š§ Brain Herniation: The Silent Descent You Must Never Miss
Brain herniation is one of the most time-critical neurological emergencies we face. It doesnāt shout at the beginning, it whispers. But when it declares itself, deterioration can be rapid, dramatic, and irreversible. Understanding the early signs, the mechanisms, and the clinical patterns is essential for anyone working in acute, critical, or emergency care. š What Is Brain Herniation? Brain herniation occurs when rising intracranial pressure (ICP) forces brain tissue to shift from its normal position into adjacent compartments. This displacement compresses vital structures, including the brainstem and threatens cerebral perfusion. In simple terms: š Too much pressure ā not enough space ā the brain is pushed somewhere it shouldnāt be. This can be fatal within minutes if not recognised. š§ The Main Types of Brain Herniation Here are the key herniation patterns you need to know: 1ļøā£ Uncal (Transtentorial) Herniation The medial temporal lobe is pushed under the tentorium. Key features: Unilateral fixed, dilated pupil (CN III compression) Ptosis and ādown and outā eye position Reduced level of consciousness Contralateral motor weakness ā progressing to hemiplegia Late: Cushingās triad (hypertension, bradycardia, irregular respirations) Think: Pupil change = uncal herniation until proven otherwise 2ļøā£ Central Herniation Downward shift of the diencephalon and brainstem. Early signs: Subtle changes in consciousness Small, reactive pupils Respiratory pattern changes Decorticate posturing Late signs: Fixed pupils Flexor ā extensor posturing changes Cushingās triad Think: A progressive decline with bilateral signs. 3ļøā£ Subfalcine Herniation Cingulate gyrus shifts beneath the falx cerebri. Signs may be subtle: Headache Altered mentation Weakness in one leg (compression of ACA territory) Often an early warning before more dangerous herniation patterns occur. 4ļøā£ Tonsillar Herniation The cerebellar tonsils are forced down through the foramen magnum. This is immediately life-threatening.