Study guide
7.4 Spinal Cord Stimulation & Intrathecal Therapy
ABPMR Physical Medicine and Rehabilitation Board Exam Study Guide Exam
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1 Chapter 1: Introduction & Exam Overview
1.1 ABPMR Part I Exam Overview & Format 1.2 Board Review Strategy & Content Blueprint Breakdown
2 Chapter 2: Musculoskeletal Medicine
2.1 Shoulder & Upper Extremity Diagnostics 2.2 Knee, Hip & Lower Extremity Conditions 2.3 Spine Pathology, Radiculopathy & Myelopathy 2.4 Inflammatory Arthritis, Tendinopathies & Concussion 2.5 Bone Health, Osteoporosis & Metabolic Bone Disease 2.6 Thoracic Outlet Syndrome & Peripheral Nerve Entrapment 2.7 Fracture Rehabilitation & Immobilization Complications 2.8 Overuse Tendinopathies & Regenerative Medicine 2.9 Gait Analysis & Abnormal Gait Patterns
3 Chapter 3: Spinal Cord Injury Rehabilitation
3.1 ASIA Examination & Impairment Scale 3.2 Spinal Cord Injury Syndromes 3.3 Autonomic Dysreflexia & Acute Complications 3.4 Neurogenic Bladder, Bowel & Secondary Complications
4 Chapter 4: Stroke & Neuromuscular Rehabilitation
4.1 Stroke Vascular Syndromes & Acute Assessment 4.2 Stroke Motor Recovery & Hemiplegic Complications 4.3 Spasticity Assessment & Multimodal Management 4.4 ALS, GBS, CIDP & Neuromuscular Disease Rehab 4.5 Multiple Sclerosis & Demyelinating Disease Rehabilitation 4.6 Parkinsonism, Movement Disorders & Functional Neurologic Disorder
5 Chapter 5: Electrodiagnostics (EMG/NCS)
5.1 Nerve Conduction Studies Principles & Physics 5.2 Needle Electromyography & MUAP Analysis 5.3 Mononeuropathies & Radiculopathy Patterns 5.4 Neuromuscular Junction Disorders & Myopathies
6 Chapter 6: Traumatic Brain Injury
6.1 TBI Severity Classification, Glasgow Coma Scale, and Pathophysiology 6.2 Rancho Los Amigos Levels of Cognitive Functioning and Disability Rating Scale 6.3 Neurobehavioral Sequelae and Agitation Management 6.4 Concussion Evaluation, Vestibular-Ocular Dysfunction, and Return-to-Play/Work Protocols
7 Chapter 7: Chronic Pain & Interventional Spine
7.1 Fluoroscopic Spine Interventions 7.2 Opioid Stewardship & Controlled Substance Compliance 7.3 Complex Regional Pain Syndrome, Fibromyalgia & Myofascial Pain 7.4 Spinal Cord Stimulation & Intrathecal Therapy
8 Chapter 8: Amputee Rehabilitation & Prosthetics
8.1 Amputation Surgical Levels & Medicare K-Levels 8.2 Socket Designs & Suspension Systems 8.3 Prosthetic Feet & Microprocessor Knee Mechanisms 8.4 Post-Amputation Care, Residual Limb & Phantom Pain
9 Chapter 9: Pediatric Rehabilitation
9.1 Cerebral Palsy Classification & GMFCS 9.2 Spina Bifida & Myelomeningocele Management 9.3 Muscular Dystrophies & Neuromuscular Disease in Children 9.4 Pediatric Brachial Plexopathy & Congenital Disorders
10 Chapter 10: Prosthetics, Orthotics & Assistive Technology
10.1 Lower Limb Orthoses — AFOs & KAFOs 10.2 Spinal & Upper Extremity Orthoses 10.3 Upper Limb Prosthetics — Body-Powered vs Myoelectric 10.4 Wheelchairs, Seating Systems & Pressure Mapping
11 Chapter 11: Medical Rehabilitation & Outcomes
11.1 Dysphagia Assessment & Management 11.2 Neurogenic Bladder & Bowel Management 11.3 Pressure Injuries & Wound Management 11.4 Outcome Measures & Medical Complications 11.5 Cancer Rehabilitation & Oncologic Rehabilitation 11.6 Burns, Endocrine/Metabolic & Medical Complications Rehabilitation
12 Chapter 12: Cardiopulmonary Rehabilitation
12.1 Cardiac Rehabilitation Phases & Metabolic Equivalents 12.2 Pulmonary Rehabilitation & COPD Management
13 Chapter 13: Foundational Rehabilitation Concepts
13.1 Kinesiology, Biomechanics & Functional Anatomy 13.2 Rehabilitation Pharmacology & Medication Management 13.3 Research Methodology, Biostatistics & Evidence-Based Practice 13.4 Nutrition, Metabolism & Energy Expenditure in Rehabilitation 13.5 Diagnostic Procedures: Imaging, MSK Ultrasound, Urodynamics & Neuropsych Assessment
7.4 Spinal Cord Stimulation & Intrathecal Therapy
Key Takeaways Explain This Topic AI
Spinal Cord Stimulation (SCS) delivers electrical current to the dorsal columns, recruiting A-beta sensory fibers to inhibit nociceptive A-delta and C fiber transmission in the dorsal horn (Gate Control Theory).
