Cerebellar herniation syndromes
What are the clinical features of the cerebellar herniation syndromes?
Mass lesions, particularly neoplasms and hematomas, often present as nonspecific symptoms such as headache.
As they enlarge, the increased pressure causes herniation of the cerebellum.
With downward herniation, the cerebellar tonsils are pushed through the foramen magnum and compress the medulla (tonsillar herniation), causing progressive vomiting, stiff neck, skew deviation of the eyes, coma, ataxic breathing, apnea, and death if not anticipated and prevented.
In upward herniation, the cerebellum and upper brain stem are pushed through the tentorial opening (uncal herniation), leading to progressive compression of the pons and midbrain.
The patient is usually obtunded or comatose with small pupils (reactive at first) or anisocoria.
Oculocephalic and oculovestibular responses are abnormal. Hemiparesis may progress to quadriparesis and decorticate posturing.
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