Hypothalamic hamartoma is a malformation, not a tumor. Hypothalamic hamartomas grow at the rate of, or slower than, the surrounding brain tissue. A hamartoma of the hypothalamus appears as a non-enhancing mass in the floor of the third ventricle posterior to the optic chiasm that is isointense to gray matter on T1 and T2 pulse sequences of an MRI, but may have distinct intensity on FLAIR (neither cranial CT examination nor cranial ultrasound examination is adequate for diagnosis of hypothalamic hamartom). Individuals with hypothalamic hamartomas may have neurologic symptoms, although most are asymptomatic. Removal of the hypothalamic hamartoma is not indicated and often results in iatrogenic pituitary insufficiency.

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