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Episode 374
DIP Episode 374 - Spinal Cord Lesions (for Step 1-3)
MixedMedium4 - HighHas Q&A
Step 1Step 2Step 3COMLEXMedicineUSMLEStep 1Step 2Step 3
Topic
Spinal cord syndromes; Myelopathies vs. Radiculopathies; Sensory and motor pathway deficits; Neuromuscular junction disorders (SMA, ALS)...
Key Takeaway
Understanding the specific anatomical location of a spinal lesion is critical for localizing sensory and motor deficits: Brown-Séquard syndrome involves hemisection damage, Central Cord Syndrome affects the central spinothalamic tracts, Anterior Spinal Artery Syndrome spares dorsal columns, and B12 deficiency causes combined degeneration affecting both dorsal columns and lateral corticospinal tracts.
Runtime: 21.7 min
Published: 2022-02-25
Completed audio: Yes
Completed notes: Yes
Anki made: Yes
Section: NEURO
Episode Notes
Source / episode info
- Episode: 374
- Title: Divine Intervention Episode 374 – Spinal Cord Lesions (for Step 1-3)
- Published: 2022-02-25
- Source: Episode page
One-liner
This episode provides a comprehensive review of spinal cord syndromes, detailing the distinct patterns of sensory (dorsal column vs. spinothalamic tract) and motor deficits seen in conditions like Brown-Séquard syndrome, Central Cord Syndrome, Anterior Spinal Artery Syndrome, Subacute Combined Degeneration, and differentiating myelopathies from radiculopathies.
High-yield summary
- Brown-Séquard Syndrome: Results from spinal cord hemisection (e.g., gunshot wound). Symptoms are ipsilateral loss of fine touch/vibration (Dorsal Columns) and contralateral loss of pain/temperature (Spinothalamic Tract), plus UMN signs on the same side as the lesion, and LMN signs at the level of the lesion.
- Central Cord Syndrome: Damage to the center of the spinal cord (e.g., cervical trauma, syringomyelia). Classically presents with bilateral loss of pain and temperature sensation in a "cape-like" distribution, often affecting the upper extremities more severely.
- Subacute Combined Degeneration: Caused by Vitamin B12 deficiency or impaired absorption (e.g., pernicious anemia, Crohn's disease). Affects both Dorsal Columns and Lateral Corticospinal Tract, leading to positive Romberg sign and UMN signs.
- Anterior Spinal Artery Syndrome: Damage to the anterior two-thirds of the cord (e.g., following triple Aneurysm repair). Results in loss of all functions except fine touch, vibration, and proprioception (Dorsal Columns are spared).
- Myelopathy vs. Radiculopathy: Myelopathy is a spinal cord problem; Radiculopathy is a nerve root problem. Myelopathies often present with bilateral symptoms or sensory levels; radiculopathies tend to be unilateral/lateral.
- ALS: A pure motor neuron disease (UMN + LMN) that never involves sensory deficits. Treatment targets glutamate excitotoxicity using Riluzole.
Learning objectives
- Differentiate the clinical presentations associated with various spinal cord syndromes (Brown-Séquard, Central Cord, Anterior Spinal Artery Syndrome).
- Recognize the specific neurological findings related to Vitamin B12 deficiency and its impact on dorsal columns and corticospinal tracts.
- Distinguish between myelopathy (spinal cord) and radiculopathy (nerve root) based on clinical patterns and physical exam findings.
- Identify the characteristic motor neuron deficits seen in primary lower motor neuron diseases (SMA, ALS).
- Interpret CSF findings associated with viral meningitis (e.g., West Nile Virus).
