6.1 TBI Severity Classification, Glasgow Coma Scale, and Pathophysiology

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

6.1 TBI Severity Classification, Glasgow Coma Scale, and Pathophysiology

Key Takeaways Explain This Topic AI

The Glasgow Coma Scale (GCS) evaluates Eye Opening (1-4), Verbal Response (1-5), and Motor Response (1-6), stratifying TBI severity into Mild (13-15), Moderate (9-12), and Severe (3-8).

Post-Traumatic Amnesia (PTA) duration is a major prognostic indicator; resolution of PTA is clinically defined as achieving a Galveston Orientation and Amnesia Test (GOAT) score >= 75 for 2 consecutive days.

Diffuse Axonal Injury (DAI) results from angular rotational acceleration-deceleration shearing forces, characteristically producing microhemorrhages at the gray-white matter junction (Grade I), corpus callosum (Grade II), and dorsolateral brainstem (Grade III).

Primary brain injury occurs at the moment of impact from mechanical forces, whereas secondary brain injury evolves over hours to days driven by ischemia, cerebral edema, excitotoxicity, mitochondrial dysfunction, and elevated intracranial pressure (ICP).

Second-Impact Syndrome (SIS) is a catastrophic complication occurring when a second head injury is sustained prior to complete recovery from an initial concussion, causing loss of cerebrovascular autoregulation, rapid malignant cerebral edema, and brain herniation.

Last updated: July 2026

6.1 TBI Severity Classification, Glasgow Coma Scale, and Pathophysiology

Traumatic brain injury (TBI) is a major cause of death and lifelong disability worldwide. For physical medicine and rehabilitation (PM&R) physicians, mastering the clinical classification, biomechanical mechanisms, and pathophysiological cascades of TBI is fundamental to guiding neurorehabilitation, predicting long-term functional recovery, and managing acute and chronic medical complications.

Biomechanics and Primary vs. Secondary Brain Injury

Brain injury is broadly categorized into primary brain injury and secondary brain injury :

Primary Brain Injury : Occurs instantaneously at the moment of impact as a direct result of mechanical forces applied to the cranium and neural parenchyma. Mechanisms include focal contact forces (causing cortical contusions, skull fractures, epidural hematomas, and subdural hematomas) and non-contact inertial forces (rotational acceleration and deceleration causing tissue shearing).

Secondary Brain Injury : Evolvative cellular damage occurring minutes, hours, and days following the initial trauma. Driven by systemic and intracranial insults, secondary injury mechanisms include:

Cerebral Ischemia and Hypoxia : Disruption of cerebral perfusion pressure (CPP = MAP - ICP).

Excitotoxicity : Massive presynaptic release of glutamate activating NMDA and AMPA receptors, triggering massive intracellular calcium influx.

Mitochondrial Dysfunction and Oxidative Stress : Calcium overload leads to mitochondrial permeability transition pore opening, reactive oxygen species (ROS) generation, and apoptotic cascades.

Cerebral Edema and Elevated ICP : Vasogenic edema (blood-brain barrier disruption) and cytotoxic edema (cellular swelling) leading to intracranial hypertension and uncal or tonsillar herniation.

Glasgow Coma Scale (GCS) and Clinical Severity Stratification

The Glasgow Coma Scale (GCS) remains the gold-standard bedside tool for assessing depth of consciousness and acute neurological impairment. Scored from 3 to 15 , the scale evaluates three discrete behavioral responses: Eye Opening (E1–E4) , Verbal Response (V1–V5) , and Motor Response (M1–M6) .

Assessment Parameter Operational Response Score
Eye Opening (E) Spontaneous eye opening 4
To speech / auditory command 3
To physical pressure / painful stimulus 2
No eye opening response 1
Verbal Response (V) Oriented to person, place, and time 5
Confused conversation, but uses phrases/sentences 4
Inappropriate words (disorganized speech, single words) 3
Incomprehensible sounds (moaning, groaning) 2
No verbal response 1
Motor Response (M) Obeys multi-step motor commands 6
Localizes painful stimulus (purposeful movement toward pain) 5
Normal flexion withdrawal to pain 4
Abnormal flexion to pain ( Decorticate posturing ) 3
Abnormal extension to pain ( Decerebrate posturing ) 2
No motor response (flaccid) 1

Clinical Pearl: When scoring GCS, always record individual sub-scores (e.g., E3 V4 M5 = GCS 12) rather than only the total score. The Motor Score is the single best predictor of ultimate neurological outcome. A GCS of 8 or less defines coma and typically mandates endotracheal intubation for airway protection.