A mandatory 3 to 7 day trial period demonstrating ≥50% pain relief and functional improvement, alongside a pre-trial psychological evaluation, is required before permanent SCS implantation.
Primary indications for SCS include Failed Back Surgery Syndrome (FBSS), CRPS Types I and II, chronic radiculopathy, and refractory diabetic peripheral neuropathy.
Intrathecal drug delivery systems (ITDD) deliver fractional doses of medications directly into the CSF; abrupt cessation of intrathecal baclofen causes a life-threatening withdrawal emergency marked by hyperthermia, rebound spasticity, and rhabdomyolysis.
Last updated: July 2026
Spinal Cord Stimulation & Intrathecal Therapy
When non-interventional therapies, oral pharmacotherapy, and routine spine injections fail to manage refractory neuropathic pain or severe axial spasticity, advanced neuromodulation therapies become essential. Neuromodulation encompasses Spinal Cord Stimulation (SCS) and Intrathecal Drug Delivery Systems (ITDD).
Spinal Cord Stimulation (SCS)
Spinal Cord Stimulation involves the electrical stimulation of the dorsal columns of the spinal cord to modulate pain signaling prior to central brain processing.
Mechanism of Action: Gate Control Theory
SCS operates primarily through the Gate Control Theory of Pain (Melzack and Wall). Electrical current applied to the posterior epidural space depolarizes large-diameter, myelinated A- β \beta β (A-beta) sensory fibers in the dorsal columns. Collateral branches of these A- β \beta β fibers excite inhibitory interneurons (GABAergic and glycinergic) within the gelatinous substance (substantia gelatinosa) of the dorsal horn. Activated inhibitory interneurons release inhibitory neurotransmitters, effectively "closing the gate" and inhibiting the transmission of nociceptive signals carried by small, unmyelinated C fibers and thinly myelinated A- δ \delta δ (A-delta) fibers to second-order spinothalamic tract neurons.
Stimulation Waveforms & Technologies
Traditional Tonic Stimulation (Paresthesia-Based) : Low-frequency stimulation (50-100 Hz). Generates a pleasant tingling sensation (paresthesia) that must overlap the patient's anatomical painful region to achieve pain relief.
High-Frequency 10 kHz (HF10) Stimulation (Paresthesia-Free) : Delivers 10,000 Hz electrical pulses. It provides robust pain relief without paresthesias by selectively modulating dorsal horn interneurons without driving A- β \beta β fiber paresthesias. HF10 is highly effective for both axial low back pain and radicular leg pain.
Burst Stimulation : Delivers intermittent bursts of high-frequency pulses (e.g., 5 pulses at 500 Hz delivered 40 times per second). Mimics endogenous neuronal firing patterns and provides paresthesia-free pain relief while modulating medial affective pain pathways.
Clinical Indications
SCS is FDA-approved for chronic intractable pain of the trunk and limbs. Key PM&R indications include:
Failed Back Surgery Syndrome (FBSS) / Post-Laminectomy Syndrome (persistent lumbar radiculopathy or axial back pain following spinal surgery).
Complex Regional Pain Syndrome (CRPS Types I and II) .
Chronic Intractable Radiculopathy .
Painful Diabetic Peripheral Neuropathy (DPN) .
Refractory Angina Pectoris and Ischemic Peripheral Vascular Disease .
Pre-Implantation Requirements & Trial Period
Before permanent SCS device implantation, patients must undergo a strict evaluation process:
Psychological Evaluation : Mandatory pre-trial clearance by a pain psychologist to rule out untreated active psychosis, severe unmanaged substance use disorder, active major depression with suicidal intent, or secondary gain issues that could compromise outcomes.
SCS Trial Period : Percutaneous epidural leads are placed under fluoroscopy (lead tips positioned at T8-T11 for lower extremity/axial back pain, or C2-C5 for upper extremity pain) and connected to an external trial pulse generator for 3 to 7 days .
Success Criteria : Permanent implantation is indicated ONLY if the trial achieves ≥ 50 % \ge 50\% ≥ 50% pain reduction along with documented functional improvement and patient satisfaction.