Board exam buzzwords
| Condition | Key Finding | Association | Board Exam Tip |
| Brown-Séquard Syndrome | Hemisection of spinal cord | Ipsilateral DC loss; Contralateral STT loss | Remember the "split" pattern: one side for proprioception, opposite side for pain/temp. |
| Central Cord Syndrome | Bilateral Paresthesia (Cape distribution) | Syringomyelia, Cervical trauma | The central location affects crossing fibers first, leading to bilateral sensory deficits. |
| Subacute Combined Degeneration | Positive Romberg sign + UMN signs | Vitamin B12 deficiency; Pernicious anemia | Must have both dorsal column and corticospinal tract involvement for this diagnosis. |
| Anterior Spinal Artery Syndrome | Preservation of fine touch/vibration | Damage to anterior 2/3 of cord (e.g., AAA repair) | The spared function is the most reliable diagnostic clue here. |
Rapid review table
| Topic | Key Point | Context | Exam Relevance |
| Myelopathy vs. Radiculopathy | Myelopathy = Spinal Cord; Radiculopathy = Nerve Root | A myelopathy often presents with bilateral symptoms or a sensory level; radiculopathy is typically unilateral/lateral. | Use the pattern of deficits (e.g., dermatomes) to localize the problem. |
| Brown-Séquard Syndrome | Ipsilateral DC loss, Contralateral STT loss | Spinal cord hemisection (e.g., gunshot wound). | This classic triad is highly testable and requires remembering which deficit crosses where. |
| B12 Deficiency | Subacute Combined Degeneration | Pernicious anemia, Crohn's disease, small bowel resection. | Always check for both dorsal column signs (Romberg) AND UMN signs (hyperreflexia). |
| West Nile Virus Meningitis | CSF: Mild pleocytosis (lymphocyte predominance), slightly elevated opening pressure, low glucose. | Viral etiology; can cause severe meningoencephalitis. | Differentiating viral vs. bacterial meningitis is key for appropriate empiric treatment. |
Board-speak -> diagnosis
| Board-speak / Vignette phrase | Diagnosis / Concept | Why it fits |
| A patient sustains a gunshot wound to the left side of the cervical cord, presenting with loss of fine touch/vibration on the left and loss of pain/temperature sensation on the right. | Brown-Séquard Syndrome | This pattern perfectly matches hemisection damage: ipsilateral dorsal column deficit (left) and contralateral spinothalamic tract deficit (right). |
| A patient presents after a severe motor vehicle accident with bilateral sensory loss, predominantly affecting the upper extremities in a "cape" distribution. | Central Cord Syndrome | Damage to the central cord affects the crossing spinothalamic tracts bilaterally, leading to this classic pattern of pain/temperature loss. |
| A 65-year-old vegan presents with gait instability and positive Romberg sign, along with hyperreflexia. | Subacute Combined Degeneration (B12 deficiency) | B12 deficiency damages the dorsal columns (Romberg+) and lateral corticospinal tracts (UMN signs/hyperreflexia). |
| A patient undergoes surgery for an abdominal aortic aneurysm repair and subsequently develops profound weakness and loss of pain/temperature sensation, but retains fine touch and vibration sense. | Anterior Spinal Artery Syndrome | Damage to the anterior two-thirds of the cord spares the dorsal columns, resulting in preserved proprioception despite severe motor deficits. |
| A 7-month-old child presents with progressive muscle weakness, absent deep tendon reflexes, and loss of motor milestones. | Spinal Muscular Atrophy (SMA) | SMA is a lower motor neuron disease affecting anterior horn cells, leading to profound LMN signs in infancy. |
| A middle-aged man complains of difficulty playing the piano and swallowing, but all sensory exams are normal. | Amyotrophic Lateral Sclerosis (ALS) | ALS is a pure motor neuron disorder (UMN + LMN) that does not involve any sensory deficits. |
Differential diagnosis / distinguishing features
Central Cord Syndrome
| Key Features | Distinguishing Findings | Next Step |
| Bilateral sensory loss in a "cape" distribution, often affecting upper extremities first. | Damage is central; commonly associated with syringomyelia or cervical trauma. | Rule out compressive causes (e.g., tumor) and perform MRI to look for syrinx formation. |
Subacute Combined Degeneration
