A 34-year-old man suffers blunt head trauma during a basketball game in prison. Imaging reveals large right suboral hematoma with 8 mm midline shift. The patient is intubated; his eyes do not open to stimulus; he has no verbal response; and limbs extend to painful stimulus. He has fixed dilated pupils.
Which of the following regarding uncal herniation is TRUE?
A. The Cushing triad is often present (papilledema, hypertension, bradycardia)Correct Answer: C
Expanding mass lesions in the brain can lead to lateral and downward displacement of the brain. Horizontal shifts of midline structures >8 mm are associated with impaired consciousness and shifts >11 mm are typically consistent with coma. In uncal herniation syndrome, lateral forces lead to asymmetric herniation of the temporal uncus. The ipsilateral oculomotor nerve (CN III) is displaced and stretched, leading to pupillary dilation, downward and outward eye deviation (C).
Subsequently, contralateral pupil reactivity may be lost with midbrain damage (B). Hemiplegia occurs with compression of the corticospinal tract, not the spinothalamic tract (D). Vestibulo-ocular reflexes are present and normal early until brainstem compression occurs (E). Clinically, these patients develop signs of elevated ICP as identified in the Cushing triad (hypertension, bradycardia, irregular respirations). Papilledema is consistent with ICP elevation but not a part of the triad (A).
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