A young boy gets hit by ball on the left side of his head and falls unconscious. He regained consciousness and refuses first aid. After few minutes, he began acting confused. By this time, an ambulance arrives and takes him to nearest government hospital. On examination, left pupil is dilated. NCCT head is done with following findings: Which of the following marked structure has lead to the current clinical finding of pupil of the patient?
Subfalcine herniation Transtentorial herniation Tonsillar herniation Subfalcine (cingulate) herniation : occurs when unilateral or asymmetric cerebral hemisphere expansion displaces the cingulate gyrus under the falx. Transtentorial (uncinate, mesial temporal) herniation: occurs when the medial temporal lobe is compressed against the free margin of the tentorium. This can lead to the third cranial nerve is compromise, resulting in pupillary dilation and impairment of ocular movements on the side of the lesion. When the extent of herniation is large enough the contralateral cerebral peduncle gets compressed, resulting in hemiparesis ipsilateral to the side of the herniation; the compression in the peduncle in this setting is known as the Kernohan notch. It is often accompanied by secondary hemorrhagic lesions in the midbrain and pons, termed Duret hemorrhages. Tonsillar herniation refers to displacement of the cerebellar tonsils through the foramen magnum. It is life-threatening because it causes brainstem compression and compromises vital respiratory and cardiac centers in the medulla.
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