Curriculum

17 Sections
1548 Lessons
100 Days

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U01.01 Biochemistry
This biochemistry review for USMLE Step 1 covers essential topics including metabolism, enzymology, and molecular biology.
126
U01.02 Immunology
Prepare for USMLE Step 1 Immunology with a comprehensive review covering foundational concepts, immune system mechanisms, and key disorders to solidify your understanding and boost exam readiness.
42
U01.03 Microbiology
Review essential microbiology topics for the USMLE Step 1, covering key pathogens, mechanisms of disease, and antimicrobial principles critical for mastering infectious disease concepts.
172
U01.04 General Pathology
Explore key concepts in general pathology essential for the USMLE Step 1. This review covers fundamental principles, disease mechanisms, and clinical correlations to help you excel in your medical exam.
35
U01.05 Pharmacology
Master key pharmacology concepts for the USMLE Step 1 with a focus on drug mechanisms, therapeutic uses, adverse effects, and interactions essential for high-yield exam performance.
43
U01.06 Public Health Sciences
Review essential Public Health Sciences topics for the USMLE Step 1, covering epidemiology, biostatistics, health policy, and ethics to strengthen your understanding of foundational public health principles.
53
U01.07 Cardiovascular system
Comprehensive review of essential cardiovascular system topics to help you excel in the USMLE Step 1 exam, covering key concepts from anatomy to pathology.
73
U01.08 Endocrine system
Master essential concepts of the endocrine system for USMLE Step 1, covering hormone regulation, feedback mechanisms, and key disorders to boost your exam readiness.
51
U01.09 Gastrointestinal system
Review key topics in the gastrointestinal system for the USMLE Step 1, covering essential concepts in anatomy, physiology, pathology, and pharmacology to reinforce your understanding and test readiness.
131
U01.10 Hematology and Oncology
This review covers essential Hematology and Oncology topics for the USMLE Step 1, including hematopoiesis, coagulation, anemias, leukemias, lymphomas, and neoplastic syndromes.
148
U01.11 Musculoskeletal, Skin, and Connective Tissue
Review essential topics for the USMLE Step 1 Musculoskeletal, Skin, and Connective Tissue systems, covering anatomy, physiology, pathology, and pharmacology fundamentals critical for exam success.
178
U01.12 Neurology and Special Senses
Master the foundational concepts of Neurology and Special Senses with our USMLE Step 1 review, covering essential topics like neuroanatomy, neurophysiology, and sensory pathways.
143
U01.13 Psychiatry
Psychiatry for the USMLE Step 1 focuses on understanding the pathophysiology, diagnosis, and treatment of psychiatric disorders, with an emphasis on key concepts like neurotransmitter imbalances, mental health disorders, and pharmacology.
83
U01.14 Renal System
The Renal System review for USMLE Step 1 covers key concepts including renal physiology, nephron function, acid-base balance, electrolyte regulation, and renal pathology, crucial for understanding both normal and abnormal kidney functions.
81
U01.15 Reproductive System
The USMLE Step 1 Reproductive System review covers key concepts in human reproduction, including anatomy, physiology, endocrinology, and common pathologies affecting both male and female reproductive health.
124
U01.16 Respiratory System
The Respiratory System review for the USMLE Step 1 covers key concepts in anatomy, physiology, pathophysiology, and pharmacology essential for understanding respiratory diseases and treatments.
61
U01.17 Rapid Review
he USMLE Step 1 Rapid Review covers essential topics across multiple disciplines, providing a concise, high-yield overview to reinforce key concepts and optimize your exam preparation.
5

Other demyelinating and dysmyelinating disorders

Osmotic Demyelination Syndrome

Also known as Central Pontine Myelinolysis.

Causes and Pathophysiology

Massive axonal demyelination in pontine white matter.
Primarily due to rapid osmotic changes, such as:
- Iatrogenic correction of hyponatremia
- Rapid shifts in other osmolytes (e.g., glucose)

Clinical Presentation

Acute paralysis
Dysarthria (difficulty speaking)
Dysphagia (difficulty swallowing)
Diplopia (double vision)
Loss of consciousness
Locked-in Syndrome: Severe cases may cause a state where the patient is conscious but unable to move or communicate verbally.

Important Notes

Correcting serum sodium (Na⁺) too rapidly can lead to severe complications:
- “From low to high, your pons will die” — Risk of osmotic demyelination syndrome.
- “From high to low, your brains will blow” — Risk of cerebral edema and herniation.

2. Acute Inflammatory Demyelinating Polyradiculopathy (AIDP)

The most common subtype of Guillain-Barré Syndrome (GBS).

