Pineal gland

The pineal gland is a small, pine-cone shaped structure considered to be part part of theepithalamus. It is unpaired and situated in the midline. 

Gross anatomy

The pineal gland typically measures around 7 x 6 x 3 6 x 3 mm in size and is situated situated in a groove between the laterally placed thalamic bodies ^1-6. Appearing Normal sizes have been described in the radiology literature up to 14 mm ⁹. Appearing to arise from the gland are two laminae. Above is thehabenular commissure and below it is theposterior commissure. 

Relations

• anteriorly: third ventricle (pineal recess)
• posteroinferiorly: superior cerebellar cistern
• superiorly: internal cerebral veins, vein of Galen (posteriorly), stria medularis, splenium of the corpus callosum and velum interpositum
• inferiorly: superior colliculi of the midbrain

Blood supply supply

The pineal gland receives its blood supply from fine branches offof the posterior choroidal arteries and drains superiorly by multiple branches eventually into the great cerebral vein of Galen ³. 

Embryology

The pineal gland arises during the seventh week of gestation from a thickening of thickening of the ependyma at the posterior most-most aspect of the third ventricle ⁵. 

Physiology

The pineal gland produces melatonin which affects the modulation of wake/sleep patterns and photoperiodic (seasonal) functions. It is also thought to have a reproductive function and has been associated with the onset of puberty ⁷. Unlike much of the rest of the brain, it is not isolated from the body by the blood-brain barrier.

Radiographic features

Plain filmRadiograph

The pineal gland has a predilection for calcification which is invariably histologically present in adults but rarely seen below the age of 10 years ⁶. Calcification is visible on lateral skull x-rays in 50-70% of adults ⁶. The habenular commissure also calcifies and is visible as visible as a small C-shaped (open part posteriorly) density above and in front of the pineal calcification. 

CT

With CT's far higher contrast resolution calcification is almost always visible in the adult pineal gland, sometimes visible as specs embedded in embedded in a small soft tissue nodule similar in density to grey matter. In children under the age of 5 years no calcification is present, but prevalence increases rapidly with age, reaching a plateau at about 30 years of age⁵. 

MRI

MRI is the modality of choice for evaluating the pineal region although its sensitivity to calcification on conventional sequences is poor (note: susceptibility weighted imaging (SWI) has a sensitivity to calcification similar to CT). 

The gland appears as a small nodule of tissue with similar intensity to grey matter. It enhances vividly during contrast administration as it is outside the blood brain barrier.