Surgical Implantation & Complications
Hardware Placement : Permanent leads (percutaneous cylindrical leads or surgical paddle leads placed via mini-laminectomy) are connected to an Implantable Pulse Generator (IPG) placed in a subcutaneous pocket in the upper gluteal or abdominal region.
Complications : Lead migration (most common technical complication, causing loss of therapeutic coverage), epidural hematoma or abscess, dural puncture headache, seroma, and painful IPG pocket.
Intrathecal Drug Delivery Systems (ITDD)
Intrathecal Drug Delivery Systems ("pain pumps" or "baclofen pumps") deliver medications directly into the cerebrospinal fluid (CSF) within the subarachnoid space.
Principles & Advantages
Direct intrathecal administration bypasses the blood-brain barrier and systemic circulation. Consequently, therapeutic drug concentrations are achieved at spinal cord receptor sites using a fraction of the oral or intravenous dose (e.g., the intrathecal morphine dose is approximately 1/100th of the oral morphine dose). This dramatically minimizes systemic adverse effects (sedation, constipation, nausea).
System Components
An ITDD system consists of a subcutaneously implanted programmable pump (containing a drug reservoir and peristaltic motor) connected to a silicone intrathecal catheter. The catheter tip is advanced under fluoroscopy to the specific spinal level corresponding to pain or spasticity targets:
Lower body pain / spasticity: T10-L1 level.
Upper body pain: T1-T4 level.
Diffuse severe spasticity: T1-T2 level.
FDA-Approved Intrathecal Medications
Morphine : Primary intrathecal opioid for chronic intractable non-malignant and cancer pain. Binds μ \mu μ -opioid receptors in the substantia gelatinosa of the dorsal horn.
Catheter Tip Granuloma : A critical complication of chronic intrathecal morphine infusion. Inflammatory non-infectious granulomatous masses can form at the distal catheter tip, leading to progressive spinal cord compression and myelopathy. New neurological deficits or loss of pain relief require urgent MRI or CT myelogram.
Ziconotide : Non-opioid peptide derived from the venom of the marine cone snail ( Conus magnus ).
Mechanism : Potent, selective blocker of N-type voltage-gated calcium channels on presynaptic primary nociceptive neurons in the dorsal horn, inhibiting glutamate and substance P release.
Clinical Nuance : Does NOT cause opioid tolerance or respiratory depression. Requires slow titration.
Contraindication : Contraindicated in patients with a history of psychosis , hallucinations, or severe psychiatric illness due to risk of treatment-emergent cognitive impairment, hallucinations, and acute psychosis.
Baclofen : GABA- β \beta β (GABA-B) receptor agonist used to treat severe, recalcitrant spasticity of spinal (SCI, MS) or cerebral (CP, TBI, stroke) origin.
Intrathecal Baclofen (ITB) Trial : Requires a screening trial (bolus 50 mcg intrathecal injection) demonstrating significant reduction in Modified Ashworth Scale scores prior to pump implantation.
Intrathecal Baclofen Withdrawal (Emergency)
Abrupt cessation of intrathecal baclofen delivery (due to pump failure, catheter kink/dislodgement, low reservoir volume, or battery depletion) causes a life-threatening medical emergency .
Clinical Presentation : Rapid onset of severe rebound spasticity, rigidity, hyperthermia ( > 40 ∘ C >40^\circ\text{C} > 4 0 ∘ C ), autonomic instability (tachycardia, labile BP), rhabdomyolysis, seizures, altered mental status, disseminated intravascular coagulation (DIC), and multi-organ failure. Symptoms mimic neuroleptic malignant syndrome or malignant hyperthermia.
Emergency Management : Immediate administration of high-dose oral or IV baclofen , aggressive sedation with benzodiazepines (IV diazepam or midazolam), supportive intensive care, and urgent surgical/pump interrogation to restore intrathecal delivery.
Neuromodulation Modality Primary Anatomic / Molecular Target Key Indications Critical Clinical Considerations
Spinal Cord Stimulation (SCS) A-beta dorsal column fibers (Gate Control) FBSS, CRPS I & II, Radiculopathy, DPN Requires mandatory psych eval & 3-7 day trial achieving ≥50% pain relief.
Intrathecal Morphine Mu-opioid receptors in dorsal horn Chronic non-malignant & cancer pain Delivered at 1/100th oral dose; monitor for catheter tip inflammatory granuloma.
Intrathecal Ziconotide Presynaptic N-type Ca2+ channels Refractory neuropathic pain Non-opioid cone snail peptide; no tolerance; contraindicated in active psychosis.
Intrathecal Baclofen (ITB) Presynaptic GABA-B receptors Severe spasticity (SCI, MS, CP, TBI) Abrupt withdrawal is a life-threatening emergency (hyperthermia, rhabdomyolysis).