Central pontine myelinolysis
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Central pontine myelinolysis
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USMLE® Step 1 style questions USMLE
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| Laboratory value | Result |
| Sodium | 108 mEq/L |
| Potassium | 4.2 mEq/L |
| Chloride | 95 mEq/L |
| Creatinine | 0.9 mg/dL |
| Albumin | 3.2 g/dL |
The patient is started on hypertonic saline. On the second day of treatment, the partner notices the patient is unable to move, but she is able to blink in response to questions. Which of the following is the most likely location of the brain lesion in this patient?
Image reproduced from Wikimedia Commons
External References
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Central pontine myelinolysis p. 538
Diplopia
osmotic demyelination syndrome p. 538
Dysarthria p. 529
osmotic demyelination syndrome p. 538
Dysphagia
osmotic demyelination syndrome p. 538
“Locked-in” syndrome
osmotic demyelination syndrome p. 538
Osmotic demyelination syndrome p. 538
SIADH and p. 349
Transcript
Content Reviewers
In central pontine myelinolysis, pontine refers to the pons of the brainstem, myelin refers to the fatty layer of insulation that wraps around neurons, and -lysis refers to destruction.
So, central pontine myelinolysis is the destruction of the myelin sheath around nerve cells that are in the pons.
The main cause of destruction is rapid osmotic changes, meaning that a lot of water leaves the cells, and dries them out, causing them to die.
So the other name for central pontine myelinolysis is osmotic demyelination syndrome.
Taking a look at the brain, the pons is part of the brainstem and it’s nestled between the midbrain and the medulla oblongata.
The pons itself has control centers that help manage the respiration rate and the depth of breathing while we’re awake and when we sleep. So if you try to take a deep breath right now - that’s your pons in action!
Neuron clusters or nuclei for cranial nerves V: trigeminal, VI: abducens, VII: facial, and VIII: vestibulocochlear are also housed in the pons.
Cranial nerve V allows you to feel things on your face and controls the muscles that help you chew, bite, and swallow.
Cranial nerve VI allows your eyes to move side to side.
Cranial nerve VII helps with facial expressions - like making a weird face, and cranial nerve VIII helps with hearing.
All of these nerves are made up of lots of individual neurons which capture signals from their dendrites, and pass those signals along through their axons.
In addition to the neurons, there are also supporting cells called oligodendrocytes and astrocytes.
Oligodendrocytes physically wrap their fatty myelin-rich cell membranes around neuronal axons that are nearby to help action potentials move more quickly through them.
Summary
Central pontine myelinolysis (CPM) is a neurological disorder caused by the rapid correction of hyponatremia. CPM is a demyelinating disease that damages the insulation around nerve fibers (called myelin). This damage disrupts the conduction of nerve impulses, leading to neurologic deficits.
Symptoms of CPM include muscle weakness, difficulty swallowing, and problems with speech, vision, and balance. These symptoms often occur suddenly and progress rapidly. Death from respiratory failure can occur within days or weeks of onset.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Central Pontine and Extrapontine Myelinolysis After Alcohol Withdrawal: Fig. 1" Alcohol and Alcoholism (2008)
- "Axonal damage: a key predictor of outcome in human CNS diseases" Brain (2003)
- "Clinical practice guideline on diagnosis and treatment of hyponatraemia" European Journal of Endocrinology (2014)