| Key Features | Distinguishing Findings | Next Step |
| Positive Romberg sign + UMN signs (hyperreflexia, spasticity). | Requires deficiency of Vitamin B12; associated with malabsorption syndromes (Pernicious anemia). | Measure serum Methylmalonic Acid (MMA) and Homocysteine levels. Supplementation (oral/IM) is the treatment. |
Anterior Spinal Artery Syndrome
| Key Features | Distinguishing Findings | Next Step |
| Loss of all functions except fine touch, vibration, and proprioception. | Damage to the anterior two-thirds of the cord; often follows vascular surgery (e.g., AAA repair). | Identify the underlying vascular cause or trauma site. Supportive care is primary management. |
Cauda Equina Syndrome vs. Conus Medullaris Syndrome
| Key Features | Distinguishing Findings | Next Step |
| Conus/Cauda: Myelopathy (Cord damage) | Myelopathy: Often bilateral; UMN signs predominate; Sensory level may be present. | MRI is required to visualize the cord vs. nerve roots. |
| Radiculopathy: Nerve Root Damage | Radiculopathy: Typically unilateral or lateral; LMN signs predominate; Symptoms follow a dermatomal pattern. | Electromyography (EMG) and Nerve Conduction Studies (NCS) are used for confirmation. |
Management pearls
- High Cervical Cord Injury: Any injury affecting C3-C5 roots/segments requires immediate consideration of respiratory failure, as these segments supply the diaphragm via the phrenic nerve; mechanical ventilation may be necessary.
- B12 Deficiency Management: Treatment involves administering Vitamin B12 (e.g., 1000 mcg IM) to bypass potential gastrointestinal absorption issues seen in pernicious anemia or Crohn's disease.
- ALS Management: While supportive care is paramount, Riluzole can be used to slow the progression by acting as an NMDA receptor antagonist and mitigating glutamate excitotoxicity.
- Syringomyelia Workup: If central cord syndrome is suspected, MRI should be performed to look for a syrinx cavity (cystic dilation of the spinal canal).
Don't miss
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The key difference between myelopathy and radiculopathy lies in whether the pathology affects the spinal cord itself or the nerve roots exiting it.
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Dorsal Columns carry proprioception, fine touch, and vibration; damage leads to loss of these senses (positive Romberg).
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Spinothalamic Tracts carry pain and temperature information; damage is often contralateral to the lesion site.
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SMA: Is a lower motor neuron disease affecting anterior horn cells, leading to profound weakness in infancy.
Integration & clinical reasoning
- Neurological Exam Integration: When evaluating spinal cord function, always systematically test: 1) Dorsal Columns (proprioception/vibration), 2) Spinothalamic Tracts (pain/temp), 3) Corticospinal Tract (UMN signs), and 4) LMN signs at the level of the lesion.
- Vascular Integration: The anterior spinal artery is highly susceptible to compromise during major vascular surgeries (e.g., AAA repair), leading to predictable syndromes like Anterior Spinal Artery Syndrome.
- Endocrine/Neuro Integration: While not directly related, understanding that peripheral neuropathy can mimic myelopathy requires ruling out metabolic causes (like B12 deficiency) before attributing symptoms solely to spinal cord damage.
OMM / COMLEX integration
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For COMLEX: know these viscerosomatics / Chapman points, but don't let OMM distract from emergent diagnosis and management.
- Acute/Unstable Pathology: In any acute myelopathy or radiculopathy presentation, standard emergency management (ABC assessment, imaging, stabilization) takes absolute priority over OMT.
- Spinal Cord Trauma: The principles of spinal cord injury classification and immediate immobilization are critical; manual traction and careful handling are paramount to prevent secondary damage.
Concept connections / cross-references
- For detailed information on the general principles of neurological examination and sensory pathways, review [Episode 370].
- Understanding motor neuron diseases like ALS is related to generalized neuromuscular function discussed in [Episode 365].
