transtentorial

Transtentorial is an adjective used in anatomy and neurology to describe something across the tentorium cerebelli or related to herniation through the tentorial notch. The tentorium cerebelli is a dural fold that separates the cerebrum from the cerebellum. In clinical neurology, transtentorial herniation denotes a downward displacement of brain tissue across the tentorial notch due to increased intracranial pressure from mass effect, swelling, or hemorrhage. The most common form is uncal (mesial temporal lobe) herniation, where the medial temporal lobe herniates over the edge of the tentorium, compressing the ipsilateral oculomotor nerve (CN III) causing a dilated pupil and ipsilateral hemiparesis. If not reversed, brainstem compression leads to rapid deterioration.

A secondary pattern is central transtentorial herniation, where both cerebral hemispheres descend toward the brainstem, with compression of the midbrain and pons and potential bilateral motor and autonomic symptoms.

Causes include space-occupying lesions such as tumors, intracerebral or subdural hematomas, cerebral edema, and hydrocephalus. Diagnosis is typically via CT or MRI showing downward displacement of brain tissue through the tentorial notch.

Management focuses on rapid control of intracranial pressure and treatment of the underlying cause. This may involve hyperosmolar therapy, elevation of the head, intubation with controlled ventilation, and neurosurgical decompression or evacuation of the offending mass. Prognosis is highly dependent on the rapidity of recognition and underlying pathology; transtentorial herniation carries a high risk of morbidity and mortality.