A 46-year-old patient with a history of known glioblastoma multiforme of the right temporal lobe has a witnessed seizure. He is now postictal and lethargic. A head CT is performed which reveals a heterogeneous mass with hemorrhage into the tumor and a large amount of vasogenic edema leading to mass effect on the midbrain. After his postictal period has resolved,
which set of clinical findings would be most suggestive of uncal herniation?
A. Ipsilateral pupillary dilation, decreased level of consciousnessCorrect Answer: B
Compression (torquing) of the outer fibers of third cranial nerve, compression of ipsilateral corticospinal tract, and the resulting effects on the reticular activating system define brain herniation syndrome. Uncal herniation is a dynamic process in which the uncus or a portion of the anterior temporal lobe prolapses into the hiatus encircled by the tentorium cerebelli. As the uncus herniates into this space, it compresses the midbrain first, resulting in ipsilateral third nerve palsy. When the lesion is cortical and unilateral, pupillary abnormalities manifest on the same side as the lesion. Contralateral weakness or hemiplegia occurs secondary to transtentorial herniation.
Option C is incorrect because it represents left-sided uncal herniation or a Kernohan notch syndrome (false localizing sign) from a right-sided lesion. Imaging is not required for diagnosis of the clinical syndrome, but it does provide supporting evidence.
Cerebral herniation is a “brain code”—life-threatening neurological emergencies indicating that intracranial compliance adaptive mechanisms have been overwhelmed. Cerebral herniation is initially treated with hyperventilation and osmotherapy. Additional therapeutic measures which might be considered for this case include administration of dexamethasone for vasogenic edema, CSF drainage to reduce intracranial pressure, pharmacological reduction of cerebral metabolic rate, decompressive hemicraniectomy, and intraoperative tumor debulking.
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