The pineal gland is a small pine-cone shaped body deep in the brain, attached to the roof of the third ventricle just above the midbrain. It produces melatonin, mainly at night, helping to set the body's daily sleep and wake rhythm in response to light signals from the eyes.
| Location | Midline of the brain, attached to the posterior roof of the third ventricle, lying above the superior colliculi of the midbrain and below the splenium of the corpus callosum |
|---|---|
| Secretes |
|
| Nerve Supply | Sympathetic fibres from the superior cervical ganglion (relaying retinal light signals via the suprachiasmatic nucleus) |
| Blood Supply | Medial posterior choroidal arteries (from the posterior cerebral artery) |
| Venous drainage |
|
Secretes melatonin in darkness to signal night-time to the body, helping regulate circadian rhythm and sleep timing.
The pineal often calcifies with age, and on older skull X-rays its position was used to spot a shift of the midline from a mass. Pineal region tumours can compress the cerebral aqueduct, causing hydrocephalus, and press on the midbrain tectum, producing Parinaud syndrome (inability to look upward). Melatonin supplements are used for jet lag and some sleep disorders.
Germ cell tumours or pineal parenchymal tumours (such as pineoblastoma) that can block CSF flow and impair upward gaze.
A common, usually harmless fluid-filled cyst found incidentally on MRI; rarely large enough to cause symptoms.
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