Study guide
4.3 Spasticity Assessment & Multimodal Management
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
4.3 Spasticity Assessment & Multimodal Management
Key Takeaways Explain This Topic AI
Spasticity is a velocity-dependent increase in muscle tone resulting from upper motor neuron lesions; clinical severity is quantified using the Modified Ashworth Scale (MAS 0 to 4) and the Modified Tardieu Scale (MTS), which measures dynamic catch angles (R1 vs R2) across varying movement velocities.
Oral antispasmodics operate through distinct biochemical pathways: baclofen acts as a presynaptic GABA-B receptor agonist; tizanidine functions as a central alpha-2 adrenergic agonist requiring hepatic function monitoring; dantrolene directly inhibits ryanodine receptor (RYR1) calcium release in muscle sarcoplasmic reticulum; and diazepam enhances GABA-A postsynaptic inhibition.
Botulinum toxin chemodenervation blocks presynaptic acetylcholine release at the neuromuscular junction by cleaving SNARE proteins (SNAP-25 for OnabotulinumtoxinA, AbobotulinumtoxinA, and IncobotulinumtoxinA; VAMP/synaptobrevin for RimabotulinumtoxinB), reaching peak clinical efficacy at 2 to 4 weeks with a typical duration of 3 to 4 months.
Intrathecal Baclofen (ITB) therapy delivers baclofen directly into the subarachnoid space, providing potent antispasmodic effects at a fraction of oral doses, making it the treatment of choice for severe, refractory lower extremity spasticity.
Intrathecal baclofen withdrawal is a life-threatening medical emergency characterized by hyperpyrexia, altered mental status, severe rebound spasticity/rigidity, rhabdomyolysis, and DIC, requiring immediate resuscitation, high-dose IV benzodiazepines, oral/enteral baclofen, and surgical pump evaluation.
Last updated: July 2026
Spasticity Assessment & Multimodal Management
Spasticity is defined as a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex as one component of the upper motor neuron (UMN) syndrome. Effective clinical management requires precise clinical quantification, tailored oral antispasmodics, focal chemodenervation, and advanced intrathecal interventions.
- Clinical Spasticity Assessment Scales
- Modified Ashworth Scale (MAS)
The Modified Ashworth Scale (MAS) is the most widely utilized clinical tool for assessing passive muscle resistance to stretch. Passive joint movement is performed at a quick velocity:
Grade 0 : No increase in muscle tone.
Grade 1 : Slight increase in muscle tone, manifested by a catch and release or by minimal resistance at the end of the range of motion (ROM) when the affected part(s) is moved in flexion or extension.
Grade 1+ : Slight increase in muscle tone, manifested by a catch, followed by minimal resistance throughout the remainder (less than half) of the ROM.
Grade 2 : More marked increase in muscle tone through most of the ROM, but affected part(s) easily moved.
Grade 3 : Considerable increase in muscle tone, passive movement difficult.
Grade 4 : Affected part(s) rigid in flexion or extension.
Modified Tardieu Scale (MTS)
Unlike the MAS, the Modified Tardieu Scale (MTS) directly accounts for velocity dependency, allowing clinicians to distinguish dynamic neural spasticity from fixed structural tissue contracture.
Velocities of Stretch :
V1 : As slow as possible (evaluates passive range of motion without triggering stretch reflex).
V2 : Speed of the limb segment falling under gravity.
V3 : As fast as possible (faster than the rate of gravity fall, triggering stretch reflex).
Key Angle Parameters :
R2 Angle : Full passive range of motion achieved at slow velocity ( V1 ).
R1 Angle : Angle of muscle catch or clonus elicited at fast velocity ( V3 ).
Dynamic Catch Zone (R2 minus R1) : A large difference between R2 and R1 ( large R2 - R1 ) indicates a large dynamic neural spastic component that will respond favorably to botulinum toxin or intrathecal baclofen. Conversely, an R1 equal to R2 ( R2 - R1 = 0 ) indicates fixed biomechanical contracture, requiring serial casting, splinting, or surgical tendon release rather than antispasmodic medications.
Oral Antispasmodic Pharmacotherapy
Oral antispasmodics are indicated for widespread or generalized spasticity. Selection is guided by mechanism of action, organ toxicity, and side effect profiles.
Oral Medication Mechanism & Receptor Site Primary Site of Action Common Side Effects & Adverse Risks Clinical Monitoring Requirements
Baclofen GABA-B receptor agonist (presynaptic inhibition) Spinal cord motor neurons Sedation, dizziness, weakness, confusion, seizure on abrupt withdrawal Renal function (renally excreted); taper slowly
Tizanidine Alpha-2 adrenergic agonist (presynaptic inhibition) Central spinal cord interneurons Sedation, dry mouth (xerostomia), hypotension, bradycardia, hepatotoxicity Baseline & periodic liver function tests (AST/ALT)
Dantrolene Ryanodine receptor (RYR1) blocker (inhibits Ca²⁺ release) Peripheral skeletal muscle sarcoplasmic reticulum Muscle weakness, diarrhea, sedation, fatal hepatotoxicity Black Box Warning : LFTs baseline & regular monitoring
Diazepam GABA-A receptor positive modulator (opens Cl⁻ channel) Central nervous system / spinal cord Marked sedation, cognitive impairment, ataxia, dependency/tolerance Controlled substance; avoid in TBI/elderly
Clinical Pharmacology Pearls
Baclofen : Agonizes presynaptic GABA-B receptors , restricting voltage-gated calcium influx and inhibiting excitatory neurotransmitter release in the spinal cord. Abrupt oral withdrawal causes rebound spasticity, hyperpyrexia, and seizures.