Pathophysiology

An autoimmune disorder destroying Schwann cells, resulting in:
- Inflammation and demyelination of motor and sensory fibers.
- Affects peripheral nerves (including cranial nerves III to XII).
Likely facilitated by molecular mimicry and potentially triggered by:
- Infections (e.g., Campylobacter jejuni, Zika virus)
- Vaccinations or stress
No definitive causal link to any single pathogen.

Symptoms

Symmetric ascending muscle weakness or paralysis.
Loss of deep tendon reflexes (DTRs), beginning in the lower extremities.
Common complications include:
- Facial paralysis (usually bilateral)
- Respiratory failure
- Autonomic dysregulation (cardiac irregularities, blood pressure instability)
- Sensory abnormalities

Diagnostic and Treatment Notes

CSF Analysis: Elevated protein with a normal cell count (albuminocytologic dissociation).
Management:
- Respiratory support may be critical until recovery.
- Disease-modifying therapies: Plasmapheresis or IV immunoglobulins.
- No role for steroids in treatment.

3. Acute Disseminated (Postinfectious) Encephalomyelitis

Characterized by multifocal inflammation and demyelination following infection or vaccination.

Clinical Features

Rapidly progressive multifocal neurological symptoms.
Altered mental status is common.

4. Charcot-Marie-Tooth Disease (CMT)

Also known as Hereditary Motor and Sensory Neuropathy.

Pathophysiology

A group of hereditary nerve disorders affecting the structure and function of peripheral nerves or the myelin sheath.
Typically autosomal dominant.
The most common type, CMT1A, results from duplication of the PMP22 gene.

Clinical Features

Foot deformities (e.g., pes cavus, hammer toe)
Lower extremity weakness (e.g., foot drop)
Sensory deficits

5. Progressive Multifocal Leukoencephalopathy (PML)

Characterized by demyelination in the CNS due to oligodendrocyte destruction.

Causes and Risk Factors

Caused by reactivation of latent JC virus infection.
Typically occurs in immunocompromised patients (e.g., 2–4% of AIDS patients).
Risk is increased with the use of natalizumab.

Clinical Features

Rapidly progressive, typically fatal.
Predominantly affects the parietal and occipital lobes; visual symptoms are common.

Summary Table

Disorder	Key Features	Common Symptoms and Risks	Treatment/Management
Osmotic Demyelination Syndrome	Caused by rapid osmotic shifts; can result in “locked-in syndrome”	Paralysis, dysarthria, dysphagia, consciousness loss	Avoid rapid Na⁺ correction
Acute Inflammatory Demyelinating Polyradiculopathy (AIDP)	Autoimmune demyelination of peripheral nerves; a subtype of Guillain-Barré syndrome	Ascending weakness, respiratory failure, autonomic issues	Plasmapheresis or IV immunoglobulins
Acute Disseminated Encephalomyelitis	Postinfectious or postvaccination multifocal inflammation and demyelination	Rapid neurologic deterioration, altered mental status	Supportive care
Charcot-Marie-Tooth Disease	Hereditary nerve disorder, typically autosomal dominant, affecting myelin proteins	Foot deformities, lower extremity weakness, sensory deficits	Symptomatic management
Progressive Multifocal Leukoencephalopathy (PML)	CNS demyelination due to JC virus, affecting immunocompromised individuals	Visual disturbances, progressive neurologic decline	No specific treatment; avoid natalizumab if at risk

Points to Remember

Osmotic Demyelination Syndrome results from rapid osmotic changes, particularly in sodium levels.
AIDP is the most common subtype of Guillain-Barré and primarily affects motor and sensory peripheral nerves.
Acute Disseminated Encephalomyelitis is often seen after infections or vaccinations.
Charcot-Marie-Tooth Disease is a hereditary disorder with typical foot deformities and motor weakness.
PML is a fatal disease in immunocompromised patients, primarily affecting the parietal and occipital brain regions.

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USMLE Step 1 Review Series

Curriculum

Other demyelinating and dysmyelinating disorders

Osmotic Demyelination Syndrome

Causes and Pathophysiology

Clinical Presentation

Important Notes

2. Acute Inflammatory Demyelinating Polyradiculopathy (AIDP)

Pathophysiology

Symptoms

Diagnostic and Treatment Notes

3. Acute Disseminated (Postinfectious) Encephalomyelitis

Clinical Features

4. Charcot-Marie-Tooth Disease (CMT)

Pathophysiology

Clinical Features

5. Progressive Multifocal Leukoencephalopathy (PML)

Causes and Risk Factors

Clinical Features

Summary Table

Points to Remember

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