Uncal Herniation

Overview

Uncal herniation is a typical type of transtentorial herniation in which uncus, which is the innermost part of the temporal lobe of brain, heads for the tentorium and eventually puts pressure on the midbrain (upper brainstem) and the oculomotor nerve. Several clinical complications may arise from this condition relating to the eye and possibly brain damage. Uncal herniation is a medical emergency and should be dealt with immediately since delaying the treatment can cause permanent damage, and possibly death.

Causes

Uncal herniation occurs due to presence of a large mass that results in increased intracranial pressure, thus causing the herniation. The mass can be formed from blood clot from a head trauma, or a tumor. Other causes may include abscess, hydrocephalus, inflammation secondary to radiotherapy and stroke.

Signs & Symptoms

  • Dilation of the pupil
  • Confusion
  • Headache
  • Depressed state or total loss of consciousness
  • Droopy eye (Ptosis) due to third nerve palsy
  • Lethargy
  • One sided weakness of the body (hemiparesis)
  • Decreased heart rate (bradycardia)
  • Deep coma
  • Respiratory depression or cardiac arrest (no pulse) that leads to death

Complications

If uncal herniation is diagnosed, then concerned physicians should be notified immediately and the case in hand should be dealt with as an emergency. However, cases that persist for some time can lead to complications:-

  1. Brain death
  2. Permanent neuronal damage leading to loss of function of the related system
  3. Duret hemorrhage: Extensive brainstem ischemia may occur due to bleeding in the midbrain and upper pons
  4. Ischemia of visual cerebral cortex due to compression of related vessels.
  5. May advance to central herniation

Diagnosis

General examination reveals high blood pressure, irregular breathing, irregular and slow pulse. Neural exam reveals marked changes in consciousness of the patient. One or more nerve functions, especially of the eye, are diminished or lost completely.
MRI is the diagnostic tool of choice for uncal herniation that shows a mass around the tentorium. CT scan can also be conducted for this purpose.

Treatment

Treatment strategy is wide and requires swift action to stop the progression of symptoms and possibly reverse them. They include:-

  1. Draining cerebrospinal fluid (CSF) to relieve intracranial pressure
  2. Reduction of inflammation with use of corticosteroids
  3. Using diuretics such as mannitol to reduce intracranial pressure
  4. Surgical intervention for excision of mass or removal of hematoma.
  5. Surgery to remove portion of meninges or cerebral cortex tissue in a procedure called decortication

Additional Monitoring

  1. Check for brain tissue oxygen levels to assess hypoxia
  2. Measure brain’s levels of lactate, pyruvate, glutamate, glucose, and other indicators of metabolic activity
  3. Check carbon dioxide levels

Sources

https://radiopaedia.org/articles/uncal-herniation-1

https://en.wikipedia.org/wiki/Brain_herniation#Uncal_herniation

http://jamanetwork.com/journals/jamaneurology/article-abstract/789938

https://www.ncbi.nlm.nih.gov/pubmed/9826793

http://www.sciencedirect.com/topics/neuroscience/uncus

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4791176/