Tizanidine : Central alpha-2 adrenergic agonist structurally related to clonidine. Reduces release of excitatory amino acids (aspartate/glutamate) from spinal interneurons. Causes significant sedation and orthostatic hypotension. Hepatotoxicity risk requires monitoring baseline and periodic AST/ALT levels .
Dantrolene Sodium : The only direct-acting peripheral muscle relaxant. Binds the ryanodine receptor (RYR1) on the sarcoplasmic reticulum of skeletal muscle cells, blocking intracellular calcium release required for muscle contraction. It spares smooth and cardiac muscle. Because it works peripherally, it produces less central sedation, but carries a Black Box Warning for severe, potentially fatal hepatotoxicity .
Diazepam : Enhances GABA-A receptor postsynaptic chloride conductance. Highly sedating; impairs motor learning and cognitive recovery after stroke and TBI.
Botulinum Toxin Chemodenervation
Botulinum neurotoxin (BoNT) is the gold standard intervention for focal spasticity (e.g., spastic equinovarus foot, flexed elbow, clenched fist).
Mechanism of Action
BoNT blocks presynaptic release of acetylcholine (ACh) at the neuromuscular junction. The toxin heavy chain binds motor nerve terminal acceptors, endocytoses the toxin, and the light chain cleaves specific SNARE docking proteins:
Serotype A (OnabotulinumtoxinA, AbobotulinumtoxinA, IncobotulinumtoxinA) : Cleaves SNAP-25 (Synaptosomal-associated protein 25).
Serotype B (RimabotulinumtoxinB) : Cleaves VAMP / Synaptobrevin (Vesicle-associated membrane protein).
Dosing and Clinical Timeline
Clinical Timeline : Therapeutic onset occurs within 3 to 7 days , reaching peak effect at 2 to 4 weeks , and lasting 3 to 4 months (12 to 16 weeks) as functional nerve sprouting restores ACh release.
Dosing Parameters : For OnabotulinumtoxinA (Botox) , the maximum recommended total body dose per injection session in adults is 400 Units (or 10–12 U/kg in pediatric patients). Higher doses increase the risk of systemic toxin spread, presenting with generalized muscle weakness, ptosis, dysphagia, or respiratory distress.
Intrathecal Baclofen (ITB) Therapy
Intrathecal Baclofen (ITB) therapy delivers baclofen directly into the subarachnoid CSF space via a surgically implanted subcutaneous abdominal pump and intrathecal catheter. ITB achieves CSF drug concentrations 10-fold higher than oral administration while utilizing less than 1% of the oral daily dose, bypassing systemic side effects.
Indications : Severe, intractable lower extremity spasticity (e.g., spinal cord injury, multiple sclerosis, cerebral palsy, severe stroke) unresponsive to max-tolerated oral agents.
Catheter Tip Placement : Lumbar puncture with tip positioned at T6–T10 for lower extremity spasticity, or C1–C4 for upper extremity and severe quadriparetic spasticity.
ITB Withdrawal vs. ITB Overdose Emergency
Recognizing and managing ITB emergencies is critical for board examinations and clinical practice:
ITB Withdrawal (Life-Threatening Emergency) :
Causes : Catheter dislodgement, kink, fracture, pump mechanical failure, low reservoir, or battery depletion.
Clinical Presentation : Rapid loss of GABAergic inhibition causes severe rebound spasticity, muscle rigidity, hyperpyrexia (fever >40°C) , tachycardia, labile blood pressure, altered mental status, seizures, rhabdomyolysis, acute kidney failure, disseminated intravascular coagulation (DIC), and death (mimicking neuroleptic malignant syndrome or autonomic dysreflexia).
Emergency Management : Restore GABAergic tone immediately. Administer high-dose IV benzodiazepines (diazepam, midazolam) , high-dose oral/enteral baclofen, supportive fluid resuscitation, and arrange emergent neurosurgical/physiatric pump interrogation and catheter exploration.
ITB Overdose :
Causes : Pump programming errors or unintended bolus.
Clinical Presentation : Severe hypotonia ("floppy patient"), somnolence, coma, hypothermia, respiratory depression, bradycardia, and seizures.
Management : Mechanical ventilation/airway protection, intravenous physostigmine (1–2 mg IV), and emergency lumbar puncture CSF drainage (removing 30–40 mL of CSF to clear drug).