neural functioning, providing reversible and adjustable symptomatic improvement for severe, treatment-refractory neurological conditions, most commonly movement disorders. 1, 2

What DBS Involves

The Surgical Procedure

DBS surgery requires stereotactic implantation of electrodes into specific brain targets, typically performed with the patient awake under general anesthesia in select cases, by surgeons with extensive functional neurosurgery experience. 3, 4

The procedure involves:

• Stereotactic frame application with CT/MRI imaging for anatomical targeting 4
• Direct visualization of the target using MR images and formula-derived coordinates based on anterior and posterior commissures 4
• Physiological verification via microelectrode recording to confirm proper electrode placement 4
• Intraoperative test stimulation to assess therapeutic benefits and potential side effects before final implantation 4
• Postoperative stereotactic brain MRI to confirm precise electrode location 3
• Implantation of pulse generator (the stimulator device) connected to the brain electrodes 4

Brain Targets

The specific anatomical target depends on the condition being treated:

• Thalamus (ventral intermediate nucleus) - most commonly for essential tremor 1, 5
• Subthalamic nucleus (STN) - most commonly for Parkinson's disease, treating tremor, akinesia, rigidity, and dyskinesias 1, 5
• Globus pallidus interna (GPi) - for Parkinson's disease and dystonia, most efficient for rigidity and dyskinesias 1, 5
• For Tourette syndrome: CM-Pf thalamus, GPi (anteromedial or posteroventral portions), nucleus accumbens, or anterior limb of internal capsule 3

Post-Surgical Management

Initial postoperative assessments should occur after electrode placement effects have subsided and stimulator settings have been optimized and stabilized for several weeks. 3

The adjustment process includes:

• Dynamic parameter adjustment by altering which electrode contacts deliver pulses and modifying stimulation parameters (amplitude, frequency, pulse width) 2
• Blinded assessment protocols where both patients and evaluators are unaware of stimulator on/off states 3
• Comprehensive evaluation including psychiatric, behavioral, cognitive, and socio-emotional factors 3
• Long-term follow-up with annual assessments to establish longitudinal outcomes 3

Patient Selection Criteria

Candidates must undergo comprehensive neurological, neuropsychiatric, and neuropsychological assessment by a multidisciplinary team including a neurologist, psychiatrist, clinically qualified psychologist, and functional neurosurgeon. 3, 6, 5

General Eligibility Requirements

For movement disorders like Parkinson's disease:

• Excellent response to levodopa during best on-motor periods, with minimal gait difficulties, instability, and speech problems 6
• Motor fluctuations and/or dyskinesias not adequately controlled with optimized medical therapy 6
• Normal or minimally affected cognitive, psychiatric, and behavioral status 6
• Age typically less than 70 years at time of surgery 6
• No serious medical comorbidities such as structural brain anomalies or coagulopathies 3

For Tourette syndrome specifically:

• Age above 20 years due to uncertainty about spontaneous remission 3, 7
• Treatment-refractory status defined as failure of behavioral techniques AND therapeutic doses of at least three proven medications, including anti-dopaminergic drugs and α-2 adrenergic agonists 7
• Severe functional impairment with stable period of severe tics independent of transient stressors 3, 7
• Tics as primary problem, not comorbid conditions like OCD or ADHD 3

Critical Assessment Components

Health-related quality of life assessment using disease-specific instruments is essential, as successful tic reduction does not guarantee improved wellbeing. 3, 7

Additional evaluations include:

• Neuropsychological testing for intellectual ability, verbal and non-verbal memory, attention, executive function, and language 3
• Risk/benefit assessment in context of individual comorbidities 3
• Social support evaluation and environmental factors that could affect outcomes 3
• Patient expectations and cooperation as important considerations for success 6

Risks and Safety Profile

DBS carries inherent neurosurgical risks including intracranial bleeding, infection, electrode malposition, and hardware complications (migration, disconnection, malfunction), but each complication occurs in ≤5% of cases at experienced, large-volume centers. 1

Condition-Specific Outcomes

For Tourette syndrome:

• Approximately 97% of published cases show substantial tic improvements 3, 8
• Additional benefits for obsessions, compulsions, and self-injurious behaviors 3
• Cognitive functioning remains intact or improved in long-term follow-up 3
• Common side effect: vertical-gaze palsy with thalamic targets 3

For Parkinson's disease:

• Dysarthria is the most common side effect regardless of brain target 5
• Long-lasting effect on appendicular symptoms, but axial features become less responsive with disease progression 5

Key Clinical Advantages

DBS is preferred over older lesioning procedures due to its reversibility, adjustability, and ability to be used bilaterally with good safety profile. 1, 2

The reversibility allows for:

• Dynamic adjustment of stimulation effects without permanent brain damage 2
• Optimization over time as disease progresses or patient needs change 2
• Discontinuation if ineffective or if complications arise 2

Important Clinical Pitfalls

DBS should never be considered first-line therapy; it is reserved exclusively for severe, treatment-refractory cases after exhausting standard medical and behavioral therapies. 3, 7, 8

Common mistakes to avoid:

• Premature surgical referral before optimizing medical management for at least 6 months 7
• Inadequate multidisciplinary evaluation leading to poor patient selection 3, 5
• Failure to assess quality of life as the primary outcome measure 3
• Ignoring family member feedback during postoperative assessments 3
• Insufficient long-term follow-up to establish durability of benefits 3

Future Developments

Emerging technologies include:

• Directional current steering electrodes for more precise stimulation 1
• Closed-loop systems capable of recording brain activity and automatically adjusting stimulation parameters 1
• Image-guided implantation techniques potentially superior to traditional stereotactic methods 1