High-yield association table
| Condition | Association | Mechanism | Clinical Significance |
| Brown-Séquard Syndrome | Spinal cord hemisection | Damage affects tracts unilaterally (DC vs. STT). | Requires careful mapping of deficits: ipsilateral DC, contralateral STT. |
| Central Cord Syndrome | Syringomyelia | Cystic dilation within the spinal canal damages central crossing fibers. | Leads to a characteristic bilateral "cape" distribution of pain/temp loss. |
| Subacute Combined Degeneration | Vitamin B12 deficiency | Deficiency impairs myelin sheath maintenance in dorsal columns and lateral corticospinal tracts. | Testing for MMA and Homocysteine is crucial for diagnosis confirmation. |
| Anterior Spinal Artery Syndrome | AAA repair / Vascular trauma | Ischemia or direct damage to the anterior spinal artery. | The preservation of fine touch/vibration (dorsal columns) is the hallmark finding. |
Key terms glossary
| Term | Definition | Context | Example |
| Myelopathy | Dysfunction or disease affecting the spinal cord itself. | Clinical presentation following trauma, tumor, or vascular compromise. | Transverse myelitis (inflammation of the cord). |
| Radiculopathy | Dysfunction or disease affecting a specific nerve root. | Compression or inflammation at the foramen exit point. | Sciatica (compression of the sciatic nerve root). |
| Dorsal Columns | Fascicles carrying proprioception, fine touch, and vibration sense. | Damage leads to loss of these senses; tested via Romberg sign/joint position sense. | Subacute Combined Degeneration affects this pathway. |
| Syringomyelia | Formation of a fluid-filled cavity (syrinx) within the spinal cord parenchyma. | Often seen in Central Cord Syndrome; can be idiopathic or secondary to trauma. | Requires MRI confirmation and is associated with central sensory loss. |
Study optimization
| Topic | Study Approach | Priority | Resources |
| Spinal Syndromes | Create a flow chart comparing the 4 major syndromes (Brown-Séquard, Central Cord, Anterior SA, B12). | High | Review board vignettes focusing on pattern recognition. |
| Motor Neuron Diseases | Differentiate pure motor vs. mixed UMN/LMN disorders; remember sensory sparing in ALS. | Medium | Use mnemonics for the signs (e.g., SMA = LMN only). |
| Differential Diagnosis | Practice localizing deficits: Is it a root, the cord, or peripheral nerve? | High | Review images of spinal sections to visualize tract damage. |
Question pattern recognition
- Pattern: Ipsilateral loss of fine touch/vibration + Contralateral loss of pain/temp -> Brown-Séquard Syndrome (Hemisection).
- Pattern: Bilateral sensory loss, predominantly in the upper extremities, with preserved deep tendon reflexes -> Central Cord Syndrome (Syringomyelia).
- Pattern: Positive Romberg sign and hyperreflexia -> Subacute Combined Degeneration (B12 deficiency) because both dorsal columns and corticospinal tracts are damaged.
- Pattern: Symptoms that follow a dermatomal pattern, often unilateral/lateral -> Radiculopathy (Nerve root compression).
Test yourself
Common mistakes to avoid
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Mistake: Assuming that all spinal cord syndromes present with the same pattern of motor weakness. Correction: The specific location and type of damage (e.g., anterior vs. central) dictates which tracts are affected, leading to unique patterns.
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Mistake: Confusing myelopathy with radiculopathy based on symptoms alone. Correction: Always use physical exam findings (dermatomes vs. sensory levels; UMN vs. LMN predominance) and imaging (MRI) to localize the lesion correctly.
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Mistake: Forgetting that B12 deficiency affects both dorsal columns AND corticospinal tracts, leading to a combination of signs (Romberg + hyperreflexia).
Common traps
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Trap 1: The "Pure Motor" Trap: If a patient has weakness but no sensory deficits, think motor neuron disease (ALS) or an anterior cord syndrome.
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Trap 2: The Sensory Level Trap: A defined sensory level strongly suggests a myelopathy (spinal cord lesion), whereas dermatomal patterns suggest radiculopathy (nerve root).
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Trap 3: The "Spared Function" Trap: When presented with severe spinal deficits, remember which function is spared to pinpoint the exact location of damage (e.g., preserved fine touch in Anterior Spinal Artery Syndrome).