TBI Severity Stratification Criteria

Classification of TBI severity incorporates the initial GCS score, duration of Loss of Consciousness (LOC) , duration of Post-Traumatic Amnesia (PTA) , and conventional neuroimaging findings (CT/MRI):

TBI Severity Category Glasgow Coma Scale (GCS) Loss of Consciousness (LOC) Post-Traumatic Amnesia (PTA) Structural Neuroimaging

Mild TBI 13 – 15 < 30 minutes < 24 hours Normal (Uncomplicated) or Abnormal (Complicated)
Moderate TBI 9 – 12 30 minutes to 24 hours 24 hours to 7 days Abnormal (Contusions, Hematomas, DAI)
Severe TBI 3 – 8 > 24 hours > 7 days Abnormal (Subdural/Epidural, Severe DAI)
Post-Traumatic Amnesia (PTA) and the GOAT Protocol

Post-Traumatic Amnesia (PTA) is the transient state of confusion, disorientation, and inability to store continuous day-to-day memories following TBI. PTA encompasses both retrograde amnesia (loss of memory for events prior to injury) and anterograde amnesia (inability to encode new declarative memories). PTA duration is considered one of the strongest overall predictors of return-to-work and long-term functional independence.

Galveston Orientation and Amnesia Test (GOAT)

The Galveston Orientation and Amnesia Test (GOAT) is a validated, standardized 10-item quantitative questionnaire assessing orientation to person, place, time, and memory for events surrounding the injury.

Score Range : 0 to 100 points.

Normal / Intact Orientation : Score of 75 to 100 .

Impaired / In PTA : Score < 75 .

Criterion for Resolution of PTA : Achieving a GOAT score of 75 or greater on 2 consecutive days .

Alternative Tool: The Orientation Log (O-Log) is a 10-item bedside tool developed specifically for inpatient rehabilitation tracking, scoring orientation from 0 to 30 points (score >= 25 on 2 consecutive days indicates orientation clearance).

Diffuse Axonal Injury (DAI)

Diffuse Axonal Injury (DAI) is a hallmark pathology of high-velocity traumatic brain injury, particularly high-speed motor vehicle collisions and falls from height.

Biomechanical Mechanism

DAI is caused by rotational acceleration-deceleration forces that create angular inertia. Because adjacent brain structures possess differing tissue densities, dynamic shear and tensile stresses develop along nerve fiber tracts, leading to microscopic stretching and tearing of axons.

Histopathological Progression

Primary Axonal Axotomy : Direct mechanical disruption of the axolemma and microtubular cytoskeleton.

Secondary Axonal Axotomy : Impaired axoplasmic transport leads to accumulation of transport proteins, focal axonal swelling ( axonal bulbs or retraction balls), calpain-mediated neurofilament degradation, and ultimate Wallerian degeneration.

Adams Classification of DAI Severity

DAI Grade Anatomic Location of Lesions Clinical Features

Grade I (Mild) Microscopic axonal shearing confined to the cortical gray-white matter junction (parasagittal frontal & temporal lobes). Transient confusion to mild coma.

Grade II (Moderate) Axonal lesions involving the gray-white junction PLUS the Corpus Callosum (predominantly the splenium). Prolonged coma, decorticate posturing, severe cognitive deficits.

Grade III (Severe) Lesions involving gray-white junction, corpus callosum PLUS the Dorsolateral Midbrain & Upper Brainstem . Deep coma, decerebrate posturing, high mortality, severe vegetative or minimally conscious states.

Neuroimaging Findings

Conventional non-contrast head CT frequently underestimates DAI, appearing normal or showing only subtle punctate hypodensities. Magnetic Resonance Imaging (MRI) —specifically Gradient-Recalled Echo (GRE) and Susceptibility-Weighted Imaging (SWI) —is the imaging modality of choice, demonstrating focal susceptibility artifacts (punctate hemosiderin microhemorrhages) at the gray-white interface and splenium of the corpus callosum.

Second-Impact Syndrome (SIS)

Second-Impact Syndrome (SIS) is a rare but fatal complication of traumatic brain injury occurring predominantly in children and adolescent athletes (< 18 years).

Pathophysiologic Cascade

SIS occurs when an individual sustains a second concussion or head impact while still symptomatic from an initial, unhealed concussion. Even if the secondary impact is minor, it triggers:

Loss of Cerebrovascular Autoregulation : Sudden, catastrophic disruption of cerebral autoregulatory mechanisms.

Malignant Cerebral Vasodilation : Rapid, uncontrollable intracranial arterial engorgement.

Fulminant Cerebral Edema : Massive surge in ICP within 2 to 5 minutes, leading to rapid brainstem herniation (uncal or tonsillar herniation) and death or severe vegetative survival.

Prevention: SIS emphasizes the critical clinical imperative that no athlete or patient may return to contact sports or high-risk activities while experiencing post-concussive symptoms.